Low Cost Programmable Decade Resistor for Prototyping Convenience

[gerrysweeney]

Hi All,

I recently published an article on my blog where I have created a simple low cost programmable decade resistor.  One of the readers suggested that the project deserved a new thread on the EEVblog forum so here it is.  It serves a specific need and I did try quite hard to find something I could buy easily and quickly before embarking on making something myself.

I was not sure how interesting the project was going to be but I wanted to get some made by machine which meant I had to make a reasonable quantity so I made 200 of them and I put them up on e-bay for sale. 

10% of the stock sold in the first hour (I guess thats all my friends then ) so I suppose there is some interest.  My goal was to make something that was both useful and cheap enough to serve the EE community.  The cost point was met by making enough to justify the pick and place setup, probably should have made 1000 or so but this was just a toe-in-the-water exercise.  I will make another batch if the interest remains. 

Please let me know what you think.

http://gerrysweeney.com/seven-decade-programmable-resistor-a-low-cost-solution/

Thanks,

Gerry

[casper.bang]

Cool, small and cheap... just ordered one. Good luck with the project!

[fpliuzzi]

Gerry,
I just ordered one of your Programmable Decade Resistor devices for my bench. Very clever design. I also built a few of the versions that utilize thumbwheel switches last year. They work fine but take a bit of time to construct.

Regards,
Frank

ps, I enjoy your informative videos too.

[gerrysweeney]

Hi Frank,

Thank you for buying one, I am glad you like it. One of the things I always find is simple is often best. While it does not address every ill, it is a solution to the problem I often run into so I am glad I am not the only one.

Thanks for watching the vids too, very much appreciated.

Gerry

[gerrysweeney]

Cool, small and cheap... just ordered one. Good luck with the project!

Thank you Casper, much appreciated.

Gerry

[dr.diesel]

I had to have one as well, very nice my friend.

[gerrysweeney]

I had to have one as well, very nice my friend.

Thank you sir! Very kind.

[Chet T16]

One for me too. I've been looking out for a reasonably priced decade box but this suits my needs perfectly, very nice

[gerrysweeney]

One for me too. I've been looking out for a reasonably priced decade box but this suits my needs perfectly, very nice

Thank you Chet, glad you like it.

Gerry

[Selectech]

I just got a pair, too handy not to have for the bench. Thanks

[gerrysweeney]

I just got a pair, too handy not to have for the bench. Thanks

Thats great, thank you Dave.

Gerry

[Lightages]

I just ordered two! Nice little package. I will wait to see how long it takes to get to Chile!

[gerrysweeney]

I just ordered two! Nice little package. I will wait to see how long it takes to get to Chile!

Thank you. I have been told by a few people that things sent via post to South America can often *not* get to their intended recipient. Any suggestions on what I can do to minimise that? I could courier them but that will be pretty expensive I believe.

Gerry

[Lightages]

I have always received things shipped to me here in Chile. Sometimes it takes 3 months but everything has arrived eventually. Just send it normal post with a tracking number if you can. Thanks.

[gerrysweeney]

Will do, I am not a prolific ebay seller so I have no idea how all the nuances of the postal system works, I will get a tracking number if I can.

Gerry

[bance]

Fantastic little project good luck!

[gerrysweeney]

Fantastic little project good luck!

Thank you

[george graves]

Very nice!  I like that it's easy to repair (unless you blow a trace - eek!).

Thumbs up!

[gerrysweeney]

Very nice!  I like that it's easy to repair (unless you blow a trace - eek!).

Thumbs up!

Thanks George.

[sleemanj]

With regard to the decimal switches you first tried in the video. 

I've bought quite a lot of these, the contact resistance on them can be bad on some digits if you don't clean them up first - probably they have been stored in some China warehouse for 10 years.  So really important to check each contact on all the switches before you do assemble, any dirty ones, squirt some switch cleaner lubricant on the back of the board, let it soak through the wiper center then work it through. 

If it's really bad, shave off the lugs on the back, pop off the board and clean up the contacts manually.  If like me you have to check and clean up about 60 of these critters at a time, you do wind up with a sore thumb for a while :-/   I considered using SMD resistors too, but the power limitation put me off, standard 1/4w through hole resistors fit fine if you bend a leg on them.

To null out the combined contact resistance across the decades, I just reduced the 1st 1 Ohm resistor to 0.5 Ohm, so as long as the last number in the series isn't 0, the contact resistance (which totalled 0.5 Ohm for me) was essentially taken care of.

[chickenHeadKnob]

hi gerry,
 I am for the general idea, so much so I made something similar for my self, but I see two improvements you can make. First you have committed the cardinal sin of all these small projects - no mounting holes on the corners, also use higher wattage on the 10R an 1R.

[gerrysweeney]

hi gerry,
 I am for the general idea, so much so I made something similar for my self, but I see two improvements you can make. First you have committed the cardinal sin of all these small projects - no mounting holes on the corners, also use higher wattage on the 10R an 1R.

Yes I did think about the mounting holes - after I done the layout unfortunately. I was focused on size, trying to get it down to something that was usable and small. As I have never envisaged it being mounted I left out the mounting holes. In hindsight though, I think mounting holes would have been a good thing.  Thanks for the feedback

Gerry

[ddavidebor]

Where can i buy this super handy thing?

[gerrysweeney]

Where can i buy this super handy thing?

If you do want one of these I have listed some on e-bay, you can search for “gerrysweeney.com” or “Seven Decade Programmable Resistor” which should find the listing.

[iloveelectronics]

I just ordered 2 as well! Thanks for offering this very handy device!

[gerrysweeney]

I just ordered 2 as well! Thanks for offering this very handy device!

Thank you for your interest, much appreciated.

Gerry

[gerrysweeney]

done similar 2 yr ago:
http://piccy.info/view3/4791938/d706e396dec6d8494713aae24112d101/
http://piccy.info/view3/4791942/1d42fe11ff9f79dfb6d0534419fecfc8/

Nice, if they were on sale I would have bought a couple, I looked quite hard for a simple solution but ended up rolling my own. 

Gerry

[Thor-Arne]

I ordered one as well. 

[gerrysweeney]

if they were on sale I would have bought a couple

me too, but found nothing similar at local stores.
Moreover, jumpers are cheaper, and more reliable than mechanical switches.

Yep, exactly my conclusions I thought when I put it together. And best of all, if your jumpers do wear out, just get some more, they are about $10 per 1000

[gerrysweeney]

I ordered one as well. 

Thank you. Really great support from everyone, I really appreciate it, I am glad to have made something that is useful to others. 

[karlmag]

.. and I just ordered one too...

I just blame Thor-Arne for me ordering it now - and so can you ;-)
He pointed it out to me.

Thanks! :-)

[Thor-Arne]

 

[gerrysweeney]

.. and I just ordered one too...

I just blame Thor-Arne for me ordering it now - and so can you ;-)
He pointed it out to me.

Thanks! :-)

Thank you both

[KedasProbe]

Nice, but I guess calling it "Programmable" is a typing mistake?

[karlmag]

Nice, but I guess calling it "Programmable" is a typing mistake?

Nah, I would call it programmable.
You do program it - using manual placement of jumpers, but you do program it.

[gerrysweeney]

Nice, but I guess calling it "Programmable" is a typing mistake?

Nah, I would call it programmable.
You do program it - using manual placement of jumpers, but you do program it.

Yeah me too, calling it "settable" does not really describe it in a way that people would recognise it.

Gerry

[Thor-Arne]

Oh, fast shipping too. 

[Dave]

Yeah me too, calling it "settable" does not really describe it in a way that people would recognise it.

Gerry

I know a term that Americans adore: "adjustable".
Everything is better if it's adjustable, especially if it's "fully adjustable". Or so I've heard.

Nifty little gadget. I like that it's really compact and handy.
You have inspired me to have my own go at making an adjustable (hehe ) decade resistance box. I was thinking about using shorting rotary switches, so the circuit doesn't get disconnected when I'm are switching values. But it won't be anywhere near as compact as yours, I'm afraid.

Good job on the blog, I really enjoy watching your videos. I especially like your power supply project, great stuff.

[gerrysweeney]

Oh, fast shipping too. 

Phew  , I just packaged and posted these things to places in the UK, Ireland, Finland, Norway, Denmark, Czech Republic, Germany, Portugal, Netherlands, Spain, Sweden, Switzerland, Brazil, Chilli, North America, Canada, New Zealand, Australia, Hong Kong and I might have missed a few.....

Rant time: F*&^% PayPal and e-bay, the devil in disguise. When I called I got through to a machine which proceeded to tell me what I could and could not say - needless to say it did not understand the words I started to use!!! then I said "Security" and it put me through to a person.  Now by this time I was pissed, so I let him have it, and then apologised because I knew he was only the call centre guy.  Basically the company line is, "Its not PayPal that is crap, its Royal Mail", well I beg to differ they are both utter crap......arrrrgggggggg - rant over - time for bed me thinks.

Gerry

[gerrysweeney]

Yeah me too, calling it "settable" does not really describe it in a way that people would recognise it.

Gerry

I know a term that Americans adore: "adjustable".
Everything is better if it's adjustable, especially if it's "fully adjustable". Or so I've heard.

Nifty little gadget. I like that it's really compact and handy.
You have inspired me to have my own go at making an adjustable (hehe ) decade resistance box. I was thinking about using shorting rotary switches, so the circuit doesn't get disconnected when I'm are switching values. But it won't be anywhere near as compact as yours, I'm afraid.

Good job on the blog, I really enjoy watching your videos. I especially like your power supply project, great stuff.

Dave,

Yes thats a good word, "fully adjustable" is definitely better.  To me though, when I think of adjusting I see a man with a wrench (oops, I mean spanner so I am not that in tune with the word in the context of setting jumpers, setting seems more appropriate somehow.  Perhaps one day I will build a real programmable resistor just to say I did, I have access to a good stock of military grade miniature reed relays

Thanks for watching the blog, I am really enjoying designing the PSU (and actually making the blog too), I have learned so much along the way - no puny ready made regulator chips for this puppy

Gerry

[c4757p]

I prefer 'programmable'. That, to me, implies either computer control or discrete steps. 'Adjustable' to me implies a continuous, tweakable range.

[george graves]

Programmable assumes that it can be machine/computer controlled.  I'm sure if a a one-hung-low company came out with a power supply with only an array of headers to set the voltage and called it "programmable", there would be pitch forks.

Speaking of pitch forks....What's up with the "I know a term that Americans adore: "adjustable"."  Sigh....

[gerrysweeney]

Programmable assumes that it can be machine/computer controlled.  I'm sure if a a one-hung-low company came out with a power supply with only a array of headers to set the voltage and called it "programmable", there would be pitch forks.

Speaking of pitch forks....What's up with the "I know a term that Americans adore: "adjustable"."

I remember having to *program* a Data General Nova 3 (yes I was very young it it was very old at the time).  Now, although I was "programming* it, I was actually toggling switches on its front panel - quality computer....

I know programmable is not the ideal word but its the best of a bunch, perhaps settable would have been better. In any case, its printed on the silkscreen now so I shall not be changing it any time soon. 

Gerry

[Dave]

Speaking of pitch forks....What's up with the "I know a term that Americans adore: "adjustable"."  Sigh....

I have noticed that Americans in particular use that term quite often when describing some tool, piece of lab equipment/machinery. Much more often than any other English-speaking people. So I got the impression, that you must really like things that are adjustable.

[cthree]

Aside: Since Americans are the largest group of English speakers by a wide margin, 5:1 over the UK, its hard to argue they are "wrong". 'English' has really been 'American' for at least the last century.

I just made a home on my bench for one of these. Great project! Perfect for getting an 'adjustment' resistor dialed in just so 

[IanJ]

Nice, but I guess calling it "Programmable" is a typing mistake?

Nah, I would call it programmable.
You do program it - using manual placement of jumpers, but you do program it.

Yeah me too, calling it "settable" does not really describe it in a way that people would recognise it.

Gerry

I like 'programmable'........but I guess 'configurable' would work also.

PS. Gerry, hope you've put one in the mailbag to Dave......?

Ian.

[gerrysweeney]

I just made a home on my bench for one of these. Great project! Perfect for getting an 'adjustment' resistor dialed in just so 

Thanks very much, glad you like it.

[gerrysweeney]

I like 'programmable'........but I guess 'configurable' would work also.

PS. Gerry, hope you've put one in the mailbag to Dave......?

Ian.

"Configurable" perhaps.... this conversation could last forever

I did think of sending one over to Dave for his mailbag section, not sure he would be that interested though, eh perhaps I will.

Gerry

[ElektroQuark]

From a non native English speaker (sort of): "adjustable" fits for me.

[KedasProbe]

You could make it smaller if you make the circuit like this but then the user would need to 'calculate' the value.
http://www.robotshop.com/elenco-rs-500-resistor-box.html
And then you would need to remove decade out of the name also

[gerrysweeney]

You could make it smaller if you make the circuit like this but then the user would need to 'calculate' the value.
http://www.robotshop.com/elenco-rs-500-resistor-box.html
And then you would need to remove decade out of the name also

Kinda misses the "simplicity" requirement

[IanJ]

Arrived today......nice one Gerry.

Ian.

[gerrysweeney]

Arrived today......nice one Gerry.

Ian.

Your welcome Ian, thanks for your support. hope its useful, I look forward to seeing it used in one of your projects

Gerry

[IanJ]

Arrived today......nice one Gerry.

Ian.

Your welcome Ian, thanks for your support. hope its useful, I look forward to seeing it used in one of your projects

Gerry

That'll be the power supply project......am in the thick of it right now, and this'll come in useful around the op-amps. 

Ian.

[quarks]

Hello Gerry,
I like your videos  and that looks interesting, so I just ordered two.
bye
quarks

[bingo600]

I also had to order two ...

/Bingo

[ElektroQuark]

It can be interesting to order directly, bypassing eBay and Paypal fees, if Gerry likes it.

[gerrysweeney]

Hello Gerry,
I like your videos  and that looks interesting, so I just ordered two.
bye
quarks

Thank you for the order, much appreciated. Glad you like the video's, thank you for watching them

[gerrysweeney]

I also had to order two ...

/Bingo

Thank you for the order, glad you like the project.

Gerry

[gerrysweeney]

It can be interesting to order directly, bypassing eBay and Paypal fees, if Gerry likes it.

I was thinking about putting a PayPal buy button on my blog page but I have not worked out what I need to do yet.  e-bay does take care of postage and stuff so its fairly convenient, I am not sure exactly what the fees are for e-bay, I think about £1, it would seem though that you pay each time you list and the listing only lasts 30 days.   If its convenient for you to order directly I don;t mind too much although I am not sure how I will deal with postage. I will see what I can put up on my blog

Gerry

[Thor-Arne]

That is not the most obvious thing to achieve, first you need to upgrade your PayPal account to a Permier account.
Then you need to add the various products to PayPal, you can add shipment and sales tax in there to. One thing that's quite convenient is that you can have PayPal manage how many items you have for selling.

After this you get some html code to add to your site. I haven't found how to make a view-cart button though.

You can find these options in: PayPal -> My profile -> More Options -> My selling tools

[gerrysweeney]

That is not the most obvious thing to achieve, first you need to upgrade your PayPal account to a Permier account.
Then you need to add the various products to PayPal, you can add shipment and sales tax in there to. One thing that's quite convenient is that you can have PayPal manage how many items you have for selling.

After this you get some html code to add to your site. I haven't found how to make a view-cart button though.

You can find these options in: PayPal -> My profile -> More Options -> My selling tools

Hi,

Thanks for the tips, I will have a look later and see what I can do.

Gerry

[ddavidebor]

Should be nice, in the next manufacturing run

-banana instead of screw contact
-a "plus" version with gold pin and jumper (or a self made jumper whit some little little pcbs for better quality) should be a good idea
-more dissipation for low value

[gerrysweeney]

Should be nice, in the next manufacturing run

-banana instead of screw contact
-a "plus" version with gold pin and jumper (or a self made jumper whit some little little pcbs for better quality) should be a good idea
-more dissipation for low value

It is possible to replace the terminal block with banana sockets, there are holes in the PCB to accommodate this.  Not sure how beneficial the gold plated jumpers would be, the tin plated ones do seem to perform OK.  I suppose it would be feasible to make some without any pin headers and people could install their own options.
Good point about better dissipation on the lower values, its just space that would concern me.

Thanks for your comments.

Gerry

[quantumvolt]

Very nice and probably much easier to program than programming children (see 13. below) . I hope the stock lasts until the 19th (I have an ex wife caught in an endless support loop and two unprogammable children so I am broke until then).


...

9.
to schedule as part of a program.
10.
Computers. to prepare a program for.
11.
to insert or encode specific operating instructions into (a machine or apparatus): We'll program the bells to ring at ten-minute intervals.
12.
to insert (instructions) into a machine or apparatus: An automatic release has been programmed into the lock as a safety feature.
13.
to cause to absorb or incorporate automatic responses, attitudes, or the like; condition: Our parents programmed us to respect our elders.
14.
to set, regulate, or modify so as to produce a specific response or reaction: Program your eating habits to eliminate sweets.

...

http://dictionary.reference.com/browse/program

[ddavidebor]

Should be nice, in the next manufacturing run

-banana instead of screw contact
-a "plus" version with gold pin and jumper (or a self made jumper whit some little little pcbs for better quality) should be a good idea
-more dissipation for low value

It is possible to replace the terminal block with banana sockets, there are holes in the PCB to accommodate this.  Not sure how beneficial the gold plated jumpers would be, the tin plated ones do seem to perform OK.  I suppose it would be feasible to make some without any pin headers and people could install their own options.
Good point about better dissipation on the lower values, its just space that would concern me.

Thanks for your comments.

Gerry

Yes i know it's possible to replace them, i've suggested for you. A banana one is more useful.

It's a bit expensive i know, but you can let people pay for it separately with option on ebay.

[gerrysweeney]

Yes i know it's possible to replace them, i've suggested for you. A banana one is more useful.

It's a bit expensive i know, but you can let people pay for it separately with option on ebay.

Oh ok, I understand now. The problem is with assembly, its more difficult to produce in lower volumes when there is different constructions. Perhaps a version where there is no terminal block installed. I will have a think about it.  thanks for the suggestions

Gerry

[gerrysweeney]

Very nice and probably much easier to program than programming children (see 13. below) . I hope the stock lasts until the 19th (I have an ex wife caught in an endless support loop and two unprogammable children so I am broke until then).


...

9.
to schedule as part of a program.
10.
Computers. to prepare a program for.
11.
to insert or encode specific operating instructions into (a machine or apparatus): We'll program the bells to ring at ten-minute intervals.
12.
to insert (instructions) into a machine or apparatus: An automatic release has been programmed into the lock as a safety feature.
13.
to cause to absorb or incorporate automatic responses, attitudes, or the like; condition: Our parents programmed us to respect our elders.
14.
to set, regulate, or modify so as to produce a specific response or reaction: Program your eating habits to eliminate sweets.

...

http://dictionary.reference.com/browse/program

Good find, option 14 pretty well describes the use of the work "programmable" for the decade resistor too

Gerry

[Chet T16]

Mine arrived this morning, thanks!

[gerrysweeney]

Mine arrived this morning, thanks!

Glad it arrived ok, I hope its useful for you

Gerry

[IanJ]

Hi all,

And here's mine in use!........does the job nicely.

I might actually modify mine to have a couple of breadboard sockets at the end for easy hook up/removal.

Ian.

[gerrysweeney]

Hi all,

And here's mine in use!........does the job nicely.

I might actually modify mine to have a couple of breadboard sockets at the end for easy hook up/removal.

Ian.

Hi Ian,

Thats great, thanks for posting..its nice to see it in use. Your project looks interesting too, nice job on the display

Gerry

[reagle]

Cool design!
Another suggestion- try using www.tindie.com for selling them. A lot more friendlier than ebay and lower fees. (Speaking from experience as I sell there)

[gerrysweeney]

Cool design!
Another suggestion- try using www.tindie.com for selling them. A lot more friendlier than ebay and lower fees. (Speaking from experience as I sell there)

Hi,

Thanks for the suggestion, its already on there:

https://www.tindie.com/products/gerrysweeney/seven-decade-programmable-resistor-1r-9999999r-1-500mw-gerrysweeneycom/

Gerry

[iloveelectronics]

Received my order today, 7 days from the UK to Hong Kong    Thanks!

[gerrysweeney]

Received my order today, 7 days from the UK to Hong Kong    Thanks!

Excellent, thanks for the order.

Gerry

[casper.bang]

And I just got mine too. Impressed by it's relative good precision, should've gotten two. 

[gerrysweeney]

And I just got mine too. Impressed by it's relative good precision, should've gotten two. 

Great news, thanks for the feedback. I tried to spec reasonable quality resistors. Although only 1% they should be pretty decent most of the time.

Gerry

[gerrysweeney]

Hi All,

I thought I should post this here. Someone (Juergen Gruendmayer - thank you) made a 3D model for a simple snap-on enclosure for the unit and he very kindly made this available for download, he posted on my blog, I thought I would re-post here  He created a simple snap-on box for 3D-printing, you can download it at http://www.thingiverse.com/thing:114201 and have it printed using your favourite on-line 3D printing service. 

Gerry

[iloveelectronics]

Just another small suggestion - perhaps it's better to provide coloured jumper caps instead of the black ones? I reckon it might make it a bit more readable as everything else (except the silk screen) is black. I will more than likely get myself some of those and replace them

[gerrysweeney]

Just another small suggestion - perhaps it's better to provide coloured jumper caps instead of the black ones? I reckon it might make it a bit more readable as everything else (except the silk screen) is black. I will more than likely get myself some of those and replace them

Good suggestion, I will see if I can source them. Thanks.

Gerry

[JeanF]

Hi Gerry, thanks to this thread I discovered your great blog and videos ! And I ordered a couple of these nice little boards. Great job ! Thanks from Brittany

[gerrysweeney]

Hi Gerry, thanks to this thread I discovered your great blog and videos ! And I ordered a couple of these nice little boards. Great job ! Thanks from Brittany

Hi Brittany,

Thanks very much for the order. Very kind words too. Thank you

Gerry

[David]

Just bought 2, could come in handy!

[gerrysweeney]

Just bought 2, could come in handy!

Hi David,

Thank you.

Gerry

[Thor-Arne]

Thanks, mine arrived today.

It's a nice and useful little board. 

[gerrysweeney]

Thanks, mine arrived today.

It's a nice and useful little board. 

Glad you like it.

Gerry

[gerrysweeney]

Hi All,

I just wanted to say thank you to everyone who bought one of the decade resistor boards.  More over, thank you for all the positive feedback and the kind words of encouragement for the project.  The outcome was totally unexpected! When I had some made I thought to myself, I will get 200 made, I am sure some people would find them useful, and 200 should last a couple of years.  Well I was very wrong, they instead lasted just 10 days - as of now I am down to just 10 boards and if current trends continue they will be gone by tomorrow.  I have had interest from a couple of on-line retailers too, I had no idea there would be that level of interest, I was thinking that the interest was just a spike but after the initial spike it has remained pretty constant so this morning I ordered another batch of boards which I should get in about four weeks time.

So again, thank you all so much, I really appreciate it.

Gerry

[ddavidebor]

And with some improvement, you should be able to sell more and more.

It's a damn good board...

[bingo600]

I also had to order two ...

/Bingo

Thank you for the order, glad you like the project.

Gerry

Got mine yesterday thank you 

/Bingo

[gerrysweeney]

And with some improvement, you should be able to sell more and more.

It's a damn good board...

Thank you for your comments. I hope so, I ordered a whole bunch more now with some slight improvements too.

1. Added mounting holes
2. Adjusted solder mask so there is better electrical exposure for 4mm banana sockets (if fitted)
3. Added a place for soldering a two-pin header onto the board so you can push jumper wires in (push fit)

Gerry

[Thor-Arne]

Great news, Gerry.

It's very nice to see your success with this one. 
Keep up the good work.

[JohannP]

hould be nice, in the next manu

-banana instead of screw contact
-a "plus" version with gold pin and jumper (or a self made jumper whit some little little pcbs for better quality) should be a good idea
-more dissipation for low value

...  I suppose it would be feasible to make some without any pin headers and people could install their own options ...

Gerry, I have ordered two of your units to South Africa and looking forward to use them. My I take you up on your suggestion to supply my order without the headers installed on the PCB. I will install the headers myself when necessary. Please supply the postal tracking number so that I can track the parcel in South Africa as the local Post Office is sometimes a problem with reliability.

Best regards

Johann 

[gerrysweeney]

hould be nice, in the next manu

-banana instead of screw contact
-a "plus" version with gold pin and jumper (or a self made jumper whit some little little pcbs for better quality) should be a good idea
-more dissipation for low value

...  I suppose it would be feasible to make some without any pin headers and people could install their own options ...

Gerry, I have ordered two of your units to South Africa and looking forward to use them. My I take you up on your suggestion to supply my order without the headers installed on the PCB. I will install the headers myself when necessary. Please supply the postal tracking number so that I can track the parcel in South Africa as the local Post Office is sometimes a problem with reliability.

Best regards

Johann

Hi Johann,

Thank you for the order.  The batch I currently have are all fully assembled I am afraid so you would need to remove the pin headers.  Perhaps in the next batch I could have some made without the pin headers installed, I will have to ask the question to see if thats viable or not.

I will look at what postage options with tracking there are, I have been using the normal international air mail which seems fine, I will check the option when I ship yours.

Gerry

[cthree]

Got mine yesterday. Very nice! Thanks for making these!

[gerrysweeney]

Got mine yesterday. Very nice! Thanks for making these!

Your welcome, thanks for the feedback.
Gerry

[SeanB]

Depending on where and how you select ( po box or physical address) the SAPO is either slow or incredibly slow. they are on strike ( but you cannot really see any difference, though it might reduce the theft of mail internally) for a while now, and are on a go slow ( from snail to glacier speed AFAIK) but regular small parcel post does get through in 4-6 weeks from arrival in the SAPO system. I haven't had one thing go missing so far ( Touch Wood) so it really just is slow.

If JohannP has a PO Box then I suggest he uses it, as then it takes less time, but you generally get the customs form to pay duty. Please declare a true value, the customs guys ( I know a few by sight now and meet them regularly on weekends in shopping centres as we shop there) are going to query lowball values for the size parcel. Unfortunately you will have to have an invoice or a declaration on the customs, and if postage is included in the price then it will be included in duty, otherwise if the price has a separate postage line ( close in value to the stamp amount) then they might subtract it. In all cases they will charge Ad Valorum and then VAT on this tax.

[ddavidebor]

Yeah i've bought it i've bought it yuppy

[gerrysweeney]

Hi Davide,

Thank you for the order, I just sent you an e-mail with regards to lead time, my first batch stock is fully depleted and the next batch are well under way in the manufacturing process. I should have this shipped to you by the second or third week in August. If thats not OK, please let me know and I will refund you.

Thanks

Gerry

[ddavidebor]

It's ok it's ok.

[sync]

Received mine today. Nine days per air mail from UK to Germany. 

Nice little product! 

Very good accuracy. Set to 123456 ohms and got


I done a little modification. I made solder bridges on the "9" pins. So it doesn't go open circuit when i change the jumpers.

[gerrysweeney]

I done a little modification. I made solder bridges on the "9" pins. So it doesn't go open circuit when i change the jumpers.

I wish I would have done this mod on the next batch but they are already in production Thanks for posting, thats a great mod and one I should have built in from  the off...

Gerry

[Selectech]

My pair came yesterday. Great !

[alank2]

I wish I would have done this mod on the next batch but they are already in production Thanks for posting, thats a great mod and one I should have built in from  the off...

If I were to put my vote in, I would greatly prefer this item without the mod.  I like the idea that if you remove a jumper it goes open instead of assumed "9"...  Without this mod one can always get some extra jumpers and do it that way too...

[mtdoc]

Got mine today. Thanks!   

I wish I would have done this mod on the next batch but they are already in production Thanks for posting, thats a great mod and one I should have built in from  the off...

If I were to put my vote in, I would greatly prefer this item without the mod.  I like the idea that if you remove a jumper it goes open instead of assumed "9"...  Without this mod one can always get some extra jumpers and do it that way too...

I agree. Instead of that mod why not just provide an extra set of jumpers to keep on the 9's.  Also - that way there would be some spares for those of us who tend to lose the little buggers....

[gerrysweeney]

Got mine today. Thanks!   

I wish I would have done this mod on the next batch but they are already in production Thanks for posting, thats a great mod and one I should have built in from  the off...

If I were to put my vote in, I would greatly prefer this item without the mod.  I like the idea that if you remove a jumper it goes open instead of assumed "9"...  Without this mod one can always get some extra jumpers and do it that way too...

I agree. Instead of that mod why not just provide an extra set of jumpers to keep on the 9's.  Also - that way there would be some spares for those of us who tend to lose the little buggers....

Thanks for the comments. From a pure practical point of view, its better with the mod IMHO. If you are working on trimming/tuning live circuits you would generally not want to make the resistor open circuit while changing value, this is why those resistance boxes use make before break switches.  The nice thing about the mod by sync is you can choose to have it or not by simply adding or removing the solder bridge.   The eleventh jumper idea is an interesting one although that could make selecting values error-prone (maybe), but the spare jumpers idea makes sense.  I have asked my assembler to see if they can include the mod at assembly time, not sure if I am too late, we will see. It can always be removed though if thats required.  As always, thanks for the comments.

Gerry

[BillyD]

Received my 2 today. Well packaged and in good time.
Well done on a well thought out and well executed idea, and good luck with the next batch.
Thanks.
Billy.

[gerrysweeney]

Received my 2 today. Well packaged and in good time.
Well done on a well thought out and well executed idea, and good luck with the next batch.
Thanks.
Billy.

Hi Billy,

Thanks very much for your comments, glad you received them OK
 
Gerry

[plesa]

I received it today,  when my coleaques saw it they imediatelly decided to buy their own pieces. Excellent piece of HW.
Just needs to be cleaned from flux residues.

Is there any upcoming version of capacitance decade?

[gerrysweeney]

I received it today,  when my coleaques saw it they imediatelly decided to buy their own pieces. Excellent piece of HW.
Just needs to be cleaned from flux residues.

Is there any upcoming version of capacitance decade?

Hi,

Yes my apologies for the flux residue, I have had a word with my assembler who promises this will be sorted for next time.

I have a 5 decade capacitance one being made as we speak, 100pF to 10uF @ 100V - 10% except for 100pF which is 5%, I should be publishing information about it very soon.

Gerry

[alank2]

I received it today,  when my coleaques saw it they imediatelly decided to buy their own pieces. Excellent piece of HW.
Just needs to be cleaned from flux residues.

Gerry said he thinks his next batch will be cleaned off better.  Just take some 100% isopropyl alcohol to it with a small scrub brush and you can clean it up easily.

Good luck,

Alan

[plesa]

Hi,

Yes my apologies for the flux residue, I have had a word with my assembler who promises this will be sorted for next time.

I have a 5 decade capacitance one being made as we speak, 100pF to 10uF @ 100V - 10% except for 100pF which is 5%, I should be publishing information about it very soon.

Gerry

Splendid!! I will buy few of them for sure.

[tld]

Got one on saturday, ordered earlier in the week through Tindie (not affiliated with either).
I'd really like some places to stick a jumper, but I understand that's probably on the way, so good chance this won't be the last I order.

[ddavidebor]

I received it today,  when my coleaques saw it they imediatelly decided to buy their own pieces. Excellent piece of HW.
Just needs to be cleaned from flux residues.

Is there any upcoming version of capacitance decade?

Hi,

Yes my apologies for the flux residue, I have had a word with my assembler who promises this will be sorted for next time.

I have a 5 decade capacitance one being made as we speak, 100pF to 10uF @ 100V - 10% except for 100pF which is 5%, I should be publishing information about it very soon.

Gerry

another thing to buy   

[gerrysweeney]

It's not a surprise really but here is the first clone! an alternative to mine, pointed out to me this morning by sp6a (thank you)

Search e-bay for: "1R - 9.999999MR Seven Decade Programmable Resistor Board, Step 1R, 1%, 1/4Watt."

eBay Item #161074502921

I should probably be flattered

Gerry

[iloveelectronics]

You should be proud But to be honest this is bound to happen somewhere from China. Funny thing is though they say item location is Hong Kong and yet they don't ship to Hong Kong!  I guess they are doing this to avoid local competition as I wouldn't have seen this item (as HK is excluded from their shipping list) without the exact item number you posted.

It's not a surprise really but here is the first clone! an alternative to mine, pointed out to me this morning by sp6a (thank you)

Search e-bay for: "1R - 9.999999MR Seven Decade Programmable Resistor Board, Step 1R, 1%, 1/4Watt."

eBay Item #161074502921

I should probably be flattered

Gerry

[gerrysweeney]

You should be proud But to be honest this is bound to happen somewhere from China. Funny thing is though they say item location is Hong Kong and yet they don't ship to Hong Kong!  I guess they are doing this to avoid local competition as I wouldn't have seen this item (as HK is excluded from their shipping list) without the exact item number you posted.

Indeed I am, I have not made these to pay the bills, I made these because I wanted to manufacture something using machine assembly and I thought it would be useful for the community.  I love the pricing they have chosen

Maybe I should clone on of their items for fun...

Gerry

[IanJ]

Gerry,

Nothing to worry about, IMO your one has the better layout.

Ian.

[gerrysweeney]

Gerry,

Nothing to worry about, IMO your one has the better layout.

Ian.

Thanks Ian,

Not at all worried - its nice to see someone else thinks its a good idea.

Gerry 

[jasonharper]

This could be made somewhat more compact, using a 2x4 header (which has 10 distinct positions where a jumper can be plugged) and 6 resistors (of two values) per decade.

One downside to this layout is that you cannot short the '9' position to keep the resistance finite when moving a jumper - that would result in an incorrect resistance in some positions due to resistors ending up in parallel.

[gerrysweeney]

This could be made somewhat more compact, using a 2x4 header (which has 10 distinct positions where a jumper can be plugged) and 6 resistors (of two values) per decade.

One downside to this layout is that you cannot short the '9' position to keep the resistance finite when moving a jumper - that would result in an incorrect resistance in some positions due to resistors ending up in parallel.

Nice idea, my concern with that would be usability, it would not be obvious and might be difficult to get a silkscreen legend to make it clear.

Gerry

[tld]

The compact design is neat, but doesn't really fit with how I imagine such a thing typically being used.

Anyone using one would be more than capable of configuring it, but that's not really the goal when you're using it. You don't want to think about it, you want to think about the circuit you're working on.

[jasonharper]

Nice idea, my concern with that would be usability, it would not be obvious and might be difficult to get a silkscreen legend to make it clear.

Good point, here's the clearest/smallest legend I could think of.  The 0/3/6/9 labels could be shared by adjacent decades, which would make the width per decade about 0.4" assuming 0.1" headers.

[gerrysweeney]

Nice idea, my concern with that would be usability, it would not be obvious and might be difficult to get a silkscreen legend to make it clear.

Good point, here's the clearest/smallest legend I could think of.  The 0/3/6/9 labels could be shared by adjacent decades, which would make the width per decade about 0.4" assuming 0.1" headers.

Hi Jason,

Yes thats very compact for sure, quite nice...

Gerry

[ddavidebor]

i've just bought a second one.

how much will it need? i'm still attending the first (it's all ok don't worry!)  O0

[gerrysweeney]

All,

Just a quick note for those of you that purchased these items while I have had them on back order.  I finally have the tracking number and they are hold up in Heathrow, they have cleared customs so should be delivered to my door on Monday (tomorrow).  Assuming there are no manufacturing issues (i am pretty sure they will be absolutely fine), I will get the shipping rolling during the course of the week.

Over the last four weeks a significant backlog of pre-orders have built up so me and the misses will be kept pretty busy over the next few days.  Thank you everyone for supporting this project by buying one or more of the units. Also, an extra special thank you for those of you that have ordered knowing I was waiting for stock and have waited so patiently over the last four/five weeks.

I have also designed a five decade capacitor board using the same form-factor and design approach which I have had made at the same time, I get those tomorrow soon. Quite a few people asked about this so I am taking a punt on the fact that people will find them useful and have funded their manufacture myself rather than doing a crowd source exercise - I will do a video soon for this and probably start another forum thread here on the EEVBlog forum.

Thanks,

Gerry

[Fsck]

Got mine from the backorder batch. They're neat.
However, one of my header pins was brutally bent over. Easily fixed with some physical therapy.
Minor quibble: some of the fiberglass from the PCB keeps flaking off the edges.
little bit of flux here and there, again, minor.

most annoying (still not that bad) is the modification to the 9 pins is extremely uneven. Some of them are pretty mangled, but doesn't really affect the product, just its appearance.

personal note: I'm not sure I like the terminal block thing. I'd be more for a banana jack so it'd be completely tool less.

I'll probably add some little feet to mine

[ddavidebor]

i've received the two boards. alredy changed the screw connector with a couple of banana ones, soldered the 2.4mm couple of pin for convenient use with breadboard.

[Zbig]

Sorry for the off-topic post but there's one thing which puzzles me since some time regarding resistance decades, be it this one (great idea, BTW!) or pretty much any other commercially available small size decade/substitution box I've seen. Is there any practical advantage of having all the resistors rated for the same maximum power dissipation? While I have no trouble understanding the need of having small valued ones rated for as high a power as it's practically achievable, I'm not sure I understand the need for using the same power rating, e.g. 0.5W for high values like anything beyond 100k or so as well. What I mean is, one would need to apply over 200 Volts across the 100k resistor to get 0.5W of power out of it and that wouldn't be the wisest thing to do with a densely SMD-populated, jumper-bridged PCB, right? Let's not even go into the megaohm area. Is it purely to keep the solution "elegant", the resistors consistent in regards to their specifications and not to overcomplicate things?

[gerrysweeney]

Got mine from the backorder batch. They're neat.
However, one of my header pins was brutally bent over. Easily fixed with some physical therapy.
Minor quibble: some of the fiberglass from the PCB keeps flaking off the edges.
little bit of flux here and there, again, minor.

most annoying (still not that bad) is the modification to the 9 pins is extremely uneven. Some of them are pretty mangled, but doesn't really affect the product, just its appearance.

personal note: I'm not sure I like the terminal block thing. I'd be more for a banana jack so it'd be completely tool less.

I'll probably add some little feet to mine

Thanks for the feedback, comments noted.

Gerry

[gerrysweeney]

i've received the two boards. alredy changed the screw connector with a couple of banana ones, soldered the 2.4mm couple of pin for convenient use with breadboard.

Glad you received them ok.

Gerry

[gerrysweeney]

Sorry for the off-topic post but there's one thing which puzzles me since some time regarding resistance decades, be it this one (great idea, BTW!) or pretty much any other commercially available small size decade/substitution box I've seen. Is there any practical advantage of having all the resistors rated for the same maximum power dissipation? While I have no trouble understanding the need of having small valued ones rated for as high a power as it's practically achievable, I'm not sure I understand the need for using the same power rating, e.g. 0.5W for high values like anything beyond 100k or so as well. What I mean is, one would need to apply over 200 Volts across the 100k resistor to get 0.5W of power out of it and that wouldn't be the wisest thing to do with a densely SMD-populated, jumper-bridged PCB, right? Let's not even go into the megaohm area. Is it purely to keep the solution "elegant", the resistors consistent in regards to their specifications and not to overcomplicate things?

Its mostly elegance.

Gerry

[Lightages]

Finally mine arrived after the usual 1 month of slow mail in Chile, and another 1 month because the mail workers went on strike. I like these things and I am sure they will get good use in testing and prototyping.

[gerrysweeney]

Finally mine arrived after the usual 1 month of slow mail in Chile, and another 1 month because the mail workers went on strike. I like these things and I am sure they will get good use in testing and prototyping.

Glad they made it, thanks for posting.

Gerry

[Alex]

Gerry,

In case this has not been covered, the 10R decade on my board was shorted by a thin solder bridge under the pin header. Once located, it was easy to repair by reheating the solder joints. I assume this can be traced back to the assembly process. Hopefully this will help anyone with the same issue.

I otherwise share everyone else's comments 

Alex.

[gerrysweeney]

Gerry,

In case this has not been covered, the 10R decade on my board was shorted by a thin solder bridge under the pin header. Once located, it was easy to repair by reheating the solder joints. I assume this can be traced back to the assembly process. Hopefully this will help anyone with the same issue.

I otherwise share everyone else's comments 

Alex.

Hi Alex,

Sorry about that. Regrettably the quality of the assembly was less than optimal - I am not going to name the assembly house at this time, I have been trying to work it out with them. Quality aside they are reasonable to deal with. I will know on the next project if they actually do what they say they will.  Anyways, if you want me to send you a replacement I will gladly do so.  Sorry you had to spend time to find a problem, my main goal was to provide a simple and usable (out of the box) tool for my fellow EE'ers, I missed the boat in this case obviously.

Gerry

[Alex]

Hi Alex,

Sorry about that. Regrettably the quality of the assembly was less than optimal

Gerry

Your support is honest and thank you for your offer. Hopefully the feedback will help you iron out any issues with the assembly house, which was my intention.

After all, some people would pay more for equipment in need of repair.


Alex.

[zapta]

Just wonder, can you use BCD scheme (1, 2, 4, to cut the resistor count by half? The thumb switches for example do come with bcd scheme.

[Mike Warren]

Just wonder, can you use BCD scheme (1, 2, 4, to cut the resistor count by half? The thumb switches for example do come with bcd scheme.

All the thumbwheel switches I've seen have a common terminal. For resistors you would need the switches across each resistor.

You would also have to think in reverse; open the switch to select the value.

The other problem would be that uncommon values would be needed.

Code: [Select]


   +--/--+--/--+--/--+--/--+
   |     |     |     |     |
---+--1R-+--2R-+--4R-+--8R-+---




[Bryan]

Could one not use 7 rotary switches (1 pole 10 position) for each decade instead of the jumpers and mount in a nice project box?.

[ddavidebor]

but it would cost 75$ and not 15$ and it would be much bigger

[Bryan]

Yes, I know. I already have the decade resistor. Wanted to modify it so it is easier to use. Looking at the schematic I can see no reason why not.

[sync]

Why modifying it? Resistors are cheap. Build a complete new one.
btw: use make-before-break switches.

[dragonflight]

This is a great idea, but it could be made better (IMHO) if you added a 10th resistor to each decade.
Why?
As it stands you are potentially limited to resistance values +/- 1%. As an extreme example if you want 100.000K?, but your 100K is 1.01K and your 99.999K is 98.999 (though it is likely to be higher), the best you can do is 100K +1% or 100K -1%.

With a 10th resistor you are guaranteed of covering all the resistance values over the 7 decades.

So now that we can cover all the values with a little setup work (accurately measure the resistance of the first 4 decades) we can set the resistance to .1% (100?-999.9K?)!

To accurately set a resistance to .1% (and by extension .02% or .03% with constant room temperature and a lot more calculation ...), the user would have to measure and build a table of offsets for each of the first 4 decades (32 entries) and add these offsets to the desired value, before setting the jumpers

an example
to set 43.34K +/- .1%

look up 40K and the value is -.31K
look up 3K   and the value is -.023K
so you want 43.34 - .31 -.02 = 43.01

if the the error sum is negative then you redo the calculation and "borrow" 1 from the first 2 digits
so to set 43.31 look up 42K + 1.31K

40 K is -.31K
2K is +.020K

so you want 42. + 1.31 -.31 +.02 = 42. + 1.02
so you set 0(100K), 4(10K), 2(1K), 10(100), 2(10), 0(1)

This may seem difficult (it ain't easy), but the complexity is a small price to pay for a .1% accurate resistance box again IMHO at this price.

[Flump]

Does anyone know what kind of resistors Gerry's programmable resistor uses as I released the magic smoke
in two of them! and a lot of smoke it was too lol.

I only need 2 (100R) but would buy 10 or so, so I have some spares
can you buy them in small amounts like that, and preferably in the UK ?

(How I did it)
I made a 4:1 Balun for a HF antenna and I needed a 200R carbon resistor and was looking around for one
and spotted the programmable resistor, so I set it to 200R and hooked it up the the Balun.
For about 10 seconds the VSWR looked great, totally flat from 7Mhz upwards then the magic smoke released,
I guess it didn't like 10watts of RF going into it.

That will teach me for messing around with things at near 1am in the morning.

[Fsck]

they're just plain old 1210 smd resistors.

[gerrysweeney]

Does anyone know what kind of resistors Gerry's programmable resistor uses as I released the magic smoke
in two of them! and a lot of smoke it was too lol.

I only need 2 (100R) but would buy 10 or so, so I have some spares
can you buy them in small amounts like that, and preferably in the UK ?

(How I did it)
I made a 4:1 Balun for a HF antenna and I needed a 200R carbon resistor and was looking around for one
and spotted the programmable resistor, so I set it to 200R and hooked it up the the Balun.
For about 10 seconds the VSWR looked great, totally flat from 7Mhz upwards then the magic smoke released,
I guess it didn't like 10watts of RF going into it.

That will teach me for messing around with things at near 1am in the morning.

Hi Mark,

They are just 2010 SMT resistors - not rated at 10W (for very long at least).  You should be able to get them from e-bay or any electronics component distributor but if you are buying 10 of them you are likely to pay a big premium for shipping/handling, ordinarily they cost less than a penny each but you need to be buying 5000 on a reel.  If you get really stuck I can probably find a few spares for you

Gerry

[Flump]

Thanks for the info Fsck & Gerry
I found some on ebay I think

http://www.ebay.co.uk/itm/271226754188?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
RESISTOR, SURGE, 1210, 1%, 100R
Resistance:100ohm
Resistance Tolerance:± 1%
Power Rating:500mW
Voltage Rating:200V
Temperature Coefficient:¬± 100ppm/¬_C
Resistor Element Material:Thick Film
Resistor Case Style:1210
Resistor Mounting:SMD
External Depth:2.5mm
External Length / Height:0.6mm
External Width:3.2mm
No. of Pins:2
Operating Temperature Range:-55¬_C to +155¬_C
Overload Voltage:400V
Package / Case:1210
Reel Quantity:5000
Series:ERJP
Termination Type:SMD

are they the right ones ?
if so i will get them as you never know I might do it again 

[gerrysweeney]

Hi Mark,

Yes those will do...£6 for 25 of em, told you they would be expensive....

Gerry

[gerrysweeney]

Mark,

The offer is still there, if you want to buy a stamp and an envelope and post me a pre-stamped empty envelope I will stick a few in the post for you - will save you a few quid

Gerry

[Flump]

Thanks Gerry, PM sent

[zapta]

Mark,

The offer is still there, if you want to buy a stamp and an envelope and post me a pre-stamped empty envelope I will stick a few in the post for you - will save you a few quid

Gerry

Hi Gerry,

Have you consider offering optional casing for your resistor boards?  Even something as simple as an acrylic plate at the bottom with four screws.

[0xdeadbeef]

Don't want to undermine nice Gerry's project but for those who are looking for an affordable decade resistor with case and switches, this might be an option:
http://www.elv.de/praezisions-widerstandsdekade-wd-100-komplettbausatz.html

It's a pretty nice diy kit. Unfortunately, they increased the price since I bought two of them.
As far as I recall, they cost 20€ back then, but yeah well.

[gerrysweeney]

Mark,

The offer is still there, if you want to buy a stamp and an envelope and post me a pre-stamped empty envelope I will stick a few in the post for you - will save you a few quid

Gerry

Hi Gerry,

Have you consider offering optional casing for your resistor boards?  Even something as simple as an acrylic plate at the bottom with four screws.

Hi,

I did but the cost was prohibitive given I was designing to a budget.  Someone designed a snap-on case which can be bought here (and other places too I believe) http://www.sculpteo.com/en/print/resistor_decade_box/gpgZ4VM9?uuid=fRAyWJ0swpGAMTRdhAaGVd

Gerry

[gerrysweeney]

Thanks Gerry, PM sent

Hi Mark,

I did not have 2010's but have some slightly bigger that will fit the land pattern no problem, I have put a bunch of them in the post for you. Thanks for the stamped envelope.

Gerry

[Flump]

The resistors arrived today
thanks very much 

However the repair didn't go according to plan
so I shall order another from you soon

[gerrysweeney]

The resistors arrived today
thanks very much 

However the repair didn't go according to plan
so I shall order another from you soon

Why what happened?

[Flump]

I could not get the contacts on the larger resistors to contact the pads on the board
as they were longer than the originals, after carefully placing the resistor centrally over the pads
the resistor contact area was outside the solder pads so I tried to bridge them with solder and the
pads on the board lifted off.

It was my first time working with SMD's and I'm sticking to that exscuse 

[zapta]

Hi,

I did but the cost was prohibitive given I was designing to a budget.  Someone designed a snap-on case which can be bought here (and other places too I believe) http://www.sculpteo.com/en/print/resistor_decade_box/gpgZ4VM9?uuid=fRAyWJ0swpGAMTRdhAaGVd

Gerry

Thanks. Yesterday I took a class of 3D printing so I will give it a try as my first 3D thing.

[Flump]

OO I could do with a couple of them Zapta as I sometimes work on t cloths and the underside of the boards
snag on it.

let us know how you get on   

[zapta]

OO I could do with a couple of them Zapta as I sometimes work on t cloths and the underside of the boards
snag on it.

let us know how you get on   

I managed today to print one from ABS, it's my first real 3D print. It looks very nice. Just ordered one board from Gerry on ebay, will see how well it will fit.

[zapta]

HI Garry, a question regarding in-circuit resistance change.

Let's say that I have a spare jumper and whenever I want to change a value in one of the columns I first insert the spare jumper in the new location and then remove the jumper from the old location (make-before-break).

Will this give clean transition from the old to the new resistance?

[zapta]

I just posted here a 3D design for a case

http://www.thingiverse.com/thing:521303

Had hard time to print accuratly the snap on version on my gettho 3D printer (Prusa I3V). This design is simple and less sensitive for tolerances. OpenSCAD source code included.

[IanJ]

Nice.......real nice!

I've a 3D printer on order......so guess what I'm printing first!

Ian.

[zapta]

Nice.......real nice!

I've a 3D printer on order......so guess what I'm printing first!

Ian.

This will be a lot of fun ;-)

BTW, possible improvements for this product are more visible jumper color (e.g. red), the black on black is not very visible) and providing an extra jumper for make before break transitions when needed.

[magetoo]

BTW, possible improvements for this product are more visible jumper color (e.g. red), the black on black is not very visible)

Or a different colour solder mask.  I'd like a tasteless yellow one for Christmas, but then of course Fluke's legal team would come knocking on Gerry's door.  :-)

Having a choice of colours could be useful too (the green board is for setting "foo" and the red one for "bar") if there was enough volume to justify it.

[zapta]

Another possible improvement of this product is the order of the 0-9 numbers in each column. Currently moving a jumper up reduces the resistance. Counter intuitive IMO.

[JohanH]

This was a cool little device, so I decided to make one. Old thread, but worth resurrecting.

I documented it here:

https://baldpenguin.blogspot.com/2023/01/programmable-resistor-decade.html

Basically I used more expensive resistors to get it to a rating of 1 W and 0.5 %.

[MarkS]

Forgive my ignorance, but what does this do, how do you use it and how does it help in prototyping?

I've heard of decade resistors, but I'm unclear on their purpose.

[JohanH]

For instance, if you have a circuit where you are adjusting a resistor value, you can use this resistor decade to quickly and very precisely find a value (in the final circuit you would use a normal resistor of course). An alternative is to use a trimmer and measure its resistance afterwards. But trimmers and potentiometers aren't that accurate and can be hard to set to an exact value (works better with a multi turn trimmer). With a more accurate resistor decade you can also verify multimeters. Of course, the point with this design was that it was cheap, so you don't have to be so careful with it. I have a few PCBs, so I might still put together another one from a bag of cheaper SMD resistors.

[MarkS]

For instance, if you have a circuit where you are adjusting a resistor value, you can use this resistor decade to quickly and very precisely find a value (in the final circuit you would use a normal resistor of course). An alternative is to use a trimmer and measure its resistance afterwards. But trimmers and potentiometers aren't that accurate and can be hard to set to an exact value (works better with a multi turn trimmer). With a more accurate resistor decade you can also verify multimeters. Of course, the point with this design was that it was cheap, so you don't have to be so careful with it. I have a few PCBs, so I might still put together another one from a bag of cheaper SMD resistors.

Awesome! Thank you. I bought two.

[Neil_UK]

This could be made somewhat more compact, using a 2x4 header (which has 10 distinct positions where a jumper can be plugged) and 6 resistors (of two values) per decade.

One downside to this layout is that you cannot short the '9' position to keep the resistance finite when moving a jumper - that would result in an incorrect resistance in some positions due to resistors ending up in parallel.

Inspired by the above post, I did some more thinking, and came up with a slight improvement (I think).



In case the improvement is not apparent, it's the fact that the altered resistor order means that the jumpers now proceed down the pin field in consistent increments of 3 per level, rather than switching from side to side. This may simplify the annotation. Or it may not, as the previous arrangement has only odd numbers one side, and evens the other.

I also take issue with Jason's assertion that you cannot leave '9' shorted. Any lower numbered jumper shorts the resistors leading up to node '9', meaning that node 9 has no effect on lower valued jumper positions. Leaving the 9 link shorted has two benefits. It eliminates one layout crossover. It means removing a jumper never gives an open circuit, required in many applications.

As well as these 6 resistor solutions, there are also two 4 resistor networks that can be shorted by a single link to yield all resistance values from 0 to 9, (1,3,3,2) and (1,1,4,3). However these do not share the elegant pin locations and easy jumpering of these 6 resistor solutions, or indeed the 9/10 resistor solution that is the subject of this thread.