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Author Topic: Low Cost Programmable Decade Resistor for Prototyping Convenience  (Read 23748 times)

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Offline gerrysweeney

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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 :-DD ) 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

Offline casper.bang

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #1 on: July 01, 2013, 07:11:28 AM »
Cool, small and cheap... just ordered one. Good luck with the project!
 

Online fpliuzzi

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #2 on: July 01, 2013, 07:13:37 AM »
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.

 

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #3 on: July 01, 2013, 07:17:27 AM »
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

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #4 on: July 01, 2013, 07:18:06 AM »
Cool, small and cheap... just ordered one. Good luck with the project!
Thank you Casper, much appreciated.

Gerry

Offline dr.diesel

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #5 on: July 01, 2013, 07:42:04 AM »
I had to have one as well, very nice my friend.

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Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #6 on: July 01, 2013, 07:44:13 AM »
I had to have one as well, very nice my friend.
Thank you sir! Very kind.

Offline Chet T16

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #7 on: July 01, 2013, 07:46:52 AM »
One for me too. I've been looking out for a reasonably priced decade box but this suits my needs perfectly, very nice
Chet
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Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #8 on: July 01, 2013, 07:49:57 AM »
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

Offline Selectech

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #9 on: July 01, 2013, 07:55:20 AM »
I just got a pair, too handy not to have for the bench. Thanks
 

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #10 on: July 01, 2013, 07:58:27 AM »
I just got a pair, too handy not to have for the bench. Thanks
Thats great, thank you Dave.

Gerry

Offline Lightages

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #11 on: July 01, 2013, 08:09:35 AM »
I just ordered two! Nice little package. I will wait to see how long it takes to get to Chile!
Disclaimer: I am a distributor for Brymen in Chile, Peru, Bolivia, Paraguay, Uruguay, Colombia, Ecuador, Venezuela, Guyana, and Suriname
 

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #12 on: July 01, 2013, 08:12:40 AM »
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

Offline Lightages

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #13 on: July 01, 2013, 08:18:17 AM »
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.
Disclaimer: I am a distributor for Brymen in Chile, Peru, Bolivia, Paraguay, Uruguay, Colombia, Ecuador, Venezuela, Guyana, and Suriname
 

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #14 on: July 01, 2013, 08:21:39 AM »
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

Offline bance

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #15 on: July 01, 2013, 11:45:58 AM »
Fantastic little project good luck!
 

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #16 on: July 01, 2013, 04:09:06 PM »
Fantastic little project good luck!
Thank you

Offline george graves

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #17 on: July 01, 2013, 04:44:34 PM »
Very nice!  I like that it's easy to repair (unless you blow a trace - eek!).

Thumbs up!

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #18 on: July 01, 2013, 05:02:07 PM »
Very nice!  I like that it's easy to repair (unless you blow a trace - eek!).

Thumbs up!
Thanks George.

Offline sleemanj

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #19 on: July 01, 2013, 05:44:24 PM »
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.


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Offline chickenHeadKnob

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #20 on: July 01, 2013, 07:05:29 PM »
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.
 

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #21 on: July 01, 2013, 07:31:17 PM »
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

Offline ddavidebor

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Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #22 on: July 02, 2013, 01:45:13 AM »
Where can i buy this super handy thing?
 

Offline gerrysweeney

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #23 on: July 02, 2013, 01:50:09 AM »
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.

Offline iloveelectronics

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Re: Low Cost Programmable Decade Resistor for Prototyping Convenience
« Reply #24 on: July 02, 2013, 01:57:24 AM »
I just ordered 2 as well! Thanks for offering this very handy device!
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