Yet another resistance decade box

[bitseeker]

Those look great, Fortran!

[Iwanushka]

Got the package, thank you!

Now need to check the thread and find out which switches to order

[blackbird]

I don't know if anyone already asked but where can I get end plates or caps for my Km2 pushwheels? Anyone got a good source? Got some without the end caps, usable offcours, although I would like to have them with the caps.

[Fortran]

The one I linked a few pages ago came with endcaps.
I haven't found any place to buy them loose.

[ez24]

I don't know if anyone already asked but where can I get end plates or caps for my Km2 pushwheels? Anyone got a good source? Got some without the end caps, usable offcours, although I would like to have them with the caps.

You probably will have to buy new switches with end caps and use those.

[krivx]

...  I thought maybe I could wire up external caps and make a cap decade box BUT it is a BCD switch. ...

There are at least two variants of the switches I know of,   BCD and (straight) decimal.   Just because I was looking for different colors ones I ended up ordering some decimal and some BCD.   

I have a feeling that the BCD and decimal switches are mechanically the same, only the PCBs are different.

Look at the pattern of traces for this BCD switch:

[Fortran]

Yes they are the same switch.

As I mentioned earlier, I bought both and only the pcb differs.

[ez24]

Fortran - there was some talk of decade capacitor boards, any new news?
Again thank you, I am learning how to solder SMDs

[ez24]

Here is a completed switch on ebay, I think using a big switch:

http://www.ebay.com/itm/Seven-decade-resistance-box-0-1-0-ohm-to-9-999999-Mohm-resistor-substitution-/152192192192?hash=item236f5c8ec0:g:stEAAOSwaB5Xjkud

I wonder if by a member.

Edit - there are more sellers than this one

[Fortran]

ez24:  Well I've had my hands full with these boards and a coffee monitoring system for work. 

I'm not even sure if I'll ever get time to make them, but since I want some for myself it might happen eventually.

[ez24]

and a coffee monitoring system for work. 

umm   a coffee decade switch -  goes to one million cups ?

Deliver and counts the coffee beans?  Seems endless possibilities

[PeterZ]

I just got a set of KM3 switches. A new through hole version is to be expected in the near future.
Here's the comparison in size against the KM2:

[garnix]

Wow those are big - nice 

I don't know if I'm the "outlier" but looking at all switches (including the ones I bought) I was wondering why the "+" button is on the bottom and "-" is on top? Instinctively I would have done it the opposite... (Up = +, Down = -) but anyway 

[Fortran]

My guess:  So you can see it increment.
Pushing the top button covers the window with your finger. Pushing the bottom doesn't.

[sq9nje]

Received my kits today. Beautifully packaged indeed. Guess I know what I'll be soldering during the weekend

Przemek

[BFX]

I have an dilema about the case

First choice is much small one.
http://www.ebay.com/itm/New-Aluminum-Box-Enclosure-Case-Project-electronic-for-PCB-DIY-100-100-48MM-/331174761868?hash=item4d1b8dd58c:g:iFAAAOxyrrpTfXRx

Second one is little bit different
http://www.ebay.com/itm/Desktop-Aluminum-Enclosure-Project-Box-Case-DIY-4-33-3-27-1-57-0-75-L-W-H/380867568516?_trksid=p2045573.c100034.m2102&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D2%26asc%3D20131003150253%26meid%3De1e988d906274c408ca17d56461141ef%26pid%3D100034%26rk%3D2%26rkt%3D8%26sd%3D401162940032

and I decided pull outside each decade output to have like divider.

What do you think about it? (I'm prepared to have also ground connected to case)

[ez24]

I have an dilema about the case

First choice is much small one.
http://www.ebay.com/itm/New-Aluminum-Box-Enclosure-Case-Project-electronic-for-PCB-DIY-100-100-48MM-/331174761868?hash=item4d1b8dd58c:g:iFAAAOxyrrpTfXRx

Second one is little bit different
http://www.ebay.com/itm/Desktop-Aluminum-Enclosure-Project-Box-Case-DIY-4-33-3-27-1-57-0-75-L-W-H/380867568516?_trksid=p2045573.c100034.m2102&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D2%26asc%3D20131003150253%26meid%3De1e988d906274c408ca17d56461141ef%26pid%3D100034%26rk%3D2%26rkt%3D8%26sd%3D401162940032

and I decided pull outside each decade output to have like divider.

What do you think about it? (I'm prepared to have also ground connected to case)

Can I ask how are you going to cut square holes for the switch.

FYI  this message is the first one I have seen with its own scroll bar because of the link

[Back2Volts]

Wow!  Those KM3 switches are like twice the size!   Very big.   I think I like better the small ones, although have not yet tried to solder the kits I received.   I still need to go through the learning experience like EZ24 has been doing.

[ez24]

Wow!  Those KM3 switches are like twice the size!   Very big.   I think I like better the small ones, although have not yet tried to solder the kits I received.   I still need to go through the learning experience like EZ24 has been doing.

Actually the large one is easier to use because the buttons are larger thus easier to get your finger on it.  But this has been a fun project and I am sure you will have fun like me.

I think I lack one thing (it is on order) is solder paste.  I think with solder paste, the SMD would lay flat, then I could tack solder it then go back and add solder.  I saw this method by watching a video on pick and place machines.  The video said the board had solder flux added to it first in order to stick the SMDs to the board.  Once I get the paste I will let you know how it goes.

[BFX]

Already prepared to finalize
Thank you Fortran 
 

[Blastcap]

Can I ask how are you going to cut square holes for the switch.

FYI  this message is the first one I have seen with its own scroll bar because of the link

Depending on the tools available, CNC milled would be the most elegant overkill solution.

Make a cardboard prototype, to ensure you have the right cutout, and everything fits, then mark the cutout on the faceplate, and drill a hole in each corner. Cut the lines between with a Dremel or other tool.
Then with a square jeweler's file, make the corners... square.
Finish by chamfering the edges slightly with a file or sandpaper so you won't cut yourself.

Mount, and enjoy.
If done right, everything will snap into place and fit snugly, and there will be no need for "hotsnot" or other adhesive.

[all_repair]

KM3 still with SMT resistor but no protruding PCB and a provision to tap out 2 resistance end point.  Just end-cap and hole on end-cap for connection, and no need for ENCLOSURE.  possibile?

[Alex Nikitin]

I've measured the relative error (for each value in each decade, the rest set to zero, and the "zero" resistance, 0.5 Ohm, subtracted) of my two 4-decade assemblies (built using MELF 0.1% resistors) on HP3458A. One unit (D0) uses selected resistors, the second (D1) - the rest. As an afterthought - it is possible to get a better relative error by measuring the resistors and arranging them in a certain way (placing the lowest error resistor as the first in the decade, and then go for the resistor giving the lowest error for the sum of the first two and so on, as the weight of the absolute error is diminishing for each next resistor). Next time I'll try that approach.

Cheers

Alex

[bitseeker]

Hi Alex,

Thanks for sharing your measurements. I was also planning on arranging my resistors as you described toward the end of your post (lowest error for 1, next-lowest for 2, etc.).

[Blastcap]

Doing some last minute shopping, could anyone confirm that these will fit?
http://www.mouser.de/ProductDetail/CHERRY/PBC1-E015/

Its a 10 pack from "Cherry", they can't be too bad.

Just a heads up, i went to mouser and got one of these, convinced it was a row of 10 pcs.
Nop... 1 segment with 10 positions... for 8,42€.

After a lot of force i got the board out (cherry glued it in), and mounted one of Fortran's (beautiful little boards) with the 100 ohm range.
It fits mechanically, but the displayed number doesn't line up with the value and the numbering is in the reverse order. Also for some reason it had three positions where I suddenly got it fluctuating from 2K to 6M ohm, really strange.

Buttom line... won't work. Don't waste 50€ on a set of these.

So anyone know where i can get some usable switches within the EU so i don't have to wait 6 weeks?