Author Topic: Yet another resistance decade box  (Read 52638 times)

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Online Fortran

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Re: Yet another resistance decade box
« Reply #25 on: May 26, 2016, 01:40:11 AM »
Looks really good!
Do you have a link to where you bought your switches?
At first glance I thought they where the cheap "KM1 Pushwheel switch" from Ebay, but it doesn't match.
 

Offline PeterZ

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Re: Yet another resistance decade box
« Reply #26 on: May 26, 2016, 02:25:38 AM »
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #27 on: May 26, 2016, 03:19:14 AM »
Great!
I'll buy a few sets of random KM2 and see if they match the design.
They might not arrive until I'm on my honeymoon though, but a group-buy should be available in August if everything goes to plan.
I'll do my best to keep costs down (I'm not taking any profits at all. This will be a zero gain deal for me).

Early estimates put this at around $5 per 6 boards, plus $2 for shipping and handling anywhere in the world.
A shoutout from anyone interested at this price would be nice. Just to get a sense for the scale of it.
Hopefully it will be lower.
 

Offline matseng

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Re: Yet another resistance decade box
« Reply #28 on: May 26, 2016, 03:39:20 PM »
Early estimates put this at around $5 per 6 boards, plus $2 for shipping and handling anywhere in the world.
A shoutout from anyone interested at this price would be nice. Just to get a sense for the scale of it.
Hopefully it will be lower.
"Shoutout" for three sets. :-)
 

Offline chickenHeadKnob

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Re: Yet another resistance decade box
« Reply #29 on: May 27, 2016, 12:11:55 PM »
I am interested in the make before break boards,20 to 24 individual (little) boards, so depends on your panalization.
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #30 on: May 27, 2016, 05:12:10 PM »
I was actually planning to get them V-scored, so any number will be fine.
Makes handling a lot easier if you don't need to cut them by hand.
 

Offline krivx

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Re: Yet another resistance decade box
« Reply #31 on: May 27, 2016, 08:25:04 PM »
Great!
I'll buy a few sets of random KM2 and see if they match the design.
They might not arrive until I'm on my honeymoon though, but a group-buy should be available in August if everything goes to plan.
I'll do my best to keep costs down (I'm not taking any profits at all. This will be a zero gain deal for me).

Early estimates put this at around $5 per 6 boards, plus $2 for shipping and handling anywhere in the world.
A shoutout from anyone interested at this price would be nice. Just to get a sense for the scale of it.
Hopefully it will be lower.

I would like a couple of sets.

If you have any plans to do capacitor boxes that uses BCD switches I would also like some :) http://www.electricstuff.co.uk/capbox.html
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #32 on: May 27, 2016, 09:14:54 PM »
I've thought about making capacitor decades as well.
If there's some interest, I'll probably make one.
 

Offline alank2

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Re: Yet another resistance decade box
« Reply #33 on: May 27, 2016, 10:18:22 PM »
Very nice!  Are you going to offer them as a kit or group buy?
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #34 on: May 27, 2016, 10:38:37 PM »
Plan is to get a few hundred boards made and sell them (board only) as cheap as I can.
Although, price per resistor is significantly lower in 1000's then in 10's, so I'll take a look at the kit option.
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #35 on: May 28, 2016, 04:43:26 PM »
So I've looked in to it.

I would be able to offer a set of Vishay Dale CRCW resistors for an additional ~$0.80.
That's for 6 values from 1R to 100K, 10 of each. Quick specs are 1/4W, ±1%, ±100ppm/°C.
And you don't need to buy in groups of 6. Since I'm getting them V-scored I don't need to spend hours cutting boards, so buy whatever amount and value you like to match the number of switches you have.
I would have loved to be able to offer higher power and precision, but even though the price per set would still be reasonable, it adds up to amounts that would make my wallet cry.

So. ~$0.85 per blank board
or   ~$1.00 per blank board +10 resistors of either value.
I can populate a few for those who really need it.

Sound good?
 

Offline matseng

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Re: Yet another resistance decade box
« Reply #36 on: May 28, 2016, 05:39:33 PM »
But 1% is really crappy... ;-(
How much more expensive would 0.1% be?
 

Offline BravoV

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Re: Yet another resistance decade box
« Reply #37 on: May 28, 2016, 05:58:10 PM »
Count me in for 2 groups (12).

Online Fortran

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Re: Yet another resistance decade box
« Reply #38 on: May 28, 2016, 07:42:57 PM »
If I do a less bulky-ish order I can manage to get 0.1% on all but 1R. (Simply because I can't FIND any 1R 0.1%)
But picking on the poor 1R only being 1% is mean since contact resistance is probably more then that.

The lineup would then be Wishay Dale CRCW 1/4W, ±1%, ±100ppm/°C for 1R,
and Yageo RT 1/4W, ±0.1%, ±25ppm/°C for 10R-100K

I'm only capable of buying these in 100 quantity at a time though. 1000 quantity would mean about $750 upfront for resistors alone and that's just too much for me.
Due to the limited number of sets I'd prefer to sell all 6 values per order to keep an even stock. When all resistors are sold I can order 100 new ones and repeat as long as there is demand.

That would add up to $12.60 for 54 resistors. (No spare to drop under the bench never to see again)
Plus ~$5.10 for the boards and ~$2 for shipping gives a total of ~US$19.7 delivered. (Actual switch not included)
 

Offline Dave

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Re: Yet another resistance decade box
« Reply #39 on: May 29, 2016, 03:37:14 AM »
I don't think 0.1% resistors would even make sense, because the contact resistance of the contacts would dominate the error in the lower ranges. You wouldn't use this sort of resistance box for any precision application, so 1% is more than good enough for the purpose.

Put me down for 6 boards. :-+
<fellbuendel> it's arduino, you're not supposed to know anything about what you're doing
<fellbuendel> if you knew, you wouldn't be using it
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #40 on: May 29, 2016, 05:37:13 AM »
0.1% doesn't make sense on 1R.
Probably not on 10R either.

But after that it would make a difference.  Even though a small one.
1% is good enough for me, and probably for most.

Majority rules.  :)
1% is practically free and that kind of money up front makes no difference to me.
0.1% isn't.  But if 10 people want a set so I know I'll sell it, it's fine by me.
 

Offline Macbeth

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Re: Yet another resistance decade box
« Reply #41 on: May 29, 2016, 07:21:28 AM »
I agree - my own resistor decade I made with the bigger version of these switches I debated even having a 1 ohm setting, then went ahead and also made sure to use 500mW resistors there and the tolerance wasn't particularly relevant. The other ranges all done with 250mW and I selected from 1% resistors for the job. Certainly the higher range resistors would benefit from 0.1% tolerance but even then, that's not good enough - 1k per 1M - renders the bottom 3 digits untrustworthy.
 

Offline julian1

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Re: Yet another resistance decade box
« Reply #42 on: May 29, 2016, 06:06:28 PM »
I'm interested - 2x sets (12) including resistors. The prices seem incredibly reasonable so 0.1% would be great if it can be managed.

Anyone scoped possible boxes/enclosures?

Offline PuterGeek

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Re: Yet another resistance decade box
« Reply #43 on: May 30, 2016, 03:52:43 AM »
Quick question on the contact plating, are you going to have them hard gold plated or just ENIG?

The gold plating on ENIG isn't very robust since it's only intended for solderability. Once the gold wears of the contacts will be the nickel underneath with its higher resistance.

Hard gold would add to the cost but it is designed for this application.

Something to consider.
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #44 on: May 30, 2016, 04:48:22 AM »
Just ENIG.
I can't seem to find a manufacturer that does hard gold and are willing to give me a quote. I'm guessing I can't afford it.

I'm not too worried though..  Even if you wear it down to the nickel it's probably still going to be better then original.
 

Offline garnix

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Re: Yet another resistance decade box
« Reply #45 on: May 30, 2016, 08:37:46 PM »
Do they still stack together despite the added height of 1206?
That was my first  :palm: moment when i got the pcbs ;)
It's not perfect, but good enough (for me):

I can't judge the gap from the pictures - but would 0805 type resistors help? They seem to be 0.1 mm less thick? Ultimately I liked your first "in-package" concept, because of the reduced amount of space it needed.
 

Offline gdewitte

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Re: Yet another resistance decade box
« Reply #46 on: May 31, 2016, 06:25:47 AM »
I would like two.
 

Offline PeterZ

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Re: Yet another resistance decade box
« Reply #47 on: June 01, 2016, 07:20:38 PM »
I can't judge the gap from the pictures - but would 0805 type resistors help? They seem to be 0.1 mm less thick? Ultimately I liked your first "in-package" concept, because of the reduced amount of space it needed.
I don't think using 0805s would help much:


The MBB ENIG boards are on the way:
 

Online Fortran

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Re: Yet another resistance decade box
« Reply #48 on: June 01, 2016, 08:07:20 PM »
Not to mention that 0805 only has half the power rating of 1206.
I wouldn't want to go below 1/4W, but maybe that's just me.

Glad to see the boards are on the way  :-+
ETA 1-2 weeks?
 

Offline linux-works

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Re: Yet another resistance decade box
« Reply #49 on: June 07, 2016, 04:14:34 AM »
I'm interested - 2x sets (12) including resistors. The prices seem incredibly reasonable so 0.1% would be great if it can be managed.

Anyone scoped possible boxes/enclosures?

if I can get a set of these, I can try to do a laser cut style box using acrylic (or maybe wood for those that like that).
 


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