EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Specmaster on November 10, 2017, 12:47:00 am
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I have long been looking at acquiring a decade resistance box but problem is being on a limited budget (pension) and they are expensive to buy new and still relatively expensive on fleabay as well so I had been thinking about making my own but today I was again looking on fleabay to see if anything was reasonably priced and was pleasantly surprised to come across a kit that comes without knobs or an enclosure so you decide on your own knobs and choice of enclosure.
Resistors are only 1% tolerance but I suspect is adequate for a lot of people.
https://www.ebay.co.uk/itm/Decade-Resistance-Box/142517028089?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649. (https://www.ebay.co.uk/itm/Decade-Resistance-Box/142517028089?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649.) I had to go to the manufacturer's website to get more information and confirm the accuracy of the resistors https://learn.sparkfun.com/tutorials/decade-resistance-box-hookup-guide/all. (https://learn.sparkfun.com/tutorials/decade-resistance-box-hookup-guide/all.)
There are downloadable/printable instructions as well, any thoughts?
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If you do mind a large size have a look on ebay for General Radio (also Genrad) decades.
Mine is from aprox. 1938 and would probably outlast me. :-+
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If you do mind a large size have a look on ebay for General Radio (also Genrad) decades.
Mine is from aprox. 1938 and would probably outlast me. :-+
Seen those already and they are so expensive, I can't really justify the cost of those, but thanks for the input.
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Depending on what you need or want it for. A little more power available in the resistor sizes is in order too.
Go vintage and tidy up the contacts :-+ https://www.ebay.com.au/itm/Resistance-Box-Tinsley-Vintage-Lab-Apparatus-Type-4231-LF2-1-1000-Ohm-Steampunk/272909153488?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649 (https://www.ebay.com.au/itm/Resistance-Box-Tinsley-Vintage-Lab-Apparatus-Type-4231-LF2-1-1000-Ohm-Steampunk/272909153488?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649)
I have most of the bits including Vishay resistors to make one 15-17V on all values. - DON'T ask the budget :palm:
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Yeah. Never understood why these things are so expensive. You would think a kit would be a goer. Some rotary knobs and resistors.
Dont need precision myself, just want to try different values quickly.
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It may be worth looking at decade resistance boxes from EDFM. They won't break the bank, are well made, reasonably accurate, and a much smaller form factor than those giant vintage boxes. :-+
https://www.edfmusa.com/product-category/electronic-design-diagnostic-equipment/ (https://www.edfmusa.com/product-category/electronic-design-diagnostic-equipment/)
I too thought about building one from a kit, but after pricing the resistors, project box, rotary knobs, and time (not high on the fun project scale to make it worth the time) etc. The EDFM box hit the sweet spot for me.
...
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Look for Jay-Jay, Tinsley, and Muirhead. They tend to be in a wood or metal case and sell for under £50. Often tatty looking as they have been thrown around a college lab, but usually in fully working order and sell for under £50. Considering the price of the circuit you have found and buying the box and other bits, then it might be cheaper to buy one of these older units.
Examples
https://www.ebay.co.uk/itm/EDUCATIONAL-MEASUREMENTS-LIMITED-DECADE-RESISTANCE-BOX-WARRANTY/192330937449?hash=item2cc7d13469:g:IuAAAOSwDC1Z3jym (https://www.ebay.co.uk/itm/EDUCATIONAL-MEASUREMENTS-LIMITED-DECADE-RESISTANCE-BOX-WARRANTY/192330937449?hash=item2cc7d13469:g:IuAAAOSwDC1Z3jym)
https://www.ebay.co.uk/itm/VINTAGE-H-TINSLEY-CO-LTD-TYPE-4171-5-HF2-RESISTANCE-BOX/202107490065?hash=item2f0e8b8f11:g:5eIAAOSwytJaA3FF (https://www.ebay.co.uk/itm/VINTAGE-H-TINSLEY-CO-LTD-TYPE-4171-5-HF2-RESISTANCE-BOX/202107490065?hash=item2f0e8b8f11:g:5eIAAOSwytJaA3FF)
https://www.ebay.co.uk/itm/VINTAGE-MUIRHEAD-DECADE-RESISTANCE-TYPE-A-25-K-BOX/202107519203?hash=item2f0e8c00e3:g:ymwAAOSwW6BaA3c2 (https://www.ebay.co.uk/itm/VINTAGE-MUIRHEAD-DECADE-RESISTANCE-TYPE-A-25-K-BOX/202107519203?hash=item2f0e8c00e3:g:ymwAAOSwW6BaA3c2)
Faulty Time Electronics decade boxes appear every so often were some student has tried to put 10 watts through a 1 watt resistor.
Couple of years ago on eBay, I bought Time Electronics decade box which has a range from 0.1ohm to 999K (From memory) for £10 on eBay with a small comment saying 'Faulty', looking inside, the unit was manufactured in 1982 had a few burnt resistors. Cost me around £20 to repair the unit using resistors from Mouser Electronics in the USA as RS Components or Rapid Electronics didn't have the parts in stock.
They are not very hard to repair if faulty, in the case of the decade box I bought, it was the 1ohm and 10k ranges which had been cooked, but the switches and circuit boards were fine, so easy to repair.
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I have long been looking at acquiring a decade resistance box but problem is being on a limited budget (pension) and they are expensive to buy new and still relatively expensive on fleabay as well so I had been thinking about making my own but today I was again looking on fleabay to see if anything was reasonably priced and was pleasantly surprised to come across a kit that comes without knobs or an enclosure so you decide on your own knobs and choice of enclosure.
If you're really cheap, you could also go something like:
https://www.ebay.com/itm/1R-9999999R-Seven-Decade-Programmable-Resistor-Board-Step-1R-1-1-2-Watt/201950865157?hash=item2f0535a705:g:gPoAAOSwVJhZOpoE (https://www.ebay.com/itm/1R-9999999R-Seven-Decade-Programmable-Resistor-Board-Step-1R-1-1-2-Watt/201950865157?hash=item2f0535a705:g:gPoAAOSwVJhZOpoE)
https://www.ebay.com/itm/1R-9999999R-Seven-Decade-Programmable-Resistor-Board-Step-1R-1-1-4W/371144195602?hash=item5669eafe12:g:slcAAOSw4CFY7zbl (https://www.ebay.com/itm/1R-9999999R-Seven-Decade-Programmable-Resistor-Board-Step-1R-1-1-4W/371144195602?hash=item5669eafe12:g:slcAAOSw4CFY7zbl)
or capacitors:
https://www.ebay.com/itm/1nF-to-9999nF-Step-1nF-Four-Decade-Programmable-Capacitor-Board/371211051386?epid=1883272417&hash=item566de7217a:g:N9gAAMXQlbVSDeOC (https://www.ebay.com/itm/1nF-to-9999nF-Step-1nF-Four-Decade-Programmable-Capacitor-Board/371211051386?epid=1883272417&hash=item566de7217a:g:N9gAAMXQlbVSDeOC)
https://www.ebay.com/itm/1uF-to-9999uF-Step-1uF-Four-Decade-Programmable-Capacitor-Board-35Vdc/191403109726?_trkparms=ao%3D1%26asc%3D41375%26meid%3Daf4ceff2832f41f09a204b3918a4b5d3%26pid%3D100705%26rk%3D1%26rkt%3D1%26&_trksid=p2045573.c100705.m4780 (https://www.ebay.com/itm/1uF-to-9999uF-Step-1uF-Four-Decade-Programmable-Capacitor-Board-35Vdc/191403109726?_trkparms=ao%3D1%26asc%3D41375%26meid%3Daf4ceff2832f41f09a204b3918a4b5d3%26pid%3D100705%26rk%3D1%26rkt%3D1%26&_trksid=p2045573.c100705.m4780)
I've got a couple of both styles, in addition to a couple of 'real' decade boxes. They're fine for casual use.
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A worthwhile alternative is Fortran's 'Yet another resistance decade box' thread. I believe he still has plenty of PCBs and 1% resistors.
https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/ (https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/n)
John
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Yup. :)
I've got at least 100 left.
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For those in Australia, Altronics sells a neat resistor/capacitor decade box kit for A$129 (see here: http://www.altronics.com.au/p/k7520-resistance-capacitance-decade-box-kit/ (http://www.altronics.com.au/p/k7520-resistance-capacitance-decade-box-kit/))
I bought one for myself the other day and it's a nice little kit. A few construction quirks but it works! :)
(Mine was from Tronixlabs, who currently have the kit on special for A$89: https://tronixlabs.com.au/kits/test-equipment/resistor-capacitor-decade-box-kit-australia/ (https://tronixlabs.com.au/kits/test-equipment/resistor-capacitor-decade-box-kit-australia/))
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Just watch out. The big old ones are electrically noisy and have terrible stay inductance.
I’m inclined to solve the problem with a couple of pots or some fixed value resistors whenever I have to.
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If you're in the mood for a little home construction, then you can make your own really cheaply (and very compact too). Thumbwheel switches are really cheap on ebay from China these days, just add your own chains of through hole resistors (quality and tolerance of your own choice) and mount them in a plastic box. Just make sure you buy Decimal ones (Not BCD... those would work for capacitance boxes by the way).
https://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=thumbwheel+switch+decimal&rt=nc&LH_PrefLoc=2 (https://www.ebay.co.uk/sch/i.html?_from=R40&_sacat=0&_nkw=thumbwheel+switch+decimal&rt=nc&LH_PrefLoc=2)
It's the approach I've taken. Ok, I bought the guts of the big one but I did make the little one from scratch...
https://www.eevblog.com/forum/chat/what-did-you-buy-today-post-your-latest-purchase!/msg1250829/#msg1250829 (https://www.eevblog.com/forum/chat/what-did-you-buy-today-post-your-latest-purchase!/msg1250829/#msg1250829)
P.S. Some have questioned what the potential contact quality of the Chinese switches might be but I don't think anyone has actually demonstrated any problem.
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Using the KM2 switches with Fortran's 1% resistors plus meter leads I have a reading of ~1 ohm with all switches set to Zero. However if one hasn't used the switches for a while it often goes up to ~2 ohms until you operate each switch then it is back to ~1 ohm. Not exactly perfect but then for most uses an accuracy of ~1 ohm is OK except perhaps for the single ohms decade. For that decade I have cheated by shorting out the first resistor in position 1 which will help a bit for that decade to compensate for the switches, leads etc. Yes the next decade could have a 10% error at the first position but this will improve as one moves up the decades approaching the 1% value. If one pursues the 0.1% resistor option the switch contact resistance is more important so perhaps other switches should be looked at for that version.
Still it is useful to have a resistor decade box, if only for convenience, as one can read off the value you have just set so easily. That said a potentiometer has always been a good old standby as you can 'tune' in the value very quickly and measure it at your leisure.
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Ok, then, I quite like the idea of the system that Fortran has been busy beavering away at, its a very neat solution but I have not read all of the posts in that thread, it'll take too much time, so I have some quick questions about it.
Precisely what is on offer, is it just the PCB's and the resistors or has anyone developed a suitable enclosure that is a part of, or could be added on as an extra? If so do any photos exist of this at all?
Has anyone thought about just using the switches as they come and wiring from them to a ring circuit of normal resistors so that higher wattages could be used?
My track record with SMD parts is not very good, my eyesight is not what it used to be, even with a magnifier glass and spectacles :popcorn:
So I'm sort of torn between having a go with the SMD approach and the thumbwheel switches and living with the 1/4 watt limit or using the standard thumbwheel switches and going with 1/2 watt resistors, maybe even with .1% for the higher values and possibly going up to 7 decades, 10M or maybe even higher.
Its main use would be as testers for multimeters with the occasional use as a substitution box for transistor radio work and general repairs to other test gear etc.
At this stage its a feasibility study and cost evaluation exercise. :-+
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Thinking thumbwheel switches again, I just wanted to make sure you were aware of this thread...
https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/ (https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/)
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Thinking thumbwheel switches again, I just wanted to make sure you were aware of this thread...
https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/ (https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/)
Yes I was aware and that is what I was referencing in my post, it uses 1/4 watt SMD resistors and I was looking to go to 1/2 watt at least and maybe extend the range to 10M :-+
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Seen those already and they are so expensive, I can't really justify the cost of those, but thanks for the input.
ESI DB877 for the win!
A few years agi I found one an Ebay for $75. Seller came back and said he had another one and if I wanted it he would pay shipping if I bought both. Well, DUH!
I also found a Heathkit resistance decade box for $20. It is surprisingly good. A little patience and shopping can yield some bargains. But, I have noticed that lately they seem to be fewer and far between.
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Precisely what is on offer, is it just the PCB's and the resistors or has anyone developed a suitable enclosure that is a part of, or could be added on as an extra? If so do any photos exist of this at all?
Just the PCB's and resistors. Switches and enclosure not included.
Has anyone thought about just using the switches as they come and wiring from them to a ring circuit of normal resistors so that higher wattages could be used?
Yup. Tried it. They are pretty much unusable. That's why we made these in the first place.
My track record with SMD parts is not very good, my eyesight is not what it used to be, even with a magnifier glass and spectacles :popcorn:
I can solder them for you if you like. Free of charge. :)
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I used a small plastic box 82x52x35 ABS Plastic Screwless Electric / Electronic Enclosure Project Box. I have a completed decade box picture but cannot persuade this reply to accept the attachment. It is only a 340K jpg so should work.
see this link http://www.ebay.co.uk/itm/82x52x35-ABS-Plastic-Screwless-Electric-Electronic-Enclosure-Project-Box/202051619303?hash=item2f0b3709e7:g:Zl0AAMXQRPRTJA7q (http://www.ebay.co.uk/itm/82x52x35-ABS-Plastic-Screwless-Electric-Electronic-Enclosure-Project-Box/202051619303?hash=item2f0b3709e7:g:Zl0AAMXQRPRTJA7q)
Edit:- I now realise it doesn't appear until you have actually posted.
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I got one from eBay for $50:
https://www.youtube.com/watch?v=n0kixB-fFM8 (https://www.youtube.com/watch?v=n0kixB-fFM8)
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I got one from eBay for $50:
Nice, well built decade box. Similar quality to the former lab decade boxes I recommended earlier and probably still holds its performance far better than the modern Chinese equivalents. The only maintenance which is probably needed is cleaning of the contacts on the switches.
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I came across this on Youtube and there are others that use the the thumbwheel switches unmodified as well, some have used SMD's other through hole resistors which is what I prefer as I'd like to go to 0.5 watt as a minimum and I'd like to make a 7 or 8 decade box to test meters etc that go up to 100M.
If I understand it correctly, the main reason for special PCB's that is being in the https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/ (https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/) was to overcome any problem, wether it is a real or perceived problem, of the circuit momentarly going open circuit between each switching action.
I doubt that will be an issue for me as I'm not into things like Arduinos etc, so any momentary break is not going to have dire consequences for me.
https://www.youtube.com/watch?v=XpyB0i2PNBc (https://www.youtube.com/watch?v=XpyB0i2PNBc)
https://www.youtube.com/watch?v=IvJqAh4nwa0 (https://www.youtube.com/watch?v=IvJqAh4nwa0)
https://www.youtube.com/watch?v=W5kov-MQceY (https://www.youtube.com/watch?v=W5kov-MQceY)
https://www.youtube.com/watch?v=6R4XLTJ-p5w (https://www.youtube.com/watch?v=6R4XLTJ-p5w)
https://www.youtube.com/watch?v=IZIMEuWF3Uo (https://www.youtube.com/watch?v=IZIMEuWF3Uo)
And a professional box that Dave did a blog on https://www.youtube.com/watch?v=37gYHdY0DAM&t=3s (https://www.youtube.com/watch?v=37gYHdY0DAM&t=3s) which also uses through hole resistors.
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If I understand it correctly, the main reason for special PCB's that is being in the url (https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/) was to overcome any problem, wether it is a real or perceived problem, of the circuit momentarly going open circuit between each switching action.
Not quite. The make-before-break was just an added bonus.
Main reason was reliability, which is seriously lacking in the cheap switches.
Oxide and sometimes even broken traces in the original PCB's make them a poor choice for decade resistors.
With the new PCB, they work pretty good. It's no standard reference, but good enough for most "hook-up-a-resistor" jobs.
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But that was with the new miniature 18mm size of switch (KM2) and the drilling out of part of the traces to accommodate the fixings to retain the pcb to switch body and thus the contacts as per photo? This switch is also available in 16mm, 18mm, 22mm and 24mm size as well but I have come across some KSA-2 types that are much bigger and maybe better built, they certainly look more robust and more suitable for panel mounting.
https://www.ebay.co.uk/itm/10x-KSA-2-Decimal-10-Position-Single-Unit-Thumbwheel-Switches/121745184682?epid=1418676722&hash=item1c589417aa:g:dZsAAOSwCbtZ1RtI (https://www.ebay.co.uk/itm/10x-KSA-2-Decimal-10-Position-Single-Unit-Thumbwheel-Switches/121745184682?epid=1418676722&hash=item1c589417aa:g:dZsAAOSwCbtZ1RtI)
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Well yeah. Traces are probably beefier on those.
I'm guessing contact resistance isn't any better though. :-//
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I have ordered some of the thumbwheel switches for evaluation purposes. I have not completely discounted the system that Fortran offers, and thank you, Fortran for offering to solder them for me if I elect to go that way. I still prefer to use through the hole resistors if possible, particularly for the lower decades as these would surely be the ones most likely to suffer from accidental overload.
The estimated delivery of these is from Nov 19th to Dec 29th which I find so annoying when dealing with Hong Kong and China but their prices are just so dammed attractive. :popcorn:
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I made my own similar to the one in this thread https://www.popsci.com/sites/popsci.com/files/import/PopSciArticles/anchors/magic-resistor-box-digitalunderpants.pdf (https://www.popsci.com/sites/popsci.com/files/import/PopSciArticles/anchors/magic-resistor-box-digitalunderpants.pdf) but I used SMT 0603 resistors like the method shown in this video https://www.youtube.com/watch?v=XpyB0i2PNBc (https://www.youtube.com/watch?v=XpyB0i2PNBc)
The resistance at zero is a couple of ohms but it works fine for my purposes; I put it in a circuit and play with the values and then read the value with a good meter.
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After ordering a decimal KSA-2 switch but receiving a KM1 BCD one had to rely on my second back up as I had a feeling that the first Ebay seller was selling BCD switches despite stating it was a decimal one so I had a backup one ordered elsewhere which did turnout to be a decimal one. Got a full refund on the KM1 so thats OK.
I decided that I wanted a little more power handling than the SMD versions that others have built so I ordered up some half watt resistors in 1% for the lower decades and 0.1% for the top 2 decades to minimise the errors and it worked out quite well. I went with the KSA-2 type of switch as it was a good bit larger in size than the KM1 and suits a mans hands better when punching in a value, reducing the chances of incrementing 2 decades at the same time.
Now begins the task of cutting a hole in a project box to fit the switch assembly in and the 2 banana jacks and the job is done.
Photos below the finished assembly, awaiting the enclosure and along side I show the KM1 switch which is a lot smaller and had it been decimal would need to be SMD resistors as I doubt TH ones would fit the switch.
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That looks pretty good. Nice work :-+
Got to love the Dale CMF/RN55's.
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That looks pretty good. Nice work :-+
Got to love the Dale CMF/RN55's.
Thanks, what are the Dale CMF/RN55's?
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The brown resistors. Very high quality ones.
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Ohh, there 1%ers , ordered 12 from Mouser but only delivered 10, good job I only needed 9 eh? Overall added resistance is only 1.7 \$\Omega\$ so not too bad either, ideal for general purpose use up to 0.5w. :-+
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Here is the finished product with the slip up I made, negative binding post is slightly lower (2mm) than it was supposed to be :palm: but overall I'm pleased with it. :-+
(https://i.imgur.com/qUkBaKY.jpg)
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Looking good! :-+
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The binding posts had flats on 2 sides, I just drilled a 7mm hole, spun the locking nut on and tightened with a box spanner and these are not rotating in the slightest either, so all's :-+ good.
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Looking good and compact. :-+
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I've just acquired this magnificent decade resistance box off ebay for £25 - it is lovely though it needs repairing (part of the higher ranges is open circuit. It is also enormous. I really got it as a work of art rather than for serious use but hope to restore it.
Here are some quick pictures.
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some more pictures....
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Very nice but so big.
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Very nice but so big.
I was a bit taken aback when it arrived - I wasn't expecting it to be quite so big. I guess it was designed to be used with a bridge for measurements rather than a substitution box as it is very large but also 0.05% which is pretty good (at least it was - I think it is rather out now).
I'll try and fix it and will have it sitting at the back of my bench or perhaps on a shelf so I can feel like a Victorian gentleman scientist.
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Love those switches, they are a work of art alright. :-+
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I am waiting on a Soviet import via the Ukraine. Rated at 0.02% so it should be interesting ???
The Price tag was a touch more than 25 Quid :palm:
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Got bit surprising "precision" with cheap eBay switches and 1% resistors...
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Yeah, you did well there, whats the last decade on the box then? Box is showing an extra 9 to the meter?
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Yeah, you did well there, whats the last decade on the box then? Box is showing an extra 9 to the meter?
First decade is 1 ohm and last one is 10 Mohm. Switches seem to have about 0.2 ohm resistance each, so didn't make
sense add 0.1 ohm decade.
My meter just doesn't have enough resolution, so it's showing 0.99999 Mohm when box is dialed to 999999 ohm.
Just pure luck that sum of errors in the 54 1% resistors (in circuit when switches are set to "00999999") happens be close to zero. In general accuracy of the box is what is to be expected with 1% resistors...