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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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20th Jun 2020, 12:16 pm | #1 |
Hexode
Join Date: Apr 2007
Location: W Yorks, UK.
Posts: 407
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Resistance Decade Box
I only recently realised my old Cropico resistance box only goes up to 10k ohms, and I really need 1Meg or more. Then I saw the prices of new resistance boxes..! Luckily I had a few high quality 20-way ELMA switches, so I made this for myself. I did try to etch the front panel, but that turned out to be a massive failure, so I used printed vinyl.
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20th Jun 2020, 12:49 pm | #2 |
Heptode
Join Date: Aug 2009
Location: Liverpool, Merseyside, UK.
Posts: 705
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Re: Resistance Decade Box
Top job, very neat and tidy!
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20th Jun 2020, 1:12 pm | #3 |
Nonode
Join Date: Mar 2010
Location: Sunderland, Tyne and Wear, UK.
Posts: 2,476
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Re: Resistance Decade Box
Very good I am also impressed with the front operating panel
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20th Jun 2020, 6:00 pm | #4 |
Hexode
Join Date: Mar 2014
Location: Fareham, Hampshire, UK.
Posts: 482
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Re: Resistance Decade Box
That looks very professional to me, I love the enclosure. Well done, Dave.
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21st Jun 2020, 5:57 am | #5 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,669
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Re: Resistance Decade Box
What a cracking job, smaller too than the other one. Big, clunking decade boxes are a pain in the bum when bench space is optimum.
"I am also impressed with the front operating panel" me too, I'm always amazed that folk have mastered PC software enough to be able to produce front panels. Labelling and front panels detail is one thing that is sadly lacking in my builds. Oh for the patience to master software and a decent printer. Andy.
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21st Jun 2020, 9:22 am | #6 |
Heptode
Join Date: Feb 2009
Location: Rotherham, South Yorkshire, UK.
Posts: 559
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Re: Resistance Decade Box
Hello
Outstanding work and it looks the part Kev. |
21st Jun 2020, 10:51 am | #7 |
Pentode
Join Date: Oct 2017
Location: Newton-le-Willows, Merseyside, UK.
Posts: 158
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Re: Resistance Decade Box
very nice, it always annoys me slightly though when I see people who have mastered the computer to be able to make such a nice front panel.I can repair cars, I can wire up complex machinery in all sorts of places, but could I make a computer turn out something like that, could I eck as like. Some people have wonderful skills.
I'm going to make one, but it won't be as fancy as that, now where's my Dymo labeller? lol |
21st Jun 2020, 5:29 pm | #8 |
Heptode
Join Date: Nov 2009
Location: Scarborough, North Yorkshire, UK.
Posts: 510
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Re: Resistance Decade Box
Is that large manufactured a Cropico decade box, we had several of their products where I once worked, they oozed quality. I'm just the same as Phil above on using a computer. Ted
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21st Jun 2020, 7:06 pm | #9 |
Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
Posts: 1,465
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Re: Resistance Decade Box
OK, so I'm going to buck the trend of congratulation, here. I would have thought that the Cropico (Croydon Precision Instrument Company - note "precision") decade box was probably precision resistances (0.5% or tighter) and probably non-inductive at that. I would venture that the switches were high-quality, too. If what you wanted was a resistance substitution-box, then you've made a nice job of it, but as a precision instrument, I have my doubts, unless you can inform us of the quality of the switches and resistors (none of those are cheap!).
Colin. |
21st Jun 2020, 8:20 pm | #10 |
Pentode
Join Date: Oct 2016
Location: Maldon, Essex, UK.
Posts: 184
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Re: Resistance Decade Box
Nice job. What is clever, in my opinion, is using 3 switches to get 6 decades in a compact box. After all, if 1% resistors are used, there is no need for more than 3 switches. I have not seen another decade box with more than one decade on each switch.
David |
22nd Jun 2020, 8:43 am | #11 |
Hexode
Join Date: Apr 2007
Location: W Yorks, UK.
Posts: 407
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Re: Resistance Decade Box
The switches are ELMA type-04, gold plated, high torque. They cost about £20 each but these were removed from some old equipment. The resistors are ordinary 1% metal film. I have no need for better precision than that, since I wouldn't be using resistors that are any better in the final appliance!
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22nd Jun 2020, 8:46 am | #12 |
Hexode
Join Date: Apr 2007
Location: W Yorks, UK.
Posts: 407
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Re: Resistance Decade Box
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24th Jun 2020, 12:46 pm | #13 | |
Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
Posts: 1,465
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Re: Resistance Decade Box
Quote:
Colin. |
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24th Jun 2020, 2:19 pm | #14 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,902
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Re: Resistance Decade Box
The way it's done has three decades available at any one time, and as it's been built with 1% resistors, having more decades available would not just be pointless, it could also be confusing due to non-monotonicity. A nice piece of appropriate design.
David
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25th Jun 2020, 8:33 am | #15 |
Hexode
Join Date: Apr 2007
Location: W Yorks, UK.
Posts: 407
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Re: Resistance Decade Box
You might also notice the high-resistance ranges come first, i.e. to access the 10-ohms range I have to turn the switch through the 10k range first. That stops me from burning out the smaller resistances with excessive current. Luckily I spotted this failure mode before I printed the front panel! (quick redesign)
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25th Jun 2020, 1:26 pm | #16 | |
Nonode
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 2,181
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Re: Resistance Decade Box
Quote:
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25th Jun 2020, 1:36 pm | #17 |
Heptode
Join Date: Apr 2015
Location: Manchester, UK.
Posts: 713
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Re: Resistance Decade Box
Outstanding work well done .
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25th Jun 2020, 3:51 pm | #18 |
Nonode
Join Date: Jan 2009
Location: Bristol, UK.
Posts: 2,062
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Re: Resistance Decade Box
I might have printed the 'alternate range' upside-down so you turn the box round when you need to use the other range. Very clever design in any case!
dc |
25th Jun 2020, 4:38 pm | #19 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,222
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Re: Resistance Decade Box
But it's not really an 'alternative range', the design is cleverer than that. You can have any 3 consecutive decades, for example the 100k (switch 2), 10k (switch 1) and 1k (switch 3), in use. So I think it makes sense to have them all reading the same way up.
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26th Jun 2020, 4:32 pm | #20 | |
Octode
Join Date: Jan 2012
Location: Wimbledon, London, UK.
Posts: 1,465
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Re: Resistance Decade Box
Quote:
I know what uses I put decade-boxes to and what I put substitution-boxes to and I have both. The OP might have some purpose for this device that he has made, but am I really the only person to think that using three high-quality, expensive switches with resistors that cost a penny or less is a bit uneconomic? OK, yes, I probably am the only one. Colin. |
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