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Author Topic: Resistance Substitution Box: A Review  (Read 999 times)

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Offline keerout

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Re: Resistance Substitution Box: A Review
« Reply #15 on: January 22, 2020, 05:46:37 PM »
 TANSTAAFL !  :no:

Gerard  :wave:

Offline Railwaygun

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Re: Resistance Substitution Box: A Review
« Reply #16 on: January 22, 2020, 08:12:42 PM »
There ain't no such thing as a free lunch

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Online ntpntpntp

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Re: Resistance Substitution Box: A Review
« Reply #17 on: January 23, 2020, 08:55:44 PM »
** A WARNING ***   

Just been playing with my resistance box and some 12V strip LEDS, working out what additional resistance to add to each strip to tone them down to the effect I'm after for my loco sheds.

The design of box I have shorts out to 0 when moving between 4 and 5 on the dial!  I witnessed it on the x1000, x100 and x10 dials, and pretty sure the x1 does it too although changing by 5 ohms is difficult to see the difference - I didn't bother to get my multimeter out.

This confirmed what I thought might be the case as I managed to blow some other LED mast lights a few weeks ago.

What a nuisance, still at least I know to avoid that in future.
« Last Edit: January 25, 2020, 06:11:13 PM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline Malc

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Re: Resistance Substitution Box: A Review
« Reply #18 on: January 25, 2020, 05:09:05 PM »
Yes, I too found this out the hard way. Fortunately I only blew one street light.
The years have been good to me, it was the weekends that did the damage.

Offline Bealman

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Re: Resistance Substitution Box: A Review
« Reply #19 on: May 22, 2020, 04:00:18 AM »
It's all sort of academic to me now.... if anyone has been looking at my layout thread, they'll know I've been rummaging around under the layout lately.

I turned up this:



A resistance wheel! Forgot I had it. Discrete resistors inside, too. Here it is on the one Meg setting, reading 0.974 Meg.
Vision over visibility. Bono, U2.

Offline Malc

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Re: Resistance Substitution Box: A Review
« Reply #20 on: May 22, 2020, 09:06:22 AM »
A proper bit of kit.
The years have been good to me, it was the weekends that did the damage.

Online Lawrence

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Re: Resistance Substitution Box: A Review
« Reply #21 on: May 22, 2020, 09:13:42 AM »
You only get what you pay for as you say George, there is always this option https://uk.rs-online.com/web/p/decade-boxes/7921976/
I was trying to get one for work but we had to settle on a slightly lesser model around the £250 mark.
I would hate to try to teach you to suck eggs but wanted to mention one thing, when you were measuring at 0 Ohm did you connect your leads together and zero your meter first? Budget mulitmeters (and associated leads etc) are much like budget decade resistance boxes  ;)

Online tutenkhamunsleeping

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Re: Resistance Substitution Box: A Review
« Reply #22 on: May 22, 2020, 09:14:13 AM »
No ohm should be without one :-[

Offline Bealman

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Re: Resistance Substitution Box: A Review
« Reply #23 on: May 22, 2020, 09:17:41 AM »
About A$45 in the local electronics store. After much head-scratching as to where it came from, I worked out that I'd ordered it way back for the science department at school. After realising there was no way it would handle the currents involved in high school experiments, it languished for years in my prep room.

Somehow it ended up in my box of stuff I salvaged from the place when I retired  :whistle:
Vision over visibility. Bono, U2.

Offline Malc

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Re: Resistance Substitution Box: A Review
« Reply #24 on: May 22, 2020, 09:28:56 AM »
Stolen goods then?
The years have been good to me, it was the weekends that did the damage.

Offline Bealman

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Re: Resistance Substitution Box: A Review
« Reply #25 on: May 22, 2020, 10:30:09 AM »
Missing in inaction.  ;)
Vision over visibility. Bono, U2.

Offline andy911john

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Re: Resistance Substitution Box: A Review
« Reply #26 on: Yesterday at 05:35:42 PM »
I found this on-line.  Looks like a reasonable compromise.   Switches rather than questionable rotary make before break. 

https://weisd.com/products/2300-elenco-rs-500-resistance-decade-box?gclid=EAIaIQobChMIq7rM5_XM6QIVEfDACh07YAlLEAQYFCABEgLeBfD_BwE

Online ntpntpntp

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Re: Resistance Substitution Box: A Review
« Reply #27 on: Yesterday at 05:46:19 PM »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline themadhippy

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Re: Resistance Substitution Box: A Review
« Reply #28 on: Yesterday at 06:39:51 PM »
only problem is you have to fink a bit  to get some values,making your own is very easy,especially if you use these type of switches


but make sure to get the decimal version,the bcd version aint no good as it outputs  binary

Offline The Q

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Re: Resistance Substitution Box: A Review
« Reply #29 on: Today at 08:02:02 AM »
You only get what you pay for as you say George, there is always this option https://uk.rs-online.com/web/p/decade-boxes/7921976/

Not too bad I suppose , if you check the values before use,  we have 3 of these https://eu.flukecal.com/products/electrical-calibration/bench-multimeters/8558a-8-5-digit-multimeter, and three of its predecessors available for me to use at work.

If you wanted us to calibrate resistance the we measure over most values  to 0.1 parts in a million, though our uncertainty is about 0.3ppm at 10k Ohm,  and about 18ppm at 1G Ohm.   :D . Though if you contact the National Physical Laboratory at Teddington,  they are even more accurate ( at vast expense) .
We actually do calibrate some cropico equipment to a slightly lower standard in the outer lab.

PS I'm not saying who I work for because I like to take the P**s out of the management occasionally and I've been recalled from furlough Next Week.

 

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