DIY Decade Resistance Box

[chromesphere]

Hey, i dont know if anyones interested in this but thought i would post it.  If you dont know what a decade resistance box is...well watch the video.

This was a cheap project, only cost about 10 bucks and i thought it had some diy guitar pedal relavance.  The link to build the project is in the description of the video page.  Also, NoPlaceForTheDead suggested building one with capaciators, i'd have to put some thought into how to lay it out (capacitors in parrellel probably) and what values to use, but it seemed to me like a good idea.

Anyway heres the video, hope you like it:

All the best
Paul

[RandomGlitch]

Cool little box! 

I had an idea for a continuously variable resistance box that would allow you to get exact values.  Just get 1k, 10k, 100k and 1M dual linear pots, wire them in series.  One of the series arrays goes to your DMM, the other to your circuit.  Then you can dial in any exact value (well within the matching of each pot track's resistance anyway)

A bit less soldering would be involved I think. You just tie up your DMM though.

[chromesphere]

Thats a good idea random glitch!  Both have their pro and cons, the pots would probably last longer though then these switches.  You could build this box with none of the lower values, i think i have used resistors in the range of 0-99 ohms about twice in the last 6 years of building pedals, i just added them (and the 10m range) for a matter of completeness.
Paul

[deadastronaut]

cool, i caught your vid on that...so thats what you used those switches for...


i built 2 boxes with rotary switches, 1 for resistors, 100 ohm to 4.7M

and the cap version ,  4.7pf to 470n....very handy for quickly testing out filter/mods/and breadboarding etc..

just saves getting lots of bits  out....i couldn't live without them now. invaluable..

[therecordingart]

Great thread. I want to do one for caps, one for resistors, and then some circuit building blocks like an opamp gain stage, a tone stack, a clipping diode box, etc. Kinda like Snap Circuits, but for DIY'ing audio stuff.

[Mark Hammer]

While not a decade resistance box. a DRB could certainly replicate the function of a little thing I made for myself.

LEDs vary in efficiency, with some being very very bright for the same voltage/current.  While they may be easily distinguished at the time of order, or for as long as they remain in the little bag you got them in, once they go into the parts bin, they all look pretty much the same, especially if they're clear.

Because some may not require very much current at all to produce near-blinding illumination in the role of status LED, I made a little gadget with a SP12T rotary switch, a battery connector, and a 2-leg machined socket, to help identify a suitable current limiting resistor for LEDs.  The resistors range between 1k and 18k at each extreme, and the rotary switch simply moves along a series of standard values, feeding 9v to the LED through the resistor.  The known values makes it dead easy to identify what series resistor value would likely yield a nice balance between visibility and current draw for a given LED.

One could easily use a DRB in exactly the same fashion.

[therecordingart]

While not a decade resistance box. a DRB could certainly replicate the function of a little thing I made for myself.

LEDs vary in efficiency, with some being very very bright for the same voltage/current.  While they may be easily distinguished at the time of order, or for as long as they remain in the little bag you got them in, once they go into the parts bin, they all look pretty much the same, especially if they're clear.

Because some may not require very much current at all to produce near-blinding illumination in the role of status LED, I made a little gadget with a SP12T rotary switch, a battery connector, and a 2-leg machined socket, to help identify a suitable current limiting resistor for LEDs.  The resistors range between 1k and 18k at each extreme, and the rotary switch simply moves along a series of standard values, feeding 9v to the LED through the resistor.  The known values makes it dead easy to identify what series resistor value would likely yield a nice balance between visibility and current draw for a given LED.

One could easily use a DRB in exactly the same fashion.

Reading this just brought out an idea...

Embed an ammeter in the decade box so you always know the current through, voltage across, and power dissipated by the resistance value that you are selecting.  Or would it be a better idea to use a voltmeter across the resistance? I'm thinking the voltmeter would need to have a really high input impedance for the higher values of resistance that you are measuring across.

[chromesphere]

Yeah i gotta build me a cap version of the decade box now.

I bought one of those LED resistor testers on ebay Mark.  Chinese thing.  I noticed that a couple of pedals i built had much greater brightness then i had witnessed on the LED resistor tester.  Opened it up.  The resistor values inside didnt match the silkscreening on the front of the box!!!  Hah...ebay, gotta love it. 

Not sure about the volt meter idea therecordingart.  You'd be able to work out the current (and then power) from the resistance and voltage though, so probably no need to embed an ammeter? (like you said)

Oh, i see this guy on youtube using a thing called a 'watts up' meter.  It tells you the power on a little lcd display.  However...its 50 bucks

http://www.hobbyking.com/hobbyking/store/__6380__Watt_Meter_Power_Analyzer_Watts_up_Ver_2_.html

Paul

[therecordingart]

Not sure about the volt meter idea therecordingart.  You'd be able to work out the current (and then power) from the resistance and voltage though, so probably no need to embed an ammeter? (like you said)

Right...one or the other...but it's a trade off. Accuracy issues when measuring the voltage drop across high values of resistance though, right? Once you get up into megaohms isn't the meter going to load down the circuit? What about the accuracy of an ammeter when dealing with low values of resistance...won't the series resistance of the meter play a large role?

[senko]

Nice project!  I like to use testing tools like this when I'm messing around with newer circuits.  I use oscillator circuits for quick and dirty audio signals or for modulating.  Another good one to have is a LM317 voltage regulator set up so that you can vary the voltage to power your circuit.  Cool stuff.

[chromesphere]

Nice project!  I like to use testing tools like this when I'm messing around with newer circuits.  I use oscillator circuits for quick and dirty audio signals or for modulating.  Another good one to have is a LM317 voltage regulator set up so that you can vary the voltage to power your circuit.  Cool stuff.

I've been thinking of boxing a madbean road rage with the voltage sage control, 18v out, 12v out each, purely in its own enclosure for testing.  Might be handy to have around as well!
Paul

[J0K3RX]

I saw this Decade box on SparkFun and decided to make a single sided etch version of it... I estimate it would cost around $20.00 to build give or take a few bucks. Maybe not quite as cheap as Paul's but not too bad. I like the Sparkfun board but not willing to pay almost $50.00 for a decade box...

Main page with eagle files
https://www.sparkfun.com/products/13006

Build guide
https://learn.sparkfun.com/tutorials/decade-resistance-box-hookup-guide?_ga=1.257089806.48619200.1432398777

 





Transfer
https://dl.dropboxusercontent.com/u/11178619/Decade/Decade%20Boxx.pdf


Here is the Capacitance box built like the original post that Paul shared
http://kripton2035.free.fr/Resources/www.electricstuff.co.uk%20-%20Cheap%20capacitance%20box.pdf