capacitor substitution box design/values?..

deadastronaut · September 10, 2010, 02:57:09 PM

hi guys. i bought 2 rotary switches today (1 pole 12 way switches) and want to build a 'capacitor substitution box' so i can use it to mess with circuits etc..instead of swapping out/in caps all the time!..

has anyone got a design? ie what common values should i use? will be only using it for 9v stuff by the way!.(breadboarding)

i want to do an electrolytic version. first...

then a film version...

and eventually a resistor/pot version...later...

i figured this would be a very useful tool for a lot of us to have too.....

so what 12 electrolytics would you recommend? 0.1uf -100uf maybe?...but what in between?. cheers rob.

jkokura · September 10, 2010, 03:33:25 PM

I'm not sure that using electrolytics would be a good place to start. From my experience, they're not the kinds of caps you'd want to switch in a circuit. They often get used in power areas, but Film value and Ceramic value caps are the ones that are in the audio path the most.

I would start with film values: 0.001, 0.0022, 0.0033, 0.0047, 0.01, 0.022, 0.033, 0.047, 0.1, 0.22, 0.47, 1 (All uF values).

Then I would do a second with pF values: 5, 10, 22, 33, 47, 100, 150, 220, 330, 470, 680, 820 (All pF values).

How's that sound?

deadastronaut · September 10, 2010, 03:39:16 PM

cool. thanks jacob...

so its.

1nf/2.2nf/3.3nf/4.7nf/10nf/22nf/33nf/47nf/100nf/220nf/470nf/1000nf

pf 5, 10, 22, 33, 47, 100, 150, 220, 330, 470, 680, 820

cheers.

robmdall · February 22, 2011, 09:50:49 AM

Rob, I am interested in building a sub box also. Did you ever build? Any build notes you can share?

(I apologize if this info is already available, I searched)

Bob

deadastronaut · February 22, 2011, 11:23:43 AM

hi bob, yep i sure did...they are invaluable to me now...

what do you need to know?..

i made a cap box and a resistor box...

my resistor box goes from 100/220/470/1k/2.2k/4.7k/5.6k/8.2k/10k/22k/33k/47k/ on 1 rotary

2nd roatary is 56k/68k/82k/100k/220k/330k/470k/560k/680k/820k/1M/4.7M

cap box is : pf on rotary 1 : 4.7/10/22/33/47/100/150/220/330/470/680/820.
nf on rotary 2: 1/2.2/4.7/6.8/10/22/33/47/100/220/470/...1spare is straight through...

hope this helps. rob.

mattthegamer463 · February 22, 2011, 04:54:02 PM

I designed and built this unit here:

http://www.instructables.com/id/Build-a-ResistorCapacitor-Selection-Box/

Assuming you aren't putting a lot of power through the resistors, pots are a great way to get resolution that non-decade rotary switches can't. For the caps, I used 1P12T rotary switches which allow for many parallel and series combinations, and thus tons of values. I have supplied a document with the calculated values, however there is likely a +-10% error rate typical of fixed-value capacitors, and some amount of compounded errors.

deadastronaut · February 22, 2011, 04:59:44 PM

@matt, yeah i remember that...very nice...

Skruffyhound · February 22, 2011, 05:30:08 PM

Quotehowever there is likely a +-10% error rate typical of fixed-value capacitors

Presumably you could just measure all the values to be sure. I have a cap measure on one of my DMM's and I built another one as a kit (8 bucks), I cross reference the two as an additional check.
I don't check all the power caps unless they are salvaged, but specific stuff in the audio path is good to check and new types of caps I always have a look at.

mattthegamer463 · February 22, 2011, 05:55:04 PM

Quote from: Skruffyhound on February 22, 2011, 05:30:08 PM
Quotehowever there is likely a +-10% error rate typical of fixed-value capacitors
Presumably you could just measure all the values to be sure. I have a cap measure on one of my DMM's and I built another one as a kit (8 bucks), I cross reference the two as an additional check.
I don't check all the power caps unless they are salvaged, but specific stuff in the audio path is good to check and new types of caps I always have a look at.

Certainly is possible. I just figured it would be easier if they were referred to by their intended values, instead of actual values which I imagine would still never be particularly accurate. You can always measure the capacitance across the cap terminals to get a measurement of a current setting, without doing math or referring to a table.

I'd be quite interested in hearing any ideas for upgrades and modifications for my device, if anyone has any.

robmdall · February 23, 2011, 12:29:14 PM

This is my next project. I am excited that both Rob and Matt are willing to share their work with us.

I have wanted to build something similar for a while now. These modules appear to be great tools.

I do have a question, while placing an order for the switches (Never used a Rotary before) I was confused by the number of Decks and also Shorting and Non-shorting? If one of you guys can chime in and maybe even point me to a proper link that would be much appreciated.

Not sure if individual Resistance and Capacitance is the way way to go or a single build covering both components.

Maybe more folks here will see these as 'must-have' tools like I am viewing the build.

Thanks in advance for any info you guys would like to share and also for the effort you have already put into this.

Bob

mattthegamer463 · February 23, 2011, 07:38:02 PM

Quote from: robmdall on February 23, 2011, 12:29:14 PM
This is my next project. I am excited that both Rob and Matt are willing to share their work with us.

I have wanted to build something similar for a while now. These modules appear to be great tools.

I do have a question, while placing an order for the switches (Never used a Rotary before) I was confused by the number of Decks and also Shorting and Non-shorting? If one of you guys can chime in and maybe even point me to a proper link that would be much appreciated.

Not sure if individual Resistance and Capacitance is the way way to go or a single build covering both components.

Maybe more folks here will see these as 'must-have' tools like I am viewing the build.

Thanks in advance for any info you guys would like to share and also for the effort you have already put into this.

Bob

The rotary switches are simple 1 pole 12 throw, that is to say, they have 1 contact and 12 different positions. Something like this would only have 1 deck, and you will want to go with non-shorting. Shorting means they will conduct between adjacent connections during the switching movement. Not a real issue but it isn't necessary.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CKC7001-ND

If you don't want to order from Digi, at least that will show you what you want.

Combining the units is optional. My unit is not electrically connected between the resistance and capacitance portions. You don't want it to be anyway.

Hope that helps.

robmdall · March 02, 2011, 01:48:27 PM

Thanks, should have the switches in tomorrow.

Curious, would it be advantageous for me to build in a serial/parallel switch? Or simply have a switch between one rotary and the other? It looks like you guys have all the 'standard' pedal values covered.

Bob

mattthegamer463 · March 02, 2011, 09:50:44 PM

Quote from: robmdall on March 02, 2011, 01:48:27 PM
Thanks, should have the switches in tomorrow.

Curious, would it be advantageous for me to build in a serial/parallel switch? Or simply have a switch between one rotary and the other? It looks like you guys have all the 'standard' pedal values covered.

Bob

Hey bob,

It offers some more flexibility, allowing to you reach more standard and non-standard values. For example, 68nF is a capacitor that is considered "standard" and is used relatively commonly, but its not practical to have enough rotary switches to have a fixed capacitance of all standard common values in a box. Using a combination of two other values, and the series/parallel switch, it can be achieved.

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capacitor substitution box design/values?..