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CV trigger to control an existing switch
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Author CV trigger to control an existing switch
JP
I have a diy circuit that has a number of switches, I was just thinking it would be rather neat to be able to trigger those switches via cv.

Is this an easy thing to add? I checked the cgs site (my go to for simple dot add-ons) but nothing jumped out.
falafelbiels
Hook some comparators to some analog switch ICs and flipflops and what not and you're golden I'd say. CD4016 or CD4066 for switches and CD4013 for flipflops. TL074 for comparators. Some resistors and stuff in there, nice!

But I'm probably supposed to draw some schematic, eh?
emdot_ambient
From what I've read, switching like that works fine for CV but can be problematic with audio, so it depends a bit on what kind of signal the switches are passing.
Low-Gain
i'd use an actual comparator IC instead of an op-amp but that's just me.

LM339 is good.
JP
OK, LM339 research commencing.

http://www.extremecircuits.net/2010/05/simple-capacitive-touch-sensor. html

and

https://www.muffwiggler.com/forum/viewtopic.php?t=9315

look promising. I'd love to find a small PCB like the bridechamber one for VC pot conversions

http://www.bridechamber.com/VC_Res_PCB.html
JP
or do I want something like this that uses a relay?

http://electro-music.com/forum/viewtopic.php?highlight=trigger+switch& t=22361

DGTom
This is all depends on what the switches are doing, how they are doing it & what kind of switches they are.

if its a bunch of momentaries that just need to be shorted to ground for a few ms then all you need are the 4066s & something to drive them - comparators may not even be needed if you are looking to use digital signals to control them.

If the switches need to be held low, then you're best off with the flipflops in there. Flip flops controlling switches is fun because its super easy to rig up a little schmitt inverter cct. & have a knob for "hold switch on for X length"

If the switches are actually carrying bi-polar CV or Audio its a whole other kettle of fish... best to use some nicer analog switches (DG etc.)


@low-gain

whats the advantage of the LM comparators over OAs? I'm assuming this application is fairly low speed & just on/off so it needn't be super accurate.
Low-Gain
i'm anal retentive wink they both cost about the same so i guess... why not use the 339? plus you can get them at radio shack still.
JP
DGTom wrote:
This is all depends on what the switches are doing, how they are doing it & what kind of switches they are.

If the switches need to be held low, then you're best off with the flipflops in there. Flip flops controlling switches is fun because its super easy to rig up a little schmitt inverter cct. & have a knob for "hold switch on for X length"


Yeah, sorry, I should have provided more info, they appear in my limited understanding to be just simple spdt switches that short current into the IC of this "voice altering" circuit I've been playing around with.

There are 5 of them.

Now the idea of flipflop sounds interesting, but also more complex.

DGTom
cool! 4066s applause

looks like they might need to be one or the other
not momentary, might need those 4013s as well
JP
How about a 4016?

http://www.doctronics.co.uk/4016.htm

I just noticed over on the sd card thread

https://www.muffwiggler.com/forum/viewtopic.php?t=23159&highlight=

I'm wondering if I'm going to be better having a flipflop which reacts to short triggers, on then off. Or a straight up voltage = on no-voltage = off type of circuit. The later would mean I could worry about length etc elsewhere and not on this circuit.

I'm assuming if I go with voltage momentary style, I can just do 4016's and no op amp ?
JP
http://www.epanorama.net/sff/Digital/Misc/Assorted%20Flip%20Flops.pdf

Hmmmm, lots of options in here.
JP
JP wrote:
How about a 4016?


Well you see JP, "The difference is that the 4016 has a higher internal resistance across the switch. This means a loss of signal fidelity. The 4016 is really meant for other types of switching and is not optimized for audio switching. The 4066 is much better for audio switching."

*cough http://www.thetonegod.com/tech/switches/switches.html
jbartee
the 4016's can introduce extreme non-linearities if you're operating on a 5V supply (not sure if you are). This caused me huge headaches on a ribbon controller design I built last year. Switching it out for the 4066 fixed my problems immediately. Just something to keep in mind.

from the data sheet:
"The CD4016B is composed of 4, two-transistor analog switches. These switches do not have any linearization or compensation circuitry for “RON” as do the CD4066B's. Because of this, the special operating considerations for the CD4066B do not apply to the CD4016B, but at low sup- ply voltages, ≤5V, the CD4016B's on resistance becomes non-linear. It is recommended that at 5V, voltages on the in/ out pins be maintained within about 1V of either VDD or VSS; and that at 3V the voltages on the in/out pins should be at VDD or VSS for reliable operation."
JP
OK, so giving this some more thought, ideally what would be awesome is to replace the SPST switch with a 4066 flipflop circuit that I can also hang a momentary push button off. That way I can manually or with trigger do the flipflopping.

Just ordered a fist full of 4066, et al chips from mouser, so that gives me 3 or 4 days to try and come up with something I can breadboard.

I'd think a small pcb which could be easily hooked up to any spst switch to add this CV control would be pretty popular. I can think of dozens of things I'd add this to from speak and spells through to vintage drum machines. Hell I want to be able to turn my toaster on with a CV trigger.
Bryan B
JP wrote:
Hell I want to be able to turn my toaster on with a CV trigger.


This is my new sig!
jbartee
JP wrote:
I'd think a small pcb which could be easily hooked up to any spst switch to add this CV control would be pretty popular. I can think of dozens of things I'd add this to from speak and spells through to vintage drum machines. Hell I want to be able to turn my toaster on with a CV trigger.


I've had exactly this idea in the back of my head for a while, mainly because I'd like to integrate my circuit bent stuff into my modular rig in some way. Currently busy with various other projects, but at some point I'm definitely considering creating some sort of module for this, that is if others don't beat me to it.

Note that for general purpose switching (of your toaster for instance) you'd want to use actual relays as the 4066 is only suitable for very low currents.
DGTom
well, I've never had a board made so I don't trust that this isn't flawed (possibly catastrophically) but here's my stab at this;



the 4066 is on the right, it also has 6 op-amps.

4 of these these can be configured 3 differant ways, depending on what parts you stick where; as R-S flip-flops, non-inverting comparators (w/ or w/out hystersis) & even a simple ADC by chaining all four (or 3 or 2)

There is also an attenuverter & a simple active HWR which can be used to process a CV before the ADC or can be totally seperate.

I might get a proto run done & see how they go, if anyone has any ideas for changes or can spare a moment to take a look over the files that'd be great grin
JP


I think this is teh circuit I really need. Momentary flip flop, I could pipe in the cv across the momentary to get both, add in a status LED and it would be perfect.

I don't supposed any feels like working out a PCB schematic for this? grin
JP
http://tech.thetonegod.com/downloads/Wicked_Switch_Momen_Invert_FF.zip
http://tech.thetonegod.com/downloads/Wicked_Switch_Momen_NAND_FF.zip

Does this look that above pcb in a format I could send to a pcb maker and get it made??

It's peanut butter jelly time!

Not sure I know if I need an inverter or a nand
daverj
JP wrote:

Does this look that above pcb in a format I could send to a pcb maker and get it made??


No. It's in a format that somebody etching their own PCBs in their basement could use. But not a format that a commercial PCB company could use.

JP wrote:

Not sure I know if I need an inverter or a nand


The two circuits are functionally identical. The NAND version simply uses NAND gates as inverters. So it only matters that you use the correct chip for each board. But functionally the two boards are identical.

And neither of these is really what you want. Neither one has any protection against the CV inputs going outside the voltage range of the logic chips used. A series resistor on the inputs might be enough to protect the inputs from too high or low voltages.

But for your use you would need to build five complete circuit boards, which is a bit of a waste since you could use a lot fewer parts if something was built specifically for the purpose.

Have you ever soldered perfboard circuits? It's harder than populating a printed board, but since you can build anything based on a schematic using that method, you could end up building something much more specific to your needs.
JP
I have done very simple perf board work. I just figured I'd try and find a pcb and get a bunch made and others might be interested in them at cost.

Just got all my CMOS chips from mouser so I'll star looking at breadboarding something based on what we have already.
JP
Bump for me. I've not had time to look at this for the last few months, but I have all the chips on hand, so it's time to try and work out a trigger and/or momentary button flipflop to add to other circuits.
JP
http://www.sparkfun.com/products/10684

Whilst expensive, is this an approach that would work well for adding trigger CV control to an old drum machine that has test buttons for each of the sounds?

I just need something simple that will act like pressing a switch. I'm assuming a relay is one of the simpler solutions.
JP
OK, bump for me again (just to remind myself I need to do something with this).

Planning on adding some sort of cv trigger control for my "megaphone" distortion module…

http://nomeist.com/meganasty-prototype-video/271

So I'll be attempting to bread board some ideas with the chips I got last year.

if anyone has any super simple dumbed down advice on how to convert a spst switch into a combo momentary/trigger CV toggle on toggle off.

let me know. I'd pay for a pcb or a kit in a heart beat, if anyone wants to make some quick money smile
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