Hi. New to electronics and helping a friend do some drum triggers for a double kick drum. I’m not a musician either so apologies if I say a lot of stupid things about stuff I don’t understand. We’re going to try out piezos for the task.
He wants three piezos/triggers on separate mono channels. The 6.5mm sockets I have are stereo so I figured I may as well give him the choice to run two different channels through the one plug (in case he’s ever short on cables or inputs or something).
I figure there are six combinations of the piezos and Left/Right channels:
Plugged into channel 1: L = 1, R = 2
Plugged into channel 1: L = 1, R = 3
Plugged into channel 2: L = 2, R = 1
Plugged into channel 2: L = 2, R = 3
Plugged into channel 3: L = 3, R = 1
Plugged into channel 3: L = 3, R = 2
I figure I’ll use switches to route the channels. On the attached diagram I also have switches for turning on/off each mono channel separately, but I just now realised it’s just as easy to pull the cable out as it is to flick a switch off, so I probably won’t do those switches.
Mainly want to ask:
- Is there a better way?
- Will the circuit work as I have it here?
- Will joining up the negative wires as I have will be ok or will it bleed signals from one channel to another?
- If there are any musicians on here will it even be useful to make the signals available as stereo rather than mono?
Thanks for reading.
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Hi Simon
A bit hard to tell what is going on here. I assume the 3 blobs above the 3 boxes are the stereo jacks so if you are connecting the 2 outer blobs as you have shown closing the top switch will short out the piezo device shown directly above it.
It should be ok to connect the negative side of the piezo devices together but the way you have the switching wired it would be possible to have the positive side of 2 of them connected together with any 2 of the bottom switches closed at the same time. If the 2 bottom switches of all 3 banks are closed then all positives will be connected which could not be a good thing. So either revise the switch wiring or as you suggest leave them out.
The fact that these are stereo jacks will not matter, just use the tip and sleeve, forget about the ring (the middle one) and treat it as mono. Will be much less confusing.
Cheers Bob
Be aware that some jacks (mono and stereo) have built in switches that make when the plug id removed. These may put shorts where this might not be a good thing.
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[quote]Hi Simon
A bit hard to tell what is going on here. I assume the 3 blobs above the 3 boxes are the stereo jacks so if you are connecting the 2 outer blobs as you have shown closing the top switch will short out the piezo device shown directly above it.[/quote]
Sorry if it’s unclear. I gave myself a bit of a crash course in schematics and though I thought I got the right symbols I might not have. The top symbol is supposed to be a piezo. The symbol below that with a box and a three pronged antenna looking thing above it is supposed to be a stereo 6.5mm socket with ground on the left, ring in the middle and tip on the right. The blobs are what I thought was the convention where there is a join from one component to the wiring - just so you could tell the ends of the component and the start of the wires.
As I said, I don’t know what I’m doing, but I thought closing the top switch would connect the positive to the tip and the negative would already be attached to the ground. If it doesn’t make sense I better have a closer look at the conventions for drawing a diagram.
Good point. I might have blown up my friend’s audio equipment. I might just skip the switches altogether. Better safe than sorry. Thanks for the advice.
Hi Simon
A common schematic symbol for a stereo or balanced line tip, ring and sleeve jack
Here you can see the switches I mentioned above which in your case can be ignored. They are used in a balanced line audio patch panel where the signal is “normalised” through to the jack below (or above) and carried on to another destination. The insertion of a plug breaks this circuit and can be used to 1) terminate a line for measurement, 2) Insert a signal for testing or 3)re-route a signal to another destination. There are other wiring techniques which allow bridging measurements without breaking the line but that is of no concern to you with this project.
Just wire the sleeve and the tip (or ring) for each (3) of your piezo devices and ignore the rest. By far the simplest solution and you won’t get into too much trouble.
Cheers Bob
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Thanks for taking the time Robert. It’s helpful people like you that redeem the internet. I’ll take your advice and just wire up the mono signal paths.
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Hi Simon,
Welcome to the forum 
What kind of signal does a drum trigger need to be so that it is useful for the kick drum?
Also, is your piezo being used as a microphone element to pick up the noise indirectly, or is it struck directly by the kicker to cause your signal?
Given you’ve decided to go with Piezos to detect the trigger I assume you just need a DC pulse of some kind.
I’ve always found the specifications of piezo elements to be far too abstract and into the realm of physics to provide any useful numbers, they aren’t likely to have a voltage or current output spec. Experimentation will likely provide the best information about what you can get out of them and it’s definitely worth checking. It would be a shame if your voltage was too weak to detect, or worse if it was too high and caused damaged to whatever instrument it was connected to.
Hi Trent
I think Simon’s friend has the drums and is the musician. Seems to know what he wants and (hopefully) knows what he is doing. Will leave the rest up to them.
Cheers Bob
