||Touch node safety/ best practices
| br>Hey folks, seems that search is down so I wasn't able to check if this topic has been asked before. I'm designing a simple circuit board for a sort of easy DIY build that I want to have use cracklebox/ touch node style touch playability. I have several questions about best practices that I would greatly appreciate some help with:
What is the best way to avoid people getting shocked in this scenario? I know that battery power can help a lot but that is still not fool proof if the user wants to plug their device into a speaker or outboard effects. I have seen Peter Blasser use TVS / Transient voltage suppressor diodes on the power inputs to his devices, will this suffice? Maybe I can put something on the board about only using it with a DI?
What is the best way to avoid a 60 cycle hum whenever the user is touching the device? There seems to be one present whenever I touch the device although the resistance change seems to work as expected.
Thanks for helping me out with this. br> br>
| br>The options for getting shocked are:
1) from whatever's powering the circuit. Running off a battery has this covered, not much hazard to be had from a 9-volt or so battery.
2) from whatever it's plugged into. If you don't get shocked from touching the audio cable / amp that you're plugging it into, then you won't get shocked using it. So while I wouldn't want to use it with an old guitar amp while standing on concrete (fun childhood garageband memories there), if your amplifier doesn't have jolt potential at it's input jack, you should be good to go. Same degree of caution you'd use with an electric guitar or microphone.
As to the hum, I would have to see the circuit, and how it's wired to the amplifier. Is it hum that appears in addition to the box's sound? Or is it hum that modulates the sounds? You might try touching the circuit ground with one hand, while operating the box, see if that changes things. br> br>
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