Need Some Recommendations For This Circuit (Schematic & Breadboard Attached)

I have a relatively simple circuit (depending on how simple working with an op-amp seems, took me forever to figure that out), but I’m definitely getting noise on the circuit.

I need some advice on the setup of this circuit, in particular decoupling capacitors (where to put them), and overall circuit flow. Fritzing is recommending some ratsnest lines grounding no-channel (NC) holes, as well as one from a resistor returning to ground to Vcc on the amp that I’m not so sure of. Also, do I need a capacitor for an RF bypass to reduce noise from that as well?

NOTE: That’s actually supposed to be an RX receiver, not TX, just used the TX because the one in Fritzing had the same amount of pins as the one I’m actually using). Rx is just doing an external interrupt on INT0 that buzzes the piezo when the interrupt is triggered.

I know the general rule is to put a capacitor as close to your IC as possible (this one is an ATTiny85), but also maybe a couple by the power source, maybe .1uf and 10uf? So…3? Not quite sure what the decoupling guidelines are with 9Vs.

Also curious as to if I set up this op-amp correctly…I used a decibel meter and I got an extra 6 decibels out of the piezo (99 db total at its resonant frequency) compared to without the amp, but any additional suggesting on the voltage differential is welcome too. Looking to get this PCB ready.

Stuff I’m using:


The noise you are experiencing is probably one of the chips breaking down because of the 9V you have zapping through it. An op-amp isn't what's required here, a good electronics tutorial is.


I think you need something like this attachment, and DO NOT power the circuit with 9V, the attiny85 is only rated for 5V supply.

Tom… :slight_smile:

Thank you, George!