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Hi there electronoobs, your projects are amazing and very helpful. I'm currently trying to create the homemade ultrasonic sensor that you created. However when I checked my signals, I can't even get a proper signal. How do I fix this? How do I check my level shifter to apply a 40khz to the transmitter speaker? Also I'm currently using 10khz variable resistor rather than 5khz that you used, will this affect my results? I'm also unable to apply a 5v square signal and get a 30V peak to peak through my speakers. Please help me.

in Arduino by (140 points)

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But you can at least create the 5V square signal with the arduino? If yes, the problem is at the MAX232 voltage doubler. As you can see in the schematic it has a PNP transistor connected at pin 16. You have to activate that just before you send the pulse. Otherwise it won't work. The capacitor must charge before.

I hope this helps!
by (34.8k points)
So I should first make sure the  Arduino applies a 5V to the MAX232 to generate a 30v peak to peak that goes to the transmitter speakers first right?
Hello again Electronoobs. I am currently stuck on another matter. The received signal from the receiver speaker is not being amplified properly. In fact, the receiver isn't even responding when I assembled the amplifier part of the circuit. Which is odd because I tested the speaker first and it responded properly albeit with small voltage. I've been adjusting my potentiometers for days and my speak is not responding properly on my oscilloscope. Could it be because I wired my oscilloscope on the wrong output? Also I noticed you didn't set up the comparator part of the LM324, may I ask why?