Hello all, UC Berkeley student who knows how to code with minimal circuitry knowledge here.
Anywho, I wanted to make a 1 way intercom to connect two different parts of my house. Something that lets you talk to the other end while pushing a momentary button. I have found a couple of old phones to get parts from.
I was thinking of using an arduino to control NPN transistors that would power the mic and speaker (or should I not even be using a microcontroller at all). Anywho, could you provide any suggestions? I saw an arduino intercom project on the internet but it used the house lines and required picking up the phones which I don't want, I'd rath just a push to talk deal.
Thanks alot!
I was thinking of using an arduino to control NPN transistors that would power the mic and speaker (or should I not even be using a microcontroller at all).
I agree, there is no value in using a microcontroller for your application. Just search the web for audio circuits. You will need a preamp chip for the microphone end and a small audio amplifier chip for the speaker end. LM386 http://www.national.com/ds/LM/LM386.pdf is a popular small amplifier chip that can drive the speaker and a LM387 is a popular chip for microphone preamps: http://www.national.com/ds/LM/LM387.pdf
Thanks for the help! I'm looking on the internet and there's a couple I may try, but do you think there'd be any way to do it without a chip (then I could do it now instead of ordering the part)
I'm pretty sure you can find both of those chips at Al Lashers electronics on University Blvd. They are both very cheap chips.
Thanks for the tip retrofly, I went there today and got the parts.
I'm going to be building this circuit:
Just one question, is s1 (switch one) a TPTT switch, just split into it's components all over the circuit diagram?
s1 (switch one) a TPTT switch
No... TTDT... but if one of those is hard to come by, just use a DPDT for S1a + S1b (two parts, one switch, split all over diagram) and put a momentary (push for on... like doorbell) switch in for S1c. (And for the switch on the slave unit.) It will mean you have to be dexterous to use the thing.... but it will also mean that you don't have to remember to "switch off" (and save batteries) after use. Or use wall-wart, and leave S1c out. With S1c and switch in slave, intercom will work if either pressed, and no (big) problems will arise if both pressed, and both batteries not nearing exhaustion. I'd be tempted to add a diode at each battery.