Help with an Intercom Circuit

[robhedley]

Hi,

Firstly apologies for jumping straight in with my first post with a request for help.

I am currently building a Race Driving Simulator (Build Thread http://www.isrtv.com/forums/topic/12567 ... ofed-room/). I realised quite quickly that I needed an intercom from the office to the sim as when it is running you can't give any instructions to the driver without screaming your head off!!

Now, I have to say that my electronic knowledge is limited to a GCSE in Electronics from a long time ago and just learning what I needed to complete task for RC Cars etc With that in mind, I spoke to my good friend google and found a circuit online for a high quality intercom (http://www.zen22142.zen.co.uk/Circuits/ ... tercom.htm). I then taught myself how to use CadSoft Eagle and designed the circuit schematic.

The question I have is on the circuit from the link above, the microphone is a triple pin Electret where there is Output, Ground and power. The Microphones I hope to be using only have an Output and Ground. I read a few sites where they are feeding the power into the same pin as the output. I have amended my circuit to reflect this and would like too ask for you guys to tell me if I am being an idiot. The section I am talking about is the far left of the schematic.

Schematic I have created in Eagle

IntercomCircuit.png (17.65 KiB) Viewed 2745 times

Any advice is greatly appreciated and also if anyone has time, as sanity check on the rest of the circuit (Be Kind). I am more than happy to let anyone that help to come and have a blast on the Sim if they can get down to just south of Guildford.

Regards

Rob

[Richard]

Yes, some electret mics are only two terminal, and your circuit looks OK, assuming that the mic is not connected in the wrong way round. BTW, check that the DC voltage to ground at the base of the first transistor is greater than the voltage on pin 1 of the mic. If not, reverse the polarity of C2.