IR light barrier kit (sending serial data to computer port)

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Joined Jan 26, 2013
I am constructing the MK120 light barrier velleman kit for an end of the semester project. Basically want I need to do is transmit and send serial data to and from the rs232 port of a computer using both parts of the circuit, transmitter and receiver. I have a couple of questions.

First question is, what would be the best way to produce a negative voltage to the Tx pin on the receiver? My professor suggested that I put in a negative voltage supply to the emitter of Q2, connect it to Tx and then connect Rx to the collector. Is there a better way to do this? Btw, the buzzer will be disconnected. I don't think that should have any significant effect on the circuit, but just in case...

Second question is, I noticed that I have a rs232 port on my de1 board, so I was wondering if I could actually connect my transmitter to that port, connect the board to the computer, and still send and transmit data. I read somewhere that the NIOS software would be needed, I'm only familiar with Quartus, and even then I am a little rusty because I haven't used it in awhile. My professor suggested if I used the de1 board that I should also use a 2n7000 mosfet to act as a switch to turn the transmitter data on and off. The mosfet would be inserted in on the base of q3, being connected to a wire to the de1 board. Makes sense, but perhaps someone here has better suggestions...The original plan was to directly connect the transmitter and receiver to the rs232 port on the computer, so if all else fails, I'll stick with that.

The schematics should be attached

Thanks for the help :)