Re: bike computer to PC interface


<pete_tomson@xxxxxxxxxxx> wrote in message
news:1173287192.402131.180590@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi All - I found this newsgroup and was wondering if anyone could help
me.
I'd like to connect a magnetic sensor (bicycle computer) directly to
my computer through one of the ports without a power supply.

Basically the reed switch will have a current induced in it so I'm
thinking I'd ideally like the circuit to be passive with minimal
external circuitry.

I have a pic of a basic circuit I found but don't know how it works
and I don't know how to post it. Basically it has a connection to pin
4 through a 4.7kohm resistor a direct connection to pin 6 and a ground
through pin 20.
If you tell me how to post a pic I can show the diagram.


Can anyone make suggestions about circuit design - can I feed the
wires directly into my parallel/serial port?

If it is a reed switch, you will need a power supply and a pull-up resistor.
A USB port should work fine.

The reed switch is passive ... it generates no voltage.

If it is a sensing coil ... a small voltage is generated when the magnet
wipes past the coil ... that will require signal conditioning.


.

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