bike computer to PC interface

Sounds as if you are attempting to connect to an old style DB25 RS232 serial port. Use Google and search for "button box". Those documents will describe the necessary software to read the switch closures.

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.

schreef in bericht news: snipped-for-privacy@n33g2000cwc.googlegroups.com...

For the bike computers I'm aware of they tie a magnet to the wheel and some sensor to the frame. That sensor can be a coil or a Hall type sensor but I never saw a reed switch so far. Nevertheless, for a simple solution I'd tie a strong magnet to the wheel and a reed switch to the frame. You may heve to do some experiments to find a reliable combination, but once you have a working reed switch, you can count pulses through a serial- or parallel port very easily.

D0(2)------+ | .-. 3k3 | | | | '-' | PE(12)-----+ | \\ o \\ \\. o | GND(18)----+ created by Andy´s ASCII-Circuit v1.24.140803 Beta

Above an example to use the parallel port. Drive D0 (pin 2 of the pp connector) high and you can read the state of the switch through PE (paper empty pin 12).

petrus bitbyter

I assume you are wanting to make a simple revolution counter for a stationary bike. I made a simple setup by connecting pin 7 (rts) to a resistor (4.7k sounds good) thru a wheel contact setup to pin 2 (rx). When the com port is opened, pin 7 goes high supplying ~+10v. When the wheel contact was made, jibberish is put in the serial port input buffer. I made a simple program using Just Basic (free) that checks the input buffer for input every 150 ms. If there is input to the buffer the wheel has made a revolution.The wheel contact was an index card stuck into the spokes such that I bowed out a little bit. l taped some aluminum foil on the card surface so that it would brush two bare wire ends from the circuit when it went by to make the circuit. This put the jibberish in the buffer. Below is a simple program I made to test it to see if it would work. It assumes that one wheel revolution is ~.00138762 miles.

open "Com1:9600,n,8,1,ds0,cs0,rs" for random as #comm

x = 0 y = 0

dataRead$ = input$(#comm, lof(#comm))

if dataRead$ = "" goto [repeat]

y = y+.00138762 print y

'print x x=x+1

if x=1000 goto [quit]

goto [repeat]

End