Re: bike computer to PC interface
- From: shb*NO*SPAM*@comporium.net (Si Ballenger)
- Date: Fri, 09 Mar 2007 00:41:03 GMT
On 7 Mar 2007 09:06:32 -0800, pete_tomson@xxxxxxxxxxx wrote:
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?
I'm also trying to write a program in VB6 to read the input, but not
having much luck.
I'd really appreciate any help anyone could give me.
Thanks
Pete
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
[repeat]
timer 150, [delay]
wait
[delay]
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]
[quit]
Close #comm
End
.
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- From: pete_tomson
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