Basic Stamp Tachometer

Archiver

I am building the tachometer cirucit from the Priactical Pulse
Measurements section of the Basic Stamp Manual 1.8.

I continue to get false triggering with the rpm value shown as 6000,
about every 5th measurement. This is without using a magnet
to trigger the circuit.

I have tested the switch with a simple reisitor led circuit and it
appear to work fine.

The cirucit uses a Hall effect switch and a 4013 flip flop input to
the Basic Stamp 1. The program is as follows:
input 7
Tach: pulsin 7,1,w2
let w2 = w2/100
let w2 = 60000/w2
debug w2
pause 1000
goto Tach

Deleting the w2/100 and 60000/w2 lines,I get a w2 value of 1054 with
a
value of 1 approximately every 5th measurement.

I have added a metal case and shielded cable to reduce noise, but
with
no effect.

Any suggestions?

Archiver

Graham:

Your code will wait for pin 7 to change from 0 to 1 to start counting. It
will count until pin 7 returns to 0. However, if no input occurs within
0.65535 secs, the Stamp manual says that it will return zero to w2. I don't
know why you are getting values of 1054 and 1. At least the fact that
pulsin does not stop and wait for input is normal.

Hope this is of some help,
Ray McArthur

> I continue to get false triggering with the rpm value shown as 6000,
> about every 5th measurement. This is without using a magnet
> to trigger the circuit.

> The cirucit uses a Hall effect switch and a 4013 flip flop input to
> the Basic Stamp 1. The program is as follows:
> input 7
> Tach: pulsin 7,1,w2