Reading the value on a wire

[Antonis Konstantinos]

Hi all,

There is a system which reads the pulses on a wire and displays them
on a series of 7segment led displays. What I want is to read/count the
pulses on the same wire without interfering with the existing system.

I want this add-on to make as less effect on the existing system as
possible.

The pulses on the wire are 3V.

Currently I'm using an 6n136 optocoupler with a limiting resistor on
the input side and counting the pulses on the output with a micro
controller.

I do not have any problems so far, but I would like to hear if there
are better/more suitable ways of doing this thing.

I hope I could make myself clear.


Thanks in advance,
Antonis

 

[John Woodgate]

I read in sci.electronics.design that Antonis Konstantinos <antonis_kons
[email protected]> wrote (in <[email protected]
gle.com>) about 'Reading the value on a wire', on Thu, 12 Feb 2004:

I do not have any problems so far, but I would like to hear if there are
better/more suitable ways of doing this thing.

If there is appreciable current in the wire, you could detect the
magnetic field. But with 3 V pulses, you should easily detect the
electric field. Put a piece of metal foil around about 5 cm of the
insulated wire, and connect the foil to the input of a FET op-amp, with
say 1 M to 10 M ohm to ground, depending on the duration of your pulses.
Ground the other input of the op-amp and set the gain with feedback to
say 10. You should get good pulses, or at least spikes, at the op-amp
output.