Re: a little RF help, please?


almo wrote:
I want to find a way to detect when a very small solenoid is energized
for about 10 msec. By "small" I'm talking about 1.5 watts, and turned
on with 6 volts, and physically very small, like 3/16 inch diameter. I
want to detect it from about 2 feet away. So, it's going to be
emitting an electro-magnetic signal, but to save me a lot of trial and
error, if someone can get me pointed in the right direction, I'd
appreciate it. As soon as I post this I'm just going to see if I can
detect it using a piece of wire as an antenna, then try a coil of wire,
etc., and just watch the oscilloscope.

Thanks

Here's a long shot. Do it the way shoplifting detectors do it. When the
solenoid is energized it's core is probably magnetically saturated or
close to it. You may be able to detect this by applying a powerful
alternating magnetic field that drives it in and out of saturation,
producing a signal at a harmonic of the driving frequency that could be
detected with a sensitive receiver. Shouldn't require more than a
thousand watts or so with coils the size of barrel hoops :-(

--
Joe Legris

.

Relevant Pages

  • Re: question regarding Wei-Ya monitor chassis
    ... impedence when I ordered it, and they sent me this model and told me ... to add 2 ohms (10 watts) to the H coil. ...
    (rec.games.video.arcade.collecting)
  • Re: How to determine what size resistor is needed??
    ... It involves running a component LED off of a coil, ... figure out what size resistor I will need so the LED does not burn ... So -- if operating voltage is 40, forward voltage is 1.4 and forward current is 10mA: ... watts -- use 2 watts for lots of leadway. ...
    (rec.games.pinball)
  • Re: Simple 555 dc pulse generator.
    ... amdxjunk wrote... ... > (except on politics;-) However I found ... About 100 watts at 12 Volts. ... I don't believe it's a good starting point for a Tesla coil. ...
    (sci.electronics.design)
  • Re: Second Question Same As The First (almost)
    ... So that little capacitor in the base of the coil can handle the full 500 ... Don't choke on the smoke. ...
    (rec.radio.cb)