What did you use for the coils?
What was the frequency of oscillation?
The circuit would be better defined if you had a decoupling capacitor on the supply line.
It also occurs to me that the circuit may be better with the base decoupled as it is basically a common base type oscillator circuit.
What did you use for the coils?
What was the frequency of oscillation?
The circuit would be better defined if you had a decoupling capacitor on the supply line.
It also occurs to me that the circuit may be better with the base decoupled as it is basically a common base type oscillator circuit.
Nice one, chemelec.
I agree Spice isn't perfect. Thought you might like to know though that it predicts ~155kHz (load dependent) oscillation frequency for a 100uH coil in your circuit. Not far off reality .
Nice one, chemelec.
I agree Spice isn't perfect. Thought you might like to know though that it predicts ~155kHz (load dependent) oscillation frequency for a 100uH coil in your circuit. Not far off reality .
What are you using for Coils?
Normally for a BFO Detector, you would use one Factory made Small Coil, than Wind a Seach Coil with the Same Inductance as the Factory Coil.
So an "Inductance Meter" would be More Useful than the Frequency Counter.
LTspice thinks it will (assuming ~ 100uH coils), but it would be interesting if you could confirm with a breadboarded version.
LTspice agrees. Oscillation does occur in the sim, but amplitude is only ~0.7V.
But, place a capacitance across the coils and the amplitude will rise greatly at the resonant frequency (assuming the transistors can operate at that frequency).
Looking at the Data Sheet, I believe this device is Only good for VERY SHORT RANGE of Detection.
It looks like it is specifically made for detection of STAINLESS STEEL, Which is Not Detected by most metal detectors.
That's what I think, too. Since the IC both drives the coil and uses the coil as a sensor I don't see any obvious way of boosting the coil current to increase the detection range. Pity.