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As some of you may have already noticed, I'm rebuilding a Coinmaster 2TRDX (well, probably) which I got free on junkyard -> http://www.geotech1.com/forums/showthread.php?t=17327
I got it broken without half of the case and without coil, however after minor repairs the detector itself seems to be working. I live in Poland so I highly doubt that I'll ever be able to buy original coil, because older Coinmasters are rather rare here. I have to build suitable coil myself.
The device uses Hartley's oscillator, so the transmit coil inductance directly affects the freuquency. The receiver's sensitivity is highest in the 2.1-2.4kHz range, so I think the transmitter should run around 2.18kHz.
With trial and error design I built the following coil:
It is a DD coil and after various fixes it works, however the detection ranges (especially for smaller items) are not very good.
I could not get it running with larger capacitance (no oscillations at all), that's why I had to increase the inductance and finally got over a 300 turns coil.
The detector probably used a 4B coil with 3 windings:
I'd like to build a copy of the 4B, or maybe a coplanar coil (which one is better?) , however I have no idea how to estimate TX inductance since there's the third coil connected to TX, in opposite direction. Also, could someone explain me why the original TX coil had 3 sections (is the 3rd section a feedback coil), and the RX had two ?
I got it broken without half of the case and without coil, however after minor repairs the detector itself seems to be working. I live in Poland so I highly doubt that I'll ever be able to buy original coil, because older Coinmasters are rather rare here. I have to build suitable coil myself.
The device uses Hartley's oscillator, so the transmit coil inductance directly affects the freuquency. The receiver's sensitivity is highest in the 2.1-2.4kHz range, so I think the transmitter should run around 2.18kHz.
With trial and error design I built the following coil:
It is a DD coil and after various fixes it works, however the detection ranges (especially for smaller items) are not very good.
I could not get it running with larger capacitance (no oscillations at all), that's why I had to increase the inductance and finally got over a 300 turns coil.
The detector probably used a 4B coil with 3 windings:
I'd like to build a copy of the 4B, or maybe a coplanar coil (which one is better?) , however I have no idea how to estimate TX inductance since there's the third coil connected to TX, in opposite direction. Also, could someone explain me why the original TX coil had 3 sections (is the 3rd section a feedback coil), and the RX had two ?
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