Tweet
I acquired this detector just before Christmas, and it wasn't long before it was in pieces on the bench. 
This particular machine was marketed by Tandy as a SMART2 M6 Motion Metal Detector, but inside it's really a Rimatron 7MX. Performance-wise (in its SMART2 guise) it performs like a bottom of the range detector. A Victorian penny can be detected at about 7" (18cm) - if you tweak the internal settings - so it's ok as a beginner's machine.
However, with a few relatively simple modifications you can turbocharge this design and give it quite a respectable performance. (I'll be posting the necessary mods on the Modifications Forum shortly, when I've finished here.)
There is some similarility between the Rimatron and the Fisher 1212X (see Geotech's Metal Detector Schematic section) as they both use operational transconductance amplifiers (OTAs) instead of analog switches. There is a fixed setting for the discrimination sample point, and the control marked Reject actually controls how hard the circuit tries to discriminate, rather than the amount of discrimination.
The coil is an 8" double-D driven by a Hartley oscillator, and powered by a single 9V battery. The TX frequency is very low at 3.48KHz.
Note: There are two capacitors (C? and C??) on the schematic and one resistor (R?) where the silkscreen was either missing or hidden on the PCB.
This particular machine was marketed by Tandy as a SMART2 M6 Motion Metal Detector, but inside it's really a Rimatron 7MX. Performance-wise (in its SMART2 guise) it performs like a bottom of the range detector. A Victorian penny can be detected at about 7" (18cm) - if you tweak the internal settings - so it's ok as a beginner's machine.
However, with a few relatively simple modifications you can turbocharge this design and give it quite a respectable performance. (I'll be posting the necessary mods on the Modifications Forum shortly, when I've finished here.)
There is some similarility between the Rimatron and the Fisher 1212X (see Geotech's Metal Detector Schematic section) as they both use operational transconductance amplifiers (OTAs) instead of analog switches. There is a fixed setting for the discrimination sample point, and the control marked Reject actually controls how hard the circuit tries to discriminate, rather than the amount of discrimination.
The coil is an 8" double-D driven by a Hartley oscillator, and powered by a single 9V battery. The TX frequency is very low at 3.48KHz.
Note: There are two capacitors (C? and C??) on the schematic and one resistor (R?) where the silkscreen was either missing or hidden on the PCB.
Comment