Elektor's Tank Locked loop oscillator

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Why no oscillation. I can't seem to make it work as drawn. I include everything required to run simulation in zip file.

[ATTACH]n428229[/ATTACH]

[Skippy]

4046's are trouble in real life, so probably are in simulations, too.
Does R10 go to ground , or -5V ? Just a thought...
Does SigIn need protection, like two diodes clamping it to +5V / -5V ? Seems you may be feeding it with more volts.

It may be an idea to split the circuit up. Get Spice to feed in a sine-wave sweep directly into the coil drive circuitry, and see that it actually drives the coil, showing the resonance on the LC circuit. About 3.5 V rms into R8 would be about right.

Then force the 4046 VCO to mid-range ( input to 0V ) and get it to produce whatever the LC circuit tuned to . Then try closing the loop.

[Carl-NC]

I don't see how this circuit will work. The overdrive clamps (Q2,Q3) can never turn off.

[dbanner]

It appears to work. I found a simulation and took a part of it.


[ATTACH]n428243[/ATTACH]

[ATTACH]n428244[/ATTACH]

[dbanner]

[dbanner]

I don't see how this circuit will work. The overdrive clamps (Q2,Q3) can never turn off.

It Is working with or without Q2 and Q3.

[dbanner]

Perhaps now to add flip flop quadrature.

[Skippy]

Are you running this with a CD4046 ( regular 4000 series ) or a 74HC4046 ? ( 5V TTL type ) ?
They aren't the same, and clearly the PSU requirements are different.

Gotta be suspicious about the original schematic, with the resistor value of 100R incorrectly shown on the TX drive ( R6 ). What else is wrong??

[Gwil]

Can anyone explain to me what is gained by including a phase locked loop in this circuit?
I don't think I've seen one in any other coil driver design. What problem does it solve?

Thanks.

[dbanner]

Can anyone explain to me what is gained by including a phase locked loop in this circuit?
I don't think I've seen one in any other coil driver design. What problem does it solve?

Thanks.

It is discussed here: https://www.geotech1.com/forums/foru...ator-front-end

[aft_72005]

It appears to work. I found a simulation and took a part of it.


[ATTACH]n428243[/ATTACH]

[ATTACH]n428244[/ATTACH]

I made the Elektor metal detector circuit more than 30 years ago. It was one of the best circuits in its time.

[dbanner]

Are you running this with a CD4046 ( regular 4000 series ) or a 74HC4046 ? ( 5V TTL type ) ?
They aren't the same, and clearly the PSU requirements are different.

Gotta be suspicious about the original schematic, with the resistor value of 100R incorrectly shown on the TX drive ( R6 ). What else is wrong??

Yes, I did not see that. The 100R is obviously wrong. The original magazine article shows correct values as far as I know. But that's beside the point. Recently while digging through pile of scrap, I found some PLL chips on an old junk board and Elektor's circuit came to mind.

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This Tx oscillator from Fisher is very good. The second harmonic is way down.

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I just happen to have a CA3086 in my parts bin. The coil looks to be bi-filar wound.

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I forgot to include coil resistance in my sim.

I found some data on the fisher 440 11inch widescan coil.

440 Coil
12.6 mh total
3.2mh 14.3 ohms per side