Electronic-Nulled Loops

[Altra]

I built this little circuit to test how well it could null a coil. The next step is to replace the X and R trimmers with digital pots, using a processor to auto null. In the video the tx is running about 14kHz at 16vpp. The pre-amp out can be nulled from about 500mvpp down to 20mvpp.

The circuit is a modified version of the Treasure Mate found here

https://www.geotech1.com/forums/foru...ate-pinpointer


https://www.youtube.com/watch?v=a8NI_632VIA

[moodz]

Here is my entry for the nulled loops competition. It uses the ARMD project core and balances the loop via two possible methods. ( internal to the DSP ) or external.
Note in external mode the RX coil "sees" the correction signal !!

The balancing is very simple in reality. We already calculate the signal magnitude and we know the NCO phase and amplitude so its a matter of a null feedback loop.

[dbanner]

Last thing to resolve is the missing track under the 4053 chip. This maybe important to the function of the circuit.

[dbanner]

Thanks. This is good.

[Mario-j23]

I will make corrections to the schematic drawing.

Maybe this will help. My diagram and PCB drawn in the old version of Eagle with the improved CD4053.
This allows you to follow traces on the PCB
Autotune4053.zip

[Mario-j23]

Please post in English. thanks.

Sorry, I'm using a translation plug-in in my browser.
Something went wrong. I noticed it after some time and I can't find the edition option.

#67 "I'm not an electronics expert. Detectors are a hobby. I was looking for circuits by pins. I don't know why I didn't pay attention to 4053. Bravo, I've almost figured out the circuit."
#68 "It doesn't fit with the PCB yet"

[dbanner]

I will make corrections to the schematic drawing.

[Carl-NC]

nie jestem elektronikiem. Detetkoty to hobby Szukałem układów po pinach. nie wiem czemu nie wiołem pod uwage 4053. Brawo już prawie układ rozpracowany.

Please post in English. thanks.

[dbanner]

Oh crap. Back to the drawing board.

[Mario-j23]

Jeszcze to nie pasuje z PCB

[Mario-j23]

Now it looks good. What you think about the 4053 in place of 4051. Here is the best schematic, everything is pin for pin with the pcb layout.

nie jestem elektronikiem. Detetkoty to hobby Szukałem układów po pinach. nie wiem czemu nie wiołem pod uwage 4053. Brawo już prawie układ rozpracowany.

[Mario-j23]

I just now realized that there is a CD4024 chip on main board. CK wire goes to pin 3 of CD4024. Now I think everything is closer to being solved.
I compare the 2b board with the 2ba board. On the 2b board nothing is connected to pin 3 of CD4024. So this question is put to rest.

I agree. Riddle solved CK=120hz pin 3 of cd4024 goes to AutoTune.

[dbanner]

Now it looks good. What you think about the 4053 in place of 4051. Here is the best schematic, everything is pin for pin with the pcb layout.

[dbanner]

The 555 closes the gate allowing the Rx signal to pass through. The 555 also simultaneously enables the digital pots by pulling CS low.

[dbanner]

Here is the circuit with 4053 instead of 4051. The pin numbers line up and make sense. What do you think?