Square wave Pulse Induction

[dbanner]

Power, generally speaking, tend to wear out those who wear it.
It has to go somewhere.

[green]

Hi Altra,

Don't know your Rigol scope. With my Rigol, I select Bit map and(invert)to print a white screen instead of black screen. My preference, maybe others prefer black screen?

I'm color blind and don't see the grid lines on the black screen if they are there. Maybe there is a reason black screen is first option? I can do black screen if others prefer.

[deemon]

This is my attempt to reproduce Deemon's amazing CCPI tx circuit.

Still a work in progress. It uses a minelab SD,GPX style DD IB coil. This proto uses manual current compensation. Deemon devised a self adjusting current tilt, which I wanted to avoid while learning.

The power transformer is the key to the circuit. Deemon was using recycled toroid cores and could not ID the material type. So I set out to determine which standard cores work. I used ferrite cores with 25mm to 29mm O.D.s. Ferrite material types tested "F", "J", "W" and metal tape type "4D". One example - 29mm J material, primary 130t #32 and 70t, 2 x #26 teflon for the secondary. The primary should have about 1 ohm resistance. On the secondary the lower the better.

Most toroids you find are the powdered iron type which will not work. Permeability between 2800u to 8000u seem to be the sweet spot. I even made a transformer from a salvaged E-core that was used in a electronic light balast. It worked but was physically too small for the heavy gauge secondary.

Attached are Deemon's drawings that I based my experiments on. Also transformer test circuit along with a proto that I am still playing with.

Hi !

Just looking at your waveforms - the circuit seems to work pretty good . Did you meet a problems while starting it up ?

[Altra]

HI Deemon
It starts without problem. I did deviate from your design. Coil 300uh and 4.7nf cap, power supply 10v. Lots of improvements to be made.

Thanks

[deemon]

HI Deemon
It starts without problem. I did deviate from your design. Coil 300uh and 4.7nf cap, power supply 10v. Lots of improvements to be made.

Thanks

It's good ! But I cannot find on the circuit the DC resistance of the TX coil ... and another question - did you use Litz or simple wire ?

[Altra]

The DC resistance is less than 1 ohm. I have tried coils with litz, enamel and Teflon all worked. 300uh to 1500uh. The difference is efficiency and output power. If you want me to try something let me know.

[deemon]

The DC resistance is less than 1 ohm. I have tried coils with litz, enamel and Teflon all worked. 300uh to 1500uh. The difference is efficiency and output power. If you want me to try something let me know.

Can you show the waveform on the kick circuit - between Q4 and Q5 ? What is interesting - how does 2N2222 perform it's task ...

[Altra]

These photos show the kick. Blue trace coil current, Yellow V coil. Green Kick voltage. Scope ground= B-. One thing I changed here was D6, D7 to faster diodes MBR160's.

[eclipse]

One thing I changed here was D6, D7 to faster diodes MBR160's.

You mean D5 and D6 /UF4004/?

How do you connect the TX shield, it should be connected to -B? In the mean time the RX shield seems has to be connected to GND. Perhaps a modification inside the coil or the connector /original Minelab coils/ is needed?

[Altra]

You mean D5 and D6 /UF4004/?

How do you connect the TX shield, it should be connected to -B? In the mean time the RX shield seems has to be connected to GND. Perhaps a modification inside the coil or the connector /original Minelab coils/ is needed?

I changed D6 and D7 on my circuit from Deemon's original design. He specified 1N4007's, attached is his original drawing.

On the minelab gpx coil, I have the tx cable shield connected to B- and Rx cable shield to AGND. I believe the coil shield is connected to Rx cable shield internally? My coil has the connector removed.

[eclipse]

Got it, I was looking at the diodes on your circuit.
I have original Minelab SD2200 DD Coil, I've measured and here is the data:
The 2 connections are inside the plug, so If I remove the bridge wire (1 and 5 pins) this may give separate TX/RX shield if these are not also connected inside the coil as well /your coil seems to be that way/

[mickstv]

These photos show the kick. Blue trace coil current, Yellow V coil. Green Kick voltage. Scope ground= B-. One thing I changed here was D6, D7 to faster diodes MBR160's.

HI Altra, Just wondering did you continue on with this design ? Also did you build the auto current tilt and how did it go in real world situations ?

[Altra]

HI Altra, Just wondering did you continue on with this design ? Also did you build the auto current tilt and how did it go in real world situations ?

Hi Mick, everything I did is in post #98. About the same time I became interested in BP THS designs and that has kept me busy since.

I never attempted auto current compensation manual only. In general, I wasn't happy with how the current compensation was implemented during the transition and the additional torroid etc.If I revisit the circuit, I want to explore the method used by Bruce Candy. He describes a low voltage pulse of about +/-2V right before the Tx pulse changes state, can compensate for current losses. John Earle also used a low voltage pulse to maintain the current at a steady state.

[mickstv]

Hi Mick, everything I did is in post #90. About the same time I became interested in BP THS designs and that has kept me busy since.

I never attempted auto current compensation manual only. In general, I wasn't happy with how the current compensation was implemented during the transition and the additional torroid etc.If I revisit the circuit, I want to explore the method used by Bruce Candy. He describes a low voltage pulse of about +/-2V right before the Tx pulse changes state, can compensate for current losses. John Earle also used a low voltage pulse to maintain the current at a steady state.

Thanks Altra, thanks for the links to read. I've been looking at all the CCPI info on sites and I think I might have play with the AMX or Moodz circuits. I have some ideas around them relating to current comp.

BTW what is the BP THS ?

[Altra]

Thanks Altra, thanks for the links to read. I've been looking at all the CCPI info on sites and I think I might have play with the AMX or Moodz circuits. I have some ideas around them relating to current comp.

BTW what is the BP THS ?

THS is Truncated Half Sine. It's something John Earle and Carl were working on at Whites.

See pdf in first post

https://www.geotech1.com/forums/foru...r-transmitters