Whites Surf PI schematic

[Mohamed Ghitas]

WHAT I AM SAYING is that maybe it should not be backwards.

doh

but never you mind.

also what iam saying is that iam connecting it CORRECTLY according to its datasheet

thanks

[porkluvr]

WHAT I AM SAYING is that maybe it should not be backwards.

doh

but never you mind.

[Mohamed Ghitas]

Judging from what you wrote in #804, I think you may have inserted your 2N3906 (Q1) backwards. It should match the silkscreen
and be facing up.

i already inversed it
does the power supply could be cause of this ??

did you made this MD before ??

[porkluvr]

Judging from what you wrote in #804, I think you may have inserted your 2N3906 (Q1) backwards. It should match the silkscreen
and be facing up.

[Mohamed Ghitas]

ok now the Q6 is not heating iam supplying my circuit with computer power supply
the discontinuous beeb stops when i touch the power supply metal body and the circuit works
but with very low sensitivity so is there ghost inside my power supply :P

i think there is some problems with ground connections

any advice ??

[Fabian]

Sorry. You're right. I have not read the previous post altogether. Just saw the picture and remembered that mistake.

[Mohamed Ghitas]

This PCB has an error, Q6 is in wrong position. Must be reversed.[ATTACH]26625[/ATTACH]

i replaced Q6:BC337 with KSP13 ---> MPSA13 so its placed correctly

[Fabian]

This PCB has an error, Q6 is in wrong position. Must be reversed.

[Mohamed Ghitas]

Better Yet, Use a 32 Ohm or a Much Higher Ohm Speaker.
This is one reason Why I use the TL026 Transformer.

maybe this is the cause of Q6 hot ??

[chemelec]

10 Ohm Speaker.

Better Yet, Use a 32 Ohm or a Much Higher Ohm Speaker.
This is one reason Why I use the TL026 Transformer.

[Mohamed Ghitas]

hello everyone
in my circuit when i plug power it made discontinuous beeb
and the Q6 gets hot
here is the circuit



Note:
i replaced Q6:BC337 with KSP13 ---> MPSA13
and replaced Q1:327 with 2N3906 and i inverse its polarity according to datasheet

any idea what could be wrong ?
iam using 10 ohm speaker

Thanks in advance

[starmoml]

help

My circuit does not work. PLEASE guide me
voltage basis of IC circuit.؟؟؟

how much voltage and Fercance TP ???????

[daverave]

Sean_Goddard made an interesting comment, by adding his comment to Erics information in post #794 makes good reading

thats a very interesting comment..that is worth experimenting with and see the clip point on the scope

[6666]

Sean_Goddard made an interesting comment, by adding his comment to Erics information in post #794 makes good reading

If you put an oscilloscope ACROSS the coil, you will actually be measuring the "equivalent" current through it (Ohms law?) So set the pulse widtch until the signal JUST starts to clip, at that point you know you have maximum current flow. Any more and you are just wasting battery power, any less and you are not developing the maximum field for your coil.

Optimising the PW in this way will give you best depth and best battery life (barring external factors not mentioned).

[Qiaozhi]

so am i right in thinking that we are only interested in the currents produced when coil switches off ????

This is correct for a conventional PI detector, such as the Surf-PI. Some experimentation has been done to try and make use of eddy currents generated during the On period, although I'm not aware of any commercial detectors that incorporate this feature.

i would imagine also that we can sample earlier if a series coil resistor is used reducing the back emf to maybe 200v instead of 400v as in many designs.

Reducing the coil current will allow earlier sampling, as mentioned by Eric, as will reducing the coil inductance. Basically, the quicker you can get rid of the flyback pulse, the earlier you can sample.
Of course, you might think that fitting a low value damping resistor would be the solution (i.e. overdamping) but this only diverts energy into heating the resistor, instead of stimulating the target.