Replies to Minipulse Plus

[WM6]

Software reading multiplier should be set at 10x to get correct results, cause sofware don't know how your probe is set.
With probe x10 and software reading multiplier x1 you cannot get correct results.

[Qiaozhi]

The coil is a hand wound magnet wire formed to a fiqure 8 to reduce chatter in my interference infested room. lol
cheers

Is the flyback voltage correct for a normal mono (not figure 8 ) coil?

[johnandles]

Is the flyback voltage correct for a normal mono (not figure coil?

Good Question, I will test and let you know.

[johnandles]

Good Question, I will test and let you know.

Untwisted the figure 8, but still the same flyback voltage so...
More investigating

[Qiaozhi]

Untwisted the figure 8, but still the same flyback voltage so...
More investigating

Does the detector actually work as it is?
If so, I suspect your scope is lying to you.

[WM6]

If so, I suspect your scope is lying to you.

Probably he should post scope settings photo here.

[johnandles]

Does the detector actually work as it is?
If so, I suspect your scope is lying to you.

Yes the detector works. not getting the distances as others reported.
is there a test for my scope?..(in case it is telling me porkies)?

[WM6]

is there a test for my scope?..(in case it is telling me porkies)?

Usually scopes has calibrating connection point at front control plate with standardized signal by shape and voltage.

You can check scope by external source of standardized signal (signal generator) too.

[johnandles]

Usually scopes has calibrating connection point at front control plate with standardized signal by shape and voltage.

You can check scope by external source of standardized signal (signal generator) too.

Thanks for your reply.
The scope has a connection for a square wave, 1khz, and 2v p-p. output test .
Just tried it,and reads correctly.
I will look into it Tomorrow...
Thanks

[Chet]

Low flyback voltage.??
coil 398 uh
1.1 ohms
scope shots with coil and without. (10nf cap)
[ATTACH]31183[/ATTACH] [ATTACH]31181[/ATTACH] [ATTACH]31182[/ATTACH]

johnandles, your scope is correct as indicated by the -12v charge waveform preceding the flyback waveform in the flyback.jpg. I believe you problem may be that the 398 uh coil is not being fully charged by the narrow 58 us drive pulse. Can you remove some of the turns to bring it down to 300 uh or do you have another coil that is close to 300 uh? Other choice would be to adjust the resistors on the 555 chip to produce a wider pulse perhaps 100 us would work.

[johnandles]

I will make a new coil and give it a try.
Cheers
John

[johnandles]

Ok, I made a new coil,300 uh,but still the same issue.
BUT...I did find something that's been causing a very noisy TP3, with a coil plugged in.
When I started my build I printed out both Rev B and Rev C build documents.
I must have got some of the printed sheets mixed up as I fitted C19 to my Rev B board..(as per Rev C document for rev C board.)
The C19 should not be fitted to the early board, as noted in the "B" build document.
This caused TP3 to show crazy patterns and noise. But dissapeared once the cap was removed.
So maybe other builders out there may have done the same.
I noticed JOOP's build picture shows C19 fitted to his Rev B board, (he was having noise issues at TP3 also....)
Hope that helps.
Cheers
John

[josewashere]

Have you tried another Q1 fet? also check the value of R1 and R3 Is the cable between your coil and the detector thick enough? Check the value of R12. What distance are you getting on a 20c coin (Aus)
I'm happy to check any voltage you are not sure about on mine for you.

Ok, I made a new coil,300 uh,but still the same issue.
BUT...I did find something that's been causing a very noisy TP3, with a coil plugged in.
When I started my build I printed out both Rev B and Rev C build documents.
I must have got some of the printed sheets mixed up as I fitted C19 to my Rev B board..(as per Rev C document for rev C board.)
The C19 should not be fitted to the early board, as noted in the "B" build document.
This caused TP3 to show crazy patterns and noise. But dissapeared once the cap was removed.
So maybe other builders out there may have done the same.
I noticed JOOP's build picture shows C19 fitted to his Rev B board, (he was having noise issues at TP3 also....)
Hope that helps.
Cheers
John

[johnandles]

Have you tried another Q1 fet? also check the value of R1 and R3 Is the cable between your coil and the detector thick enough? Check the value of R12. What distance are you getting on a 20c coin (Aus)
I'm happy to check any voltage you are not sure about on mine for you.

I have checked the resistors, all ok.
a 20c coin at about 9".
Haven't replaced Q1 yet.(but that's where I am heading, but need to order some)
Thanks for your offer.
More investigating to do.
Cheers

[Qiaozhi]

Ok, I made a new coil,300 uh,but still the same issue.
BUT...I did find something that's been causing a very noisy TP3, with a coil plugged in.
When I started my build I printed out both Rev B and Rev C build documents.
I must have got some of the printed sheets mixed up as I fitted C19 to my Rev B board..(as per Rev C document for rev C board.)
The C19 should not be fitted to the early board, as noted in the "B" build document.
This caused TP3 to show crazy patterns and noise. But dissapeared once the cap was removed.
So maybe other builders out there may have done the same.
I noticed JOOP's build picture shows C19 fitted to his Rev B board, (he was having noise issues at TP3 also....)
Hope that helps.
Cheers
John

On the REV-B board, C19 has its positive wire connected to -5V, and the negative wire connected to pin 1 of U10. In other words, it's connected across R37. This is (of course) incorrect, and the simple solution is to leave out C19. All this is mentioned in the REV-B Build Document. However, if you want to fit C19 correctly, then wire it between U10 pin1 (negative wire) and U10 pins 4/8 (positive wire).