Delta Pulse

[kt315]

When I turn it on, the red led turns on, the coil sends out pulses (When placing some metal inside the coil, the object starts to emit a sound)

norm

and the irf720 gets a little bit warm,

norm

but I get no sound or current at the Ameter. I tried all pots and the tuning button, but nothing worked.
When I touch Pin2 at the D9A 4066 with my finger (tried it accidentally) the speaker starts huming and when i touch Pin11 of the same or push tune, it stops again.

you use a strange way in my opinion. it is not an radio... but if this is working for you...

My coil is around 1,4mH and 4Ohm and I'm running it at 120Hz.

unnorm. DP can work with the coil, but norm is 350-500 uH. (MICRO-)
disconnect NE555 sound part according to attached schematic and try to get the ruffle sound via P5 pot - from nothing to rare clicks and further hight tone.

[akademiker]

Did it, same as before, no sound at turning on or adjusting pot P5 and now no sound when touching Pin2.
This means there is something wrong in the 555 part, right?
Shouldnt the sound start by itself, without touching with fingers? :S

[kt315]

Did it, same as before, no sound at turning on or adjusting pot P5 and now no sound when touching Pin2.
This means there is something wrong in the 555 part, right?
Shouldnt the sound start by itself, without touching with fingers? :S

no sound when touching Pin2 because you disabled the sound part from all. something wrong in the NE555, you are right. check pot P5 itself.

recorded sound of DP. some moments would be clearly heard:
1. to turn on.
2. to push RESET, it is approx. 3-5 sec.
3. to tune THRESHOLD

[kt315]

desolder T9 off, connect accordingly a schematic here. you must get A CLEAR tone. THAT IS SIMPLE CLASSIC GENERATOR ON 555.

let Qia or whom yet with perfect English to tell you how the generator works!

[akademiker]

did it, now 555 creates simple sound like a monostable multivibrator.

I also checked the coil with my scope, between the two ends.
Is it even detecting? The difference seems too small to me.

[porkluvr]

akademiker,


Please do not post your scope shots on that POPUP adds hosting site.

You can post pictures here directly using the attachments icon.

I hate popup adds and I think I'm probably not the only one.

[akademiker]

oh sorry, thought this board allows only 620x280 pics, but its only for jpeg.

I also saw a similiar problem on some pages before and tried the advise:

Nelson,

stay o-scope probe in R37-R41 point. you must see some slightly negative noised level. if you bring a metal over the coil coil you must see INCREASE voltage level in the point. it is normal working state of DP.

tried that advise, I get NO change, when I move something near the coil, I just get the following signal.
I guess its just the gap when smoothing voltage with capacitors, right?

[akademiker]

I cant believe it! I finally found the error
Thanks to the other posts, I located the error somewhere near Pin2 of D5, cuz there was first no signal and there was a microscopic (not really, just pretty small, ok... the pcb was very "homebrew") error, also near T3, cuz E- seemed to be wrong and now it finally detects metall! Thank you very much for your patience

[porkluvr]

I cant believe it! I finally found the error.

Outstanding! I had a rather lengthy reply ready but I was loathe to post it. Now I'm glad I took time to eat.

But just one thing. I thought maybe it was a typo when you mentioned your IRF720 getting warm but then you repeated "IRF720".

If you were to use IRF740 the FET would probably run cooler because of the low Rds. Just a thought.

[akademiker]

Outstanding! I had a rather lengthy reply ready but I was loathe to post it. Now I'm glad I took time to eat.

But just one thing. I thought maybe it was a typo when you mentioned your IRF720 getting warm but then you repeated "IRF720".

If you were to use IRF740 the FET would probably run cooler because of the low Rds. Just a thought.

Oh, my mistake, I used IRF740, but I got plenty of IRF720 which I use more often in other projects so I mixed up.
With my 17cm coil, which I shielded with tinfoil (left out a gap with the tinfoil and connected the shield to -12V), I can detect a Euro coin (2x2cm) only at about 5cm :/ at the highest sensitivity. Maybe the pulses arent strong enough (consumes only 100mA at highest TX Power) ?
Also the source of IRF720 is directly connected to the -12V, old pcb version, without R50/R51/C32, could that be the cause for the dramatic decrease?

[kt315]

I can detect a Euro coin (2x2cm) only at about 5cm :/ at the highest sensitivity.

I only recently answered Qiaozhi that DP is not sensitive to small target because having BIG MAIN DELAY.
decrease MAIN DELAY to 5-15 usec (MICRO-) and you will dramatically encrease the sens to coin. on the long MAIN DELAY Delta Pulse is REJECTING/ IGNORING out the small targets like - nails, COINS, pull tabs etc.

[kt315]

akademiker,


Please do not post your scope shots on that POPUP adds hosting site.

You can post pictures here directly using the attachments icon.

I hate popup adds and I think I'm probably not the only one.

if I note popup add I speedy push 'X' key of keyboard, that stops browser far action. use this way

[porkluvr]

if I note popup add I speedy push 'X' key of keyboard, that stops browser far action. use this way

I didn't know that, thanks, KT315! ("X")

Still, when I click a link in these forums, I don't appreciate getting directed to a website that invades me with a noisy animated pop-up and sex chat advertisement at the same time.

[akademiker]

I didn't know that, thanks, KT315! ("X")

Still, when I click a link in these forums, I don't appreciate getting directed to a website that invades me with a noisy animated pop-up and sex chat advertisement at the same time.

get adblock for firefox, no more advertisments at all!
https://addons.mozilla.org/de/firefox/addon/1865/

[kt315]

pardon, porkluvr! push ESCAPE, not X! mistaked...