Delta Pulse

[kt315]

I took the timing pix from the article of Carl...

[kt315]

hmmm... for Delta... with comparatively huge MAIN SAMPLING DELAY... that you ask is not so principally... if you do Hammerhead... with only 10 (minimum) us... and you want particularly repeat Eric Foster legendary 5us MAIN DELAY... it is really worth-while.

[akademiker]

stupid. really. open Carl's Moreland's HAMMERHEAD article and you will see where you do. look last #15 page. FIG 24 and 25.

i have already printed the whole article out and readed it twice before asking this question. Its just not clear when the sampling takes place, is it in FIG 26 15µS after the start of the ramp or is it 15µS after the end of the pulse? Its hard to tell, because there is no timescale.

[kt315]

stupid. really. open Carl's Moreland's HAMMERHEAD article and you will see where you do. look last #15 page. FIG 24 and 25.

[akademiker]

Need some help again.
This pic shows the output of LF357 at pin 6. I searched all across the board, but couldnt find an explanation of this signal. As far as I know, this shows the signal the coil recieves after turning off, right? The first ramp is the decay of the field, about 2µS after turn off it is at the minimum and then the circuit waits about 80µS till it takes a sample of the signal? I already changed the main frequency to about 900Hz and the delay time to be adjustable from 1,5µS to 65µS and the delay width to 1µS to 10µS, but I still get this long time before the ramp goes up again and i can take a sample. Is this long time in conjunction with the decay-speed and thereby the quality of the coil or is it set somewhere in the circuit. As I read on the internet, I need to take a sample after about 15µS to anything golden.
Btw, is it possible to take the sample on the "ramp" or before the "ramp" or just "ontop" of the ramp?
Sorry if my questions sound stupid, but I couldnt find relevant information on the net or on the board explaining this signal.
I use a 2,3Ohm 469µH 24cm coil.

[kt315]

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

[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/

[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.

[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

[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.

[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?

[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]

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

[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?

[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.