SURF PI 555 QUESTION

[daverave]

kt can i send you my address for my christmas metal detector book...im really looking forward to reading it this year

[kt315]

dave anyone has to buy me a good scanner for my christmas present =)
and voila this pulse induction technology deep seekers' book under your christmas fir there )))

[daverave]

a time to give direct link on good book -?

http://www.geotech1.com/forums/content.php?125-inside-the-metal-detector

ITMD = RTFM

kt can you buy this book for my christmas present ????

[daverave]

With a higher voltage the TX current raises faster and you reach the desired Amps in a shorter time.
With a longer TX time you can reach the same peak Amp, with a few u/s longer TX.
What counts is the Peak Amps just before switching OFF.

A shorter TX ON time allows for more pulses per second, PPS or repetition rate. More pulse response can be integrated for the same sweep speed, while maintaining the same reaction time.
More pulses integrated gives a better S/N, signal to noise ratio.

Higher TX peak current can give more depth, but only when several other factors are adjusted for it.
The most important factor for more depth is more coil diameter.
With more coil diameter it needs more peak coil current to be able to find the small targets.

i did some experimenting and decreased the tx pulse and increased the voltage say to around 16v i did notice some better depth proformance on low conductive small gold.

[kt315]

a time to give direct link on good book -?

http://www.geotech1.com/forums/content.php?125-inside-the-metal-detector

ITMD = RTFM

[Monolith]

ive ordered some of those ICL7662....i just wanted to increase coil voltage to get a bit better depth..but some people think higher voltage has no effect and someone said just increase tx on time instead so not sure which way to swing ????

With a higher voltage the TX current raises faster and you reach the desired Amps in a shorter time.
With a longer TX time you can reach the same peak Amp, with a few u/s longer TX.
What counts is the Peak Amps just before switching OFF.

A shorter TX ON time allows for more pulses per second, PPS or repetition rate. More pulse response can be integrated for the same sweep speed, while maintaining the same reaction time.
More pulses integrated gives a better S/N, signal to noise ratio.

Higher TX peak current can give more depth, but only when several other factors are adjusted for it.
The most important factor for more depth is more coil diameter.
With more coil diameter it needs more peak coil current to be able to find the small targets.

[daverave]

ive ordered some of those ICL7662....i just wanted to increase coil voltage to get a bit better depth..but some people think higher voltage has no effect and someone said just increase tx on time instead so not sure which way to swing ????

[chemelec]

i really like the hammerhead now ive got it working and also the vco is interesting...ive had to change different values of resistor to get the vco working but i may have to increase supply voltage to around 16.5 - 17v and hope the 555 does not go pop !!!! the ICL 7660 im going to replace with a different type with higher voltage rating.

The ICL7662 is good, up to 22 Volts.

[daverave]

i really like the hammerhead now ive got it working and also the vco is interesting...ive had to change different values of resistor to get the vco working but i may have to increase supply voltage to around 16.5 - 17v and hope the 555 does not go pop !!!! the ICL 7660 im going to replace with a different type with higher voltage rating.

[daverave]

been experimenting with the vco audio which i know very little about...when i scope the output of the vco chip the mark to space ratio changes when metal put near coil instead of frequency change...is this normal or have i done something wrong ????

[daverave]

ive got the hammer head working but with only the vco audio...the non vco does not seem to work for some reason...also i loose depth if i disconnect the auto tune function...ive got the vco running at around 300 hz as i do not like the click click audio...its a shame that the hammerhead was designed for only 12v supply...not sure if could be modified for 16v supply ???

[kt315]

yup

[kt315]

???

DESOLDER THE CAP & CONNECT THE LINK. what is NOT CLEAR SO I DRAW????

[daverave]

you want me to connect pins 4 & 5...and link out cap ???

[kt315]

try this. a pitch is/no?