Another P.I. link

hello xavier , dont have an inductance meter , so used an online calculator ,
wanted somewhere between 350uH and 400uH ,

wanted a good compromise between a "fast coil" and sensitivity so aimed for that inductance.

and setled for 25 turns of 0.6mm (about 22-24s.w.g) pvc covered (0.3mm of pvc) bundle wound around a 30cm (12") former ,
which acording to the online calculator i think was around 370uH ,

must say though , allthough 30cm (12") dia coil gets good distance , and is still quite sensitve to small items , pin pointing objects is a bit tricky , i'll do it better next time on next project , poss stick to 10" or even 8"





Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,3797.msg190705.html#msg190705

hello 6666 ,

u5a is 100% correct , it is a voltage folower , it's there to follow the voltage of c15 without loading it.

once the other bits are removed around the TL071 and the 1k to top rail added , then its as i have done it ,

all i can say is that it works ,

poss only other thing that i thought of doing with this design was to have a switch on the control panel going to
a duplicate r4 thats preset at a different delay ,

if you look at my previous post of my decay curves , poss set one sample point at the begining and one at the end ,
then by using the switch could make detector either more sensitive to FE or NON-FE simply by flicking the switch.

note: threshold will reqire adjustment after delay altered.

pps : threshold is two pots linked in series , a 10k for coarce and a 1K for fine , think i mentioned this.

happy building.

Posted on: August 11, 2011, 09:37:52 AM

---

cheers xavier ,

a meter would take alot of guess work out of it ,

had considered buying one , quite expensive  arn't they , did see a fellow on a forum with one built into a multi meter ,

would certanly have a go at building one,

thank you.

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,3797.msg190711.html#msg190711

cheers xavier ,

schematic will be fine , i dont req lay file , dont use that program , and i still build on varioboard / stripboard
straight from a schematic ,

think i'm still in the dark ages.

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,3797.msg190742.html#msg190742

hello xavier ,

looks like i'll have to start and learn how to program a pic chip looking at that schematic ,

ive never experimented or done anything with pic's ,

i shy away from them , old dog , new tricks and all that.

Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,3797.msg190778.html#msg190778

When I remove remove c12 , r11 ,c13 what happens to pin 3
does it go direct to ground ?

looking at the 4066 its looks a bit of a waste why not use a fet ?



Linkback:

You are not allowed to view links.
Please Register or Login

http://www.thunting.com/smf/index.php/topic,3797.msg190802.html#msg190802