Blind Squirrel PI.

[TH Jim]

Hi DanZ, I would like to know more about the coil housing you used in this photo ->

After a day with it out in the field I've built two more coils to try with it next. A 6" and a 9.5". Both using 24 SWG (.558mm) enamled copper wire. I'll try the suggested PVC coated/insulated wire for the next coil(s).[ATTACH]28548[/ATTACH]

Did you make those yourself or is it something originally used for another purpose that you have adapted to do this job. I like them

Cheers, Jim

[DanZ]

Hi DanZ, I would like to know more about the coil housing you used in this photo ->



Did you make those yourself or is it something originally used for another purpose that you have adapted to do this job. I like them

Cheers, Jim

Hi Jim. They are washing machine drum pulleys. Work great because they're made of some durable non-metallic (nylon?) material, easy to wind on, and many sizes you can use. I filled in the remaining space over the coil with RTV to make it smooth with the pulley edge and submersible. Painted over everything when done. Just be sure to remove any metal pieces, some may have a little drive shaft key/pin in the center.


in addition, if you want to shield it (i didn't) I guess you could run a strip of foil tape around the pulley first, creasing it inside, then wind the coil over it and fold it over after the wind (following standard shielding practice, gap, etc.).

[DanZ]

Hi DanZ

Excellent design.

Can you precisely explain what sort of controls you put on it?

Hi, I brought out and mounted almost all the adjustments, including the transmit pulse freq/width, receive delay/width, threshold coarse/fine, volume (power switch, earphone, coil jack). Being my first (and only,so far) PI detector build I wasn't sure which adjustments I would need (or want) to get at often.

[WM6]

This is how it works my
https://www.youtube.com/watch?v=0SFrksJmfzY

Nice design solutions reiv. I like it.

But sensitivity not really impressive? You need to almost touch coil for detecting small targets (as coins p.e.). Are you satisfied with such sensitivity?

Thanks for info on power supply possibility directly from 12V AA battery block without regulator. How long last such supply before need to change batteries or recharge it (only 2 hours as per original is not acceptable using AA block)? I definitely don't like 16V or more power supply battery-block.

200mA current draw is not low too. Is this happen at 109 pps or at higher pps rate? Thanks.

[reiv]

I have no longer this MD, pulse induction it`s not for me...soe it was my first and last PI. About sensitivity it wasn`t soe bad as You wrote, I can`t remember precise distance for coins (I do not built this unit for coins also), but it wasn`t so bad. I used 1300mAh 12V aku, and he was enough for all day searching.

[6666]

They are washing machine drum pulleys.

Thats very smart thanks

[DanZ]

Thats very smart thanks

I should be thanking you and Dooley for your Blind Squirrel modified circuit work because it works so well for me.

[6666]

reiv could you please tell me what was the LED meter that you used on your PI, thanks.

[reiv]

It is signal strenght meter, helps also to set up sensitivity at "edge of stability" (2leds flashing).

[6666]

Thanks , is the strength meter project on the net somewhere ?

[reiv]

It is just a simple voltmeter using LM3914, soe You don`t need any project just check datasheet

[6666]

Ok, thanks, similar to this ? looks easy to adapt.

[reiv]

Yes, in datasheet 3914 is simple explain everything U need to know about connections etc.