PI-1 build

[raygdunn]

Did you build it exactly as the book says or did you change something ?

Hi 6666,
(This doesn't really warrant a new thread but avoids poluting a Barracuda one.)

Mostly the build (about 12 months ago now) was as in the emailed final schema. (So quite different from version one book schema!) I reduced the pulse width to match a low resistance coil and I probably played with the audio to reduce the volume a bit for what seems to be a sensitive headset. So no real changes.

Current was I think adjusted down to 100ma with battery a little under 12V (3 cell LiPo as I had it to hand) . I think a blew a chip at some point, when using a full 12V (bench supply) and found that the chip was actually rated for about 6V. Maybe there are chip variants. I wouldn't have expected rating variations back then.

The coil is very low inductance (now I have a meter) 149uF, 0.7ohms, 300pF. Resistance is probably approximate. I don't trust accuracy of either of my meters at that low resistance.

It uses loosely tied, thick insulated, 12V multicore wire... Nothing fancy like screening. The figures look wrong I think. Capacitance should more like 100pF.. I do experience marginal ground effects, which are distinguishable from true object contacts. If shielding reduces sensitivity, I'm all for omiting it☺

Threshold was marginal at 9V and the unit felt like it ran better with the higher voltage.

Does your query mean you have had trouble with the build?

Ray

[6666]

Hi thanks for reply, I was just interested in your build, for example did the circuit work straight from the book or did you have to alter anything from original
but I think your reply above covered all the bases.

[bernte_one]

Hello Ray, can you post the schematic here or can you send it by E-Mail?
I have the book too, but nothing heared from a new schematic.
I am very frustrated with the pi Projects from the book, only PI4 works from start.

[raygdunn]

Hi Bernte_one,

Can I refer you to this post http://www.geotech1.com/forums/showt...325#post201325

As it is copyright you need to contact Qiaozhi.

Ray

[bernte_one]

i would really love if someone who build one of the itmd Projects could upload a Video to YouTube
that we can get an Impression how it works

i build pi4 and made i Video, hope that others can do it same way

[geoscash1]

So what your saying is the other ones in the book don't work either???

I was thinking I was going to give PI - 1 a try but if it doesn't work then no point. You mentioned you have an updated PI-1 schematic, was that from George?
What were the differences between the update and whats in the book (my book is in pieces although I still have all the pages...lol), then maybe we can make the corrections on our own to be able to build it. Or never mind, I'll just pm George and see if he can just email me the updated version.

[6666]

So what your saying is the other ones in the book don't work either???

I was thinking I was going to give PI - 1 a try but if it doesn't work then no point. You mentioned you have an updated PI-1 schematic, was that from George?
What were the differences between the update and whats in the book (my book is in pieces although I still have all the pages...lol), then maybe we can make the corrections on our own to be able to build it. Or never mind, I'll just pm George and see if he can just email me the updated version.

http://www.geotech1.com/forums/showt...-PI-1-oddities

[geoscash1]

Hey thanks 6666,

I hadnt seen that thread before, much appreciated. I also got a message back from George, apparently the only issue with the original schematic is on the 74HC221 with a couple of the pins mislabled so it looks like its good to work with. will be starting a layout today with some vero board.

[raygdunn]

So what your saying is the other ones in the book don't work either???

I was thinking I was going to give PI - 1 a try but if it doesn't work then no point. You mentioned you have an updated PI-1 schematic, was that from George?
What were the differences between the update and whats in the book (my book is in pieces although I still have all the pages...lol), then maybe we can make the corrections on our own to be able to build it. Or never mind, I'll just pm George and see if he can just email me the updated version.

PI-1: Works well. I've clocked up about 40 hours using it. The schema has two pins of the 74HC221 IC4a wrongly marked on right hand side.
For 5 read 13. For 12 read 4. However I can't vouch for the PCB, as I put it on Veroboard.

PI-5: This is the one that needs the updated schema from Q. I've breadboarded and worked OK. Low on sensitivity compared with the PI-1, but I didn't go beyond initial testing. Time I dug it out again. As I need to make a pointer.

I hope that helps.

Ray

[6666]

Hi Ray
because the PI-1 has no EF cancel , do you get a beep at the end of each sweep ?

[bernte_one]

hello ray

if you want to build a pinpointer use pi-4 Project
right size

i dig out the pi-1 and will see what i can do
cant imagnine that i am to stupid to get this working

can you say what depth you reach with pi-1
so i can imagine the performance

[geoscash1]

Hi Ray
because the PI-1 has no EF cancel , do you get a beep at the end of each sweep ?

Is that something that could be fixed by adding another 74hc221 for a second sample?

[6666]

Is that something that could be fixed by adding another 74hc221 for a second sample?

By adding the second sample you are building a surf PI.

[geoscash1]

By adding the second sample you are building a surf PI.

So what would be the suggested fix (beep at end of each swing) if this were to be an issue with this particular project. Just asking since I have seen something mentioned elsewhere about the same type of thing but I do not know what or how to go about fixing it.

[Qiaozhi]

So what would be the suggested fix (beep at end of each swing) if this were to be an issue with this particular project. Just asking since I have seen something mentioned elsewhere about the same type of thing but I do not know what or how to go about fixing it.

You could also change the transmitter from unipolar to bipolar, and then you don't need an EF sample.