Baracuda Build (silverdog kit Rev2)

[6666]

My pcb Rev2

[Michaelo]

It also has the TIP127 (IRF9640) but everything else appears fine....
Now to check my parts...

Pretty sure I've got the right values now, just one update to the schematic (should be MPSA13, is MPSA42)...
Thanks guys...

[Koala]

Juts doing a preliminary check and it has a TIP127 but we use the IRF9640... makes you wonder if there are more differences...
Think that's an older version as the board I have has the correct MOSFET marked on it...

Will do some googling and see if I can find some more board, you never know...

This was discussed a few years ago. From memory the IRF9640 needed more volts and lost the ability to discriminate (or was it not so good)but was slightly deeper.

[raygdunn]

The 7660 has a 220uF between two of its pins, but the datasheet specifies 10uF. It might be worth changing that as well.
The 7660 on Impulse's board seems to be ok temperature-wise.

Yes I noticed the 10uF in the specification as well and wondered... Presumably that makes the 7660 slow to initialise.

I've added the extra 220uF on the 78L05 output. I found some space near the edge of the board. I'll swap in the 10uF mentioned above as well.

Frustratingly the new 7660 gets as hot as the old one (my last), when using 11.8V, from the regulated desk top supply. It's fine at 9V. I think I'll start with the easy option and wait until I've got a good 40106 in there. (Parts delivery due) I'm thinking, if the present 40106 is damaged, that might be pulling more current.. If that fails, it's either start cutting the bottom of board strip and monitor the current, or just replace the 79L05 again. I have double checked the 7660 is actually a 7660S, so should be good to 12V (extreme limit 13V). My intention is to power with 3 x 3.7V cells, so expecting 11.8V as a maximum.

Unlike Impulse it's not my first detector, so not quite the same sense of urgency to get something working. The delays should be all good practice: use of 'scope, hacking the board, understanding more about the circuit. ☺ It's what most of us do, I think. Get something working then find ways to improve it☺

Ray

[Old cart]

My pcb Rev2

Can you post higher resolution version of this? Maybe each side as a separate image, but the same size image for both sides.

If if no one has a layout with both sides superimposed I wil have my son give it a go with photoshop. This wil give an x-ray like view and make editing and analysis easier.

[Michaelo]

Ray, I haven't had issues with heat since the first time I turned my build on. I was powering it with 14.8 volts (4 * 3.7 18650 Lithium Ion) but since, I change to 11.1 volts (3 * 3.7), everything cooled down to just warm and not very warm either... I didn't even realise the 7660S had a 12 volt limit...

I've never used a voltage regulator without the obligatory output cap (most often a 10uF tantalum), but almost any cap of at least 10uF will do... strangely enough the +5 is very clean without it but the -5 is a bit noisy and would probably benefit from one...

If the pulse is 100uS or less and a duty cycle or 600 or more, and the voltage is 11.1, and the coil is more than 2 ohms... it should not heat up... I thought I read the power was about 100mW... I do some calculations and check...

I kinda fix things and loose interest... but I do want one or two metal detectors for the summer... I intend walking quite a bit... just have to decide which part of Ireland I want to visit

BTW, the TGSL looks real nice have you build one? (it's my next project )
Mike

@6666, if you mean the one I posted above, I haven't got the board layout done yet... once I'm happy the components are correct I'll make a start...
If on the other hand you mean existing PCB's, that's the issue... they are all different albeit slightly... I think I have everything sorted out now...

[6666]

Can you post higher resolution version of this? Maybe each side as a separate image, but the same size image for both sides.

If if no one has a layout with both sides superimposed I wil have my son give it a go with photoshop. This wil give an x-ray like view and make editing and analysis easier.

Later today @ 600 dpi.

[DOOLEY]

hello michaelo,

erm,
be carful going to Ireland metal detecting...............

unless rules have changed recently the only place you can detect in Ireland legally is the beach. ( and i'm not toooooo sure about that even !! )


permissions and licences are required to detect inland,

best check it out before taking detector !!

[Qiaozhi]

Frustratingly the new 7660 gets as hot as the old one (my last), when using 11.8V, from the regulated desk top supply. It's fine at 9V.

Does the 7660 still get hot if the 40106 IC is removed?

[Paul B]

This is my PCB that I got from Silverdog earlier this year
Mine is also sensitive to movement,
I can not use it on land, to much noise when I move it

I use it on the beach but it makes noise at the end of the swing and when I twist it
Apart from that it is good on the beach
One dollar coin @ 11 inches
Wife’s thin gold ring @ 6 inches

[Qiaozhi]

This is my PCB that I got from Silverdog earlier this year
Mine is also sensitive to movement,
I can not use it on land, to much noise when I move it

I use it on the beach but it makes noise at the end of the swing and when I twist it
Apart from that it is good on the beach
One dollar coin @ 11 inches
Wife’s thin gold ring @ 6 inches

Sounds like the Earth field elimination is not working.

[Polymer]

@old cart, 6666, Paul B

Here a superpostion of Paul B's jpgs of the bara board. Hope it's x-rayey enough ...
Made the bottom traces green so as not to mix them up with the top ones.

[Michaelo]

@Paul B... the image is perfect... now I have something solid to work with... thanks for posting...

@polymer... ?

[Polymer]

My pcb Rev2

Just looked at my pcb Rev2, it's different ... the holes and traces for the MPF 102 and resistors are missing ...

The plot thickens ... drum rolllllll.

[Koala]

Just looked at my pcb Rev2, it's different ... the holes and traces for the MPF 102 and resistors are missing ...

The plot thickens ... drum rolllllll.

[ATTACH]35721[/ATTACH]

666 is an early board. The 102 was connected to a switch that was never connected on the original detector. A few people's detector would not fire up until it was taken out. Been dropped from builds ever since with no problems until now. All info on it is in the original long thread