Baracuda Build (silverdog kit Rev2)

[Koala]

Noticed that if you have the machine right arts its edge of stability that moving your hand over the board but not touching it affects the threshold.

Guessing in the field it would alter as you swing unless its in a shielded case.

[kt315]

In a detector with 1500mA cells
---
have you nicad one in your house?

[ODM]

The graph kt315 linked shows a presumably 600mA AA cell discharged at 220mA which is about 0.3C. In that graph, the cell voltage starts from 1.4 and slips relatively linearly down until it starts to flat out, 40 minutes after start. In a detector with 1500mA cells and 150mA consumption, the discharge is 0.1C and cell voltage is slightly higher under load.

After charging the cell voltage will be higher than a "stored full" cell voltage is. If you hold a voltmeter to a cell during charge and after releasing the charger, you'll see it maintain charge peak voltage for a good while before it recovers. Most wall wart 4-cell chargers run trickle charge and don't peak as high as RC battery fast-chargers will, so using RC toy packs and RC chargers will show it even more pronounced.

Overvoltage damage in ICs is usually fast and permanent, it can happen either instantly or gradually degrade spec, particularly in opamps.

This is something to consider when doing engineering, instead of moving goalposts.

[Koala]

1.2V under even the slightest load

[kt315]

really nicad gives only 1,2. have you nicad one in your house?

[ODM]

Depending on speed of discharge the battery terminal voltage will vary. Discharging at 0.1C has lower terminal voltage compared to low discharge rate, such as 0.01C, and discharge rate varies. Depending on battery quality and temperature you have different recovery rates, with rechargeables it is generally an order of magnitude faster than primary cells.

Either way, you have a higher voltage than 1.2V per nicd cell before it flats out during discharge. Especially after charging without much recovery time. CV/CC 0.1C limited charge is slightly better than fast charging where cell voltage can be up to 1.6V before recovery.

If your old school teacher told you 1.4V is closer to 1.2V than 1.5V, I'm not sure what to say? If you expect 8 nicads to be 9.6V when they can be 11.2V to 12V, a 10V-rated charge pump is still out of its spec. It may survive, sure, but the maker doesn't guarantee it will.

[kt315]

Fully charged nicd is 1.5V though it flats on 1.2V for majority of discharge. Peak voltage still matters so full spec 7660s are required.

so good old school time eah? looking at this pic

http://www.electrodynam.com/rc/totm/images/nicd-dis.gif

[ODM]

Fully charged nicd is 1.5V though it flats on 1.2V for majority of discharge. Peak voltage still matters so full spec 7660s are required.

[Koala]

8 pcs nickel cadmium cells give you 8 x 1,2 - 9,6 volts. bara is from a time there was yet not modern
lithium ion batteries. all pi's of the time were projected under that power way - 8 NICAD.

at pic you see

[ATTACH]35736[/ATTACH]

It is worth while pointing out 7660 are not all created equal. If you read the original thread a few people got caught out with a 10V version that did not last.

[kt315]

The schema just says ICL7660, which I read as the original 10V version. They seem to be a mixture of 10V and 12V. The ICL7660S is definitely 12V (max.13V) which mean's one is pushing it with a fully charged 12V battery.

Ray

8 pcs nickel cadmium cells give you 8 x 1,2 - 9,6 volts. bara is from a time there was yet not modern
lithium ion batteries. all pi's of the time were projected under that power way - 8 NICAD.

at pic you see

[raygdunn]

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...

The schema just says ICL7660, which I read as the original 10V version. They seem to be a mixture of 10V and 12V. The ICL7660S is definitely 12V (max.13V) which mean's one is pushing it with a fully charged 12V battery.

Ray

[raygdunn]

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

Hi Paul

Yes acceleration and deceleration. Apologies if you have already tried this...

Have you definitely eliminated my problem of the pair of wires between the board and the coax. being the wrong way round? Cable has to be earth to earth (Battery minus in the PCB case). That got rid of most of my swing noise. (For ease of dismantling, I have a slightly loose plus/socket into the electronics box still giving me some residual noise on a very windy day).

If you have a coil with some screening, that also has to be the right way round. I'm experiencing some ground effect, so I'm hoping I have the spider coil the wrong way round still.

Ray

[Polymer]

@ 6666

Great! High res is always better.

I have made the two versions of the rev2 board as xray in high contrast.
Thought that might be better for printing and checking, although I find the lower contrast ones easier on the eyes when on screen.

[Polymer]

@ Koala & Old cart (about different Rev 2 boards)

Thanks! I'm seeing some light at the end of the tunnel...
I always thought different boards have incremental revision numbers.

[6666]

My pcb in high res for what its worth.