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Very cheap molded enclosures?

Hello Carl,

No, you can't, not even a Schottky. That would require dropping the uC clock too much to allow for a deep enough battery depletion. The usual tricks are to split up VCC and run 'naturally protected stuff' such as LED directly so the heavy current hitters are taken care of. The (hopefully low current) remainder gets the resistor and diode to GND treatment. This will deplete a battery when it's left in the wrong way but that's a small price compared to a fried unit. As long as nothing gets hot and the electronics can stomach the reverse that the diode allows. Fuses are usually a no-go because that's nowadays considered a field failure by the discerning consumer.

Regards, Joerg

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Joerg
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Hello Don,

It depends. The ads look nice but upon further inquiry things can get out of hand quickly when mods are required.

I always wondered where the naugas are grazing ;-)

Regards, Joerg

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Reply to
Joerg

Hello Rich,

Ah, I still learn something every day. So they are from Wisconsin....

Regards, Joerg

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Reply to
Joerg

I guess I should pause before typing, sigh :-). Of course, I meant "use a bridge rectifier" on the input so the device works no matter which way it's plugged in, when you have the supply voltage to spare.

Interesting. I'd pretty much guessed about the LED's, but I wasn't sure what you did for a uC or other ic's.

-- Regards, Carl Ijames carl.ijames at verizon.net

Reply to
Carl Ijames

Hello Carl,

That would be even worse, causing two diode drops.

It boils down to a detailed study of all the data sheets. With discretes you can sometimes get enough safety for the highest possible battery voltage and some of the chips might be for automotive and, to some extent, tolerant enough. In a car a battery reversal can easily happen although I doubt that the very 'modern' vehicles with all their processors would survive. Worst case you'd be wielding the fire extinguisher.

For many newer parts the data sheets have become skimpy and one may not be able to find out how much of a polarity reversed current will have damaging effects. That leaves only external protection.

One fact that is often overlooked is the temptation of consumers to plop NiMH or NiCd in there instead of alkaline AA cells. Those can pack an incredible punch and some are able to sink well over an amp into anything that gets in the way, causing undesired pyrotechnical effects.

Regards, Joerg

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Reply to
Joerg

I think you want the world, and you want it cheap!

NT

Reply to
meow2222

1A? NiCds can kick out 60A for short periods.

NT

Reply to
meow2222

1A? NiCds can kick out 60A for short periods. Ask the r/c modellers.

NT

Reply to
meow2222

Yes! I once had a flatmate that thought it would be funny to discharge one of my AA NiCds with a paperclip. Turned red hot and caused deep skin burn.

--

John Devereux
Reply to
John Devereux

Hello NT,

In this case it's not just me that wants the world. It's like "Can we pour this $500 machine into something that costs a pittance?". But guess what, sometimes we got it!

The rather pathetic thing is that most of those projects succeeded by reducing integration, replacing chips with discretes and so on.

Regards, Joerg

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Reply to
Joerg

Hello NT,

Yes, especially D cells. With some of them you could start a car. Cheap NiMH AA cells are a bit more wimpy but can still do quite a few amps.

Regards, Joerg

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Reply to
Joerg

Dear Roger,

How are these production-way's are called in the UK?

Can you link some companies who do that way of business?

THX in advance Hubert

Reply to
Hubert Ball

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