Re: Help needed w/battery charger circuit

lsmartino spake thus:

David Nebenzahl ha escrito:

The problem is finding a battery charger for a cordless drill. I
inherited a Skil 12-volt drill and battery, but no charger. The only
hope of finding one seems to be getting a used one, which I haven't been
able to find.

I opened my friend's charger and drew the circuit, which I've attached a
link to. (PDF, and a big one, sorry; somehow a little bitty 35 KB JPG
made the file bloat up over a megabyte.)

Can someone comment on this? I've got all the values except for the one
resistor in series with the LED, which I can probably figure out (or
maybe just omit altogether, as it seems only to be an indicator lamp).

What's the function of the capacitor? (I believe it's a non-polarized
electrolytic in the original unit.)

Would this work if I constructed it?

The other problem is that the battery has 3 terminals instead of just 2.
Two are marked "+" and "-", but there's an unmarked middle terminal. But
the charger only had connections to the two terminals. What's the 3rd
terminal for? (Picture of bottom in the PDF.)

Oh, yeah, the PDF is here:
http://www.geocities.com/bonezphoto/misc/BatteryCharger.pdf

That charger seems horrendous to me. If for any reason you touch any of
the exposed battery terminals of the charger, without the battery in
place, while the charger connected to the AC, you will get instantly
shocked by 120 VAC. I can´t believe that such a charger, without any
interlock switches can be manufactured, and approved to be sold.

Look, save your horror and outrage, OK? The thing is mass-produced by a well-known reputable company, is UL, SA and who knows what else approved up the wazoo, so apparently the regulators think it's safe. The whole thing is safely encased in plastic, so there's hardly a chance someone's gonna get their fingers zapped by line voltage.

Or maybe you prefer the version of the world where everything is covered with soft foam rubber bumpers, with flashing lights, sirens and klaxons going off every time you attempt to plug something in?


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
.

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