On 12/8/2012 12:01 PM, Woodman wrote:
On Friday, December 7, 2012 10:01:55 PM UTC-6, mike wrote:
On 12/7/2012 4:31 PM, Woodman wrote:

I ordered two new SCRs on FleaBay. After I ordered, I was thinking that it might be a good idea to mod this battery charger into a bench power supply. Any tips, ideas, comments, etc. on doing this?



Woody

Publish the desired features and specs.

The devil is in the details.

Not sure what features and specs would make a basic bench power supply, that could be also used for electroplating copper, gold, and silver. My electronics circuit knowledge sucks, but could probably mod charger if had a design.
I have an extra Harbor Freight #45005 car battery charger that has a center-tapped Transformer. On the 6/12 volt, and 2/6 amp settings my meter measured some nice stepping voltages including 8.5, 12, 14, 17.5, 24, 28.5. Not sure if present circuit board could be adapted or not because I don't yet understand it. Or if it should be bypassed completely and only the transformer, metal case, and amp meter be salvaged. Any tips, suggetions, etc. would be appreciated.


Woody

The most important part of the project is to decide the result you want.
People give me crap when I say that.
When you call the airline, the first
thing they want to know is your destination.
Then they figger out how to get you there.

I used to have a running argument with the EX.
"you never take me anywhere!"
"OK, dear, where would you like to go?"
"I don't know, you pick..."
"I pick here."

She couldn't decide what she wanted.
But it was definitely my fault.

No specification no project no EX.

But I digress.

If you can decide the voltage range and the range of the current limit
and what connectors you want to use and how you want it metered,
ripple/noise/regulation, what do you want to happen when you stuff voltage
on the output, like charging a battery,
and...and...and...
you can get some help on how to create that.

Be aware that most of what you read on the interned has fundamental
flaws. Power supply designs are no exception. There certainly
exist good designs, but average Joe won't be able to tell the
difference until it makes smoke, or blows up his iPAD.

You're gonna find that almost nothing in the typical battery charger
is useful in a general purpose benchtop power supply.
Even the transformer is unlikely to be able to sustain current anywhere
near the current number on the faceplate. And it's probably specifically
wound to have high leakage inductance to make it a better/safer battery
charger.

Don't even think about designing a power supply without an oscilloscope
to test it. Power supplies are well behaved...except when they aren't.
And how you connect the wires between the components matters.
There are subtleties that don't show up as components on the schematic.

A power supply is not a simple project. I've had to fix a bunch of 'em
for engineers who thought they were smart enough to design one.