Comments on: Humankind's Endless Quest for a Substitute Plugpack

by: spodosaurus

Sat, 19 Jan 2008 23:40:57 +0000

How does one determine when a left over powerpack from one dead device can be used on another device whose plug pack has returned to the wild to join the feral plug packs? What are the rules with volts, amps, and watts to prevent 'bad things' happening? For instance, I have to ADSL modems. One is dead, but with a 10V,1A power pack. The other is alive, but needs a 7.5V,1A plug pack. A friend of mine wants to relieve me of my modem and plug pack, and I want to know if 'bad things' are going to happen with this compination? (such as fire, release of magic smoke from the working modem, etc)

by: Daniel Rutter

Thu, 06 Dec 2007 01:35:05 +0000

Power supply design is both sufficiently boring that it doesn't attract a whole lot of attention, and surprisingly difficult. Just making a plugpack replacement isn't that hard, but modern switchmode plugpacks are actually generally very good; there's no need to roll your own for mainstream applications these days. The electronics project magazines do still regularly come up with power supplies for various purposes, though. Here's a starting point.

by: joel

Thu, 06 Dec 2007 01:28:38 +0000

So how about posting a Dan-approved general plug pack design? I can't imagine a plug pack would be all that difficult to make and it's only slightly more dangerous than your average electronics projects (because you're playing with mains). But it would be nice to have the ability to make an any-voltage regulated plug pack that didn't leech power while it was off. Even changing the output voltage should only require substituting a few parts. How about it?

by: KnightRT

Wed, 05 Dec 2007 15:20:21 +0000

This is a clear case of, how the hell do you know so much about plugpacks? Very impressive and useful post.

by: peridot

Wed, 05 Dec 2007 11:53:53 +0000

Well, if I wanted to be devious, I could take a plugpack that delivers (say) 6V/1.5A and rig it up to the battery compartment. A bit mechanically awkward, as I don't want to permanently convert the camera, but something could probably be arranged. I assume the concern is that the DC input might be connected after the voltage regulator? (It must have one to deal with the varying battery voltage, I would think...)

I guess option B is to wire up a simple voltage regulator circuit for 4.3V and feed it with whatever plugpack.

by: MorePower

Wed, 05 Dec 2007 06:30:15 +0000

I suppose I should have mentioned that. I soldered the wires from a 4 D pack directly to the appropriate tabs in the battery bay itself.

by: Daniel Rutter

Wed, 05 Dec 2007 04:38:26 +0000

This is likely, but not certain; the DC input jack on a sophisticated device like a camera (as opposed to a simpler device like a radio) is not necessarily just connected in parallel with the battery bay.

If the batteries feed the camera's power supply differently from the DC input jack, then you can't just attach the same nominal voltage to either input and expect the same results.

by: MorePower

Wed, 05 Dec 2007 04:20:39 +0000

In the case of the Canon A95, 4 D cells in an external pack would probably be fine. The camera takes 4 AA cells, so 6V is not out of the normal range of operation.