Pauldy's House of Geek

I recently became a father and found myself in a delima.  Tons of baby gadgets!  The only problem with this is these devices require batteries and lots of them.  This diaper disposal unit requires 4D batteres and they have no external power supply.  So I did what any other geek would do, I set out to add an external power supply.  It wasn’t as straight forward as you might think so I thought I would put up this little post to help anyone else out there looking to do the same thing.

First youare going to need a couple of things I chose to get a mountable power receptical.  I found one at Altex Electronics.  They had a Philmore No. 247 2.1mmx5.5mm with a 1/2 mount.  Perfect for me as I happen to have a 1/2inch drill bit.

Next I needed a power supply capable of 6V, 4Ds at 1.5V each.  I found a Philmore power supply with the 6V rating so I picked it up as well.  I then got some wire wrap wire to use for my conductor.  the reason I chose this is I knew the load for this thing wasn’t high enough to require much more.

Quickly after disassembling the device I noticed the following.  There where two leads coming off the batteries.  One off the 4th battery and another of the 3rd.  Immediately I thought oh, ttl logic circuit being driven off 4.5V and the motor would be running off the full 6V.

I was stuck however as I don’t have any more of the 7805s from my EE classes.  Played around looking for a zener diode that might do the trick and after figuring out the one I had was busted I decided to poke around while the unit was on batteries.

One big thing I noticed was the battery at the 3rd position was hooked up directly to a resistor feeding back on itself causing a slow drain even when the unit is off.  This is when the conspiracy theories and four letter words flew.  After regaining myself I decided the had to be a way to get around all this and go straight off wall power.

I checked the components and decided to bridge the 6v and 4.5v connections.  The device sputtered a bit and started up.  I waved my hand above it and viola it opened right up.  This also removed the slow drain the the number 3 cell.  I then went to town hooking the unit up so it would run off the wall wart or batteries should we ever need it to.

First I cut the green wire coming from the number 3 battery to the motion sensor board.  Then I removed the common ground from the sensor board and wired it to the inactive outside of the receptacle.  Then I took the active lien from the receptacle and wired it to the ground on the on/off switch.  There is a ground here already connected to the sensor board.  this means when the wall wart is connected there is no path to ground from the batteries and when the wall wart is removed the battery ground is connected.

I then shorted the two incoming lines for the switch.  I wired the tip from the receptacle o the bridged leads on the switch and tested it out.  with the wall wart in I turned the unit on and waved my hand over the sensor.  The device opened right up.  I removed the wall wart and waved my hand.  the device opened again.  I then replaced the wall wart and removed the batteries.  A wave of the hand and the unit opened right up.

Feeling confident everything was working as expected I tested the unit off an on for a few hours checkin the temp of the various components as I went.  Everything seemed to function perfectly and I’m at a loss for why they designed the unit the way they did other than to make it difficult to use anything but batteries with the unit.

In the end I have a diaper pail that doesn’t eat batteries for lunch and seems to be functioning perfectly.

Here are some pictures after I started the reassembly process.