Building a dmmy cell?

[webley445]

Hope this is the right place to ask. Any suggestions for building a dummy cell? Need one in AA and D.
In the recent past I modded some 4AA closet lights [sold as the Tap Light] for use with LED's. I would just run a piece of wire from one terminal to another to bypass the 4th cell, but this can't be done in the light I am currently playing with.

 

[PaulW]

There's the old trick of wraping aluminum foil around a used cell. But that seems sloppy. I recall someone saying to buy aluminum stock of the right diameter, cut it to size, and wrap in tape. Now that's neat enough. But being frugal, I would like to avoid having to buy a long rod. I look forward to hearing about other alternatives.

Paul

 

[Unicorn]

How about getting a wood dowell, drilling a hole through the center, and then using a cheaper aluminum or maye even a brass welding rod?

 

[Rebus]

I use the wood dowell and wrap it
with aluminum foil and tape. Usually
I use a strip of foil 3/8" wide and
triple layer it on the ends to make
it more durable. Be sure to cut the
dowel to the length of the positive
nipple not the battery case.

-Rebus

 

[X-CalBR8]

Before I was able to find dummy AAs to buy, I made some by drilling a hole down the middle of a wooden dowel and then running a threaded rod down the middle of it. To keep the dowel in place, you can put a nut on either end. It also works to put a machine screw threw it and cut it down to the perfect length with a Dremel tool.

I still have not found a place to buy dummy D cells so they pretty much have to be of the homemade variety. To build a dummy D cell, all you need to do is get the right size PVC pipe and then put 2 end caps on it and drill a hole down the center of it. Then just put in a machine screw or threaded rod cut to the perfect length. This method will make for a dummy D cell that looks very near professional if done properly. In my own particular case, it made for a dummy D cell that was within less than 1mm difference in diameter of that of an actual D cell so it should work in just about anything.

I've posted all of this info in the past, and in a little more detail, in some older threads from last year. Just do a search for "dummy" and you should be able to pull up all kinds of useful information on the subject. Hope this info helps. Have fun! /ubbthreads/images/graemlins/smile.gif

 

[PaulW]

Thanks X-CalBR8. I like the machine screw in a dowel method. That's easy, and I can cheat by using a carved wooden block instead of a dowel. That way, everything needed is already here -- no cost! /ubbthreads/images/graemlins/grin.gif

Paul

 

[MR Bulk]

Would the dummy need to be the same diameter along its entire length? Otherwise use a couple of wood/plastic/stiff-material discs (maybe even thick cardboard in a pinch, one front & one back) threaded onto a long machine screw or whatever. You can picture the necessary format: I--I

 

[Doug Owen]

Years ago I solved the problem with a long screw wrapped in electrical tape. As I recall, it was a flat head brass wood screw (not that that matters all that much) that I filed the tip off since I couldn't find a machine screw long enough handy.

As Charlie suggests two wraps of tape, one near each end, built the diameter up until it fit.

Doug Owen

 

[Steelwolf]

Not necessary to have the same diameter along the entire length of the body.

I have used a nut and bolt wrapped in insulation tape for AA size.

 

[whiskypapa3]

I usually make these up by the dozen out of wood or polyethylene.

Rip a square length a couple feet long (a little bigger than 3/8in for AAs and 1/2in for 123s) and reset the blade to cut a 3/32 slot down the middle of opposite sides. Slice them off like baloney to just short of the cell length and wrap bare wire around the ends through the slots. Not the prettyist thing but they are inside of the light anyway. The one with the resistor goes into a 3-123 adapter for using 2-123s and a 1W LS..

 

[webley445]

I was thinking along those lines! But I thought of a wooden dowel witha screw in each end. I could wrap wire under the head of each screw and have it set in the "groove" that runs the length. Figured it was a fast easier alternative for those who can't or don't want to solder any connections.
Also figured of using a small washer at each end for better connection. Good idea, then taking a lesson from others a bit of tape wrapped around to prevent rattle and offer a bit more protection [plus I like to play with tape] and its done. Think I'll be giving this a try reallt soon.

 

[reviewum]

Wow, I really like the idea of having the resistors in the dummy battery! I'm just new at all this so I make a bunch of mistakes... so instead of having to take everything appart because I put in the wrong resistor, I can just create a bunch of different dummy cells with different resistors to swap around!

wooohooo... more stuff to solder!!!

 

[whiskypapa3]

I don't even bother to solder them until I am happy with the fresh battery drive current. I have a good stock of 1, 2, 3.3 and 10 ohm 1/2W resistors. I can parallel and series together to adjust the current then just spot solder the ends to keep them from falling off..

 

[milkyspit]

Haven't done this (yet!), but what about cutting an appropriate length from the appropriate diameter of PVC pipe, filling it with something (even smaller diameter PVC pipe!), and running a flathead bolt down the middle? Perhaps even with washers over the ends a la Mr. Bulk's method.

 

[Empath]

You could buy one of the AA to C to D plastic adaptors. Fill the AA or C with aluminum foil and put it into the D.