If you are anything like me you hate to throw anything away...and as devices die, you end up with an endless supply of 110 VAC to DC at some voltage/amp rating "wall warts".
A few weeks ago trout season started and I needed an aerator to keep the minnows alive longer. I ended up with a battery powered one and usually use it at home, so consuming D cell batteries seemed like a bad plan.
The blue tape and grey plastic pipe is my prototype device for providing the DC voltage the aerator required, and yes that is tinfoil on the ends.
So today I decided to iterate on my design and use some great new tools at my disposal. Steps involved:
1) Create a 3D model of a D cell battery shape.
2) 3d print the parts.
3) Assemble the battery eliminator.
4) Give the minnows oxygen :-)
Step 1: My Prototype and 3d Model Creation.
The aerator had a space for 2 batteries, but I just needed to connect the right voltage to the plus and minus terminals.
RIGHT VOLTAGE (and current): This is dependent on your wall wart and the device you are running. If you don't know how to confirm these critical aspects please ask a knowledgeable person.
I first made a crude prototype to just make sure that it was all going to work OK. A piece of PVC pipe, some masking tape, and tinfoil was all I needed (no soldering!).
After running the aerator a few weeks with the prototype I decided to use a great app for iPads called Morphi.
The last picture is a screen shot of the cylinder in edit mode. This software is amazing and doesn't require any CAD skills to quickly master. I am guessing anyone that can use the iPad can use this software.
For the pro user on a budget, you might want to check out www.onshape.com
I found the D cell battery dimensions online.
Once the model is completed and exported as an STL file, you are ready for 3d printing!
Step 2: 3d Print the Parts
I have an awesome printer, Robo 3D R1 and printed my parts in less than an hour.
If you don't have a 3d printer then you can use "3d Hub" www.3dhubs.com
With over 16,000 printers around the world, there is sure to be one near you.
Step 3: Assemble the Parts
I found a good positive and negative spring form that I cut in half. Did you know that battery compartments must not make contact when installed backwards? That is cleverly achieved by the shape of the plastic on each end and the shape of the contact.
I bent a loop on the end of the springs and and drilled a hole in the end of the 3d printed battery halves. Then I used some hot glue on the inside and outside of this hole to hold the spring form in place. I filed a slot on each side of the battery halves and hot glued the assembly together.
Then its just like installing a battery, you just need to provide a non pinching path where the wires leave the battery box.