Multi Calculator Kit

[revwillie]

I've been slowly working on an enclosure with that Hammond case I linked to earlier.

To make the multicalc fit, a lot of plastic material has to be removed from the case. The real challenge is getting the switches, keys and display to an optimal height for the type of overlay membrane you use. I might be able to buy another case now and use the first as a measurement guide such that I could possibly remove less plastic from the front face.

Also, to keep the PCB secure inside the case, I ground notches into the pcb that you can see in the pictures. I used a rotary tool (aka dremel) and took things slow and careful so as not to damage the circuits in the PCB. About 1/8" of PCB material had to be ground off the end by the USB port as well.

I obviously had to move the battery holder around which is clear in the photos. I was pretty happy to fit everything inside including the battery holder. I filed out a hole to allow access to the USB port. For now, my overlay solution is quite crude. I print an overlay on paper, trim it with scissors and lay it under a piece of clear packaging scrap secured with electrical tape along the edges. placement of the overlay requires a feeling through the paper for the key tops below. I think the clear plastic I chose is too stiff because the '9' key gets accidentally pressed often and I believe that multiple keys are being pressed at times causing the calculator to reset.

I tried blacking out the clear plastic over the LED display using a black permanent marker. The effect can be seen in the last two pictures. It's kind of cool.

So for the time being, I have something I'm not afraid to drop into my briefcase. I can stick with the HP-55 for a while until I try another overlay solution. Tony suggested printable magnetic vinyl sheets and I think I'll try to buy some.

Pictures so far