I'll be going to OpenSauce this year and it's giving me motivation to do a bunch of projects I've been putting off. One of which is powering the TI-84 Plus with solar!

I did a proof of concept a while ago and the results were extremely promising! I started with 3 panels and even got it working on a single panel!

I wanted to improve on similar projects like Mateo's Ultimate Calculator by making the solar panel to look like it's designed to go with the calculator. I originally tried modeling a whole new face plate but that was way too complicated. Instead, I've modeled a module that will plug into the I/O and mini USB port just like the Orion talking module.



WIP model download. Be warned, the file is quite janky.

My circuit diagram is pretty simple. I just have a solar panel connected to a capacitor. Then, I plan to route the power through the mini USB port where I'll solder some wires from the USB port to the battery terminals. I'm unsure if passing power through the mini USB port is a good idea (should I use the I/O port instead?) but no one in SAX seemed to know if this would break something so it's the plan for now.

My other concern is that the extra power from the solar panels will try to charge any AAA batteries in the calc which would obviously be bad. Will I need to wire up a diode as well?


(click for full size)

I'm pretty excited to get this working. The module design is close to final, I just need the electronics connected!

Ohhh, that's why you were asking about putting 5V-6V through the USB port. Powering the USB port's VCC externally doesn't seem like a good idea, especially up to 1V over the USB spec, and you definitely shouldn't be driving either of the DBUS's two data lines with any appreciable current unless you plan on disconnecting them as data lines and just using them for power.

I think you've also put your capacitor in the wrong topology, since putting it inline like that would block DC from the PV cell. Presumably you meant it to be a bit of decoupling, by putting it across the positive and negative leads of the solar cell.

Thanks for your feedback!

Kerm, I was thinking of disconnecting the 5v pin from the calculator since, from what I can tell, the calculator never uses it. I could pass the current through that pin and the ground. There's no way I'd ever put current through the data pins.

I've updated my circuit diagram with Tari's recommendation. The capacitor is meant to smooth out any fluctuations when the panel can't see the sun. I found a 6.3v 1000uF capacitor which I think will work?