TI-84 Plus - Hardwired External Power Supply

Iambian · New Member Joined: 31 Jul 2010 Posts: 90

Since what I'm doing with my calculator will eat too many batteries across what it's doing (it's a secret), I strapped my calculator down to a breadboard and hooked in a spare stripped cellphone charger to supply it with the juice that it needs for the fraction of the price. And so, I leave this with you:

EDIT: The tape probably wasn't necessary but I wanted it strapped in good. Also, this makes operating the calc a bit more difficult. Whatever works, I guess. The voltage source is probably 5V. Not sure. Most likely. It's a cellphone charger after all. Doesn't really matter to me. Just as long as the calc powers on and doesn't complain to me about low batteries. Which it did when I had a 5V regulator in the circuit (leftover from a previous project). That's what the capacitors were in for, but I guess they might help keep the calc going long enough to reach a place where it can shut down if the power cuts. I haven't tested that one. Should I?

EDIT2: Shrunk the image down further to be more friendly on smaller screens. And maybe bandwidth.

comicIDIOT · Posted: 20 Jan 2012 09:47:16 pm Post subject:

Haha, nice dialog on the calculator!
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-Alex

Sorunome · Posted: 21 Jan 2012 01:46:44 am Post subject:

Nice! Now you just have to build in that it's wireless Razz

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KermMartian · Posted: 21 Jan 2012 08:06:25 pm Post subject:

Do I also see at least one AAA acting as a shim underneath that calculator? Razz

I caution you against running it on unfiltered power from the adapter, and at 5V, but it's not the worst thing you could do to your calculator. Kudos for a respectable hack.
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Iambian · New Member Joined: 31 Jul 2010 Posts: 90

KermMartian · Posted: 22 Jan 2012 03:13:01 pm Post subject:

Iambian, it probably does filter it enough; I just wouldn't trust a very delicate $120 piece of equipment to a $5 charger. Smile

It sounds like it works fine to me, so it's probably nothing to worry about. Hooray for unintended ideas for sure, and I love to see this sort of a necessity-mother-of-invention hack in action.
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Iambian · New Member Joined: 31 Jul 2010 Posts: 90

I'm probably gonna go ahead and make the internal modifications, since the setup came unglued about 15 minutes ago, which caused data loss and a setback of about a day or two. Had I taped the calc down from the other end, this might've been avoided, but I suppose this hack needed to have been done anyway.

After I play a round or two of Touhou Soccer (it's easy to forget that they're even playing soccer), I'll see what parts and plans I can pull together. Mostly plans as I probably have all the parts I need stashed away somewhere in the house. I could probably use a new soldering iron, tho...

Aes_Sedia5 · Posted: 22 Jan 2012 10:15:46 pm Post subject:

Side note: I clicked on all of those, and almost froze my computer. haha.
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benryves · Posted: 23 Jan 2012 04:28:27 am Post subject:

As an aside, the reason it probably didn't work with the 5V regulator is that is that linear regulators have a certain drop-out voltage, which translates to requiring an input voltage somewhat higher than the output voltage. A typical 7805 will have a drop-out voltage of a couple of volts, meaning the input voltage should be higher than 7V for it to work.