Great news everyone! I've fixed the USB port and completed the project!

Second Battery Updates:
Not a whole lot here has changed, the main difference is I've used Kapton tape to isolate it from the PCB and I've covered the battery contacts in tape. I've also secured it to the PCB so it doesn't jiggle around at all.

Wireless Charging Updates:
I've basically redone everything on the inside and did it right this time. I received a wide variety of soldering iron tips which made soldering in such tight places much easier! Who knew that the right tools would make a job much better? Laughing

First, I de-soldered the wires from the USB port and cleaned up the connections. I made certain there were no shorts in the port then I plugged it into my computer. Voila! I've never been happier to see TI Connect CE bring up my calculator's contents! I immediately backed up all the files on the calculator and ran a USB self test which it passed with flying colors!

(As usual, click for full size)

I'm still unsure why the USB port didn't work even if unconnected wires were on it, but I'm just glad it's fixed now. I then soldered the wireless charging leads to the charging station contacts at the bottom of the calculator which I should have done in the first place! Finally, I wrapped everything up in Kapton tape and I closed up the calculator. Fortunately, it works even better than new! The wireless charger works, so does the second battery, and the USB port is fixed.

There is something a bit odd with the wireless charger. For some reason when I put it on my new charging pad it makes the pad emit noises like chirping or sometimes a tone. It's not very high pitched which is what confuses me. It doesn't make any noise at all when I put just my iPhone on it. My best guess is maybe the receiver inside the calculator is too far away since the charging pad didn't emit noise when I was testing the receiver outside the shell. The only negative effect I've noticed is the charging pad and the shell of the calculator are warm where the coils are. The temperatures aren't even close to alarming though.

Backlighting Keys Update:
I think I'm going to hold off on this one for now. It appears that I just can't find small LEDs out there that are bright enough without drawing a ton of amperage. Even if the batteries can handle the load, I'm not sure I'm comfortable with how much they heated up during my tests. That's not to say I'll never come back to this again, I'll just have to look deeper, or get a 3D Printer to create thinner keys (which is more likely to happen).

Unless there's something drastically wrong with with what I've done, I'm going to call this project complete. Would I recommend doing any of these mods yourself? I'd say no to double batteries due to the risk of something going drastically wrong. However, the wireless charging mod actually isn't dangerous if you do it the right way. All you need to do is cut away the shell to make room for it, secure it to the back shell, and solder the leads to the charging station contacts which hardly anyone here uses anyways. I may even do it to my own revision M CE. I had a lot of fun with this project, even if I got scared to death last post. I'm looking forward to trying more modifications in the future!

I have considered adding built in recharging into Casio Prizms (FX-CG10/20/50) but was not sure how to do it - the calculator has 4 removable AAA batteries and supposed to work on both alkaline and Ni-MH baateries (changable in the settings) and it has a mini usb port for data transfer with the calculator acting as slave device but does not charge batteries as far as I can see - what would be necessary steps and parts to make the Ni-MH batteries charge in the the calculator when it is connected to a usb power source via existing USB port on the calculator please?
I'd suggest creating a new topic amazonka, it's quite an interesting project!

I do forsee a lot of issues though
  • I highly discourage soldering anything directly to the USB port, it can cause data transfer to fail.
  • Even if soldering to the USB port works, you'll probably need to find a way to disconnect the calculator from USB power while charging the batteries.
  • Rechargeable battery chargers have a lot of bulky components inside. I don't know how much space is free inside the Prizm but you could easily run into clearance issues.
  • The batteries are probably hooked up all in series so you'll need to connect each battery to the charger separately and potentially find a way to disconnect each battery from each other while charging.
  • I doubt you'll be able to use the calculator while charging which is probably the whole point of this project.

I'm not sure it's worth the trouble to try and get AAA charging implemented. Perhaps you can find a Li-ion battery of the correct voltage and implement a small BMIC. I don't know where you'd connect the charger if not on the original USB port though.

As I've proven in this thread, I'm no hardware expert so don't let this shoot down your idea. Just be sure you're thinking of potential issues and be sure you can find a way around them! Good luck!
All good points, thank you. I will resurect a post where I first planned to have this as part of a slightly bigger project - and share your insights. Thanks again
All right, for those who wanted to try adding wireless charging to your calculator, I've made a tutorial! It's not difficult if you're familiar with soldering but I offered alternatives if you've never soldered or if you don't have certain equipment like a multi meter.
Nice job on the project and the video, TheLastMillennial! Those final clips of putting the calculator down on a charging pad and the charging LED lighting up are pretty impressive, and I don't have any major criticisms of how you did it (maybe a minor nit of passing the amount of current used for charging through magnet wire). Keep up the good work.
Thank you for this detailed tutorial - any idea why charging stations would no longer work with the mod please?
Thank you Kerm! I had quite a fun time with this project!

Amazonka: when I first tried to connect the wireless receiver I connected it to the USB port which caused major issues when I tried to use it for data communication. Although the charging contacts have no data communication abilities, I highly doubt that forcing current through the receiver is any good for it.

I never measured exactly how much current was going through the receiver that shouldn't have, so it may have not been very much. However, I decided to take precautions and disable charging stations than risk components breaking.
Although the charging contacts have no data communication abilities, I highly doubt that forcing current through the receiver is any good for it.
Just pop on a diode or two and you'll be fine. Smile
KermMartian wrote:
Although the charging contacts have no data communication abilities, I highly doubt that forcing current through the receiver is any good for it.
Just pop on a diode or two and you'll be fine. :)
Thank you both for your answers - so are diodes needed for sure please? And if so which ones shall I get please (considering the voltage drop may be an issue presumably)? I also conteplated bulding in the recever into the cover enabling wireless charging only while the cover is on the back but it appears the contacts on the cover will be an obstraction for putting the cover on the front ;-(
A few days ago, I took apart an old Bluetooth speaker (it's a Jellybox by OrigAudio) that didn't sound very good. When I took it apart I was surprised to see that the vast majority of it was empty and that the circuit board was only 6cm x 4cm! That gave me an idea, since one of my previous projects was getting a second battery on the inside of the calculator, I can use the original battery bay to fit the circuit board in!

Of course it became a larger project than I expected. When I tried to turn the calculator and the Bluetooth module on at the same time, I blew the fuse that was originally for making sure when there were two batteries that nothing would catch on fire. Since I don't have a second battery anymore there's no need for the fuse so I just took it out and bypassed the connections. Unfortunately, without the original battery in, the calculator won't charge because one of the battery terminals wasn't connected so the calculator couldn't tell if the battery was safe to charge. Therefor I had to take the calculator apart and solder that contact to the battery bay. This took forever because I had a tiny bit of solder in a crevice shorting two contacts and I couldn't clean it! Thankfully, due to Nik's pro tips, I was able to get it wiped off cleanly eventually!

Next I cut down the speaker's circuit board so the length and width was small enough to fit inside the battery bay. I de-soldered its battery contacts, the 3.5mm input jack, the on/off switch and mic in order to make the height short enough as well. I re-soldered the mic on so it was facing directly up rather than to the side so it was more space efficient. I have no idea what kind of board this is, I couldn't find it online anywhere (although I didn't look too hard).

I was originally going to just short the on/off switch so it was always on, but I decided to extend the switch's reach with wires then hot glued it where a charging station contact use to be. This means I can turn it on and off without opening the battery bay! Unfortunately, I didn't glue it very straight so it's difficult to get the switch in the off position. It's not that big of a deal so I've just left it this way for now.

Since I don't have a speaker small enough to fit inside the battery bay (yet), I have to leave the battery door open while I connect the original speaker. I hooked up the circuit board's battery contacts to the battery bay (since they conveniently both use 3.7v Li-ion batteries) and it powered on! I connected it to my phone via Bluetooth and successfully made a phone call to one of my friends! I can also play music (even if it is only mono rather than stereo) over Bluetooth or even a micro SD card! I saw on the board a port marked FM which may mean the board supports FM radio as well? I may look into hooking that up sometime!

In order to get this project fully complete, I just need two things. First, a speaker small enough to fit inside the calculator. Second, I need a diode so the speaker circuit board doesn't get damaged if I forget to turn it off while the calculator is charging. I'm not sure what diode I need. The board takes 4.2v max and about 240mAh max. While looking at Digikey I saw fields like Voltage - Forward (Vf) (Max) @ If, Current - Reverse Leakage @ Vr, and speed but I have no idea what those fields mean or what I should choose for them. I'd appreciate it if someone could help me out here!
I want to be able to make a phone call through my calculator!

that'd be cool

I'd love seeing people call their parents/comrades during school without getting their phones/watches taken away. But you can't play sound on a TI-84+ CE, only older calculators!
Made some progress today! Instead of going for a purpose built speaker, I took a cheap contact microphone, connected it to the shell of the calculator, and used that as my speaker! It works fairly well for phone calls so long as it's not too noisy in the room. I even managed to get it just underneath the wireless receiver so the calculator should still wirelessly charge!

(Click for full size)

I made the connection from the contact microphone to the Bluetooth speaker circuit board just some pins I could easily take off and replace with a larger, louder speaker if I wanted. Then I closed it all up and tried it out. It works pretty well! I was able to have a whole coherent conversation with my friend over it! Thankfully the mic isn't impacted by the battery bay cover and my friend informed me that the sound quality was actually good on his end. I still haven't tried charging the calculator because I still need some help figuring out which diode I need, but overall I'm pretty happy with how this has worked out! Here's what it looks like in the battery bay:

(Click for full size)
OMG I'd love to make a program that could interact with that speaker/mic so that you could toggle the volume/enable speaker mode.
Me too, unfortunately there's nothing I can control on the calculator that would allow me to control the board. There is one unintended feature I notices, for some reason the battery door bulges in one spot. When I press down on the bulge it actually activates the play/pause button so that's convenient! Laughing

During HCWP last night I discussed with geekboy101 about what diode I would need. As it turns out, I don't actually need one because it wouldn't stop any potential damage if the calculator was charging. Unfortunately, there's no way to know for sure if any issues could arise if I left the bluetooth circuit board connected while I charged the calculator so I just need to be sure I disconnect the circuit before charging my CE.

I guess that means this project is done! I'll let you guys know if there's any updates about this!
I just published a video showcasing this project! I cover the build process, play some music, and even answered a phone call!
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