Fantastic job, the calculator looks freaking amazing! I can't believe those key caps are hand printed, they look so professionally done! You've made such great progress I'm seriously excited about seeing the final product!

EDIT: I don't know if you've answered this previously, but will you be releasing the 3D model of the case to those that buy the final product? It'd be nice to have for those who want to add even more to the calculator. Like a massive slide case to protect the keys. Laughing
It is quite amazing to see how far you have progressed on this project. I've seen tens, maybe hundreds, of hardware calculator projects that just fade into oblivion. Way to stick with it and make something awesome Smile
A small update/stumbling block:

I began soldering the switches, LED's, and the backlight power toggle circuit last night.

The LED's are plenty bright when powered from the calculator's battery. I will check total power draw when I get them all soldered. The light from the LED shows through the keycaps, but not in a meaningful or useful way. It's just pretty.

The momentary-to-power-toggle circuit that I purchased from Adafruit does not seem to work. It turns on and off inconsistently, and only when touching the contacts on the circuit itself, and never whole using the keyswitch. I will try the wiring again tonight, and see if I missed anything (thank goodness I made a schematic of the PCB over a month ago, as I forgot how it was wired after all this time). In the mean time, I ordered a bistable flip-flop latch circuit from eBay that may do the trick as well, but with a slightly higher quiescent current.

This circuit is used to turn on and off the LED backlight with the use of a momentary switch. Ideally, the circuit is placed between the power source (calculator battery via testpoint), and the load (LED's), with a momentary switch (keyswitch) to toggle the flow of power, while using very little current when the load is not powered. Any ideas on how this can be accomplished?


Thank you everyone for the support so far. The end is close, I can taste it.

I have 4 sets to go out to people, and I think they have all been accounted for. If 5+ more of you want to have a kit, I can make another manufacturing run. Here are the 4 that have claimed a kit:

TheKnightsWhoSayNi (?)

Due to the amount of materials and time needed to make a kit, the price will be $80, (or really whatever you are willing to pay, I understand times are tough rn.) I know it's gone up from what I said earlier. It's a tough call I have to make.

If you are on this list and don't want to be, let me know, and of you are not on this list but would like to be, also let me know.
At the risk of asking the obvious, what's the point of increasing the size the calculator to add huge keys? More room to add other stuff?
If you are on this list and don't want to be, let me know, and of you are not on this list but would like to be, also let me know.
I am on the list and want to continue to be on the list. Wink
Yes I am more than happy to remain on the list - the price is fine with me, you are doing excellent work Smile.
I would like to remain on the list and the project is excellent. But $80 is a bit much. If anyone else wants to be on the list, I'd be happy to give up my spot. I can spend $80 but I'd also have to buy another calc so the price would be pretty high for a simple project. (I'll probably buy a used one from ebay with a bad case) I think I might pull the trigger, but I'd love to give my spot to someone who really wants it.
It would make your life easier if you reduced the size of the keyboard, in terms of taking an incomplete keyboard as a basis.I'd give 40 bucks for that.
What do you mean by reducing the size? It still has to have 50 keys (19mm square) and a screen, so it can't get much smaller. Starting with an existing keyboard and soldering that key matrix to the calc would probably not work either, as the matrix of a standard keyboard most likely does not have enough rows (6 on a standard keyboard, 7 needed for the calculator), nor would the layout make any sense.

Making this project less costly would be great, and any suggestions are welcome.


Sorry for the lack of update yesterday, there were a few minor hiccups. I did figure out the bistable flip-flop latch, so the backlight turns on and off correctly now. Turns out you have to solder the switch in order for the switch to work Razz
ArmengSan wrote:
It would make your life easier if you reduced the size of the keyboard, in terms of taking an incomplete keyboard as a basis.I'd give 40 bucks for that.

you realize the calculator price is well over 90 USD. he's simply taking all of that and making it way bigger. so the price should be well over 100 (if he wants profit anything lower than that is not profit).

Edit: Nevermind it's a kit. 40 - 60 USD will be well priced ... maybe 45$
The kit that I am selling does not include a calculator, nor does it include any switches (as the switches would be very personal to each user).

The kits include:
3D printed Case
Custom PCB
LCD ribbon extension cable
Laser-cut steel Plate
Pre-cut and tinned Wiring
Custom hand-printrd keycaps
3D printed Screen bezel
Associated 3D printed parts
Reset switch and power circuitry
LED's for backlighting
Screws for assembly
Printed detailed assembling instructions
3D models and CAD of all parts for further modifications.

The customer will need to provide:
A sacrificial TI-84 CE
51 MX-compatible mechanical switches (Cherry, Gateron, Hako, Zeal, etc.)
A soldering iron and solder
A Torx-T6, T5, and a Phillips screwdriver that fits the CE battery compartment.
Hot glue and electrical tape to secure things a bit better, as needed.

Hope this clears things up.
Thank you everyone for your feedback and suggestions.
I think I owe everyone a look at the expense sheet for this project. Here is a screenshot, and a link to a Google Sheet containing URL's.

~~~~~~~Link to Google Sheet~~~~~~~
In the pink box, it costs $81.11 for the parts to make each kit. This is why the price is at $80, I'm not making a profit. In the dark blue, I have spent over $600 ($1200 if you count the 3D printer) on this project, including the 4 kits to sell.

The most expensive part is the laser cut plate. The decision to go stainless steel was made on chat a while back. Perhaps aluminum would be cheaper, but making it out of plastic would probably be too flimsy.
The keycaps, PCB, obscure screen ribbon cable, and the backlight LED's and circuity are the other expensive components.

KnightsWhoSayNi has given his spot to MateoConLechuga, so the 4 lucky recipients are:
- Mateo
- Kerm
- tr1p1ea
- Millennial


And with that said, the first prototype is finally done!

With the bezel re-designed and holding the screen securely in place, and all parts assembled and working, the first copy of the project is done. Now, all that is left to do is make 4 more (I am keeping one for myself)! Here are some pics:

The final build looks amazing! Fantastic work, you should be very proud Smile.
Well done, that's beautiful! Looks even better with the backlight on! I don't really expect the battery to last too long with it on though, I might modify the case model to fit in a significantly larger battery. So long as I keep it a 3.7v Li-ion, nothing should blow up. Razz
I'm really impressed with how it turned out and I'm super excited to get my hands on the kit!
Wow, this is awesome! You did a great job prototyping and putting this together. The final result is really clean. I'd be interested in paying for plans which would contain assembly instructions, CAD files, and other documentation. Since there seemed to not be enough interest in a second round at this point, this is a nice compromise for those who have access to a makerspace and could reasonably build one themselves. The keycap printing method looked like it worked really well.
This looks realllly nice. I'm with TheLastMillennial, it would be great to get a substantially larger 3.7V battery (with the same connection pad layout?) so that this more solid calculator will also have a more solid battery life. Wink
@RascalJack I will probably upload the files to my website I'll post here when I upload them there.

@tr1p1ea Thank you, I am super excited!

@TheLastMillennial/KermMartian Wonderful idea with the longer battery life! There is plenty of empty space in the case on the right side to fit any flat lithium ion/polymer battery, such as from a phone or tablet. I have tested, and the calculator does not care if the third middle pin from the battery is connected, so you could wire any 3.7v cell that you want. The spare "Vin" and "G" pad on the backlight switching circuit would be the most convenient place to solder a second battery, in parallel with the first. I will have a demonstration in the instruction manual.

After talking with TheLastMillennial (who has tried to cram extra battery in a normal CE before), the third middle pin on the battery is required for the battery to charge. So, you can connect an extra battery cell in parallel with the + and - terminals, but the original battery must still be in place for charging to work properly.


I am currently printing the last case on the 3D printer, and will make the rest of the keys this week. I had accidentally ordered the "+" key with "e" and "M" as secondary legends, instead of "MEM" and ". The new legends are in the mail. We are on the final stretch. I'll be in contact with the first round of buyers soon to work out shipping details.
If you plan on doing a second round; I'd be interested Smile
Mateo.. you're in the first round Razz

KnightsWhoSayNi has given his spot to MateoConLechuga, so the 4 lucky recipients are:
- Mateo
- Kerm
- tr1p1ea
- Millennial
Oh cool Very Happy Um how do I pay/give you shipping address
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