I learned of the PX-15C on hackaday, and ordered one as soon as they were back in stock. I am a fan of HP RPN calculators and of electronics kits, and found this to be a super easy, fun build. In addition to being a fun project, the calculator is useful too!
Oct. 22, 2021
Best DIY HP calculator emulator kit (PX-41C variant)
For the last 5 years, I've been trying solder-your-own calculator kits. The easiest ones are usually basic algebraic calcs with limited functions. But in this case, I ordered the HP-41 variant and was very impressed. I've never owned a true HP41 but I knew how powerful they are. This kit combines the function catalog and keystroke programmability of the HP41 with an extraordinarily well designed through-hole PCB. I had the soldering done in under two hours with only one mishap caused by my impatience when I bent a lead on one of the tactile keys. The component spacing and clear labeling printed front-side made soldering child's play. The kit worked correctly as soon as I inserted a new battery. If you have the enclosure and overlay, finished product looks very nice and can be pocketed without fear of damaging anything. If not, there is still a very attractive PCB with printed key labels and rubber feet so it will rest on your desk without wobbling. The backlit display is a real delight. So, you don't have to sacrifice power for ease of assembly. You could teach a middle-school or high-schooler to solder with this kit and then teach them the power of RPN on a classic device with a rich history and readily available programs found on the internet.
I got the assembled version and it works very nicely. It is a bit smaller than the original (I have an HP 12 and can readily compare). The software is rock solid and I have not had any issues with it. I have not tried programming the calculator, however, which I suspect would be a tougher test.
I had a friend print the 3D case based on the STL files provided, and -alas- the case does not fit. I tried dremeling off some of the excess material to get it to fit, but was not successful.
For someone who likes calculators, a definite good find here.
Response from HobbyStone | Sept. 29, 2021
There are 2 different displays. One has a black metal bezel and the other doesn't.
As such there are two different cases.
For display with bezel: https://www.thingiverse.com/thing:4969303 For display without bezel: https://www.thingiverse.com/thing:4936677
The printed 3D case will vary depending on the printer used and the filament type and brand. The source files are includes so that you can adjust them to match you needs.
I've wanted an HP-16C for years but never been able to afford one. The other versions seem to pop up on auction sites regularly at fairly reasonable prices but not so the programmer's version. As soon as I saw this, I ordered it. Delivery from the USA to UK took about a week, much quicker than I expected. I built the calculator in less than an hour and it worked as soon as I switched it on. I managed to have the original HP manual printed using an online service which cost me £8.53 (UK prices) including postage. This was much less than I could buy a used manual from an auction site. Now I have the manual, I can try to learn RPN and put the calculator to some serious use. I asked a few questions to "HobbyStone" before placing my order and they were answered very quickly, something I really appreciate. I'm absolutely thrilled to finally own something that I've lusted after for years.