December kit builds: DIY electronics calculator

[@UReasonIt]

That is a nice kit, and commentary as you soldered. I ordered one this past summer, and plan to make an RPN calculator. The STC15W is an 8051 core chip with a TTL serial ICP interface. The SDCC compiler supports it, so it's a relatively easy chip to work with.

[@LasloMildenberg]

I love your kitbuilds! Thanks and enjoy your beer.

[@snakezdewiggle6084]

Great video.😎 There is something cathartic about watching someone else do the soldering. Like when you have guests around and they wash the dishes. Tip No.7392 solder order. Smaller to Taller. Changing the battery is going to be a pain. Can you flip them to the other side of the pcb.. All the best for the silly season. Stay Safe.

[@GnuReligion]

Yes, the batteries may be an issue. The backlight on those LCD displays can be a big drain.

[@snakezdewiggle6084]

Yeah, you're right, like 100 mA IIRC. Maybe a "thumb wheel" type pot would be useful.

[@AnotherMaker]

That's a very cool kit. Just knowing about those button caps makes this video worth the price of admission. Thanks for sharing.

[@johncoops6897]

LOL what? Why else would the switches have that square shaft and ridges on the sides? Your computer keyboard is the same, with caps on the switches 😂 Clear 2-part caps have been available since the 1970s, and those tactile switches were designed to suit them.

[@AnotherMaker]

@johncoops6897 I have lots of the switches and lots of button tops, but I haven't come across the clear ones on AliExpress

[@GnuReligion]

Yeah, I haven't seen those labeled key caps before either. Want some. The ones I have are just round.

[@romancharak3675]

What a nicely documented kit. A good stocking stuffer for a teenager.

[@pileofstuff]

It's rare to see a kit with this level of instructions these days. Maybe not quite as detailed as the old Heathkit kits, but still nice to see.

[@pault6533]

This has a high quiescent current and eats CR2032s while not being used. I converted mine to lithium ion rechargeable with TP4056 micro USB port on the side with a hot glued hole to see the charge status. Now opening isn’t necessary anymore. Also, added a main power rocker switch on the back for longer life between charges.

[@pileofstuff]

That's a good mod. The power circuit in the calculator is an attempt to cut off the power until you trigger it with the on button, but it still leaks some current.

[@ivolol]

I've had an idea floating in the back of my mind to recreate the PCB for this, with a better microcontroller (or one that's more accessible to program in popular environments), and print different labels so you can do more functions. For instance converting between different orders of units, frequency and hertz, V=IR, being able to 'directly' enter unit orders (i.e, enter 3k, instead of 3000), etc.

[@Gossamer2]

I might have to order one too! Looks like a fun DIY project!

[@frankowalker4662]

I built a very similar kit a few years ago. It has a transparent case and the key inserts were on a seperate sheet of paper, but only one copy. (I screwed up the number 7 somehow). I found the resistor mode useful. But new batteries only last a month.

[@retireeelectronics2649]

That is cute

[@michaelwolak3098]

Hi built this kit and it works well although I believe there are two versions, and one version there is no power off so you have to remove the battery, the other problem is cutting out the numbers it’s a bit of a pain and I photocopied them so I had a spare in case of problems

[@erikburman530]

For me the problem is I end up swilling back more than one pint during my kit builds. The result is I've become very proficient at desoldering and repairing my mistakes.

[@pileofstuff]

Whatever it takes to practice a skill!

[@wardprocter2371]

Really nice kit (and successful build)! I still use standalone calculators both at work and in my workshop. I hate having to grab the phone and open an app when something I use so often is available right where I need it. I might have missed it but where was this kit from? Apologies- now that I actually read the dooobli-do down below, I see the source. 😊

[@tinygriffy]

it is probably relatively easy to build an adapter for the IC socket for a wroom or something similar.. *pling .. wireless keyboard for controlling OBS or such things :)

[@sparkyprojects]

For the led calc, i think that's Vi minus Vd, Vi being input volts, so if you had a 12v supply, and a 2.5v led, you would enter 9.5V Correct me if i'm wrong

[@jantepas7511]

I have had this kit. The backlight is very low. But nice kit.

[@pault6533]

You can adjust the backlight intensity by changing the value of the appropriate resistor. Alternatively, pick up the LCD board in “yellow” instead of reverse contrast.

[@johncoops6897]

You can also add a trimpot to adjust the LCD contrast, which allows you to optimise for your desired viewing angle. So the trimpot replaces R3 and R4. Note that the backlight will chew throught CR2032 batteries, so they probably added a high value backlight resistor R5 to help with that.

[@TheSonofruss]

That is a handy kit for a beginner that doesn’t know how to do electronics calculations

[@pault6533]

Anybody need keys, let me know. I made my own Excel sheet. If you have a good printer it will look nicer than the original printout.

[@DavidPlass]

I've been considering buying this kit, and then thought... nah, I can make this myself with all the crap I've got floating around..... Did I? No. Will I?A Also no.

[@lasersbee]

That's a pretty bad Design when you have to completely take the unit apart to change the batteries. Could have designed the Battery Holders on the rear of the PCB.

[@AlanEvans721]

Can I suggest you spray paint it electronics workbench pink to be more official?

[@pileofstuff]

There can be only one kink palculator.