In any calculator there is a black dot blob such as this :

enter image description here

After searching on what it is, I find that it is a Chip-on-board controller but i can't find what is the type of or how to buy or how to program it. can any one supporting me with any information about it?

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    \$\begingroup\$ This is not the kind of part that you could find retail. You even can't program it, as it isn't a programmable chip. What do you intend to do? \$\endgroup\$
    – mguima
    Commented Nov 7, 2017 at 18:43
  • 1
    \$\begingroup\$ @mguima I wanna make a calculator \$\endgroup\$ Commented Nov 7, 2017 at 21:12
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    \$\begingroup\$ If you want to make a single or small number of custom calculator(s), you can get an MCU, preferably with an on-board LCD controller, and program it. For example the Qama calculator uses a 32-bit processor. If you want to make 200,000 ordinary calculators talk to someone who knows about this kind of project. \$\endgroup\$ Commented Nov 8, 2017 at 2:21
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    \$\begingroup\$ Look, datasheet of a chip like these. This is not intended to be built for a hobbyst. \$\endgroup\$
    – mguima
    Commented Nov 8, 2017 at 17:09

3 Answers 3


@Ahmed, if you want make a calculator, of course is just for fun, right?

If you were NEEDing a calculator, you would buy a chinese one VERY cheap, and it would be better than anything you could build yourself.

But, as a hobby project, it can be really fun build one for yourself.

The starting point SHOULD NOT BE a commercial product. Forget about it. The chip for this calculator isnt available to be sold retail, and even if you can get some samples, you wouldn't be able to apply this chip to a circuit, because it requires expensive industrial machinery.

I think that the approach should be different.

An easier form would be to buy a complet kit, like this or this. If the links don't works, try search for KIT DIY CALCULATOR on Aliexpress or Banggood.

Even if you don't want to do it so easy, I think that kits like these are a good starting point to you decide what you want to do by yourself and what you'll buy for your project. You should think about the hardware and the software.

you could just use an Arduino, attaching a keyboard and a 16x2 display to it...

you could buy a simple keyboard to attach to Arduino (and there libraries to Arduino work with those keyboards), or could build your own with your own PCB and switches...

You could use a LCD display, or 7-segments led displays, and the hardware and software shall be able to use them.

You could chose a microcontroler and write its software yourself, and load it in the microcontroler, even you could need a chip programmer;you should learn a lot about software, because the calculator use numbers of many digits, sometimes more than the microcontrolers registers use.

you can use the PCB from a kit, you can build your PCB from an online project, or even, you can project and build your own PCB... or have your PCB project made in a factory...

I'll stop here, since you started only asking how to get the calculators chips. I fell that this question doesn't exactly address what you were needing, since the correct approach to build a calculator as hobby project is not try to reproduce or copy a commercial product. Good luck!

  • \$\begingroup\$ thanks for your answer, actually i want to build a commercial project. \$\endgroup\$ Commented Nov 9, 2017 at 7:52

The pcb looks like it used to have a more traditional square IC. Those pads can be used as a breakout or test contacts for the chip while installed.

The COBs are not meant for hobby work. If you can find out what chip it is you may be able to find (a clone of) it in a more manageable form factor.


This isn't really an answer, just some information.

You might be able to find info on it on the internet, either because its a super common chip that all calculators use, or because the specs for the exact calculator model youre using are online (but you would need to tell us what model it is), however you will never be able to tell for certain. That black blob is just some epoxy, with the real chip underneath.

This is an incredibly common technique, used in hundreds of thousands of different products. Because the actual chip is obscured, and there is no visible manufacturer or chip information, all you can do is guess about what it might be. The only way to fully identify the chip would be to remove the epoxy and decap the chip, and compare the silicon die inside it to some other chips until you found the right one. You need a pretty powerful microscope for this, some very strong acid, and lots of patience, so I would avoid that if I were you.

  • \$\begingroup\$ There wouldn't be any decapping, it's just a bare die under the epoxy. \$\endgroup\$ Commented Nov 7, 2017 at 16:53
  • \$\begingroup\$ I've already decapped the epoxy blob of a calculator's chip and there were just a bare silicon die. \$\endgroup\$
    – mguima
    Commented Nov 7, 2017 at 17:30
  • \$\begingroup\$ Thanks for your info. do you have any idea of where can I buy it ? \$\endgroup\$ Commented Nov 7, 2017 at 21:09
  • \$\begingroup\$ From the manufacturer, once you've managed to identify them. \$\endgroup\$
    – Finbarr
    Commented Nov 8, 2017 at 12:13
  • \$\begingroup\$ Also, once you buy it, you probably wont be able to use it because of it's size (unless you can find a bigger version) \$\endgroup\$
    – BeB00
    Commented Nov 8, 2017 at 12:30

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