Pimp My Microwave

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Mechanical keyboards are the entire rage this demonstrate day! People love the classy tactile sensation, and some scamper on mountainous lengths to customise them to their exact liking.

That begs the quiz: If we worship it that mighty, why dwell at appropriate computer keyboards?

Ought to you focus on about it, there are heaps of day to day enter devices in determined need of mech-ing up!

Shall we dispute… a microwave keypad??

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Yep you heard that first-payment!

Right here is the legend of how I added a RGB OLED hot-swap mechanical keypad to construct doubtlessly the most pimped-up microwave to your entire world!

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Click me for prime-res video with sound!


A 300 and sixty five days ago, I picked up a former microwave for £5 at a carboot sale. It became a “Proline Micro Chef ST44“:

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It appears to be like to be from early 2000s, and is moderately unremarkable in every manner. But it undoubtedly became cheap and it in actual fact works, so only enough for me!


That is, till practically exactly a 300 and sixty five days later. I pressed the same old buttons to warmth up my meal, but nothing took internet web page online.

After the preliminary disbelief, my thorough investigation by randomly prodding buttons published that the membrane keypad is seemingly damaged. At the foundation a pair of buttons tranquil worked, but rapidly the entire buttons stopped responding.

At this point I would possibly perhaps perhaps well even possess appropriate chucked it and tranquil bought my money’s price. But it undoubtedly gave the affect worship a raze appropriate because an inexpensive plastic keypad failed. Plus I also can keep a pair of pounds if I fastened it as a replace of shopping a brand fresh one.

So I took it apart and peep if there became anything I also can dwell.


After casting off the case, we are able to peep the important circuit board:

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  • Microcontroller at high-center

  • Buzzer at high-first-payment

  • Blue ribbon connector for keypad at center-left

  • Transformer and regulate relays attain the backside

  • Entire board is thru-hole, but I assume if it in actual fact works it in actual fact works!

Right here is the entrance aspect:

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The board is successfully marked, and or not it is interesting to watch it makes exercise of a Vacuum Fluorescent Display (VFD), which became already falling out of favour by the time this became made.

I also observed this board, and in actual fact the entirety inside, became designed by Daewoo, a Korean conglomerate making the entirety from vehicles to, successfully, this.

Anyway, encourage to the matter at hand. I believed I also can appropriate neat up the ribbon cable contacts and rep in contact with it a day. Excluding I didn’t take into story the contacts had been made of carbon(graphite?) as a replace of the same old metal, and I rubbed some first-payment off:

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So if it wasn’t damaged then, or not it is certainly damaged now. Expedient job!

Enter the Matrix (Scanning)

Restful, it wasn’t the dwell of the arena. The keypad practically absolutely makes exercise of Matrix Scanning to interface with the controller.

There would possibly perhaps be an intensive introduction of this matter on Sparkfun. But in quick, matrix scanning enables us to learn so much of inputs from limited selection of controller pins.

Shall we dispute, there are higher than 100 keys on our computer keyboard. If we merely join every key to an enter pin, the controller chip will must possess higher than 100 pins! This is able to perhaps well perhaps be fat, hard to route, and costly to develop.

As a replacement, with fair a limited cleverness within the firmware, we are able to put collectively the buttons in a grid of columns and rows, AKA a matrix, worship this:

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This fashion, by scanning a single row and column at a time, we are able to settle which key(s) are pressed. Needless to sigh there are plenty extra technicalities, so learn extra right here in expose for you.

Anyway, within the example above, as a replace of 4 4=16 pins, we easiest need 4 + 4=8 pins, a saving of half! And with our computer keyboard, we are able to easiest need round 20 pins as a replace of upper than 100!

Thus, we are able to peep that Matrix Scanning simplifies the pin count and develop complexity of enter devices.

Figuring Out the Matrix

Assist to our microwave keypad at hand. We can peep its ribbon cable comes in two parts, every with 5 pins:

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So if my assumptions are appropriate, it would possibly perhaps perhaps perhaps well perhaps be a 5×5 matrix with 25 buttons. Ought to you scroll the entire manner encourage up, it is doubtless you’ll perhaps well perhaps secure the keypad has 24 buttons, so it assessments out!

Now all people is conscious of there are 5 columns and 5 rows, or not it is far time to settle out which secret’s which.

To entire that, I desoldered the ribbon cable connector and modified it with a straight male header:

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As a side repeat, the microcontroller is a TMP47C412AN designed by Toshiba. It is a 4-bit processor with 4KB of ROM and 128 Bytes of RAM. It will possess to also in the present day drive Vacuum Fluorescent Tubes. So all in all, a in actual fact specialised chip for dwelling equipment. Very underpowered in contrast to Arduinos and STM32s. But tranquil, it gets the job done!

I connected some jumper wires:

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And labeled the rows and columns with 1-5 and A-E:

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I then effect the board encourage, powered on, and touched every pair of wires to watch which button it responds as.

It took a while, but at final I figured out the matrix internet web page online of the buttons I need:

1 NP_4 NP_1
2 NP_5 NP_2 NP_7
3 NP_6 NP_3 POWER NP_8

So all in all, 10 numpad keys and 4 regulate buttons. There are a bunch of utterly different buttons, but I didn’t worry since I put not exercise them anyway.

I hasty whipped up a straightforward schematic:

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With that, I laborious-wired some buttons on a perf board as a quick and dirty repair:

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It in actual fact works! As a minimal I could possess hot meals now! And it didn’t fee me a dime.

But because it is doubtless you’ll perhaps well perhaps peep, it is terribly messy with 10 wires coming out of the case, and I am obvious I also can dwell better.

Pimp It Up!

Spherical the same time, I became working on duckyPad, a 15-key mechanical macropad with OLED, hot-swap, RGB, and complicated enter automation with duckyScript:

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Genuinely feel free to verify up on the project page while you are alive to!

I called it a "Raze-It-All Macropad", to be able to are living as much as its name, it became easiest natural that I rep it working on my microwave too!

And if I pull this off, my lowly 20-300 and sixty five days-feeble 2d-hand damaged microwave will change into into the easiest one to your entire world with mechanical switches and RGB lighting fixtures! Now that’s what I call … a Korean Custom-made 😅.

On the opposite hand, it wasn’t as easy because it sounds. There are many challenges:

  • I must exercise the existing duckyPad as-is, so no redesigning.

  • I must serve it neat and orderly, so the fewer wires the easier.

  • It must be powered by the microwave itself too.

PMM Board

Lawful now, there are 10 wires coming out of the case and into my hand-made keypad, very messy.

Ideally, with duckyPad, I’d to find it irresistible to exercise easiest 3 wires: Vitality, Floor, and Recordsdata. With so few wires, they are able to even be inside a single cable, which can perhaps well perhaps be mighty extra neat and orderly.

On the opposite hand, the microwave controller tranquil expects 10 wires from the keypad matrix. So which manner I’d need an adapter of some sort. Let’s appropriate call it PMM board.

duckyPad would test with PMM board, which in flip talks to the microwave controller. Something worship this:

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No longer too contaminated! On the opposite hand, till now now we had been the exercise of exact switches with the keypad matrix. But with PMM board, we are able to must regulate the key matrix electronically to idiot the microwave into pondering we pressed buttons! How will we dwell it?

Blast From the Past

It came as a limited of a shock, but after some digging, it grew to change into out that I solved this exact grunt 3 years ago! Assist then, I became searching for to automate inputs of Nintendo Swap Joycons, and they also also former matrix scanning for his or her buttons.

And the solution? Analogue Switches! You’re going to be in a internet web page online to deem of them as regular switches, but as a replace of pushing them in conjunction with your fingers, they are controlled electronically.

The chip I former is ADG714 from Analog Devices. There are 8 switches in one chip, and they also’re controlled by the exercise of straightforward SPI protocol:

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I hasty designed the PMM board:

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It is a pretty simple board. A STM32F042F6P6 is former, and I broke out all of its pins on headers in case I need them.

Since there are 14 buttons that I must regulate, two ADG714s are wanted. With SPI, they are able to even be daisy-chained without problems.

You’re going to be in a internet web page online to peep within the schematic that the analogue switches are wired up in precisely the same manner as my shoddy hand-soldered keypad. Excluding now they are able to even be pressed electronically by the microcontroller.

I had the PCB made, and soldered on the entire parts:

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I did a preliminary finding out with continuity beeper, and it regarded as if it would possibly perhaps perhaps perhaps well perhaps work ravishing, but we’ll easiest know for obvious once it is effect in on the actual thing.

Serial-ous Talk about

Now the PMM board can regulate the button matrix, how also can merely tranquil duckyPad test with it?

With easiest 1 wire for recordsdata, I reckoned that a straightforward one-manner serial hyperlink needs to be higher than enough.

duckyPad would ship a straightforward serial message at 115200bps at any time when a secret’s pressed. The PMM board receives it, and if the layout is appropriate, it would possibly perhaps perhaps perhaps well perhaps momentarily shut the corresponding analog switch, simulating a button press to the microwave.

I added a high-secret UARTPRINT repeat to the duckyScript parser, and created a profile for my microwave keypad.

They keys on duckyPad is arranged as follows:

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Why So Unfavorable?

It’s all coming collectively! Which brings us to the final quiz: How are we going to energy it?

I believed it would possibly perhaps perhaps perhaps well perhaps be straightforward. There would possibly perhaps be already a microcontroller on the microwave circuit board, so appropriate tap its energy and job done! Appears, practically but not rather.

Analyzing the circuit board intimately, it appears to be just like the entire thing runs on negative voltages.

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We can peep it gets -26V from the transformer, steps it the total vogue down to -12V, on the opposite hand to -5V. The voltage regulator is a S7905PIC fastened-negative-voltage regulator, additional confirming this theory.

I’m not obvious why it is designed this kind, doubtlessly has one thing to entire with the AC transformer. Restful, it doesn’t basically matter that mighty, as or not it is appropriate from a obvious point of reference.

I tapped two energy wires from the circuit board to energy the PMM board, and in flip, duckyPad:

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To carve encourage confusion, I marked them 0V and -5V.

Typically, we would join 0V to GND, and a obvious voltage to VCC. But on this case, 0V is at all times at the higher doubtless. So all I wanted to entire is join -5V to GND, and 0V to VCC. The doubtless distinction is tranquil 5V, so the entirety works.

(Eagle eyed viewers would possibly perhaps perhaps well take into story I also covered the buzzer with a sticker. It became so loud!)

A Duckin’ Expedient Time!

I reinstalled the circuit board, crooked the entirety up and did a quick test, it in actual fact works!

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You’re going to be in a internet web page online to peep the 3 wires going from duckyPad debug header to PMM board, as successfully because the 10 wires going into the regulate board the put the blue ribbon cable former to be.

I connected the duckyPad to the microwave, chopped off the ends of an inexpensive USB cable, and former the 4 wires inside to join the entirety up through a vent at the backside.

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Voilà! It’s done! The first and (doubtlessly) easiest microwave to your entire universe with mechanical switches, OLED, and RGB lighting fixtures!

Have you ever ever skilled the crisp and clicky tactile and audible perfection of Gateron Greens while heating up some frozen junk food at 2am because you are too sluggish to cook dinner? Correctly, I possess, so there would possibly perhaps be that!

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Click me for prime-res video with sound!

I’d like one too!

Ought to you are drawn to duckyPad, it is doubtless you’ll perhaps well perhaps learn extra about it and rep one right here😅!

And in expose for you the entire kit, sadly it would possibly perhaps perhaps perhaps well perhaps be mighty extra concerned.

Each microwave possess utterly different keypad matrix layouts, so that you just are going to must settle them out, and develop and kind a PMM board your self. No longer a miniature feat, but at the very least the entire recordsdata is right here! Ought to you dwell scamper down this course, let me know while you are going to possess any questions!

Needless to sigh there are high voltages and doubtless of microwave radiation while you happen to build up it apart, so be careful!

Other Stuff

I’ve done a pair of utterly different fun initiatives through the years, feel free to verify them out:

Daytripper: Veil-my-dwelling windows Laser Tripwire: Saves the day while you slack off!

exixe: Miniture Nixie Tube driver module: Eradicate the necessity for vintage chips and multiplexing circuits.

From Aduino to STM32: A detailed tutorial to rep you started with STM32 building.

List of all my repos

Questions or Comments?

Please feel free to originate a controversy, request within the official duckyPad discord, DM me on discord dekuNukem#6998, or electronic mail dekuNukem@gmail.com for inquires.

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