EDDMicrowave
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Raspberry Pi Microwave + bar code Scanner

Wed Feb 10, 2016 8:52 pm

Hi! My engineering group and I are working on our senior capstone project which is a microwave with a bar code scanner and raspberry pi attachment that enters in how long a product needs to cook for once the bar code is scanned. Right now we have our microwave dissembled and the original circuit board has been removed. We are looking for a way to connect the touch-pad button matrix to our pi. We have considered removing the original touch pad connector from the original circuit board and placing it on the row of pins on our raspberry pi A+, but the connector won't budge from the original board. We are not sure that this method will work, however, so we don't want to rip the connector off the board. Also, we need to find a way to power our pi through the microwave but the power connectors don't appear compatible with the pi as of right now. We have never used a pi before and any advice would be appreciated. Here is a link to pictures of our microwave [https://drive.google.com/folderview?id= ... sp=sharing]

scotty101
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Re: Raspberry Pi Microwave + bar code Scanner

Thu Feb 11, 2016 9:24 am

Wow! You've set yourself a difficult challenge and a potentially dangerous one given the high voltages inside microwaves and the RF radiation risk.
I have no idea what a capstone project is or what level you are in your education but consider getting some professional guidance before taking on this task.

How to power the Pi
You could strip apart a 5V USB power supply and connect this directly to the mains feed that comes in to the microwave. A fuse on the mains side would be a good addition here too.

How to connect to the touch pad.
Personally I wouldn't. I'd use a small touch screen instead of the touchpad. That way you can display a virtual touchpad and additional information about the food stuff that the barcode scanner reads.

If you don't want to do that, you'll have to rip the connector off. Supply some photos of how it connects to the main PCB and maybe someone can give you some advice. Odds are that it is a row/column matrix that you'll need to connect to some GPIO pins and periodically scan the pins to tell whether the buttons have been pressed.
Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

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karrika
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Re: Raspberry Pi Microwave + bar code Scanner

Thu Feb 11, 2016 10:51 am

I would concentrate on the bar-code scanning with the Raspberry Pi and leave the microwave alone. Tampering with dangerous unknown electronics without schematics is not what you should teach your students.

You could get the same wow-effect with less danger by using a toaster oven. Basically you just need one on/off relay to cut the main power of the oven and temperature measurement. No need to tamper with the settings.

The problem with microwaves is that eddy currents gets induced to all metallic components. Including any wires and sensors you try to insert into the oven.

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GTR2Fan
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Re: Raspberry Pi Microwave + bar code Scanner

Thu Feb 11, 2016 11:00 am

It would be far safer (although only physically compatible with one make/model of microwave oven most likely) to attach an actuator mechanism onto the outside of the oven to press the appropriate buttons for you. You may also earn extra 'brownie points' for making it clear that this approach was taken to avoid accidentally frying anyone during the development process. ;)
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EDDMicrowave
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Re: Raspberry Pi Microwave + bar code Scanner

Tue Feb 16, 2016 8:27 pm

Hi everyone thanks for all the concern about our project. A little bit more background on the project we are currently part of a PLTW course called EDD where you pick a project and spend the school year developing it. Our group is four high school senior girls and we have been working on this project for five month and have just gotten to the construction element. We have decided to try and connect the old circuit board to the raspberry pi because the display screen is mounted to it which we weren't expecting. Any tips for this? Thanks! (Also we are not touching any of the dangerous elements of the microwave)

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Burngate
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Re: Raspberry Pi Microwave + bar code Scanner

Wed Feb 17, 2016 10:07 am

EDDMicrowave wrote:... (Also we are not touching any of the dangerous elements of the microwave)
Unlike ordinary electricity, which stays in the wires, microwaves will get out through quite small gaps.
I'm no expert regarding microwave ovens, but I know a few people who are. And my advice is talk to experts, before doing anything with a microwave oven.
Even taking the front off can leave you at risk of serious internal injury.

An interesting site: http://www.wikihow.com/Check-a-Microwave-for-Leaks

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GTR2Fan
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Re: Raspberry Pi Microwave + bar code Scanner

Wed Feb 17, 2016 10:52 am

Burngate wrote:And my advice is talk to experts, before doing anything with a microwave oven.
Agreed. I think the lack of help you're getting here is because of the extreme danger you're risking putting yourself and others in. Put it back together and work out a way of doing this externally. It's the only safe way.
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flyswatter12
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Re: Raspberry Pi Microwave + bar code Scanner

Tue Feb 23, 2016 11:36 pm

Cool project. As others have mentioned, it could be a bit hazardous, but that's no reason not to try it. Just understand the risks first, ask for help if you need it, and be safe.

1) I would definitely keep the original touch pad and timing device from the microwave.
Why? The microwave was designed to be programmed using the touch pad, and all the necessary functionality is already in the controller board. The only alternative would be to really reverse engineer the microwave's internals and do a full-control type of system using the raspberry pi. This would be much more difficult, expensive, time consuming, and duplicate so much that can already be done by the microwave's computer, so there's no need to bother with it.

I'd tap into the original touch pad, and determine if it's a Serial or a cross-matrix touch pad. This will require some electronics test equipment, probably an oscilloscope and logic analyzer, so you can see what's going on when you press each of the buttons. From the photo it looks like it's probably a serial communicating touch pad. Great, either one is fine, just figure it out and understand exactly how it works, and how you can copy the commands it sends using the PI.

Next, make a map of what each button press does. Does it send a serial command? does it activate the microwave? Something else? Gotta understand it all and map it out before you can override it's functionality with your own.

Once it's all mapped out, figure out a way for the Pi to send the commands instead of the touch pad. It could be a simple piggy-back set of wires soldered onto the original communication lines, so it could inject commands into the microwave's control board. Probably is... but your group's EE should be able to help you figure it out if they even halfway showed up to class.

Then, bench test it and use the PI and see if you can use it to set a timer and start the microwave. Or even just input some numbers. Once you get that working, the rest should come along fairly easily. Make a format for the bar-code that you can decode in the Pi, and use that to set the timer and start the microwave. For example, if the barcode data is "180HI" that might mean that you microwave this item for 180 seconds on HI power level. Easy to decode. IF you'd rather use the original UPC barcode, then you need a lookup table for the Pi to see what the cooking directions are for whatever item you scan, and you'd have to manually load all the items you like to cook into the database.

As far as powering the Pi, just get a 120VAC to 5VDC wall wort, and power it from the AC power cord where it enters the microwave. Solder it on, keep it safe, and don't shock anybody.

As others have already mentioned, I wouldn't mess with the high power bits of the microwave, or try to operate it with the covers off. Microwave radiation is invisible and can really do some damage. Don't want to cook your eyeballs or anything. Also the flyback transformer usually has thousands of volts on it. So don't touch anything in there, and replace the covers before you try it out.

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