Need a clock or timer ( for me to turn on drip irrigation ) ? You can salvage parts from an old microwave oven with minimal effort and make one. Since it is smaller and less functional than a microwave over I call it a NanoWave.
Now one thing I thought I had learned before writing an instructable is check what others have written first ( did you know that there are 13 instructables, all with the same idea, on how to reuse the clip on a 9 volt battery? ). So my idea here has already been discovered. But since it is almost done, and the most recent project was 5 years ago, I am going to finish it.
The other instructables are:
- Digital timer for any electrical appliance by marquoise https://www.instructables.com/id/Digital-timer-for-any-electrical-appliance/
- The Microwave digital timmer hack. by Koil_1 https://www.instructables.com/id/The-Microwave-digital-timmer-hack/
Step 1: Materials and Tools
- An old microwave oven.
- An extension cord
- Case - I made mine from wood, but you could use an olive oil can
- Soldering iron and hand tools.
Step 2: The UnBuild
You need a microwave with the control panel intact. Plug it in, set a duration, and see if it counts down. If it does you are probably ok. If it does not then you might take it apart anyway, perhaps free of the other junk it will work. If it does not there are still great parts in there, no way this instructable can fail ( except stay away from the high voltage capacitor ).
First take the oven apart, there are lots of instructables on this and a lot more parts than we will use.
- Taking Apart A Microwave by dog digger https://www.instructables.com/id/Taking-Apart-A-Microwave/
- Getting Useful Bits from a Microwave Oven #1 by Treknology https://www.instructables.com/id/Getting-Useful-Bits-from-a-Microwave-Oven-1/
You want to keep the control panel intact while you take the oven apart. You can cut any of the wires leading to it, but may are connected by plugs that can be removed by pulling ( sometimes a tab on the connector needs to be pushed/pulled/.... . After some work you should get the whole panel off. The photos show several control panels I have obtained.
Step 3: Find the Connections That Matter
There are a few connections that matter:
- AC Power – just what it says plugs into wall 120 volts. The power connection is 2 wires, you may trace them from the original oven, or identify them from the pictures I have posted.
- Door interlocks – these are connections/wires that usually go to micro switches to make sure the door is closed before powering up the oven. We short them, that is jumper them togethe,r so the panel thinks the door is closed. The door interlocks can be identified as the ones going to the door switch or the pictures I have posted.
- Connection to the Microwave power, this is a relay. Usually a small black box box.
The microwave power is switched through a relay on the timer board, this is a small ( often black ) box with leads that normally come out the top. It also has connections into the board which are not normally visible. We will use this if you want to switch output power. Again see the pictures. When not powered this relay is normally open.
Step 4: The Build
You may or may not find bits of wire and connectors from the UnBuild useful in the following.
Cut your extension cord in half, you use one end for the input to the oven, the other to the output. Connect it to the power input on the board. Now it is time for the “smoke test” Plug it in, keep clear of all the leads on the control panel board. The board should power up. The control should generally work. “Start” typically does not as the board thinks the door is open. If everything is alright continue, if you get smoke or sparks, you have a problem, probably the wrong connections, you may need a new control panel.
Find the "door closed" connections. These connections need to be shorted together to simulate the door closed condition. Test the panel again. Now start should work.
If you want to switch on an external circuit wire up to the relay as shown in the schematic and pictures. Test again.
If everything is good put the guy in a case. I made mine of wood and Masonite. I glued some wood blocks into the panel and used screws to fasten into the the case.
Step 5: Use
Use just like the microwave. Set the time. Set the timer. Set microwave time, the power plug will turn on instead of the oven. Thats it, pretty simple.
Make something with the other bits in the oven, maybe: Magnetic Lamp and Tool Holder - Using Microwave Salvage Parts by russ_hensel https://www.instructables.com/id/Magnetic-Lamp-and-Tool-Holder-Using-Microwave-Sa/