The time relay is used to automatically limit the operating time of the load. It can, in particular, prevent the occurrence of a potentially dangerous situation in the event that the load is forgotten to be switched off.
Instructions
Step 1
Take a faulty microwave oven with an electronic control device. Allow it to stand for at least two weeks, disconnected from the mains, so that it is guaranteed that it has time to completely discharge the high-voltage capacitors in the magnetron power circuit.
Step 2
Remove the front panel from the oven together with the electronic time switch located on it. Note that the large transformer that powers the magnetron is not the only one in the oven. There is also a second, small one, from which the timer works.
Step 3
Disconnect all connectors from the board. Find a place on it to connect the oven cover sensor. Close the corresponding contacts to simulate the closed state of the lid.
Step 4
Try applying power to the primary winding of a small transformer on the board. Make sure that the indication appears and that the timer reacts to button presses and counts down.
Step 5
Without touching the parts of the primary circuit of the timer power supply, using a multimeter operating in ohmmeter mode, check which of the three relays on the board closes at the beginning of the exposure, remains closed throughout its entire length, and then opens. Use it in the next step to switch the load. The load can be powered, at your choice, from the mains or from an external source. Its current consumption should not exceed 10 A (with a margin, since the relay is designed for 16).
Step 6
Disconnect the power from the board, and then complete the structure in a fireproof insulating housing with a fuse and a socket. Select full power before starting the shutter speed, otherwise the load will periodically turn on and off.
Step 7
Take the rest of the furnace parts, including the housing, high-voltage transformer, capacitor and rectifier and magnetron to a workshop. Use the fan and backlight at your own discretion. Remember that the latter can be designed for a supply voltage of 110 V. In this case, they must be powered through an autotransformer.
