In this Blog entry we will introduce a LM555 restart module for Raspberry PI. During our research we found several solutions and from those we selected this one. This does not mean that this is the best / most elegant / simplest solution. On the images you can see the implementation with extra parts, of course you can / should leave out.
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Who worked with Raspberry PI knows how painful it could be a power outage which can ruin the content of the SD card. We can easily solve this which cheap UPS modules. What happens if the UPS runs out of juice and our unit it stopped? In case our unit is stopped and the power brick does not supply any power we are good, as if the power comes back the Raspberry will be started just like it was pulled out from the plug. When we use UPS it is unlikely that we use all energy from it as then we would be in the same position as without it. In case we shut down our microcomputer but it still receives power from its power supply then when the power is back it will not start.
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On the official forums – thread you can read that if you shorten Pins 5-6 it will generate a signal which restart the device and it will boot up. Based on our information leaving the Pin 5-6 connected for a longer period does not cause any damage to the unit but we wanted to avoid it anyhow just to be sure. In our solution a relay is used to connect the pins and terminated after 5 seconds which is more then enough for the signal.
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On the images below you can see the diagram for the LM555 restart module for Raspberry PI module.
 If needed this circuit can be implemented in a very small area which makes it possible to use many different projects. The circuit stable and with replacing the resistors or modifying the capacitor value the timing can be adjusted for the project needs.
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