Archive for the “Raspberry Pi” Category

After building and testing the Raspberry Pi Supply Switch I moved on to adding an lcd display and rotary encoder. I sort of forgot how to wire the Pi Supply switch to Raspberry Pi. After figuring it out all over again I decided to document it.

First of all, if you haven’t build a Power supply switch yet, here are detailed instruction and the Eagle files on how to do so on a single sided PCB.

Connecting the two goes like this:


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I2c-level-converterLevel-shifter-sideviewHooking up an I2C LCD display to a Raspberry Pi is pretty well documented. The only hard part is the level shifter. You need one in order to hookup the 3.3V GPIO pins of the Raspberry Pi to the 5V I2C pins of the LCD. This off course assumes that the I2C LCD is 5Volts, but they usually are.

I found a level shifter using two 2N7000 Mosfets. That’s great as they are really cheap and easy to get, so I decided to build it. I ordered 10 of Ebay for less then $2. I stuck to the 2.2K resistors but you can off course apply 10K resistors as in most level shifters. Another source, using BSS138 mosfets can be found here.

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pisupplyswitch-1Turning a Raspberry pi into a internet radio player is fun, but safely powering down requires (access to) a computer. The people of launched a successful kickstarter project and now have a pretty device available to switch a Raspberry Pi on and off. Where the off signal triggers a halt command on the Raspberry Pi so it shuts down properly. All of it is open source so buy a small one of or build a bigger one yourself and read on.

The schematic is shared and I ported it to Cadsoft Eagle for convenience. Instead of having two switches on the board I decided to have two pinheaders there only. I recon that in practice you want the on and of switches not per se near the power cables and I might build it all into a small case and then I definitely don’t need the switches on the board. The third switch, the hard off, I don’t need as it’s basically the same as unplugging the power cable.

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