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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 pi-supply.com 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 pi-supply.com 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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Triad-finishedAs promised, the second part of the build showing the finished project.

Transistor-tester.zip First of all the Cadsoft Eagle schematic and boards. The schematic is not my own but from Mats Engstrom. He posted the schematics on github, I only modified the board to be single sided. Well actually there are two single sided boards on top of each other so that make it semi double sided.

The small board was attached by 3 wires that were soldered on both PCB’s. I had two additional via’s planned on the PCB’s but instead of soldering wires I opted to use small screws of 1.2 mm width 4mm long. Mainly because I have a kit of various sizes lying around waiting for a project and it also looks nice.

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