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To connect a PIC16F877A to my computer using a serial link, I needed a MAX232 level converter to convert between RS-232 and TTL signal levels. This post describes the schematic diagram and the board. The schematic diagram and the board layout are included in Eagle format.
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The flight computer I am developing for my next rocket uses an atmospheric pressure sensor to calculate the flight altitude. I chose to use a Motorola MPX4100 sensor, since it is readily available through Conrad.be (MPXA4100A6U, article number 150110-89; 25,55€, expect 5 weeks for delivery). It outputs a voltage proportional to the pressure; 0,3 V at 20 kPa and 4,9 V at 105 kPa.

The MPX4100A sensor is an SMD part (SOP case), so I needed a breakout board to be able to breadboard it. Below are the circuit diagram and the PCB layout in Eagle format. The breakout board brings out the MPX’s 8 pins onto two pin headers at either edge of the board. Even though only 3 pins are relevant and connected inside of the chip, the breakout board connects all eight pins. The schematic includes the necessary components for decoupling the power supply, and for output filtering as according to Motorola’s application note AN1646.
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I have recently started using Eagle to make my electronics projects, and it works so great that I finally got round to making a few boards I need very often. One of them was a power supply that plugs into the power rails of the bread board I use for prototyping my circuit. This way I have a regulated source of 5V and/or 12V available for my circuits without using up any bread board space.

The power supply can be fed from a wall wart, and supplies 5V and 12V to the breadboard’s power rails. It uses a pair of 7805 and 7812 IC’s for regulation.
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