Maker

I’m going to demonstrate how we

make a circuit board in the fab lab.

1. We'll start with a schematic of a circuit board that was designed at the Ghana lab. We call this design an “Efe,” which in Ghanian means “it's beautiful.” This circuit board has a proximity sensor and an LED, and it can communicate with a computer.

2. We make circuits boards in the fab labs by machining rather than the more conventional process of chemical etching, because the solutions used for etching produce nasty chemical waste. The tabletop milling machine we use has metrology good to a tenth of a mil, which along with Q" end-mills makes it possible to make circuit boards with the pitch of fine surface-mount components.

3. Ed Baafi from SETC is “stuffing” the circuit board. Surface-mount circuit boards are usually assembled by “pick and place” machines because of the resolution needed to align the parts. What enables us to do it by hand is a trick based on surface tension. Molten solder prefers to be on the hot traces, not on the cold places in between, so if you get the part and solder close enough, they’ll all end up in the right place. These circuit boards use microcontrollers from Atmel that can cost less than a dollar. But they can run faster than a million instructions a second, which makes it possible to implement things like communication modulation, video drivers, and sensor signal chains in software. Together, the milling machine and microcontroller make microns and microseconds accessible to the masses.

4. We’re programming the chip to instruct it how to read the sensor, drive the LED, and interface with a computer. Instead of using dedicated programming hardware, a cable is used from a parallel port to generate the signals required for in-circuit programming. A serial port is used for power and communications.

5. “Hello World” is the first program one usually writes when learning a new programming language. We’ve adapted it to say “Hello Make.”

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28 Make: Volume 01