Time to wire everything up. My first challenge was working out how to turn on the 12 volt 10 amp air compressor from an Arduino. I have some Power MOSFETs, STP55NF06L, sitting in my shop from some previous research I did looking for a power solution for a Quadcopter. These are more than sufficient to power the air compressor.
They turned out to be a bit more tricky than I thought getting the wiring correct. I ended up getting help from a coworker, Jack Creasey, who understands the electronics side of things better than I. It was nice working with Jack again, the last time we worked together was February in 2004 when we were building some early Windows PC robot prototypes.
The Festo valves are 12 volt so I also needed an amplifier for the Arduino digital out pins. I was hoping to use some cheap transistors I had in stock, the Fairchild PN2907A, but it turned out they didn't have the current to actuate the valves so I used two additional MOSFETs -- overkill I'm sure but it was what I had readily on hand.
The rest of the work it pretty straightforward Arduino tasks -- attaching an analog sensor & two servos.
Circuit Diagram
Photo of the breadboard prototype
Joshua with the prototype
My son Joshua helped with the assembly, double checking all the steps and doing most of the soldering. He impressed me with how much he has learned from working through his Make: Electronics book. I haven't read through it yet, so I picked up a Kindle version for myself.
There's still some work left to do here -- I have a 12 volt industrial warning light that hasn't arrived yet and I have a coworker who's working on a potential design for a smoke generator. Once I get this all locked down I'll look at moving it all over to a Maker Shield instead of a breadboard. I don't think I'll need the breadboard for the Maker Faire booths, I'll probably stick to circuit diagrams to talk through the design there.
- Breadboard with power posts, $16
- Maker Shield (not yet used), $17
- 3x Power MOSFETS (STP55NF06L), $1.56 ea
- 3x 100kΩ resistors
- Miscellaneous Molex wiring connectors & matching pins
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