How to run a Compressed Air Engine using Adruino?

Bear with me as I am a mechanical engineer major, but have almost no background in the programming/software side of engineering. This project would be for my senior design.

I'm looking to convert a 4 cyl engine which would run off of Compressed Air. It would use a series of 120v solenoids to fire the Air at the different rates depending on the piston position.

I want to use an Arduino to fire the solenoids at the correct points of the stroke. I was thinking of using some exponential function to work with the delay between the 1&4 solenoids and 2&3 solenoids when the RPMS increase. There is also the possibility of using the crankshaft position sensor already built into the engine, having arduino read it and basically act as a relay to fire the solenoids. There is the possibility of also wanting to use an external potentiometer to increase the "throttle" (rate of solenoid fire/valve controlling air pressure to solenoids) on demand.

Now since I have never used an Arduino before, I am not sure of where to start. I have found projects like 2JZduino who uses an Arduino Mega to control supercharger boost, but I feel like his application is much more advanced then mine.

Any guidance of which Arduino to use and how to write the program would be great. I am willing to learn and will catch on quick.

Thank you for taking your time to read this, Austin

I'm looking to convert a 4 cyl engine which would run off of Compressed Air. It would use a series of 120v solenoids to fire the Air at the different rates depending on the piston position.

Are you sure your solenoids can fire fast enough? I think you might want to characterize what kind of response you can get from them before going too much further.

There is also the possibility of using the crankshaft position sensor already built into the engine, having arduino read it and basically act as a relay to fire the solenoids.

I think this has more promise than a pre-cooked delay function.

Any guidance of which Arduino to use and how to write the program would be great.

That should probably be your last choice. Your first order of business is figuring out what you need to hook up in terms of sensors and actuators. For your solenoids, you will need to know how much current they draw and find a solenoid/motor driver/transistor that can drive them properly. For the crankshaft sensor, you need to characterize what it outputs in terms of voltage and current, and possibly how noisy it is.

The choice of which Arduino to use based on what you've written so far doesn't sound critical. The ATmega328P-based devices have so much FLASH and RAM, the Megas have more FLASH and more RAM. Whether you need it depends upon how complicated your code is going to get. If it's just going to be a simple application to read the sensor and drive the solenoids, it doesn't sound that demanding of FLASH and RAM and the devices with smaller FLASH/RAM will probably be fine.

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RuggedCircuits

Thanks for the response. I am researching the solenoid actuation rate, but I believe they will be able to keep up with the speed’s I am looking at. There has been research done by Lotus to create a cam less engine with solenoids.

Regarding the Arduino board, it is true that I will have a very simple code. It’s not like I need to be programming fuel maps. Just the on and off pulses sent to the valves. There will be at least 8 Solenoids to be fired so this could complicate things to a small degree.

Richard Crowley

The crankshaft position sensor doesn’t have to be the one used by the engine, If there are better ideas that can keep up with high speeds I’m all ears.

The specs for the solenoids claim that they will draw .42 amps @ 120 VAC

I’m sure this is a relatively simple Arduino Task, I just have no knowledge of how to perform it. I have checked the arduino playgrounds solenoid guide, and assuming I figure how to power the 120 V instead of the 24V they use, and add my sensors it should be easy.

Hey guys, Thanks again for the responses.

After much research, I found that the solenoids would be able to keep up with my demands, but unfortunately they have a short life cycle. Around 500,000 to 1 million cycles. While that sounds like a lot, at 2000 rpm, they would only last for around 20 hours. Looks like I'm going to mechanical linkage at the moment. Thanks again!

Looks like I'm going to mechanical linkage at the moment.

Probably would be good to look at steam engine design. You might get away with reground camshafts and use air at a low enough pressure such that it won't pass thru the intake valve when closed. You might have to provide block heating so you don't run into cold temp issues.