Any guesses what I am building? Sound like a fun game to play?
I am anxious to hear your guesses.
Update: An easier way.
TheAndroidMan posted a tip/walkthrough on adding pnuematics to a robot. That will make this project much easier.
Update: The answer!
This is a prototype of and electrically controlled air valve. The intention is to make a bunch of these, each connected to a pipe tuned to a different note. What I am building is a calliope, but it will be driven with stored air pressure, rather than steam, and controlled by a microprocessor (Arduino).
The large white cylinder is the valve. I based the design on this web page. I'm adding solenoid, so I can control the valve electronically.
I have some new solenoids on order, which are different than the one used in the prototype. If they work well, I'll order more and start construction.
The small white tube is the case from a ball point pen, made into a whistle. A notch is carved near one end. A wedge of pencil eraser is pushed into the tube so that one end just about lines up with the flat edge of the notch. Together these force a restricted stream of air over the beveled side of the notch, which makes a whistle.
Different length tubes will create different notes. The final product may use brass tubing instead of pens.
If the core of the solenoid has a spring or other return mechanism you can use PWM for pseudo-analog control… can be tricky but I’ve seen it done in more than a few applications.
I don’t really have written plans, but I will post details of my progress.
I already posted a link to the design of the valve itself. I’m just adding a solenoid to actuate the valve plunger. My current design uses a wooden plunger, which may have too much friction. I’d like to replace it with either plastic or possibly brass.
I’m considering using two pieces of brass tubing, one of which just fits inside the other. The outer tube would be short, and just act as a sleeve on the solenoid side of the valve. The inner tube would be carefully cleaned with rubbing alcohol to remove oils, which add friction. One end of the inner tube would be connected to the actuator of the solenoid. The other end would plug the o-ring on the far side of the valve.
The solenoid needs to have a spring return, in order to ensure the valve closes when voltage is not applied to the solenoid. I rigged up a spring return in my prototype. One of the new solenoids I ordered includes a built in spring return, so I’m hoping it will work OK. I’m a bit concerned that the new solenoid will not be a strong, which is why I will probably redesign the valve mechanism to be lower friction.
