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Here is what I call the “poor man’s piston tank proportional controlâ€. It’s really very basic and I believe that virtually everyone can do it. That said, if you’re capable of building the piston tank itself, this should be basically a “no brainerâ€.
The electronics needed can pretty much be had from virtually any servo. I haven’t found one yet that can’t handle an amp of current. But the drawback is that servos are generally rated for a max of 6 volts and the voltage generally used with a piston tank is 7.2 and higher. What to do? Go to Tower Hobbies (http://www3.towerhobbies.com/cgi-bin...?&I=LXLN93&P=7) and get one of their heavy duty CS-80 servos and “hack itâ€. All you’ll need are the circuit board and the feedback pot. The beauty of using this servo is that the amplifier uses an “H†bridge to drive the motor. To allow the use of higher than 6 volts, just cut the high (positive) track on the circuit board (see pic 1), solder a wire to the transistor side of this trace, and then connect the positive wire from your main battery to it. Now you basically have a speed control (almost - there are differences).
Now you’ll have to get creative. The feedback pot must be able to “see†the piston’s position so you’ll have to come up with something. The pictures show how I did it which consists of a rod which is connected to the feedback pot and makes contact with the piston. One thing to keep in mind is that I have this set up so that I can control the last 10% - 15% of piston travel. I see no need or benefit to being able to control the surfaced waterline but submerged.....that’s another story.
Before I forget, I use limit switches just to make sure the piston doesn’t bottom out in either direction.
I’ve also modified the transmitter so that flipping a toggle switch allows dive/surface commands but I’ve also incorporated a pot so that I can control exactly where I want the piston to be.
As soon as I can get to it, the whole process will be posted on my web site and, hopefully, in the SCR.
Skip Asay
Pot with link - bottom view
Pot with link - side view
How the link makes contact with the piston
The electronics needed can pretty much be had from virtually any servo. I haven’t found one yet that can’t handle an amp of current. But the drawback is that servos are generally rated for a max of 6 volts and the voltage generally used with a piston tank is 7.2 and higher. What to do? Go to Tower Hobbies (http://www3.towerhobbies.com/cgi-bin...?&I=LXLN93&P=7) and get one of their heavy duty CS-80 servos and “hack itâ€. All you’ll need are the circuit board and the feedback pot. The beauty of using this servo is that the amplifier uses an “H†bridge to drive the motor. To allow the use of higher than 6 volts, just cut the high (positive) track on the circuit board (see pic 1), solder a wire to the transistor side of this trace, and then connect the positive wire from your main battery to it. Now you basically have a speed control (almost - there are differences).
Now you’ll have to get creative. The feedback pot must be able to “see†the piston’s position so you’ll have to come up with something. The pictures show how I did it which consists of a rod which is connected to the feedback pot and makes contact with the piston. One thing to keep in mind is that I have this set up so that I can control the last 10% - 15% of piston travel. I see no need or benefit to being able to control the surfaced waterline but submerged.....that’s another story.
Before I forget, I use limit switches just to make sure the piston doesn’t bottom out in either direction.
I’ve also modified the transmitter so that flipping a toggle switch allows dive/surface commands but I’ve also incorporated a pot so that I can control exactly where I want the piston to be.
As soon as I can get to it, the whole process will be posted on my web site and, hopefully, in the SCR.
Skip Asay
Pot with link - bottom view
Pot with link - side view
How the link makes contact with the piston
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