Air Solenoid
Withdrawn AIRSOL
Air Solenoid $44.00 USA & Canada 
$49.00 All other countries
This product is in stock but due to quality concerns it is withdrawn from general availability. Please send email to Pete Sevcik psevcik@techno-stuff.com if you are interested in this product.
The Air Solenoid lets your RCX control Lego air cylinders.
The Air Solenoid is an electric valve to control air flow in a Lego pneumatic (air cylinder) system. It replaces a Lego manual air valve, and allows control from a Lego RCX computer brick. The Techno-stuff Air Solenoid is compatible with the Lego Mindstorms™ Robotic Invention System.
The Lego Pneumatic system uses air pressure in cylinders to create movement. In the past, movement was controlled by a manual air valve. This was difficult to control from an RCX. The Techno-stuff Air Solenoid provides an easy way for the RCX to control Lego air cylinders. The solenoids come with an RCX interface module. This module connects two air solenoids to a single RCX motor output. Motor direction determines which solenoid is activated. The two solenoids can be used independently on two single-acting cylinders, or together to control one double-acting cylinder. A single acting cylinder uses only one air inlet, and uses gravity or a rubber band to move in the unpowered direction. A double-acting cylinder has two air inlets, and uses air pressure to move in both directions.
The Air Solenoid is sold as a package containing:
- Two air solenoids. (3-way)
- One RCX interface brick.
- One air hose "T" connector.
Each air solenoid has an input port, an output port, and a vent (exhaust) on top. When the solenoid is on (energized) the input port is connected to the output port. When the solenoid is off (not energized) the input port is closed and the output port is connected to the vent. This allows pressure on the output side to be vented to the atmosphere. The venting process in needed so there is no back-pressure in the cylinder.
When the air solenoid is off, the output port is vented. This means your cylinder can be moved. It is different from the manual valve sold by Lego. When the manual valve is "off" (middle position) your cylinder is not vented, and is harder to move.
Note: To keep the price down, this product uses air solenoids that have been removed from used equipment. All parts are fully tested and warrented by Techno-stuff.
Air Solenoid.
Interface Brick
Two Air Solenoids and interface Brick, connected to a double acting cylinder.
A solenoid is an electromagnet with a movable iron piston in the center, and a return spring. It requires a relatively large amount of power to move to the ON position, and relatively little power to stay there. The control brick has a special power booster circuit to provide an initial power spike, and then reduced power. This circuit requires special programming.
For reliable operation, your program must first charge the power booster
circuit. You do this by applying power in the opposite polarity for
about 50 milliseconds. Next you float the motor output, then you
immediately apply power in the direction you want.
The example program below will cycle a valve on and off every seconds.
Private Sub DnldPgm_Click()
VersionLabel.Caption = PBrickCtrl.UnlockPBrick
PBrickCtrl.SelectPrgm 4
PBrickCtrl.BeginOfTask 0
'Start definition of program
PBrickCtrl.Loop 2, 0
'Start loop
'Charge the capacitor
PBrickCtrl.SetRwd "0"
'Set reverse direction
PBrickCtrl.On "0"
'Turn motor on
PBrickCtrl.Wait 2, 5
'Wait 50 milliseconds
PBrickCtrl.Float "0"
'Float the output
'Turn the valve on
PBrickCtrl.SetFwd "0"
'Set forward direction
PBrickCtrl.On "0"
'Turn the power on
PBrickCtrl.Wait 2, 300
'Wait 3 seconds
'Turn the valve off
PBrickCtrl.Float "0"
'Turn the power off
PBrickCtrl.Wait 2, 300
'Wait 3 seconds
PBrickCtrl.EndLoop 'Loop forever
PBrickCtrl.EndOfTask 'Download the program.
End Sub
Interface Brick