Air Solenoid
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Limited Availability    AIRSOL    Air Solenoid    $44.00  USA & Canada                    
                                                                                               $49.00  All other countries        

This product is in stock but may not work with high back pressure.  Please send email to Pete Sevcik 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.

Electric air valve for Lego     

Air Solenoid.

Air valve control for Mindstorms RCX  

Interface Brick

Double acting electric air valve

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


Solenoid valve

Interface Brick