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*Instructions are at the bottom*
This circuit represents a DC motor which operates a valve. These valves usually have built in limit switches (change over) which switch when the valve is at its opened or closed position. The electric motor is connected is such way, when the valve engages the limit switches they cutoff the power supply to the motor and so, the motor will not break the whole thing. Parallel to the limit switches, there are diodes. When a limit switch is opened, the current cannot flow to the motor and so, the motor cannot turn. The parallel diodes allow current to bypass the opened limit switch to the motor. When the valve turns the other way, the opened limit switch closes again and the bypass diode is not used anymore.
On the 3rd connection of the limit switches, lamps or relays can be connected. When the valve reaches on of the limit switches, the switch changes over and the lamp or relay is activated to signal that the valve is either opened or closed.
How to use:
On the left there are 2 switches.
The top switch activates the relays who activate the circuit to the DC motor. The DC motor is able to turn left or right.
The bottom switch activates the relays to change the direction of the motor.
The 2 limit switches at the bottom can be switched randomly.
At the start, the right limit switch is "engaged" by the valve, meaning the motor cannot turn right anymore.
When switching the top switch, the motor will turn CCW (left). Note the current flowing through the bypass diode. Directly after the motor starts to turn, switch the right change over limit switch to simulate the valve turning away from the limit switch.
After a while, switch the left change over limit switch to simulate the valve engaging the limit switch. Note the power being cutoff due to the diode.
Switch the lower relays to simulate CW rotation of the motor. The motor will turn due to the bypass diode. Directly after the motor starts to turn switch the left change over limit switch to simulate the valve turning away from the limit switch.
Now switch the right change over limit switch to simulate the valve engaging the limit switch.
Play with it for a while.
Enjoy!
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