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How does current limiting work on a DC motor?
When motor power comes on to close the valve the RC circuit begins to climb until it surpasses the reference voltage. When it times out it can shut off motor current. With a little thought you can further expand the circuit so that it holds itself off until you manually reset the system so as to open the valve electronically as well.
How often does a DC motor need to be operated?
As the valve reaches the end of its travel the motor will load and begin to stall. This valve will be operated at most once a day. The motor/gearbox does not have enough torque to cause damage to the valve, just enough to close it tightly.
Do you have to energize a DC motor?
However, using the time delay method, you still have to energize it. Meaning the operator will switch the switch to “Open” or to “Close” and then push a “Start” button. I’m also assuming your system is DC powered. AC power won’t lend itself well to reversible motors or time delays.
How to keep the temperature of a DC motor down?
The key is to keep the temperature of the motor down – either by limiting the current to 2A, or allowing it to cool down, or by improving cooling e.g. with a fan. 2) DC motors usually have brushes – either carbon blocks or metal contacts rubbing against the commutator.
How do you stop a motor control circuit?
As the circuit exists right now, the motor will run either forward or backward once the corresponding pushbutton switch is pressed and will continue to run as long as there is power. To stop either circuit (forward or backward), we require some means for the operator to interrupt power to the motor contactors.
Can a timer be used to shut off a motor?
When it times out it can shut off motor current. With a little thought you can further expand the circuit so that it holds itself off until you manually reset the system so as to open the valve electronically as well. Again using the timer circuit to control operation.
Why do I need to build a timer circuit?
A lack-of-rotation sensor would then switch off the motor. Why not just build a timer circuit. If under normal operation the motor takes – oh, lets say 5 seconds to close the valve, then a drop-out timer could supply power for 7 seconds.