Motor Relay Circuit | Electronic Project Circuits

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Water Pump Relay Controller Circuit Schematic

Water reservoir automatic level control
Simple circuitry – 12V supply

Device purpose:
By means of a Relay, employed to drive a water pump, this circuit provides automatic level control of a water reservoir or well.
Circuit operation:

The shorter steel rod is the “water high” sensor, whereas the longer is the “water low” sensor. When the water level is below both sensors, IC1C output (pin #10) is low; if the water becomes in contact with the longer sensor the output remains low until the shorter sensor is reached. At this point IC1C output goes high, Q1 conducts, the Relay is energized and the pump starts operating.
Now, the water level begins to decrease and the shorter sensor will be no longer in contact with the water, but IC1C output will be hold high by the signal return to pin #5 of IC1B, so the pump will continue its operation. But when the water level falls below the longer sensor, IC1C output goes low and the pump will stop.

SW1 is optional and was added to provide reverse operation. Switching SW1 in order to connect R3 to pin #11 of IC1D, the pump will operate when the reservoir is nearly empty and will stop when the reservoir is full. In this case, the pump will be used to fill the reservoir and not to empty it as in the default operating mode.

Parts:
R1,R2___________15K 1/4W Resistors
R3______________10K 1/4W Resistor
R4_______________1K 1/4W Resistor
D1______________LED any type and color
D2___________1N4148 75V 150mA Diode
IC1____________4001 Quad 2 Input NOR Gate CMos IC
Q1____________BC337 45V 800mA NPN Transistor
SW1____________SPDT Toggle or Slide Switch (Optional)
RL1___________Relay with SPDT 2A @ 230V switch
Coil Voltage 12V – Coil resistance 200-300 Ohm
Two steel rods of appropriate length

Read more source: http://www.redcircuits.com/Page129.htm

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Categories: Electronic Control Tags: motor relay circuit, relay driver circuit, water control

DC Motor Reversing with Relay

A DC motor reversing circuit using non latching push button switches. Relays control forward, stop and reverse action, and the motor cannot be switched from forward to reverse unless the stop switch is pressed first.

Notes:
Except for the back emf diodes across the relay coils this circuit is identical in function to the example shown on the relay contact labeling guide in the practical section. At first glance this may look over-complicated, but this is simply because three non-latching push button switches are used. When the forward button is pressed and released the motor will run continuously in one direction. The Stop button must be used before pressing the reverse button. The reverse button will cause the motor to run continuously in the opposite direction, or until the stop button is used. Putting a motor straight into reverse would be quite dangerous, because when running a motor develops a back emf voltage which would add to current flow in the opposite direction and probably cause arcing of the relay contacts. This circuit has a built-in safeguard against that condition.

Circuit Operation:
Assume that the motor is not running and that all relays are unenergized. When the forward button is pressed, a positive battery is applied via the NC contacts of B1 to the coil of relay RA/2. This will operate as the return path is via the NC contacts of D1. Relay RA/2 will operate. Contacts A1 maintain power to the relay even though the forward button is released. Contacts A2 apply power to the motor which will now run continuously in one direction. If now the reverse button is pressed, nothing happens because the positive supply for the switch is fed via the NC contact A1, which is now open because Relay RA/2 is energized. To Stop the motor the Stop switch is pressed, Relay D operates and its contact D1 breaks the power to relays A and B, (only Relay A is operated at the moment). If the reverse switch is now pressed and released. Relay B operates via NC contact A1 and NC contact D1. Contact B1 closes and maintains power so that the relay is now latched, even when the reverse switch is opened. Relay RC/2 will also be energized and latched. Contact B2 applies power to the motor but as contacts C1 and C2 have changed position, the motor will now run continuously in the opposite direction. Pressing the forward button has no effect as power to this switch is broken via the now open NC contact B1. If the stop button is now pressed. Relay D energizes, its contact D1 breaks power to relay B, which in turn breaks power to relay C via the NO contact of B1 and of course the motor will stop. All very easy. The capacitor across relay D is there to make sure that relay D will operate at least longer than the time relays A,B and C take to release.

Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk
Source: http://www.zen22142.zen.co.uk/Circuits/Switching/reverse.htm