Principle and precautions of relay driving circuit

The relay drive current generally needs to be 20-40ma or larger, the coil resistance is 100-200 ohm, so the drive circuit should be added

1. The transistor is used to drive the relay and the transistor's emitter must be grounded. Detailed circuits such as the following:

NPN transistor PNP transistor

NPN Transistor driver: When the transistor T1 base is input high, the transistor saturation conduction, the collector becomes low, so the relay coil power, contact RL1 Suction.

when the transistor T1 Base is input low, transistor cutoff, relay coil power off, contact RL1 Disconnect.

the PNP transistor driver circuit is not currently available, so it is not introduced here.

1.2 The function of each component in the circuit:

TransistorT1visible as control switch, general selectionVCBO≈Vceo≥24V, magnification β general selection in -~ -Between: ResistorR1main limiting current, reducing transistorT1power consumption, resistance to2 KOmega. resistor The R2 makes the transistor T1 Reliable, with a resistance of 5.1KΩ. Diode D1 reverse flow, suppress surge, general selection 1N4148 we can .

2 IC 2003 Drive Relay

The left figure 1~7 is the signal input (in), the 10~16 is the output signal (out), and the 8 and 9 are IC power supplies. The diagram on the right is the inner schematic of the integration block.

2.1 Simple introduction of working principle

According to the input and output characteristics of IC Driver 2003, it is referred to as "drive" "inverter" "amplifier" and so on, now frequently used model: TD62003AP. When the 2003 input is high, the corresponding output is low, the relay coil is energized, and the relay contact is suction; When the 2003 input is low, the relay contact disconnects and the relay contacts are disconnected, and in the 2003 the diode is integrated in the reverse flow, so it can be used to drive the relay directly.

2.2 Overhaul inference 2003 good or bad method is very easy, with a multimeter DC file measurement of its input and output voltage, assuming that the input 1~7 is low (0V), the output terminal 10~16 must be high (12V); Conversely, assuming that the input 1~7 is high (5V), The output end 10~16 must be low (0V); otherwise, the drive is bad.

Test conditions: 1. Standby; 2. Boot.

Test method: The multimeter is transferred to 20V DC file, the negative pen to connect the electric Control Board ground (7812 voltage Regulator block heatsink), the pen is touching 2003 feet respectively.

Principle and precautions of relay driving circuit