Relay Driver – Electromagnetic

This circuit is a standard way of driving Small Power Relays from Control Signals generated by Logic or Opamp Circuits.

C2 and R5 form a snubber which improves the life of the metal contacts, the contacts can erode due to sparking when switching inductive or even big loads. reduces EMI_RFI.

Basics of Electronics

The Electromagnetic Solenoid Coil is rated by Volts and Ohms. If you choose 12V ensure a stable 12V is provided, more voltage will heat coil, less voltage will cause sparking or will drop out the magnetic holding. A high coil resistance is better as the heat will be less and power consumption of your design is low.

Relay Driver - Electromagnetic

Q2 is any 500mA-50V-NPN device. For a relay drawing 100mA-12V use a 200mA-50V device or better. D1 is a freewheeling diode, inductive kickback diode or snubber or something that stops the coil from zapping the Q2. Q1 and Q2 form a Darlington pair to amplify the low current drive of some CMOS gates.

Infrared Optical Proximity Switch

R2 and R1 is to hold the bases to ground and avoid floating or else they will pick up noise and relay will chatter….. the contacts will spark ……. the motor or heater will fail to work well……… and your product will get rejected ……….. the payments will be held up …… the customer may even ……………………… stop that right now !

R3 and C1 is a dampener for the signal so that quick relay operations can be avoided, this is important if your relay is driving a three phase contactor which runs a huge Motor. C1 can be increased if required. When huge loads are switched on-off in a factory, lots of spikes and drop outs will reset timer and logic circuits, this will turn on off above relay … leading to the load switched by this circuit going on-off. This may even lead to a Oscillation with the spikes as feedback which can cause great trouble during the troubleshooting process. R4 limits current.

  • Battery Backup for SRAM or Microcontroller
    This circuit can be used as a low cost SRAM and Microcontroller-Microprocessor Battery Backup. All the diodes are 1N4148, The diodes prevent battery discharge back [...]
  • InfraRed Detector for Proximity SwitchInfraRed Detector for Proximity Switch
    The proximity switch can work for a wide range of power, from 8v to 18v DC, D3 protects reverse power supply connections, and U1 regulates [...]
  • Monostable Multivibrator CD4538Monostable Multivibrator CD4538
    CD4538 is a dual Monostable Multivibrator. When you trigger the chip the output sends off one single pulse or one high-low event. Mixed Circuits Analog [...]
  • Sample and Hold with Standby CD4053Sample and Hold with Standby CD4053
    A, B, and C are the Digital Control for x, y and z input and output pairs.The voltage at Vinx is stored in C1 when [...]
  • Display On Timer with 555Display On Timer with 555
    This is related to the earlier post. This was done to save battery power. The output of some equipment may be in the form of [...]
  • Blind Dial Analog Temperature ControllerBlind Dial Analog Temperature Controller
    This is a Low cost controller, Analog Dial Temperature Controller. It is also called Blind Controller. This essentially means Open Loop, just control the fuel [...]
  • Two Op-Amp Differential AmplifierTwo Op-Amp Differential Amplifier
    The Input Impedance of this module is very high and is symmetric. This circuit can be used for strain gauges and for four wire measurements. [...]
  • RTD Pt-100 Four Point AlarmRTD Pt-100 Four Point Alarm
    Here 4052 is used as an analog multiplexer, U3A TL062 opamp is wired as a 1mA Constant Current Source. It pumps 1mA into U2 4052 [...]
About delabs 160 Articles
Product Design - Industrial Automation and Instrumentation. -

Be the first to comment

Leave a Reply