Relay Circuits, Page 2

Relay Circuits, Page 2
Relay Circuits: #'s - B C - H I - O P - S T - Z
Last Updated on: Monday, October 03, 2011 06:07 PM

Circuits Designed by Dave Johnson, P.E. :

CHARGE COUPLED BI-DIRECTIONAL POWER MOSFET RELAY
The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply. Since the coupling capacitor values used to drive the FETs are small, the leakage current from the power line into the control circuit is a tiny 4uA. Only about 1.5mA of DC is needed to turn on and off 400 watts of AC or DC power to a load.

Computer Controlled Power Relay
Often there is a need to turn on and off a 120vac device using a low power +5v logic signal from a computer. The circuit below shows how this could be done. The circuit uses a power relay with a 120vac coil and 10 amp contacts. A small solid state relay turns on and off the relay. The solid state relay provides 5KV isolation from the computer.

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Charge Coupled Bi-Directional Power Mosfet Relay - The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply.…. [Designed by David A. Johnson]

Circuit Drives Latching Relays - 02/01/96 EDN-Design Ideas....Figure 1 shows a low-parts-count circuit that can drive one- or two-coil latching relays. Latching relays are useful in sensitive analog designs. The 74ACT174 hex flip-flop has ample capability to drive the Aromat TQ2E series of latching relays. Both windings for the TQ2E-L2-5V two-coil relay are on the same magnetic element, so the windings' fields add. You.... [Design Idea by Roy McCammon, 3M Austin, TX]

Circuit removes relay-contact bounce - 27-Nov-03 Issue of EDN Advances in semiconductor technology have allowed ICs to replace many mechanical relays, but relays still dominate in high-current circuits that must stand off high voltages of arbitrary polarity. Contact bounce in those relays, however, can prove troublesome to downstream circuitry. One approach to contact bounce combines a relay with a hot-swap controller.... [Design Idea by John Guy, Maxim Integrated Products, Sunnyvale, CA]

Circuits drive single coil latching relays - 13-Nov-08 Issue of EDN Five driver circuits operate single-coil latching relays.... [Design Idea by Alfredo H Saab and Tina Alikahi, Maxim Integrated Products, Sunnyvale, CA]

Circuits protect outputs against overvoltage - 11-Oct-07 Issue of EDN Adding a solid-state relay and control circuitry to an amplifier's output provides overvoltage protection.... [Design Idea by Dimitri Danyuk, Kiev, Ukraine]

Clap Relay - Clap sensitive on-off Relay. 3V Battery operated, small portable unit, (added 6/06)

CMOS Toggle Flip Flop Using Push Button - The circuit below uses a CMOS dual D flip flop (CD4013) to toggle a relay or other load with a momentary push button. Several push buttons can be wired in parallel to control the relay from multiple locations. A high level from the push button is coupled to the set line through a small (0.1uF) capacitor. The high level from the Q output.... [Bill Bowden's site]

Control 120 Volt AC Relay with TTL - ASCII format (electronic schematic / circuit added 4/02)

Control 120VAC relay with TTL - ASCII format (Circuit design added 11/06)

Controlling Relays with Logic Voltages - (electronic schematic / circuit added 4/02)

Countdown timer with Relay - (design added 8/03)

Dancing LEDs redcircuits - A LED sequencer, following the rhythm of music or speech 9 Volt Battery-operated portable unit....

Dark/Light Activated Relay - The potmeter adjust the trigger 'on' level. The diode in the diagram shows to be 1N914. This is ok if you have a light-duty relay, also the 1N914 is a signal diode so actually does not qualify. Use a 1N4001 (Tony van Roon's or better) instead. A couple of substitutes for the 2N2222 transistor are: NTE123A, ECG123A, PN100, etc.... [Tony van Roon's circuit]

Dual Relay Driver Board - We have used two Goodsky RWH-SH-112D 12V relays, coil resistance 400 ohm. It is rated to switch 250VAC at 12A. However, because of the PCB track thickness and width we do not recommend using the
relay to switch more than 5A. If you….(design idea circuit added 09/08)

Dual-coil relay driver uses only two MOSFETs - 22-Oct-09 Issue of EDN Differentially drive relays to minimize power consumption.... [Design Idea by Mehmet Efe Ozbek, PhD, Atilim University, Ankara, Turkey]

Electronic Thermostat Relay Circuit - Here is a simple thermostat circuit that can be used to control a relay and supply power to a small space heater through the relay contacts. The relay contacts should be rated above the current requirements for the heater. Temperature changes are detected by a (1.7K @ 70F) thermistor placed in series with a 5K potentiometer which produces about.... [Bill Bowden]

Electronic Toggle Switch No.1 - This simple circuit will energize and de-energize a relay at the push of a button. Any type of momentary action push-to-make switch can be used. Pushing the button once - will energize the relay. And pushing it a second time - will de-energize the relay.... [Design by Ron J.]

Electronic Toggle Switch No.2 - Pushing the button once will energize the relay. Pushing it a second time will de-energize the relay. Any simple momentary action push-to-make switch will do. The prototype has a single-pole relay. But you can use a multi-pole relay.... [Design by Ron J.]

Electronic Toggle Switch No.3 - This versatile circuit provides a selection of different switching modes. It can be used as two entirely separate toggle switches - with each push button successively energizing and de-energizing its own relay. Or the two switches can be interlinked with diodes - to produce a number of different switching patterns. For example - the circuit can be used to reverse the direction of DC motors.... [Design by Ron J.]

Generating a Delayed Pulse with a Dual 555 Timer - The circuit below illustrates generating a single positive pulse which is delayed relative to the trigger input time. The circuit is similar to the one above but employs two stages so that both the pulse width and delay can be controlled. When the button is depressed, the output of the first....

Relay Circuits: #'s - B C - H I - O P - S T - Z