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I've been trying to design a latching relay driver circuit, with using a push-button switch. Basically when the circuit is powered on, first press in push-button switch make the relay SET, then the second press will make the relay RESET state.

I've searched online and find this normal relay driving solution. But I couldn't figure out how to implement this into single coil and/or dual coil latching relay. I guess dual coil latching relay is easier to drive than the single coil one. Push-button relay control

Any help is appreciated. (if possible please provide falstad simulation)

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  • \$\begingroup\$ switch to shunt cap and pullup R to D FF Clk is /2 functional toggle \$\endgroup\$ Commented Mar 10, 2018 at 0:12
  • \$\begingroup\$ Nowadays the most sensible way to do things like this is probably with a $0.50 microcontroller. Traditionally you would use a T flipflop (which can also be made from a JK or D flipflop) \$\endgroup\$ Commented Mar 10, 2018 at 2:59
  • \$\begingroup\$ @immibis I've been looking at maxim drivers, they're pretty easy way to drive latching relays, but I think they're overpriced. maximintegrated.com/en/app-notes/index.mvp/id/3288 \$\endgroup\$ Commented Mar 10, 2018 at 9:13

3 Answers 3

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There are many ways to do this. Discrete, D FF /2 counter Astable FF

Choose whatever Relay meets your needs and select Base R to drive 5% of Coil current. Use Darlington and 1% if this exceeds 20mA.

Avoid crosstalk of power grounds between Relay and CMOS , like the plague.

enter image description here

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    \$\begingroup\$ tinyurl.com/y9fd3ztw \$\endgroup\$ Commented Mar 10, 2018 at 2:31
  • \$\begingroup\$ Many thanks @Tony, I've been thinking of using open drain DMOS(tpic6c595) instead of darlington(uln2803a + 74hc595), to avoid extra 8bit shifter chip. Do you think this is suitable, or could you recommend any better way to drive eight latching relays ? \$\endgroup\$ Commented Mar 10, 2018 at 9:07
  • \$\begingroup\$ what relays ? ? \$\endgroup\$ Commented Mar 10, 2018 at 9:12
  • \$\begingroup\$ ah sorry, dual coil latching relays \$\endgroup\$ Commented Mar 10, 2018 at 10:11
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can't remember where i found this image, so credit to whoever was the original authorenter image description here

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    \$\begingroup\$ Hi Antony, welcome to EE.SE. Can you provide some explanation of the circuit, and how does this circuit answer OP question. Posting only a circuit without any context or explanation is not recommended. \$\endgroup\$
    – Hazem
    Commented May 29, 2018 at 4:47
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The dual coil relay will need two NPN transistor switches similar to your J1. One for SET and one for RESET.

The single coil probably requires coil voltage reversal for SET and RESET. This requires a H-bridge arrangement and, while the relay is simpler, the switching electronics is more complex.

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  • \$\begingroup\$ a latching relay has another advantage ... no power needed to keep it latched \$\endgroup\$
    – jsotola
    Commented Mar 10, 2018 at 1:50

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