# Triggering multiple relays with a single momentary switch #2

#### computerlen

Joined Nov 26, 2011
8
Hi. I too have been trying to build a circuit using one touch switch that controls two relays. Pressing the normally open switch would latch one of the relays but then I need to press that switch again to undo the latch condition. Attached is a rough idea of what I keep coming up with. I truly would appreciate any help that you can give me. Len.

#### Rich2

Joined Mar 3, 2014
241
Hi. I too have been trying to build a circuit using one touch switch that controls two relays. Pressing the normally open switch would latch one of the relays but then I need to press that switch again to undo the latch condition. Attached is a rough idea of what I keep coming up with. I truly would appreciate any help that you can give me. Len.View attachment 237643
The only way to unlatch it is to remove the power briefly or put a switch in the lower cable.

Joined Jan 15, 2015
6,581
This thread is going on 4 years old. You would likely do better starting a new thread. That said if you are not adverse to using a chip a 4013 D flip flop would be my choice. Push button once to latch relay on and push again to unlatch relay. Also, as just pointed out your circuit as drawn will not latch and then unlatch unless you want to add a NC push button.

Ron

#### AnalogKid

Joined Aug 1, 2013
10,050
Hi. I too have been trying to build a circuit
You are redirecting someone else's thread that is over years old. Please start a new thread with your question. If there is something in the old thread that you feel is relevant, provide a link to it in your post.

ak

#### MrChips

Joined Oct 2, 2009
26,064

#### AnalogKid

Joined Aug 1, 2013
10,050
An impulse relay will do what you describe with zero external electronics.

ak

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#### Tonyr1084

Joined Sep 24, 2015
6,884
To have a single push button do what you want - the best way is to use a Double D type Flip Flop (DDFF). Amazon has many different types. Click HERE to see some.

Here's a circuit you may want to investigate: The NOT Q (Q with the bar over it) sets D opposite of whatever Q is. With each push of the button the D type FF (the box with the D, C, Q and NOT Q) will turn the transistor on or off. The transistor will control the relay. I've left out a ton of details just to show you the basic idea. The exact FF you choose will depend on the use, as well as will the transistor and the relay. Without details I can't give you any further support. The ONLY thing I can add that isn't in the drawing is a snubber diode across the relay coil. But you'll get there with the help of others from this website.

#### ElectricSpidey

Joined Dec 2, 2017
2,146
Tony, your transistor is a common collector, and bounce much?

Joined Jan 15, 2015
6,581
I like the impulse relay.

Ron

#### AnalogKid

Joined Aug 1, 2013
10,050
It is large and expensive, but all you need to go with it is one SPST switch and one diode (for a DC coil). Otherwise, a hex inverter can form three independent toggle circuits with only one relay each. AND, relay coil power does not go through any contacts, possibly saving relay \$.

ak

#### Tonyr1084

Joined Sep 24, 2015
6,884
Tony, your transistor is a common collector, and bounce much?
I did say there was a lot of missing information.

#### crutschow

Joined Mar 14, 2008
29,756
Below is the LTspice simulation of a fleshed-out version of Tony's circuit.
The R1-C1 delay in the D input feedback is to ignore any switch-bounce (shown in the first yellow trace PB pulse).
The relay turns on and off (red trace coil current) for each push of the button (PWSW).

If you need the circuit to come up in a particular mode when power is applied, an RC power-on circuit can be connected to either the FF PRE or CLR input.

#### xox

Joined Sep 8, 2017
678
This simple circuit works with any normally-open push switch. It's composed of just five components. A quad opamp, three resistors, and a capacitor (to ensure a properly initialized state).

I've used an LM324 with it, but if you need a broader range of voltages you can simply use another opamp. Everything else is the same. It draws very little power and also tends to be more hardy than say the typical CMOS logic chip.