Hello,
Im designing a circuit where with a simple press of a button a relay switches between two contacts.
From what I understand: Latching relays have 2 coils therefore require 2 different buttons, or if they have one coil it requires to invert polarity to change position.
What could I use to make a relay switch position (and hold it) with only one impulse?.
I know I could do it via Arduino code but I would prefer not to.
Thanks
Which is it? That will change the answer.
I'm thinking a flip-flop and some transistors...
Hi, @francescoranchi
What you want to do is "toggle" a relay ON /OFF.
One button and a standard relay and some software will do the job.
Have you Googled;
arduino toggle a relay
This may help;
Tom.. 
That simple:
Wow! geniun! I know I could use a switch, a ATTINY or an arduino to do the job, but that's exactly what I dont want. That's why I wrote button and not switch..
Hey Tom!
Yes I'm, aware I could o the job with an arduino or an ATTINY but I would prefer not to...
Possibly using a normal relay monostable and some logic (not using arduino or similar)
I think you can do it with 74hc00 and a few sundry components. I'll draw a schematic for you in the morning.
Are you talking about driving a bare relay or a relay module with a built-in driver circuit?
By your description in OP, You want an “impulse relay”… 1 impulse relay, 1 (or as many in parallel as your heart desires) momentary push button, no logic required… the relay will switch and hold between NO and NC every time it receives a “pulse” from the push button.
Search that on google, amazon, aliEx, mouser/digikey and you’ll find what you need, descriptions and prices, etc…
Hello Paul!
A schematic would be amazing! Im talking about driving a bare relay.
Ideally, for the schematic you'll draw tomorrow, the relay's coil would be 12V as this will go in a car, but If you decide to use any other relays (with different coil voltages like 5V or so...) I'll use a boost converter or similar!
So ideally 12V coil, if not its gonna be okay anyways!
Hello!
Yes I'm aware of impulse relay, only issue is that they are usually quite big since they have mechanical moving parts inside, and since the relay goes on a PCB which needs to be as small as possible, I was hoping of finding other options, but if I don't I will have to use an impulse relay
Gotcha 
… i must have missed that you needed pcb option in details somewhere. Sorry. You are right, impulse relays are large.
Sounds like @PaulRB is the right person for this and already on the electronics for you. Good luck
So you need a push-on/push-off button or latching button.
https://www.jaycar.com.au/spst-pushbutton-black-actuator-latching/p/SP0718
Tom...
hello tom,
thanks for stating the obvious, I'm not a complete noob. the reason why I need the relay to activate/deactivcate with a signal is because It can be controlled by 3 buttons in 3 different areas.
Well you need to explain yourself earlier in the thread.
Anything else you need to tell us?
What is the whole scope of your project?
Tom...
These are not finished designs, just ideas. You need to test and if necessary adjust/adapt these circuits!
The top one uses quad NAND gates (HCF/CD4011). The lower one uses a jk flip-flop (HCF/CD4027).
I thought using 4000 series chips might be easier with a 12V supply. However, vehicles are harsh places for electronics and you need to take measures to protect the circuit from damaging spikes, noise, higher-than expected input voltage etc. I'm no expert in vehicle electronics, perhaps other forum members can suggest what might be needed.
Tom,
I don't understand why when I ask how to grow tomatoes, you tell me to go buy an hamburger at McDonalds.
If I wanted to use a pushbutton which locks / a switch or anything else than a toggle button and a relay I would have told you
You can simply use a relay with 2 sets of contacts. Use one set of NO contacts to keep the relay energised once the initial impulse has closed the contacts. You can parallel up several NO pushbuttons to energise the relay from different locations. You can have 1 or more NC pushbuttons in series to de-energise the relay.
are nice because they do not require continuous power to hold state.
Both single coil and dual coil are easy to use. Without extra circuitry beyond the always-necessary driving transistors or MOSFETs.
Both types, using just the driver transistor(s), would need two output pins.
With a two coil relay, each coil uses a regular MOSFET or transistor circuit.
For one coil, this ugly circuit will work, but you can do better at the expense of a few more parts.
Latching relays need a certain pulse width to reliably switch. With the circuit I posted, it would be best to keep the energized time to just that short, typically 5 milliseconds or so.
a7
