I find myself in need of a latching relay for a project that can be operated at 5v. I have also found that Australia is basically a third world country when it comes to cheap electronics with a single relay cost north of $30 without shipping. So i was wondering if there is a "solid state" version of them that i could make myself (would be great if it only used BJTs, FETs and basic resistors to keep the cost down)

I couldn't find anything out there about this idea but i might just be not using the right keywords. Any input would be great.

Cheers,
SimpleJoe

 

Hi there,

Just google latching relay transistor

http://www.homemade-circuits.com/2011/12/simple-and-useful-transistor-latch.html

For use with normal relay

or

http://www.brighthubengineering.com...c-transistor-circuits-for-beginners-explored/

Half way down the page - HEADING LATCH

Hope this is what you are looking for

 

A 555 and a Mosfet latch/unlatch equivalent of latching relay.
Max.

 

What load current/voltage do you need to control with the "relay"? AC or DC?

 

Do you need isolation between the control input and the output?

 

Could you use a SCR?

 

wow... didn't expect this many replies, to answer a few questions;

This is for a bluetooth speaker i made, specifically a low voltage cutoff of a 6S 24.6V li-ion pack like this:

the speaker only draws a maximum of 2amps in random peaks

yes i know that you can buy BMS online but for some reason they will simply not work for me, i still have no idea why, so i decided to go relatively low tech so when or if this setup goes wrong i will actually have a chance at being able to diagnose the problem.

Cheers,
SimpleJoe

 

So do you want a latching relay or a low voltage cutoff relay?
They are not the same.

 

The battery already includes a low voltage cut-off - no?

 

I was going to use the latching relay as shown in the video (the pulse that would normally sound the alarm on a lipo/li-ion monitor switches the relay off and a pulse of the opposite polarity latches the relay on) did not know there was such a thing as a low voltage cut off relay, I have tried to make my own with a comparator before but it wasn't always accurate and only monitors overall voltage not individual cells. Also no this isn't a premade pack, I did it myself with 18650s sorry should have mentioned earlier.

Cheers,
SimpleJoe