I have found a few diagrams, and simply can't get anything to work right. I have been working with many different circuits lately, and have been able to figure out almost everything with out issue. I am now losing my mind...

I am looking to use the momentary output output of an lm339 comparator to latch a circuit. I have an LM339 circuit that already has an output based on something else I am doing (< 1sec.). I have been trying to do this with 555 timers, but simply can not get anything to work. At the end, I am basically trying to turn on a relay, and keep it on until another pulse is sent from the LM339 to turn it off. The circuit is run off of 11.1V lithium batteries if you need a voltage reference (9-12.6V roughly between full/dead). What is the simplest way to make a latch circuit that works?

 

The easiest is probably to use a Flip-flop such as the CD4013 D type. Connect the /Q output to the D input and connect the clock input to the LM339 output. The 4013 will alternate states for every pulse input. Make sure the LM339 has enough hysteresis (using a small amount of positive feedback) so you only get one pulse per transition.

You will likely need to add a buffer transistor at the flip-flop output to drive the relay coil. Make sure you add a diode transient suppressor across the relay coil (cathode to positive side of coil).

 

The easiest is probably to use a Flip-flop such as the CD4013 D type. Connect the /Q output to the D input and connect the clock input to the LM339 output. The 4013 will alternate states for every pulse input. Make sure the LM339 has enough hysteresis (using a small amount of positive feedback) so you only get one pulse per transition.

You will likely need to add a buffer transistor at the flip-flop output to drive the relay coil. Make sure you add a diode transient suppressor across the relay coil (cathode to positive side of coil).

Like this circuit here, put the clock (pin 3) to your op-amp output, make sure you have a pull-up resistor on your op amp output( remove all the other components on pin 3)

http://www.google.co.uk/imgres?q=40...220&start=0&ndsp=16&ved=1t:429,r:10,s:0,i:100

 

555 Bistable Multivibrator

The 555 Projects

Bill's Index

 

You might find the following thread useful. Scroll down to my response in the last message of the thread.

http://forum.allaboutcircuits.com/showthread.php?t=29365

 

555 Bistable Multivibrator

I built this after you posted it, and it is almost exactly what I am looking for, but I was hoping that it could be triggered by a high or low input only, where as this one needs to be triggered from another part of it's own circuit. Any way to alter it for that?

I will look at other options posted here as well, but I just happen to have a ton off 555's, so I was hoping I could utilize them. I also liked the above circuit because it uses very basic components that I have tons of!