The Tube Doctor

I've built a similar latching relay using a dpdt relay, momentary switch, two resistors and a capacitor. One push on (latch) one push off. Returns to off when the ignition source is removed. I'll look up my notes and try to post it in the near future. Simpler than the three spdt relay latch circuit. I tried to use a 4013 logic IC to make a latching relay, but that one didn't work out. It was something I found online, not one of my own. I've never been very good with logic circuits. Too old for that stuff......

Sinemeup

Found a good page on transistors

Transistors

and if you could find a diagram for that latch, it would be much appreciated...

Adhdcanuck

great tip, you can also just buy one already made up to your specs for a handful of nickels and dimes... Im using one as a timer to control the activation of my 200amp battery isolating contactor.

The Tube Doctor

Here's the latching relay I mentioned.
The side of the relay with no connections show is the one you'd use for whatever
load you're driving. Relay coil DCR for the cap & resistor values shown is 750 ohms.
You may have to experiment with the cap & resistor if your relay coil is different from the
value I've used in this example.
Ignition goes in through the 330 ohm resistor, relay latches on when the momentary switch is pressed, unlatches on the next press. Ignition turn off resets the relay to "Off".

http://s790.photobucket.com/albums/y...chingrelay.jpg

nghtrdr

very nice
want to try this out. i have several relays for extras i have added to the truck. one of which HID's creates some noise through my stereo system when they are on. the relay is sending transient noise through the system. i have tested without the relay and the noise goes away, have tried different relays with no luck. i want to keep the relays as it adds a level of protection to my trucks electrical system.
have a few questions if u dont mind.
was wondering if u have pictures to show what it looks like all together. also wondering how to get more than 5amps from the transistor. is it as simple as changing the transistor all together? how can this be used under the hood of the car (water/heat proofing)?

thnx
Dan

d4rin

I get clicks/pops when I changed sources and shut off the car.

But if it does no damage I do not care.

Adhdcanuck

if you look through a couple catalogs and phone an electronics supply store they can usually find you a high quality solid state (no moving parts) relay that will suit..
Rather than put something together yourself and end up with issues... unless youre really a DIY'er and like to tinker all the time.
I like to tinker then have it work and not worry about it.

I'm switching power only no signals with mine, and theres no other electronics in the car being an 89 Turbodiesel... so no transients or noise at all... my batteries take care of volume of energy supply and theres a cap in line to the amps... so i have nice filtered power to the amps.
I ran a fresh #14 from the battery to the cab for my power to the deck... through a really nice LED switch... total system control, doesnt need any auto relays or switching beyond that since its on/off power not connected to the ignition. (way better for listening to tunes with the car off, no other power sources active draining the battery)

So my only isolation is between the front and rear power.. which doesnt cause any problems.

another benefit to buying a proper 12v Solid state relay is they come moulded, weatherproof, shock proof, etc.. use insulated terminals and youre pretty much good no matter what.

if you ever get the chance, run your car ignition power through an oscilliscope and see how awful the rectified DC voltage your alternator puts out is.. its disgusting. no wonder electronics hate it. Cars generate AC voltage, like your house, the alternator has a DC Rectifier on it, and theyre not always clean... I got an upgraded high power alternator and its better, but i still run my stuff through a huge capacitor filter.

the deck has its own, but it will help eliminate clicks & pops if you run a dedicated power to it from the battery, and also give it a way better ground than the car provides through its usual wiring..

I ran a new #12 ground from my ground distribution block to the cab for that purpose.
cleanest sound in town.

Sinemeup

I run a filter on constant and ACC wires to the deck (no more alt whine)