Ok, thinking about a semi-automatic torque converter circuit...
 

Ok, I was thinking... On my 81 Buick the torque converter no longer locks because of some problem in the computer which I don't care to spend the time to trace. I thought of a toggle switch, but that's just not me. I know I'll forget and leave it on, and cause myself problems. I spent some time sketching out possible circuits on notebook paper today, and when I found one I was happy with I made a prettier version in paint for everyone to look over.

I'm proposing to use (2) 12v SPST relays. One normally open, one normally closed, and a SPST monentary contact switch. The switch will energize the relay. Once energized the relay will hold itself closed until the brake pedal is pressed, energizing the second relay, and breaking the ground on the first, thereby resetting everything until the next time the button is pressed. I guess if this works out I could use a lighted switch, and have the light glow when the converter is locked. Anyone see any flaws in my logic here?

Thanks, Jay

https://www.fuelly.com/attachments/fo...b743cc5d90.jpg

it won't hold itself closed unless you have a set of contacts across that switch.

similar to a start stop station.

----l/l-----l l-----(load)---

this is what you have right now with the first relay being actuated by the brake pedal and is normally closed, the second being the relay remotely operated by the switch but once you release the switch the circuit is broken.

you need to parallel a set of contacts from the second relay (the normally open one but not the same contacts that you are using) across the push button so that it will hold itself until the brake pedal resets itself.

----l/l-----l l-----(load)---
............l.......l
............--l l--

that last one is terrible. I may look up a start stop station ladder logic drawing if I have time. ignore the dots as this site won't let you put spaces.

*edit* sorry for the large file but it was the best one I could find with a small amount of time. https://www.sea.siemens.com/step/pdfs/cc_1.pdf there is a drawing on page 17.

*edit again* scratch all that, I noticed that you have it set up that way. never mind.

https://www.streetperformance.com/par...219-60109.html

I only know one person using that but it does work!

BEEF - all I can say is you lost me... Won't the relay hold itself closed once its energized by the pushbutton? What does the pushbutton have to do with the relay breaking the ground to the primary relay? I have a tendency to make things complicated, but I think you may be worse than me... :)

dkjones96 - I have seen those kits before, but I can probably build what I have posted here for almost nothing as I already have most of it in a spare parts bin. The kit you mention costs $160.

Only a latching relay would hold itself closed once it's energized by the button. Common relays are normally on or normally off, and only hold the opposite state as long as they remain energized.

I was thinking of a latching relay but every time he hit the brakes then let off and went back onto them it'd throw the system out of whack.

What you could do is a normally open DPTS relay and a normally closed SPST. You can make a 'latching' relay by running your 12v power through one pole then through the coil. You bypass the relay switch with the momentary switch and put the normally closed relay in line with those as an interrupter when you hit the brakes. Your load then goes on the second pole of the DPST.

The system starts in the off position, you press the button and it bypasses the double pole to apply power to the relay, when it turns on it will latch and hold until the other relay switches and cuts power to the first coil. DIY latching mechanism.

Yes, but I have the output +12v going to to top where its also energizing the coil... In theory it should hold itself closed, right?

This looks like a job for color coding! Red is +12 VDC, blue is ground, black is floating. The left relay could be replaced by a pull down resistor I would imagine.

https://www.fuelly.com/attachments/fo...ed3b40f6fb.jpg

Thanks for the color coding... You understand what's going on in my brain. That can be scary at times. I don't like the resistor idea because what "should" happen and what does happen can be very different in a 28 year old car.

-Jay

I don't think the second relay can be replaced.

Don't forget to run a resistor in line with the relay coils. The 12v relays at radioshack are exactly that, 12v relays. I used 100 ohm to bring the 14.x volts from the charging system down to a reasonable level of I think 11 volts(read voltage dividers, I used the first example, a series divider). I used the little blue SPDT relays on protoboard with cat5 hookup wire. You'll be hard pressed to find single throw anything anymore.

My brain isn't running at full capacity today, but I think I understand that...and it's brilliant! So simple and elegant. Why doesn't that show up in any of the web pages about automotive relays I've read? I could really use that!

Maybe not. Need to know the relay specifics to run the math.

Thanks dkjones... I know that single pole are hard to come by, but for purposes of illustration I put SPST switches & relays. I'm sure I could use DPDT relays and just ignore the extra terminals.

-Jay

sorry, after I went through all the trouble to do that, I realized that you had it strapped to latch itself.

I was too lazy to erase it all plus if someone had seen it and comented on it, their post wouldn't have made sense.

That's good of you. On my "optimal car shape" thread somebody deleted their posts and it makes me look like a wacko talking to himself.

I save that for offline. :p

No, but you did delete one of your posts in this thread.... ;)

Mea culpa. I am obsessed with revising mine to make 'em clearer. I try not to if it'll ruin somebody else's. Soemtimes I think of ways the tone could be misinterpreted too.

Just like the credits in a game show... Portions of this show not effecting the outcome may have been edited for time and content...

On my blog I've started saving drafts of posts and delaying them by a few hours, since I have a couple readers who get automatic email updates when I first publish. They were always getting the rough drafts before.

You could replace the brake light relay with a diode.
Assuming your brake light circuit is a positive switched design (one side of each bulb grounded, with switched power on the other), the wire between the switch and bulbs always sees 12V+ or ground. It gets 12V+ when the switch is activated thanks to the resistance of the bulb filaments. It sees ground when the switch is off because the unlit bulb filaments have a relatively low resistance, so small-ish currents (such as those that flow through a relay coil) fed to the bulb-switch wire can drain to ground through the bulbs without lighting them. In your design, these are the same conditions seen on the wire connecting the two relays.
The only consequence of connecting that wire directly to the brake light circuit is that stepping on the brakes would cause power to flow back through your relay coil (the ground path being the lockup solenoid), energizing it and either latching it or maybe causing it to cycle on/off (it would sound like a buzzer) as the relay contacts make and break.
To avoid that, you need a diode (a 1N4001 should do nicely and be easy to find) on the wire between your relay and the brake circuit, banded side towards the brake circuit. That will allow current to flow only from the relay to the brake circuit (when the circuit wire is grounded / lights are off), or not at all (when the circuit wire has 12V+ / lights are on).

Again, that sounds a little bit iffy... As I said earlier, what should happen, and what does happen are two totally different things in a 28 year old car. The idiot lights have decided to work backwards... I now am concerned when the alternator or oil pressure lights go out.

-Jay