Electrical limits

[chevynut]

I have been thinking about how to stop my electric cutouts at the end of their travel, open or closed. Sure, I could listen to the exhaust note and stop when it "sounds" like they're open or closed, but it should be more definitive than that. These things don't have limit switches to tell you when you've reached the end of travel and you can't see them.

So how do you do it?

I believe power windows typically don't have limit switches and use a circuit breaker to keep from frying the motors or the wiring. When you put them up or down, you can SEE them and can even hear when they're closed if you're driving. Even if you hold the switch, you don't damage the system. Some vehicles now use a control module that senses the increase in current and shut the motor off. That's typically how an "auto down" or "auto up" window controller works.

I have a pair of power window control modules that do what I described above. I was thinking these could be used to drive a pair of electric cutouts too. You could have a momentary switch and all you would have to do is tap it to open or close the cutouts. You can also stop them mid-way if you want. They sense the end of travel by the current increase and shut off power to the motors.

Any reason this wouldn't work? Is there a better way?

[MP&C]

They don't have limit switches built in?

[chevynut]

No Robert, there are no limit switches in either power windows or electric cutouts. That's why I asked about your Rocky Hinge fuel door. ;)

I'm using DMH cutouts. They come with a wiring harness that has a momentary rocker switch. I'm just looking for an easier way to control them.

[Bihili]

I guess I would say my DMH cutouts are activated by my ear.
After you use them several times you hear when they are fully open and mentally can time that function.
The overlap between when they are fully open and when I take my finger off the switch is probably a second.
When closing them the overlap is probably less than a second.

After they stuck closed one winter I now open them every few weeks.

[chevynut]

Bill, you're still guessing at when they're open and closed. ;) I'm looking for a way to remove that guesswork and to open and close them with just a tap.

[Rick_L]

I am sure that a qualified electrical engineer could design a circuit for what you want to do. Everything would probably fit on a small circuit board.

But is it worth the trouble? It wouldn't be for most of us.

The other half of this is that if you have some carbon buildup or a foreign object in the cutout, it's not going to close any better than just operating the switch manually. So to me it doesn't solve any problems, just has the possibility of new ones in addition to the old ones.

If you don't know any qualified sparky types (and most EEs don't do power), then google might be your friend.

[chevynut]

Rick, I can design this myself if I need to. I've done quite a bit of electronic design, building, and troubleshooting. But I don't think you have to go to the drawing board to do this. The one-touch power window controllers are pretty cheap and it seems to me like they would work well in this application. So why not? Then you don't have to guess when they're open or closed. It's not about closing "better", it's about getting them to open and close with a touch of a button instead of holding it. Apparently there isn't a problem with blowing a fuse when you reach the end of the travel and the motor stalls, but it seems to me that you could blow out the motor if you kept doing it. It's already hot from the exhaust. So maybe it's about reliability too. ;)

Another way to do this, and to control power windows, is to use a latching relay and a self-resetting circuit breaker that trips when the window motor stalls. The switch latches the relay, and when the circuit breaker interrupts power it unlatches the relay. The only thing is trying to stop it part-way which would require a little more circuitry.

I have a couple of one-touch up/down power window controllers so I may just wire up my cutouts and see if it works. ;)

[OLKY55]

I'm using Doug's cutouts with power window switches on my white car. I use the 3 second method - push the button and count to 3. I did have to rework them a little to keep them from hanging.

I like the idea of your power window controller, but I'm not sure how well it would work if they hang. I had wondered myself why they don't use limit switches, but they are pretty simple without and have been reliable. They're fun to play with at the stoplight.

[chevynut]

I did have to rework them a little to keep them from hanging.

What did you have to rework? When you say "hanging" do you mean they won't open and close all the way?

[OLKY55]

Doug's are a gate valve design. The gate is laser cut stainless plate. They use ball detents to put a little pressure on the gate and force it to seal, when it gets near closing.

After they got a little soot in them, the gate would hang at the detent and not quite close. I took them apart, beveled the edge of the gate, and greased the ball detents. They've worked fine since, but I suspect the detents may require regular attention. I have not had any problem with the motors.

I believe DMH are a butterfly valve. It would be interesting to hear a comparison of the different brands.

[chevynut]

I believe DMH are a butterfly valve. It would be interesting to hear a comparison of the different brands.

Yes the DMH are a butterfly valve, and I think that design is less prone to hanging up.

[Rick_L]

I didn't realize anyone was selling anything other than a butterfly valve.

For me, (and mine have never been used) the design and precision of the DMH valves seem adequate. I do know some satisfied users - one has had his several years and they've worked flawlessly with no tricks needed for open/close.

Olky55, do you have any photos or a link on the gate valve design?

[OLKY55]

https://www.youtube.com/watch?v=qi1VAtl6M9g

There seem to be complaints about most every brand online.

[chevynut]

- one has had his several years and they've worked flawlessly with no tricks needed for open/close.

Nothing is "needed", it's a matter of convenience. But let me ask you this....when you open your windows would you rather hold the switch down until they're down all the way, or do you like the more modern one-touch controls where all you have to do is tap the switch to make them go down? I like the latter, and I think it would be cool for the cutouts to work the same way. ;)

[chevynut]

Olky55, do you have any photos or a link on the gate valve design?

http://www.jegs.com/i/Dougs-Headers/776/DEC250A-1L/10002/-1?parentProductId=1282659

http://www.jegs.com/images/photos/700/776/776-dec250a-1l.jpg

[Rick_L]

Thanks for posting that, I've never seen that style before.