Robotics/RC People - Servo question (throttle control)

Tech11

Tech11

Well-Known Member
Joined
Dec 7, 2007
Location
Greensboro
Okay, lets start off and get this out front, I'm a TAD eccentric when it comes to some things.

In my LJ switch panel I've swapped in 2 Cherokee fog lamp switches for my future offroad lights and rock lights (I wanted a clean look)
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In looking around at various projects I found an extended idle switch from the police package Cherokees.
aimg805.imageshack.us_img805_8190_extidlesw.jpg

When wired up correctly it will bump the associated police packaged 4.0 idle up to about 1000ish rpm, it was for running police lights and all the extra police "stuff".

1000 RPM isn't really much of a bump for anything that I have in mind, mainly winching.
So from what I've read on this switch, it looks like I would have 2 wires to play with, which should give me a 12v signal (+/-)

I've not messed with RC stuff/servos and the likes in years, but just poking around a few sites it looks like I SHOULD be able to wire up a servo with an arm, and once it receives the signal from this switch with appropriate adjustments I could have it pull the throttle back and idle at whatever RPM I finally adjust the servo to pull to.

Yeah, hand throttle, sure, but this is just how I do things sometimes. I'm really looking for input on making this work. Or maybe pitfalls or something I'm overlooking.

I'm thinking servos because I'm not really sure about solenoids, I was thinking servos would be simpler, well more simple in this rube goldberg contraption.

waterproof high torque servo most likely?

or is this just crazy?
 
have to have a "free wheeling" servo. Or it will bind up and not allow you to move to WOT. Or set the servo so it will only "hit" the throttle once energized. Make it non contact in other words
 
So I CAN do it with a servo and 12v? Just need a 360 degree servo?

I'm looking at a robotics/rc site now. I've seen some simple circuits, but I'd really rather not do that if I can avoid it.
 
yeah but all this will be with the servo only, You need a servo that will run out a certain distance and hit your throttle but never touch it if you are using your go pedal
 
should be able to use wire similar to whats used in hand throttle.

I think a pull solenoid would be too much of a sudden pull.

I'll have to get a servo and see if I can dig up or borrow an old circuit trainer/builder and see what I can come up with, as most servos ssem to be 6v max anyway.

I need an indoorsey project to fool with this winter anyway.
 
I think I have it.

http://www.robotshop.com/images-scientific-manual-servo-controller-assembled-1.html

12v from the ext idle switch is applied to this circuit, and the servo is activated, and would pull back on the throttle.

The servo would be attached to the throttle similar like a hand cable, and adjustments to the servos pull can be made with the potentiometer.

It seems to be a matter of bracketry for the servo, a case/waterproofing for the circuit, and wiring the switch.

There is also an option of using actuators, but they are around 80 bucks(was trying to keep it inexpensive), but if I can't get the servo to work I may try one anyway, just for the CDI factor.

Ideas/opinions?

Flick the switch and idle goes to whatever I set it to.
 
Tech11 said:
Ideas/opinions?
Click to expand...

Appears you're intent on reinventing the wheel from scratch and slinging a bunch of $$ in the process?

Dashpots were used on carbs for 30 years to bump the idle for a variety of reasons... reliable & just plain work. About 75% of pre-'86 vehicles have them when equipped with A/C.

astatic.summitracing.com_global_images_prod_large_hly_46_74_cp.jpg


That AND the bracket can be had for <$5 at any self-pull yard... DONE
 
Dave has the right idea. What you don't realize is that a servo is a stepper motor. It's not controlled by a simple variable voltage, it's all computer controlled. That's how they can run such high torque and precise control. That circuit you showed runs off 9 volts, and might burn up at 12. Now you could dial that pot on the board to a preset, then apply voltage to energize the circuit, and the servo would move to that position. However, to return it to home, you'd need to dial the pot back to zero, otherwise the servo would just sit there. Plus, having a linkage attached means that the servo will have to move with the throttle arm even when it's not energized. This will put added drag on the throttle and potentially tear up the servo. Basically, you're better off using an actuator of some sort that's not constantly in contact with the throttle arm.
 
I think its an awesome idea regardless of which way you execute it. You can always do a hand throttle if you aren't happy with it, but you'll be the only guy around with an extra idle switch that works! Why not try to find the device used to increase the idle in the police cherokees, and modify it to fit your needs with a lever and pivot.
 
The cruise control servo from a jeep can be used as a throttle kicker too. I installed one on my f150 for pinching and welding. There is a write up on mallcrawllin that even shows jeep guys how to wire it so it functions as a throttle kicker when activated, but still functions as a crises control when off. It used two switches and four relays if I recall.
 
Sorry double post.
 
If I wire up the switch as intended it'll bump the idle to 1000 rpm, Dave tell me if I'm right or wrong.

I have the schematics and pin outs to wire it up as intended, but I was thinking 1000 rpm wasn't enough of a bump for winching. I idle like 680ish.

I'm looking for all the input I can get, I was thinking servos, because that's what came to me off the top of my head.

What kind of bump (length) does a dashpot usually have?

I'm not looking to reinvent the wheel, but maybe put some spinners on it.:lol:
 
Tech11 said:
What kind of bump (length) does a dashpot usually have?
Click to expand...

Usually not much of a "throw", but since all it does is keep the throttle arm from going all the way home (basically a dynamic "throttle stop") and depending on the distance from the TB's shaft> that spot on the arm (radius), it doesn't take much to bump the idle up.
 
seems to me that an electric actuator would be easiest. hold the button down for more actuatioin and you are able to self control the RPM every time?
 
IS 1000rpm enough for winching?

I was winching some huge ass concrete barricade things at work, and my low batt light/warning came on, and I sat in the cab and held rpms around 1500 or so.

Some of the electronic throttle controllers I've seen seem to hold rpms around 1500-2000 rpm for winching or welding.

It's looking like a 12v actuator is the animal I need, if I stick with this idea.
 
This has got me thinking...
An electric motor with a 2 way toggle and a worm gear would allow you to adjust as needed.
 
Tech11 said:
IS 1000rpm enough for winching?
I was winching some huge ass concrete barricade things at work, and my low batt light/warning came on, and I sat in the cab and held rpms around 1500 or so.
Some of the electronic throttle controllers I've seen seem to hold rpms around 1500-2000 rpm for winching or welding.
It's looking like a 12v actuator is the animal I need, if I stick with this idea.
Click to expand...

Im pretty sure your winch will outdraw your alternator...so even if you run the idle ay up you will still draw the battery down over an extended period.

That said you will certainly increase the time to dead by increasing the idle. So this is a worthwhile deal. My mind kind of works backwards from yours (and most folks for that matter) my first question is:
"What is your goal?"

Do you want to be able to winch for 30 minutes non stop?
I would start from a goal then calculte the draw, heat loss, etc and see what input you need from the alternator, then se what idle you need to approach that, and then build your throttle bump from there.

As for doing it...heck your imagination is your limit....I swear though Id have my movement under the hood on the throttle arm not in the floorboard at the pedal.
 
Forget all about a servo or linear actuator or any of that crap. Make yourself a vacuum leak with an electric dashpot.

Warn motors pull in the neighborhood of 500A at full draw. I don't know what the chinese motors do... but your alt should be near peak output at 1000-1200 engine RPM.
 
The "mechanicals" will be right near the throttle, in the engine compartment. I'll attach to the throttle using wire cable so at rest and in normal use there will be slack, then when the mechanicals activate they will draw up the slack then pull the throttle increasing the rpms.

The electronics will be in a project kit box, and wires run to the switch in the dash.

From the schematics I've seen so far, it looks like I can't wire the switch up to the pcm as in the Cherokees as the I'm missing the correct wires, I was thinking power steering pressure wire, but I think that would be 100 rpm tops(if it's even there)

There's a kit out there that does this with a hand held controller to increase/decrease rpms for 400 bucks. I've just got a few kinks to work out, and all winter to fool around with this.
 
I used a servo to command a certain choke position, and I designed a simple spring mechanism so that the servo wouldn’t burn itself up trying to get to a position when the throttle was closed and the position of the fast idle cam can’t be adjusted. I didn’t have my CNC machine running at the time or I would have made a housing and ordered a smaller servo so that it all had about the same appearance of an electric choke, except for an extra wire. That extra wire would go to a temperature sensor in the coolant circuit.
Click to expand...

I'm KINDA close. :bounce2:
 

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If everything is working correctly in your charging system and you have a good battery you don't need the idle speed bumped. I've done some extreme winching in situations I could not even think about cranking the engine and got through with one battery on a double line pull and a 8274 strung out to almost 140 ft. I hung a 1 ton Suburban from a bridge and swung it like a penyatta! All without the engine running at all.:rolleyes:
 
Your Hot Dog Guy! said:
If everything is working correctly in your charging system and you have a good battery you don't need the idle speed bumped. I've done some extreme winching in situations I could not even think about cranking the engine and got through with one battery on a double line pull and a 8274 strung out to almost 140 ft. I hung a 1 ton Suburban from a bridge and swung it like a penyatta! All without the engine running at all.:rolleyes:
Click to expand...

Thats somethin else I've read, and i'm wonderin. My red top optima maybe aint so optima, and the oem alternator isn't that big to begin with.

But come on man. BUTTONS. that do STUFF.
 
I may be WAY off base here, but I think there's an easier way to accomplish this. If your vehicle has A/C, there should be a wire that when energized bumps the idle up for the compressor and high speed electric fan (if equipped). You may want to look for it. I know the Painless wiring harness that I used for my TPI swap into my YJ had that wire and I used it to bump up the idle for my OBA since I didn't have A/C in my YJ
 
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