# High power servo



## Dr Morbius (Sep 21, 2004)

I came across this website. I want to turn a windshield wiper motor into a high power servo. Anyone ever build one? Any advice on the schematic? I don't see where the potentiometer goes. The Schematic has a Pot, but I think that's for adjusting the gain. HELP!:googly: 
http://homepages.which.net/~paul.hills/Circuits/PowerServo/PowerServo.html


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## randyaz (May 26, 2006)

Not a roll your own solution, but, Ive been doing something very similar to this with a wiper motor and a window motor but taking the easy way out...a BasicStamp 2/Prop2 and HB25 motor controller. Im getting good control of motor speed and shaft direction. The motor basically becomes a continuous rotation servo. Im now tinkering with a QTI sensor as an encoder to sense precise shaft position.


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## Dr Morbius (Sep 21, 2004)

Cool! That's the key really..The whole thing needs to know where the shaft is at any given time. Just like a POT in a servo does. I know SOMEONE knows how to decipher the schematic I linked to....


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## Dr Morbius (Sep 21, 2004)

Anyone?


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## Richie (Jan 4, 2007)

Hi there Mobius,

I skimmed through your first post and link, and if I'm understanding correctly, you seem to want to do what my other robot club has already done, and I'll be doing in the coming months. I myself haven't modified my life size robot yet for programmable torso movement, but I do have all the components for the job. I'm using an excellent Dewert wiper motor connected to OOPIC ll motor controller. There is a lazy susan beneath the torso on my robot, which will accept the proximity sensors, about 8 of them.

With some fancy programming, the OOPIC always knows precisely what position the torso is at any given time. My robot will be programmed to appear as if he is on sentry duty, very slowly moving from about 45 degrees left from a center position, back to the right, and pauses in between. For the OOPIC controller, I do have the code written already thanks to a friend giving me a hand with it. The link below is to one a members website showing how this is done.

I hope the moderators don't mind I'm forwarding you to a non-halloween website, but it appears you really could use some help with what you're trying to do, so I thought I'd chime in. I hope this helps.

http://www.b9robotresource.com/b9_rotation.htm


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## Dr Morbius (Sep 21, 2004)

A B9er! I used to belong to that club a LONG time ago! How is Dewey? I'm a moderator, and I can say first hand that ANY link that points someone in the right direction is OK, Halloween related or not, especially in the Prop section. How many resource sites for parts are actually Halloween specific? Not many.
Thanks for the link. I actually want to turn a wiper motor into a servo, so it can be controlled with a servo controller board. If it isn't possible, then I'll have to give your guys' suggestions a try.


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## Richie (Jan 4, 2007)

Hey Mobius,

Thanks. As for Dewey, he quit the club years ago and Mike J is the club president now and actually acquired a license for the club, which we all work under as vendors for parts or services for people around the world or here in the US. Our club is the only B9 builders club that has a license to produce parts and was the main reason I and several others, including the link I sent you to, actually where blessed to get interviewed by Forbes Magazine regarding our robots. 

Anyway, back to your Halloween project. By using the Magnevation dual PWM driver board (motor controller), it's designed for high amp motors, such as a wiper motor. The components are a bit expensive due to the fact they are used in robots or other high end props, but are well suited for the task. It's possible one of the more normal vendors we all tend to use for our halloween props may have something equally suited for your purpose and for less money. 

When I purchased my OOPIC ll starter kit which is the main control board and cables, it was $69.95. The Magnevation Dual PWM motor driver board was $75.00, and the last components was a 6" 40-pin ribbon cable for $5.95. I forget what the sensors cost or their model number, but should you require more information, I'd be happy to get it for you.


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## Dr Morbius (Sep 21, 2004)

It seems what your saying is that a specialized controller is necessary for high amp motors anyway, so converting a wiper motor to a servo would be pointless as the PWM motor controller handles the positioning of the motor shaft as well?


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## Richie (Jan 4, 2007)

Well, as I understand it, a wiper motor may require several amps to run correctly. Perhaps someone else may know the basic specs for the Dewert or Saturn type wiper motors normally used. The Magnevation PWM controller does what the OOPIC ll control board tells it to do and can _NOT_ track position by itself. . There are 3 components required for what you need to do using the OOPIC electronics. The OOPIC ll control board, Magevation PWM motor controller, and sensors to track position.

The following links on the SuperDroid website are what you'd need plus the sensors.

http://www.superdroidrobots.com/shop/item.asp?itemid=3 (OOPIC ll MicroController)

http://www.superdroidrobots.com/shop/item.asp?itemid=254 (PWM Motor Controller)

http://www.superdroidrobots.com/shop/item.asp?itemid=124&catid=2 (I believe this is the correct starter package, please verify before purchase)


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## Dr Morbius (Sep 21, 2004)

Thanks..BTW Super job on that B9...I'm Mega impressed! Now, if anyone else has a take on the Schmatic I posted above, I would greatly appreciate it.


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## DeathTouch (Sep 6, 2005)

Hey, that maybe me. The op amp that they show in this schmatic, I don't think could generate that type of power for the wiper blade that you need. YOu need a op amp with a little more kick to it, and one that one screw up with the motor's noise. It looks like they just use a servo in this one, which doesn't take a lot of power. What you may need is relays. That should be good enough to power your wiper blade motor.


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## DeathTouch (Sep 6, 2005)

You remember that relay I sent you in the mail. That would do the trick.


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## Dr Morbius (Sep 21, 2004)

Oh yea! Thanks!


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## .id. (Jul 3, 2006)

Hmm....The opamps should be able to do 3 amps normally and 4 amps surge. I'm not sure what a wiper motor would draw, so DT may be correct about needing a bigger opamp or Power transistors designed for that load. I'm just not sure you'd want to use a relay as it is either on or off (think digital), nothing in the middle like a servo (think analog).
As for the potentiometer, I'm a bit rusty on my feedback circuits, but here goes.....
The center terminal would connect to the "Actual Position" input , one of the end terminals would connect to the V+ (or Vbatt), and I'd guess that the other end terminal would connect to the ground. I think pin's 1 & 3 of the L149's wouldn't connect to ground (as shown), but would connect to V-. My assumptions would be that you would feed a voltage between 0V and V+ (or Vbatt) into the "Demand Position". So.....If you fed in 0V, the motor should turn one direction. If you fed in V+, the motor should turn the opposite direction. And if you fed in V+/2 (half of V+), the motor should stop. Between V+/2 and V+ or ground would be varying speeds. 
Hope this helps (and isn't too wrong)!


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## Dr Morbius (Sep 21, 2004)

Thanks Id...I knew there was something screwy in that circuit.


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## Dr Morbius (Sep 21, 2004)

.id. hit the nail on the head on this one. Seems the 3 schematics are to be connected together to handle the loads and feedback. The position POT goes in the summing junction section, the two pins on the pot v+ and V- and the third, reading the wiper motor shaft goes to the actual position pin. The demand, V- and V+ would be akin to the 3 wires of a normal servo and would connect directly to the servo controller board. I just hope I'm not wrong either, or I may just blow a Parallax board, but nothing ventured nothing gained!


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## .id. (Jul 3, 2006)

Well, just build it with a Potentiometer in the demand position first to make sure it works as designed before hooking the demand line up to you Parallax board...


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## Dr Morbius (Sep 21, 2004)

Thanks ID , but I don't know how to do that...should I just apply a voltage to the POT and see what happens? How do I know the POT is in the demand position?


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## Death Master (Jul 1, 2007)

Hay Doc, I found this site when I was making my known high power servo, hope this helps you.http://www.webcom.com/sknkwrks/mowers.htm


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## Dr Morbius (Sep 21, 2004)

Cool, but I really want to convert a wiper motor to a servo.


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## Death Master (Jul 1, 2007)

Doc, If you keep looking through this site it has a section on how to make a wiper motor into a servo. Look under Powerful servos, the guys in this project need one and ended up making one out of a wiper motor.


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## Dr Morbius (Sep 21, 2004)

I did look through it, but I'll try harder this time!


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## Dr Morbius (Sep 21, 2004)

OK, I looked and all I found was a dead link to "Powerful Servos".


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## Death Master (Jul 1, 2007)

Doc, Go down the page until you get to CONVERTING STANDARD R/C SERVOS INTO MONSTER SERVOS, then look in that section, you should find it, I just went there and it worked for me. It should show you how to hack a servo and a wiper motor, it also has a section on how to make the H-bridge for the more powerful motor, and it should also show you how to hook everything up.


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## Dr Morbius (Sep 21, 2004)

Ok I see it now...It appears that it's possible to use an ordinary servo's PC board in conjunction with an H-bridge driver to power the wiper motor. This seems like a much easier solution for building a high power servo, although it doesn't say what value the feedback pot should be?


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## Death Master (Jul 1, 2007)

Check the pot that you take out of the hacked servo with a ohm meter.


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## Dr Morbius (Sep 21, 2004)

Oh of course..makes sense, as that's the same pot used in the original circuit.


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## .id. (Jul 3, 2006)

Good catch, Death Master. That would be the easiest as the Parallax should already support a normal servo motor.


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## Dr Morbius (Sep 21, 2004)

Now I'm concerned about voltage. To get the best speed/torque from a wiper motor, I would need 12 volts. That seems like alot to run through the servo board and the Parallax. UNLESS the motor voltage is bypassed completely through the Hbridge circuit..?


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## .id. (Jul 3, 2006)

Yeah, the H-bridge becomes the driver for the motor and the servo board becomes just the "controller". The H-bridge buffers the control signals coming in and allows you to drive any voltage/amperage of motor (limited by the design and components in the H-bridge).


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## Dr Morbius (Sep 21, 2004)

Cool! Thanks alot, DM and ID...You have helped me tremendously and I am truely grateful. I think I now have what I need to make my................


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## gmacted (Jan 18, 2006)

Dr Morbius said:


> Cool! Thanks alot, DM and ID...You have helped me tremendously and I am truely grateful. I think I now have what I need to make my................


I'm guessing it has something to do with a skeleton attached to your 3-axis skull. A full motion skeleton? Am I right????


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## Dr Morbius (Sep 21, 2004)

Hmmmm.....close, buuuuut....no.


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## Shock (Apr 14, 2012)

*A link to converting standard servos to monster servos please*

Can someone please post a link to "converting standard servos to monster servos" Thanks


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