Asked — Edited

Ping Toymaker

Hey Tony, Just got those Bosch servos... thank you so much... Can I ask one more favour? What are the pin outs on these?... There appears to be 5 pins with a recessed sixth... I assume 2 are for a 12V battery and the others are used to drive the motor... Just don't know which one is which...

Thanks Richard


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@Richard R

Open it. The 2 powers the motor and the 3 pins go to the pot ;)


@DoomBot... my electronic knowledge is not as polished as yours Marc LOL.... I did open it... So the 2 lower pins go to 12V and the 3 upper pins plug into the ezb for control? That doesn't sound right.... Can you confirm?


Ok, I think I get it. It needs some kind of H-bridge motor controller... I managed to read the pot... Before I hook up a motor controller to the motors... Is this thing 360 deg rotation or is there a physical stop like a regular servo? I am thinking it is something like max 250deg rotation or so?


As far as I know it's 360 but you can use scripting to read the ADC pot and call your positions like that... the wiper is the middle pin of the pot so it goes V+, Signal, Ground. As far as the 2 pins yes you need an hbridge to get PWM and direction


Richard R, I had this saved for bosch, but the spec page will not display. This is the closest I can find till Tony responds. Post 276

Steve S


@Doombot... I have been rotating the motor worm gear by hand... Slow process LOL... Stops at 225 - 230 ... So these must be limited rotation since the pot can only read to a certain value... Looks like 1 - 225 degrees...

@Steve S Thanks, I will have a look....


Richard R, I think the pot only controls 100 degrees. Steve S


I was able to read 1 to 225 slowly cranking the motor by hand... Either way I get how they work now... I need a servo or motor control board with them.....


@Steve... actually you're right... The pot value doesn't necessarily reflect degs of rotation.... Thanks for the link, it helped immensely...


Richard R, I finally found this. DAVES POST #313 First real look... "I hope you can use these motors. Although I cant use them to lift my heavy 8 pound B9 arms I still think they are good little motors. I think they can be used in a lot of tight places to move loads up to what I show below. Also I think they would be great in lighter robot arms in smaller robots. Smaller then my full sized B9 anyway.

Here's what I've found in testing them:

The pot inside only reads for 100 degrees of the rotation. Attach an ADC port's signal pin from EZB to the center pin of the lower set of three pins on the motor and 5v & GR pins to the two outside pins. Install a ADC control in EZ Builber and assign it the the ACD port you have the motor's pot attached to. When the motor rotates, the ADC control in ARC will move from Zero to 5v as the motor rotates within that 100 degree ark. When the motor passes outside of that zone the ADC Control will fall to Zero till the shaft come back around to the start of where the pot starts to read the 100 degree ark again. If you remove the actuaitor arm from the shaft by carfully cutting it free with a Drummel or hacksaw the shaft will continully rotate.

The motor runs fine on 24vdc although it's only rated up to 12vdc. The two pins side by side on top of the three used for the pot are the power pins. I ran it for 6 hours with no load at this voltage. I never ran it for any leangth of time under load at this voltage. The higher the voltage is the stronger and faster it will run. With the motors doubled up I was able to lift a 3lb load 12" out from the shaft at 24vdc. I could lift nothing at 12vdc. I did not test lifting with only one motor but I'd guess the proformance is cut in half. It will hold a load without creaping down when power is cut.

The motor runs almost silent but does vibrate and hum a little when it moves under load. The noise is louder if you have it attached directly to a surface without useing it's attachment holes. These attachment holes have rubber inserts and if used with #8 machine screws absord moat all noise and vibration."


Thanks Steve... That's awesome....

Cheers Richard :)


Thanks @Steve. I was just going to dig this info up and you saved me the trouble. Good luck Richard. These are good and strong little motors. Double them up if you need more power.



could one of you post a link as to where to buy these bosch servos pls

United Kingdom

Richard R, I have just seen your post, sorry I probably did not explain the Bosch units properly. They are precision worm driven motors with internal feedback pot and are made for Audi cars and must control something like a ventilation opener.

The top three pins are the pot - the lower two are the (12v) motor.

To use as a servo here are some options

  1. Use an H bridge and read read the pot via an ADC port
  2. Use a Kangaroo/Sabertooth combo - this would allow control of 2 Bosch units
  3. This would probably do the job

I have designed a custom board and PIC for these units but I only did a small run of the boards and need them all for my beta test robots.

User-inserted image

Here is how I mechanically use them, first I carefully cut off the actuator arm with an hacksaw blade to reveal a nice 6mm spindle which fits all the 6mm hubs like

Here is a photo of the arm joints. The Bosch motors in the biceps are inside the white enclosure all other units are visible . User-inserted image

Here is a link to one supplier of the Bosch servos



Absolutely no worries Tony... I figured it out.... Just was confused for a bit when I opened it and didn't see a control board inside.... I got it working using a sabertooth 2 x 5 and wiring the pot to an adc port on my EZB4

Thanks again Richard

United Kingdom


I must admit I am not a robot maker, I am interested in the use of the Bosch VMC motor that are being used in your projects. I am a auto electrician in the UK, the Bosch VMC are used in a variety of applications on a number of Cars and Trucks (heating and ventilation valves, flap controls, headlight adjusters, etc) , the motors are available as 12 or 24 volt DC, Bosch part numbers :- 0 132 801 141 = 24 volt; 0 132 801 142 = 12 volt.

I am interested in how you control the motors in your applications ? I am currently attempting to use the VMC motors in a application to control water valves, I cannot find a control unit that will control the motor position using the internal potentiometer for position reference.

Can anyone suggest a controller that will work from a 24v dc supply ?




The way we control movement and postion of these little motor here is through the computer software called ARC. It connects over wifi to a remote control unit called EZB. That unit will receive feedback potion information from the motors built in pot thats attached to it's ADC ports. To move the motor back and forth to the wanted spot the EZB needs to send a single to an h bridge or motor controller reated for your motors voltage and amp draw attached to the power feed wires of the motor. Once this is all set up you need to write a script in ARC that will read the voltage of the ADC port the pot is attached to, then send a signal to the h bridge to move to a position of your choice. You can adjust your 24 volts down to a voltage the ezb can use through voltage regulators. Hope this helps.