Does any one have a schematic of the circuitboard on a servo?

Thread Starter

born2dive00

Joined Oct 24, 2016
285
Does anyone have the schematic of the green circuit board inside of a servo?? It needs to have the feedback loop and the H bridge.

Please let me know Thanks.
 

jpanhalt

Joined Jan 18, 2008
10,246
Last edited:

Thread Starter

born2dive00

Joined Oct 24, 2016
285
On the princinton were does the connections go?
schematic for servo control.png

This is an industrial/hobby controller, but not for your typical model drone: http://www.uhu-servo.de/servo_en/UHU_Servo_Controller_300_en.pdf

And here's another link more focused on hobby servos: https://www.princeton.edu/~mae412/TEXT/NTRAK2002/292-302.pdf

If you want a particular brand, open it up and see what chip is used. Be aware that servos have evolved from discrete components to integrated to highly integrated circuits over the years.
 
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bertus

Joined Apr 5, 2008
20,773
Hello,
On the princinton were does the connections go?
The schematic shows a hobby RC servo.
The pin 5 is the input. A pulse between 1 and 2 mS with a repetition time of 20 mS is given here for the position of the servo.
The motor is connected between pin 6 and 10 in the schematic.
The chips powersupply can be between 3.5 and 7 Volts.
See the attched datasheet for more info

Bertus
 

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jpanhalt

Joined Jan 18, 2008
10,246
upload_2018-7-28_8-51-4.png

My ground answer may be confusing. Assuming the servo wires are black red white. The ground is the black wire. The PWM is the white wire. And VCC is the red wire. If the coding is brown red orange/yellow, then brown = black, red = red, and orange/yellow = white.
 

ebp

Joined Feb 8, 2018
2,332
The servo control IC in the above posts has the advantage that the position feedback mechanism uses a potentiometer as a voltage divider whose output is compared to a linear ramp generated by the IC. This is very well suited for the pan-tilt because that is exactly the sort of signal that it produces. It might be necessary to change the fixed resistors in series with the potentiometers in the the pan-tilt to get the required voltage range. The "top end" of the pots int he pan-tilt would be supplied from the servo IC.

The internal NPN drivers for the motor could be used directly (current limiting resistors needed) to drive the inputs of triac-output optocouplers to control triacs to run the AC motor. The external PNP transistors are not required (these controllers used external PNP transistors because putting them on-chip isn't compatible with the IC fabrication process used).
 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
Here is an updated schematic so I understand everything and their placement. do I have everything correct?schematic for servo control.png

View attachment 157063

My ground answer may be confusing. Assuming the servo wires are black red white. The ground is the black wire. The PWM is the white wire. And VCC is the red wire. If the coding is brown red orange/yellow, then brown = black, red = red, and orange/yellow = white.
The servo control IC in the above posts has the advantage that the position feedback mechanism uses a potentiometer as a voltage divider whose output is compared to a linear ramp generated by the IC. This is very well suited for the pan-tilt because that is exactly the sort of signal that it produces. It might be necessary to change the fixed resistors in series with the potentiometers in the the pan-tilt to get the required voltage range. The "top end" of the pots int he pan-tilt would be supplied from the servo IC.

The internal NPN drivers for the motor could be used directly (current limiting resistors needed) to drive the inputs of triac-output optocouplers to control triacs to run the AC motor. The external PNP transistors are not required (these controllers used external PNP transistors because putting them on-chip isn't compatible with the IC fabrication process used).
 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
Ok so assuming that the resistors are giving 180 degrees of rotation, what would the resistors need to be replaced with to give 360 degree NON Continuous, What I mean is the servo arm travels from 0 to 360 stopping at 0 and at 360.
I am attempting to use this in another project as EBP knows about.


 

Thread Starter

born2dive00

Joined Oct 24, 2016
285
EBP could you send me a schematic or a drawing of what you mean, with the triacs... You already know that I am trying to use a lower power PWM to drive a slo-syn motor. but I do not have the theoretical knowledge how to do this, I am very much a visual learner.

The servo control IC in the above posts has the advantage that the position feedback mechanism uses a potentiometer as a voltage divider whose output is compared to a linear ramp generated by the IC. This is very well suited for the pan-tilt because that is exactly the sort of signal that it produces. It might be necessary to change the fixed resistors in series with the potentiometers in the the pan-tilt to get the required voltage range. The "top end" of the pots int he pan-tilt would be supplied from the servo IC.

The internal NPN drivers for the motor could be used directly (current limiting resistors needed) to drive the inputs of triac-output optocouplers to control triacs to run the AC motor. The external PNP transistors are not required (these controllers used external PNP transistors because putting them on-chip isn't compatible with the IC fabrication process used).
 
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