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So I've got a couple servos that I would like to hook up to an Arduino Uno. The servos come with an attached circuit board which I can't identify it's purpose.

Should I try to use the circuit board? Or just scrap it and use the motor and pot directly?

Edit: Just going to find a servo driver board and hook it up to the motor and pot directly.

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  • \$\begingroup\$ put your edit at the end of your post, don't delete the whole question!!! a huge reason this site works is so people can get answers to questions that have already been asked \$\endgroup\$
    – Ocanath
    Mar 30, 2020 at 17:51

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Your circuit diagram is incomplete. You should trace the connections to all pins of the ICs. Some tracks may go under them, so use a multimeter on 'continuity test' to find where they go. Include all component labels, wire colors etc.

You should also learn how to read designations, and search for datasheets based on them. U2 says '393' so it is probably an LM393 dual analog comparator (if it is then pin 1 should be connected to something). AQV252G is a 'PhotoMOS' relay. '385-25' is probably an LM385 2.5V voltage reference. Once you know what the parts do you can identify power supply rails etc. and lay out the circuit more logically.

Should I try to use the circuit board? Or just scrap it and use the motor and pot directly?

It doesn't appear to do anything essential, so if you can't use the original controller then scrapping it and controlling the motor 'directly' may be your only choice. However the Arduino may not have enough processing power to control two of them, so it might be better to dedicate a separate MCU to each servo.

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  • \$\begingroup\$ Great info, thanks. I had a lot of trouble finding datasheets on the components. For example for the 393 I was searching for 393 and EZ727 from STMicroelectronics specifically. I couldn't be sure an LM393 was the same thing. \$\endgroup\$
    – BottleZero
    Mar 24, 2020 at 2:12
  • \$\begingroup\$ As for the traces to the IC pins; I'm fairly certain the ones I left unconnected are just that. I went over them carefully with the multimeter. Is there a different way I should indicate that they are not connected to anything? \$\endgroup\$
    – BottleZero
    Mar 24, 2020 at 2:18
  • \$\begingroup\$ Pins 3 and 4 of the LM393 are connected to other components, so pin 1 (output of the comparator) should go somewhere. Set the multimeter to continuity test, put one probe on pin 1 and rake the other probe across all other other contacts on the board until you find a connection. What do the wires on the small plug-in board go to? \$\endgroup\$ Mar 24, 2020 at 3:53
  • \$\begingroup\$ Right, not sure how I missed that... added that trace. As for the wires in the plug in board, those just terminate in a d-sub connector. Ultimately I expect they will be what I connect with to interface with this board. \$\endgroup\$
    – BottleZero
    Mar 24, 2020 at 14:55
  • \$\begingroup\$ I guess my question now is; how might the brown and pink leads work together to drive to motor? \$\endgroup\$
    – BottleZero
    Mar 24, 2020 at 19:44

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