Programming HS-322HD Servo

We found an old hs 322hd servo while digging through old stuff.
We tried programming it using the Java Servo class, but it’s not moving.

We know the servo moves because we took it home, plugged it into an RC sailboat, and caused it to move, but when we plug it into our roboRIO, PWM, it won’t move.

We are sending signals to it, because setAngle() affects getAngle() correctly, but the hardware is not interacting.

Has anyone else experienced similar issues with servos?

We figured out the problem:
The amperage provided by the roboRIO is 15 mA. The servo requires a minimum of 180 mA.

We plugged signal and ground into the roboRIO, and sent the red voltage wire over to the 5V/500mA ports on the VRM. It worked like a dream!

Make sure to search the manual for the rules on how to legally power a servo. R31 is the main one to read.

I don’t think your reading the spec correctly. 15ma is the limit on the data pin. 2.2a is the limit on the 6v power line on the PWM header.

Is the power LED red indicating an issue with one of the power supplies?

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These are the roboRIO specifications provided on the NI website.
Maximum output current (pin not specified) says 15 mA.
The user manual does say 6 V
Where are you getting 2.2 A for the PWM?

Page 6.

+6.0 V power output
Output voltage: 5.5 V to 6.1 V
Output voltage with load > 360 mA: 5.75 V to 6.1V
Maximum current: 2.2 A total

For some reason, the PWM is not providing power to the servo then. We tested two of the PWM ports. We might try a multimeter to see if there’s anything out of the 6V pin.


you gotta be kidding me!

we were not able to get it working off the pwm ports, and we don’t have the time to figure out new hardware.

do you have any advice or pointers?

On your roboIO is there a red light for Power?

Check the Driver Station bottom tab, too.
That lists any power faults the roboRIO encounters.
A short on the PWM 6v power rail could be cutting off all the PWM power pins.

A lot of the PWM cables that FIRST provides have the red wire cut. Make sure the red conductor is continuous to the servo.

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