Extra Voltage for Servos using Adafruit 16-Channel Servo Hat

Support Product Questions
1

Hi all,

I’m running multiple servos off an ‘Adafruit 16-Channel PWM / Servo HAT for Raspberry Pi’. My understanding is that this servo hat can only take a maximum of 5-6v power input (which is then provided to the connected servos).

If I want to provide a higher voltage to the connected servos (8.4v), am I able to provide the power from an external source directly to the servos?
And would this just involve only connecting the signal and ground wires to the servo hat PWM connections (to allow for control signals to be transmitted to the servo), and then have the servo’s power and ground wires connect to the external source (to provide the 8.4v power)?

Thanks in advance!
Andy

2

In theory it should be fine.
Driving/working voltage can from a good power source while the pwm/control voltage will have less power from your controller (and as you say, a common ground)

That said, what does the datasheet say for your servo. That will be the specs you need to work within.

3

Thank you @Michael99645!

Servo specs allow up to 8.4v, so that should be fine. Is there anything else I should be checking re the servo specs? The servo is a PowerHD TR-5 - datasheet here

4

This is the relevant bit from a similar device, the DFRobot 8.4V servo SER0063

Control characteristics
• Control Signal: PWM
• Angle: 180° (at 500→2500µsec)
• Angle Difference: ≤5°
• Return Difference: ≤1°
• Neutral Position: 1500µsec
• Dead Band Width: ≤4µsec
• Rotation Direction: Counterclockwise (from 1500 → 2000µsec)
• Pulse Width Range: 500→2500µsec
• Signal High Voltage: 2-5V
• Signal Low Voltage: 0-0.45V
• Signal Period: 20ms

Note the signal high and signal low voltages - that confirms that it can be controlled from a 3.3V controller, so it would be fine with the servo hat. The datasheet you reference does not include that detail, although there is a Control Characteristics section with some of the corresponding data. It is possible that the signal voltage detail is left out because it would be unusual if it was different than most any other similar servo, but it would be good if you were able to confirm something close to the DFRobot figures, namely a high no greater than about 2.5V and a low that is less than about 0.5V.

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5

The ground of the external power source must be connected to the Servo HAT’s ground. Please check if you are doing that.

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