I have a 5 Volts, 4 Amps power supply that gives power to a Raspberry Pi Zero W (120-230mA at 5.19V), and a servo motor with these specifications:
Operating Voltage Range (Volts DC) 4.8V ~ 6.0V
Current Draw at Idle 8 mA
No Load Operating Current Draw 240 mA
Stall Current Draw 1,200 mA
Maximum Torque Range oz. / in. 42 ~ 49
Maximum Torque Range kg. / cm. 3.0 ~ 3.5
Sometimes it is able to perform its action, and some other times it stalls half-way with the voltage dropping in the 3.5 V – 4 V range. Even though my power supply should be good enough in theory, I thought that adding a 4 F (16 V) capacitor could alleviate the problem, but it does not seem to make any difference.
Do you think the voltage drops because I am using the servo to perform a task at the limit of its strength, or that the servo stalls because it does not have a good enough power source?
Unfortunately, I do not have any tool to measure the torque of the item the servo is rotating.
Servo Motor: Hitec 32085S HS-85MG Metal Gear Micro BB HS/HT Universal Servo
Please bear with me. I have some electronics notions, but I am no electrical engineer. If you think I posted this message in the wrong stack, please let me know. It just seemed the most appropriate one to me for this question.
Best Answer
You basically had the right idea to use a cap for voltage stabilisation. But a cap with 4F capacity is a supercapacitor, and those have a very high output resistance. So your Supercap is not able to deliver the current needed for the servo.
Please try to use a few 220uF aluminium electrolytic type caps. They have output resistance in the milliohms range and they should do the trick of stabilizing your voltage.