Voltage decrease 16 servos on uSSC

Hello I have a problem with my powersupply.
I got 2 uSSC (Micro Serial Servo Controller) to control upto 16 servos (4,8-6V), with only one board everything works fine if I calibrate my powersupply to 5V. After plugging in the second servoboard my sourcevoltage decreases from 5V to 2-3V.
I think the reason is the start-up peak, because 16 servos need high current. How can I set up my powersupply that the voltage doesn’t decrease at turning on? I want to limit the current, but don’t know how :question: .
My power supply is:
cgi.ebay.de/ws/eBayISAPI.dll?Vie … NA:DE:1123
Thanks for your help


I suspect that your power supply just isn’t strong enough. Do you know what current is being drawn by all 16 servos? If you have the current limiting enabled on your power supply, you probably want to turn it off. As it is, the problem is that the current is already limited, and that’s why you’re seeing the voltage go down (that’s the only thing that the power supply can vary when you pick the load and set the current limit).

So, if you’re not intentionally limiting the current from the power supply, I suspect that you’ll need a more powerful supply. Computer power supplies are often a cheap way to get 5V with a lot of current.

- Jan

Hello Jan,
Thanks for your help.
Yes my powersupply only provides 2A. I think when turning on all servos together they need more than the 2 Amps. This causes the collapse. I can’t find a datasheet for the servos i am using which tells me something about the Watt or Ampere. In the servo-datasheet only the voltage is mentioned. For testing, i’ll try it out with 2 powersupplys (5V and 2 Amps), because I have found a mobilephone-adapter which provides 5V.
It was a failure to set up my power supply before calculating the restistors and current needed :frowning: .
But no problem :slight_smile: I think with the second power supply it should work.

Is it dangerous for my servos to use a computer powersupply with 5V and 25amps current?
I don’t want to blow them up :wink:
Thanks for the good support!

Current ratings on power supplies are maximums: a 25 A supply will supply up to 25 A; it will not force it into your circuit if the circuit isn’t trying to draw it. However, you might want to put in an appropriate fuse in case your circuit does try to draw 25 A (e.g. because of an accidental short circuit).

- Jan