I'm attempting to run multiple servos off of a power supply, but the servos are currently receiving too much current. I've used buck converters to step down the voltage to 5.5V as the servo runs from 4.8V to 6V. Each servo is on its own buck converter.
A single servo works fine powered off of an Arduino. Using a multimeter, I found that the servo idles at about 0.01A (It may not be precise as that is as many decimals the multimeter would display) and ran at a maximum of 0.22A while turning.
When hooked up to the power supply, the servos would initially jerk but then stall ignoring commands from the Arduino while receiving a constant 0.9A.
I have attempted to use resistors to mediate the issue. The problem is I'm not sure exactly how much resistance I need, so it has been mainly a guess and check game up to this point. I've narrowed it down to somewhere between 220 and 1000 Ohms to achieve 0.01A of idle current, but the servos still don't work with the combinations I've tried in this range. Using the Arduino's power for the servos, I found that the resistance needs to be within 10 Ohms for the servo to function.
Servos usually require at least 1A each. If you fail to provide adequate power they will misbehave and pull down the supply voltage.
The 0.22A you saw was erroneous as the peak currents will not show up on a multimeter which averages over
timescale of a second or so. The supply must provide the peaks without struggling.
Servos are more difficult than they should be. They are supposed to be powered from batteries and most batteries have no difficulty supplying lots of power for milliseconds or seconds. So the servo manufacturer never tells you what the maximum current is; you have to guess at the current.
A buck converter can be built for high current but that gets expensive quickly.
Resistors are completely wrong. That's like slowing down your car that's "too fast" by dragging a lump of concrete behind it.
You never actually said what is the source of power for your project. We need to know the voltage and current specifications. Or what type of battery it is.
MorganS:
You never actually said what is the source of power for your project. We need to know the voltage and current specifications. Or what type of battery it is.
Many servos do pull 1A or more when stalled.
Some servos can be powered from the 5v pin under some circumstances. But this very often leads to power problems like those you describe using your buck converters.
Do you have specs for your buck converters?
So you have deceived yourself. Of course, the USB pin is "rated" for only 500 mA and the (was it?) UNO has a polyfuse to limit this, but that in no way means that the servo was not transiently drawing up to an Amp.
You mean to say it "appeared to work" connected that way.
