Servos Receiving too Much Current

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.

I have also tried to look up online the operating currents of the servos (Tactic TSX35 Standard Sport Servo), but I have not had any luck. Link from where I got the servos: https://www.towerhobbies.com/cgi-bin/wti0001p?&I=TACM0235&P=FR&gclid=EAIaIQobChMI79Ks2e7n5AIVVf_jBx2SSw_KEAkYBSABEgI-UPD_BwE

Does anyone have a different approach or fix for this?

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.

The power supply is 12V and 400W (so 33.3A) shown at GALYGG 12V DC Switching Power Supply 33.3A 400W, Universal Regulated Transformer AC 110V-220V to DC 12V, for LED Strip Lights, 3D Printer, Electronic Equipment, Computer Project - - Amazon.com

How is it wired? Got schematic?

MarkT:
Servos usually require at least 1A each. If you fail to provide adequate power they will misbehave and pull down the supply voltage.

I still don't think the servo would be needing more than one Amp if it works perfectly fine on an Arduino 5V pin powered over USB which can only output 500 mA (safety - How much current can I draw from the Arduino's pins? - Electrical Engineering Stack Exchange)

Ok, so which buck converters did you try and did you connect the grounds?

Captivcreative2:
I still don't think the servo would be needing more than one Amp if it works perfectly fine on an Arduino 5V pin powered over USB which can only output 500 mA (safety - How much current can I draw from the Arduino's pins? - Electrical Engineering Stack Exchange)

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?

MorganS:
Ok, so which buck converters did you try and did you connect the grounds?

vinceherman:
Do you have specs for your buck converters?

The buck converters are advertised as outputting 1.5V to 35V and a maximum of 3A (https://www.amazon.com/eBoot-LM2596-Converter-3-0-40V-1-5-35V/dp/B07RT95J4Q?th=1). The grounds are all connected back into the power supply.

Delta_G:
How is it wired? Got schematic?

I’ve attached a schematic on this reply.

You need to connect the grounds. Both the Arduino and the servos need a common ground reference.

OP's image:

Captivcreative2:
I still don’t think the servo would be needing more than one Amp if it works perfectly fine on an Arduino 5V pin powered over USB which can only output 500 mA (safety - How much current can I draw from the Arduino's pins? - Electrical Engineering Stack Exchange)

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. :roll_eyes:

You mean to say it “appeared to work” connected that way. :astonished:

Thanks everyone! The common ground was the issue. Didn't realize it was so important.