# QUESTION: servo noise (3 servo motors used)

Hello, I'm onto a project for school where I've to write a code to control 3 servo motors with the Wii Nunchuk. This will be used to drive a sentry gun. The software ain't a problem. But the hardware is freaking me out. The servo motors are on the same seperate power supply. Arduino has its own power supply also. I'm using 2 diffrent servo's; Hitec HS-325HB and 2 rextors RX-325MB. The rextors have both got a torque of 6kg and the hitec one 3,7kg. They're connected on a 6V supply. Rextors are used for x- and axis, hitec for trigger. When the code is running and the rextors are moving then it seems that the hitec is receiving noise of the other 2 servos. Even when the trigger button to move the trigger servo (hitec) isn't pushed. The servo moves a certain amount of degrees left to right whole the time. Myself I thought to attach the trigger servo to its very own supply. But its looks stupid if I need 3 power supplys. Any advice? Thanks.

Queation is if the powersupply for the servo's is heavy enough.

Do you have a voltmeter to measure current? Voltage drop ? when the servos switch position

The Hitec draws 180mA, ==> http://www.servocity.com/html/hs-325hb_bb_deluxe.html - The rextor draws ?? could not find 3x 180mA = 540 mA - Can the power supply deliver?

my 2 cents, Rob

The arduino power supply is 4x1,5V(AA). The servo power supply is 4x1,5V(AA).

I can't find how much current the Rextor RX-325MB Power MG draws. But I guess that it ain't the problem. But if it's true, how can I solve it?

That's 180 mA with NO LOAD...

These servos have a load on them.

What you need to do is get yourself a fixed 6VDC power supply capable of outputing several amps, then measure the current each servo takes under load (alternatively, if you can contact the manufacturer and find out what the stall current is on the servo, that would would too).

With that information, you'd be able to size the battery supply properly.

I do think that 4 AA batteries won't cut it, though (unless they're LiPoly or similar) - I would actually go with 4 C or D sized batterys, or a 6 volt SLA. Another possibility would be 5-cell 6V NiMH R/C packs. A couple in parallel would give you the current needed for both the Arduino and the servos, most likely.

All this is a guess though without knowing the loaded current needs of the servos, though...