Tuesday, 27 January 2015

Value-for-money - SG5010 servo

If you are looking for a low-cost standard size servo on Aliexpress, eBay, Banggood and such, you will stumble over the SG5010 servo. Four of these servos can be bought for USD 17.40 including shipping, which makes it an astonishing low USD 4.35 per servo. And that includes worldwide shipping!

But are those servos any good? Lets find out...

The servos came packaged in zip-lock bags, which were in turn wrapped in bubble-wrap. The servos come with the usual kit of servo arms, rubber grommets, bushings and screws.

The servo is "Tower Pro" branded. However, that may not necessarily mean much.

First impressions are quite positive. All four servos worked perfectly. The plastic feels sturdy yet flexible. The servo wire is about 30cm long and quite thick, so it should be able to carry a lot of current.

The size is 40.5 x 20 x 39.5 mm and the servo weighs 50g without an arm, but including the servo wire.

Like most servos, the case is held together with four long screws from the bottom. The screws are strong and tuck into thick plastic.

As advertised, the servo has two ball bearings on the output shaft. The gears are made from nylon. Unfortunately all four servos have quite some slop in the gears that can be felt on the output shaft.

The spline of the output shaft is 25 teeth, so it is compatible with Futaba, Tamiya, Feetech, Bluebird and many other brands. However, the spline seems to be a hair thinner in diameter and therefore the Tamiya or 3 Racing servo saver fit very loose on the spline. This will have to be taken care of when building a car kit, for example by using a Teflon tape to fill the gap.

The motor occupies the whole depth of the servo. It is wedged-in on all sides of the case. The bottom case cover has a recess for the bell-end of the motor. One slight issue with the design is that the can of the motor pinches the motor wires. None of our servos had any damage to the insulation, but it is certainly not ideal.

The electronics are wedged into the case and secured by the bottom case cover. Much better than other low-cost servos that let the circuit board float in the case, suspended only by the motor and potentiometer wires. Overall we give the construction of the SG5010 a thumbs up: very clever engineered by securing all components through mechanical parts of the case.

The soldering is very good. While the servo is advertised as digital servo, it is using an application-specific servo IC rather than a micro-controller. The motor driver employs MOSFETs, which make the servo perform much better than traditional analog servos with transistors.

The servo controller is from KC Semi in China. It is a KC2462 chip. This IC is rated for a maximum supply voltage of 9V, so in theory the servo should be able to operate directly from a 2S LiPo. The input bypass capacitor is an MLCC (Multi-Layer Composite Ceramic) type. It is hard to guess its voltage rating, but the larger size MLCC are usually 10V and higher.
We have ran two servos for several hours on a servo tester at 8.4V and they worked fine, but your mileage may vary. Some sellers advertise the voltage range of the SG5010 as up to 6V only. It may well be that there are different variants of SG5010 servos with different electronics inside.

The servo wire seems to be the same as used in Feetech servos. It is a thick 24 AWG and has a nice, flexible feel. The wires are soldered directly onto pads on the PCB so it is very easy to shorten the servo cable to the optimal length required in your vehicle.

The seller we got the servos from claimed a speed of 0.11s/60deg and 11kg torque at 6V. Yeah, right...
Compared to a Feetech FT5513M rated at 0.12s, the SG5010 is significantly slower. Some sellers list the SG5010 as 0.16s at 6V, which seems to be realisitc. Those sellers also rate the torque at 6.5kg, which again seems to be realistic. The servo is certainly quite strong. We wish they had made it weaker, yet faster.
At 8.4V the SG5010 is about as fast as the FT5513M at 6V.

With its high-power motor driver, the servo consumes more than 2 Amps when stalled. We have seen peaks of more than 4 Amps when the servo is reversing direction. Ensure that your BEC can provide sufficient current when using this servo.

Bottom line: A bit slow, slop in the gears, but good construction, build quality and use of decent materials. Certainly usable.

We wouldn't put this into anything fast or expensive, or a rock crawler, or a buggy. But to get an old TT01 going or for a M-chassis this servo would certainly work.

have fun with RC!

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