Servo - December 2013

BotBitz

10A ESC

Voltage: 3V–12V

Current: 10A peak

Dimensions: 0.91 x 0.71 x 0.32 inches

Weight: 9 g

Cost: $15 AUD

Comments: BotBitz approaches the ESC market from an unusual angle. Their motor controllers are actually reprogrammed Chinese brushless ESCs. The reprogramming is used to convert them to dual direction brushed motor controllers. Recycling these ready-made mass-produced motor controllers and reprogramming them puts BotBitz on the bottom of the price range while still having a solid reliable ESC.

With a 10A rating, the BotBitz 10A ESC is well suited for 1 and 3 lb fighting robots. If you’re looking for advanced features, you’ll have to look elsewhere for now. However, if you want a bare-bones ESC in a compact easy-to-use package, the BotBitz 10A ESC is a strong contender.

BotBitz

85A ESC

Voltage: 6V–24V

Current: 85A (1 minute)

Dimensions: 2. 58 x

1.34 x 0.69 inches

Weight: 80 g

Cost: $75 AUD

Comments: This is the larger of the BotBitz reprogrammed ESCs. With an absolute 200A maximum and tests proving that it can handle 85A for a full minute without melting or catching fire, the BotBitz 10A ESC is a strong contender in the 12 and 30 lb classes if you’re looking for a bare bones controller.

Holmes Hobbies BR-XL

Voltage: 6V–25V (2-6s lipo)

Current: 80A continuous

Dimensions: 1.97 x

1.54 x 0.83 inches

Weight: 45. 6 g

Cost: $99.99

Features: BEC, regenerative brake, active hold brake, Castle Link programmable.

Comments: The BR-XL is the least robotics-specific ESC presented. These controllers were originally made for high powered RC rock crawlers. The features that were needed for these crawlers happened to closely match the needs of 12-30 lb fighting robots, so over the last few years they have seen widespread use. Unlike many RC car ESCs, the BR-XL actually appears to live up to the published specs, and has been used in the drive system on 30 lb fighting robots with high powered drive systems. These ESCs are durable, compact, and easy to use. For a 12-30 lb robot, they are certainly worth putting on the short list of options.

Holmes Hobbies has also recently released a BR Mini rated for 30A continuous and 80A peak with otherwise similar functionality and specs at a price of $69.99.

They look promising, but I have not yet seen them in use in a robotic combat application.

Equals Zero Designs Ragebridge

Voltage: 12V–36V,

50V absolute limit

Current: 30A continuous, 90A peak with limiting

Dimensions: 4. 5 x

2.0 x 0.5 inches

Weight: 99 g

Cost: $185

Features:

Adjustable current limiting, channel mixing, flip control, regenerative braking, BEC.

Comments: The Ragebridge is one of the newer ESCs on the market, and it has quickly gained popularity. The biggest feature on the Ragebridge is the adjustable current limit. This feature allows you to tweak the performance of the ESC to balance pure power vs. reliability. This also reduces stress on motors and batteries; when they’re limited, you’re never pulling the sometimes massive peak current loads, while still getting the vast majority of the usable power band of the motor.

Whether it’s due to the way the regenerative braking code is written or just an aspect of how throttle ramping is handled, the Ragebridge also has an extremely smooth throttle response. For the 12 and 30 lb class, the Ragebridge is a fantastic motor controller option and should be considered in most applications.