All about speed controllers

Few things in the industry have evolved over the years as much as the speed control. What started as a large, power-robbing wiper / resistor setup is now a highly efficient fully electronic unit roughly the size of a mini post-it pad. Electronic speed controls receive signals from your radio and receiver and translate them into motion with an infinite range. It’s not too technical at all. Read on to understand the differences between mechanical speed controls and electronic units.

MECHANICAL SPEED CONTROLLERS (MSC) WHAT IS IT?

A Mechanical Speed Control (MSC) is a mechanical device that regulates vehicle speed. RC History lesson: MSCs were originally based on slot car speed controls. An MSC for an RC car is made up of several components similar to those found in a slot car control. These include a contact board with wiring and wiper arm and, to fit it to a car, a throttle servo and mounting bracket. Early MSCs often included a four-cell AA battery receiver pack, but in recent years most have included battery eliminator circuitry (BEC) that powers the receiver with current taken from the drive pack.

The MSC’s job is to deliver power from the battery to the motor in gradations so that you have the ability to reduce or increase vehicle speed. The position of the wiper arm on the contact board (a kind of resistor) increases or reduces the amount of power that gets to your motor. When the wiper arm is at a slow speed position, the MSC burns off a certain amount of energy as heat that is lost through the resistor. This process is relatively inefficient, reduces run time and doesn’t offer as smooth a throttle response as an electronic speed control (ESC).

MAINTAINING AN MSC
While most enthusiasts eventually replace their MSCs with ESCs, there are a couple of things you can do to get the most out of what you have. Keep on top of dirt and corrosion. At the end of a day of running, let the electronics cool down and clean the MSC’s contacts with a pencil eraser and spray with a good quality motor cleaner. If your MSC came with some kind of protective cover, USE IT! Dust, dirt, grit and grime will all shorten the life of electrical components, especially those that are out in the open. While an enclosure may retain some heat, keeping dirt out of the mechanism works to your advantage.

ELECTRIC SPEED CONTROLS (ESC) WHAT IS IT?
An ESC electronically controls speed and does everything better than an MSC without the extra parts—and more. The benefits of an ESC are huge and include nearly infinitely adjustable throttle speeds, not just the three typically seen in an MSC. Many provide reverse and electronic braking. Some are programmable and allow you to pick “throttle curves” that fit a stock or modified profile, or that best match your customized vehicle. The ESC is extremely efficient as it only provides the precise amount of power needed by the motor and does not burn off excessive amounts of energy as heat. An ESC requires less gear to mount and operate. You’ll be able to toss the MSC unit, second servo, mounting bracket, and receiver pack (if your car has one) and install one little solid-state gem of a speed control.

ELECTRONIC, IS IT EASY TO USE?
Setting up an ESC is just plain easy. Most sport-level ESC’s are pre-wired with Tamiya battery connectors and a plug-in “bullet” connector for the motor. Once you have mounted your ESC, all you need to do is power on your transmitter, plug the motor and battery in, push the setup button and you’re ready to rock. Even Bob Hastings, the guy who writes Finish Line, can handle that! If you plan on racing, pick up a forward-only unit as reverse is illegal for sanctioned competition. You can even get an ESC that has a reverse lockout. Whatever speedo you finally go with, the most important fact is that even the worst ESC is better then the best MSC.

CONCLUSION
Today’s electronic speed controls are extremely programmable, can handle high current applications, and are extremely durable. Mechanical speed controls ultimately take a bow to their more efficient electronic counterparts.