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myRC
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« on: December 16, 2008, 09:16:24 AM » |
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If you don’t have a digital servo in your car or truck, you need to stop right now and read this article. Digital servos perform significantly better than their analog counterparts. They offer higher resolution that reduces deadband for ultimate control, and they offer a faster control response and increased acceleration. They also produce constant torque throughout their range of travel and have noticeably increased holding power when in a stationary position (this helps to keep even the biggest monster truck tires in line while you’re steering through a high-speed turn). So if you want to know about the hottest digital servos on the market, they’re all here! We also include a few tips for you to bear in mind when you decide to make that jump up to the digital world.
Analog or digital?
Digital servos first appeared over a decade ago, and every major servo manufacturer now sells them. They offer two advantages over analog units: speed and holding power. The main difference between the two types is that the microprocessor that controls a digital servo’s position is up to six times faster than an analog one. When the digital servo’s "brain" gets a signal from the feedback potentiometer telling it to update the position of the output shaft, it responds so quickly that any deadband is effectively eliminated. "Deadband" is the degree to which the servo’s shaft must be deflected from its current position before the servo responds to correct it. And because the servo position is updated so frequently (300 times a second is typical; 50 or 60 times a second in an analog servo), a digital servo can hold its position more forcefully, which is the holding power. One result of this is the "buzzing" sound it makes, even sometimes when idle. The disadvantage of the constant position updating is that a digital servo uses more battery power, so when you use one in a nitro car
Plastic gears or metal gears?
When you shop for a servo, its gear is one of the first things you should consider. Servo gears are typically made of molded plastic or machined metal (brass or aluminum alloy). As you’d expect, plastic gears are much cheaper to produce than metal gears, but they aren’t as strong. Certain manufacturers offer a servo in both plastic and metal versions, and the plastic one almost always has a lower torque rating. But there’s one area in which a plastic gear excels—low radio frequency (RF) noise. When metal parts move against one another, they generate RF noise, and an electrically “noisy” servo can cause glitching. This is why many top drivers use plastic-gear throttle servos in their vehicles.
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