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Using Hobby RC parts in DIY projects

I’m always happy when I find a new kind of part that is cheap and easy to use with DIY electronics projects or robotics, the more standardized the better.

There’s a whole world of smart electronics and helper things in the hobby and remote control world that are great for robots and other things.

You probably already know that hobby servos are easy to control from any microcontroller like the arduino, but there are a bunch of other things that are just as easy to use. Generic motor controllers, battery systems are also equally as useful, but are sometimes hard to sort out the jargon and acronyms that R/C hobbyists use.

Some of the terms are pretty confusing, and a lot of acronyms and other R/C only rating systems are used. I’ve made this short reference to make it easer to sort out what all those things mean. I've found myself wondering more then once what the difference between an ESC and a BESC, or what a 2S2P 10C battery is.

Power / Voltage Regulation

  • ESC
    (Electronic Speed Controller)
    • Uses a PWM signal to control the speed of a motor
    • ECS’s are made for either brushless or brushed motors (See motors)
    • ESC's are rated in Amps (A) for how large of a load/motor they can control
  • BEC
    (Battery Eliminator Circuit)
    Steps a higher voltage down to a lower voltage, a kind of voltage regulator
  • UBEC
    (Ultimate BEC)
    Same as a standard BEC, but made for higher voltages
  • BESC
    (Battery eliminator speed controller)
    An ESC with BEC
  • LVC
    (Low Voltage Cutoff)
    Keeps LIPO batteries from becoming too drained, which can be dangerous, usually a feature of a controller
  • DVM
    (Digital VoltMeter)

Controller Acronyms

  • RX – receiver
    • Receives a control signal from the transmitter, output's a PWM signal for servos or speed controllers
  • TX – transmitter
    • (The remote you hold in your hand)

Battery Terms

  • LiPo, LI-PO, Li-Poly
    Short for lithium ion polymer battery, the standard type of R/C battery
  • LiFe - LiFePO4
    Lithium Iron Phosphate battery, generally safer then LIPO batteries, better shelf life, faster charging
  • NiMh
    Cheaper, but generally not as good as LiPo or LiFe
  • S Rating (Like: 1S, 2S, 4S, 6S, etc)
    Number of cells in a battery pack
    A single LiPo cell is 3.7v 
    A single LiFe cell is 3.5v
    A single NiMh cell is 1.2v
  • P Rating (Like: 2P, 4P, etc)
    Number of parallel lines in the battery, each parallel doubles the mAh the battery can deliver

    A 2S2P battery has 4 cells in 2 parallel lines
  • C Rating (Like: 1C, 10C, 20C, etc)
    Amount of current battery can discharge in an hour
    1C = Batteries entire capacity

    A 10C, 500mAh battery can discharge at 5,000mA (5A) max, and have about a 6 minute life at max discharge

    A 20C, 500mAh battery can discharge at 10,000mA (10A) max, and have about a 3 minute life at max discharge
  • Charging Bag, Charge Pack
    A fireproof safety bag for storing batteries
  • LIPO Monitor
    An alarm that goes off if the battery voltage drops too low. Batteries that drop too low can be damaged, or possibly explode.

Motor Terms

  • Brushless Motor
    A motor that runs off of A/C power, and has no "brushes" that transfer current into the rotating spindle. Brushless motors are similar to stepper motors, but only have two coils.
  • Brushed, Canned, Standard Motor
    A traditional DC driven motor
  • Coreless motor
    A motor without the iron core in it's windings
  • Outrunner motor
    Brushless motors where the casing spins and the center stays still
    • Motor is mounted by the back of the shaft
    • Low RPM's, high torque
    • Silent
  • Inrunner motor
    Brushless motors where the center core spins, and the casing is fixed
    • Motor is mounted by motor casing
    • High RPM's, low torque
    • More efficient than outrunners
  • GB
    Gear box, usually for planes
  • KVM, kv-RPM, KV
    A motors' RPM in thousands per volt supplied

Servo Terms

  • KG Rating (Like: 10kg, 20kg, etc…)
    Amount of force the servo can exert in kg/cm
    Can also be rated in oz-in (Imperial)
  • G Rating (Like: 30g, 50g, etc…)
    How heavy the servo is
    Can also be rated in oz (Imperial)
  • Sec Rating (Like: 0.20sec, 0.50sec)
    How fast the servo can rotate in seconds (usually for 60 degrees)
  • "Digital" VS "Standard" Servos
    Digital servos are still controlled with a PWM signal, but are generally more accurate and have better control. The actual performace will very with brand and quality.
  • "Standard" servos only have proportional regulation, and may overshoot
  • "Digital" servos have a proportional and derivative regulation loop, meaning it will be able to respond faster without overshooting.

Print | posted on Saturday, June 05, 2010 2:29 AM | Filed Under [ DIY Tech Robotics ]

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# Discharge current units

"A 10C, 500mAh battery can discharge at 5,000mAh (5Ah) max"

should be:

"A 10C, 500mAh battery can discharge at 5,000mA (5A) max"

"h" here stands for "hour" and is right on the capacity (500 mAh) but not on the current.
6/5/2010 1:41 PM | Ed Davies
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# re: Using Hobby RC parts in DIY projects

A123 is also a term to refer to LiFe batteries. It's a brand name, but one of very few suppliers, so it's pretty common.
7/8/2010 7:12 PM | ridefst
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# Servo Terms

"Digital Servo
Pretty much like a non-digital servo, but uses a microcontroller brain"

The practical difference between them is that a non-digital servo only has proportional regulation.
A 'digital' servo has a proportional and derivative regulation loop, meaning it will be able to respond faster without overshooting.
8/19/2010 7:12 AM | Astrolite

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