Making a Continuous Rotation Servo

NOTE!  There are a couple of different designs of these servos, even from the same vendor.

• The written notes below are for a through-hole style board
• The video covers the non-through-hole syle
• One kind of Potentiometer has rotation stoppers which must be broken off.
• One kind of Potentiometer rotates freely and doesn't need to be modified.
• If you don't need to modify the pot, you don't have to remove the stack of gears.

Continuous rotation servers are popular for cheap robotics projects because a pair of them give you a complete drive train (motor, controller, and gears).  A pair of 9 gram servos (such as the popular HXT900 from hobbyking) should be less than $7 or so.

Start by testing your servo, either with a servo tester or with an arduino sketch that drives the servo back and forth.  There's nothing more discouraging than having bad results, only to find out that it's not your fault because you started with a bad unit!  Likewise, be sure and test your battery voltage.

Motor Balancing

Not just props, you should balance your motors too:

• http://www.rcgroups.com/forums/showpost.php?p=15936915&postcount=8839

howto: bind a transmitter and receiver

Procedure

1. power off receiver
2. power off transmiter
3. insert bind plug onto BAT pins
       - actually, I think it can go on to any pin
       - orientation doesn't matter, it just connect out neutral and control pins
4. power on receiver
       - light will blink
5. put transmitter throttle to zero position
6. toggle and hold bind switch on transmitter
7. power on transmitter
8. hold until binding is made
       - usually just a couple of seconds

Potential Problems

• plugging in servo, power connections into receiver backwards
• turning on transmitter first
• plugging in servo, power connections to wrong terminals

HowTo: Using a Watt Meter

Using the Hobby King X1 Watt Meter

The instructions in the package are pretty inscrutable, so here's a quick HOWTO.

Basic Idea

• This thing sits between your battery and your ESC.
• It measures voltage, amperage, and wattage.
• It has a HOLD mode that keeps the highest values.
• When it's set up, you fiddle with your props, motors, etc, and see the power requirements of various setups.
• You can send it aloft to record the flight's peak power requirements.

 Setting Up

• The unit doesn't come with any power connectors, so you need to attach your own.
• The wires labeled IN attach to the battery.  Put a male power connector here.
• The wires labeled OUT attach to the ESC.  Put a female power connector here.
• Black wire = Neutral (-)
• Blue wire = Hot (+)

Turning It On

• Plug the unit into a battery.  Whatever battery you use to fly a plane is fine (the manual says the voltage rage is 8-30V, but it seems to work fine with 2S batteries as well, as seen below).
• The display of the unit will turn on.
• If you use a 2S battery, you will see something like this:
• Voltage (U=7.93V).  Over time this will go down, as your battery discharges.
• Amperage (I=0.1A)
• Wattage (P=1.0W)

Trying It Out

• Attach a motor to your ESC.
• Plug your ESC into a receiver.  It's OK if there are servos attached.
• Attach the OUT wires to your ESC.
• Your setup should power up and work as normal.
• The power levels should go up a bit, since you're running servos and a receiver.
• Wiggle your servos.  You will see the numbers jiggle in response.

Testing a Motor

• Make sure your motor is secure, and bring the speed up.
• You will see the amperage (I=) and wattage (P=) increase.
• Bring the speed back down.
• You will see the values decrease back to the original values.
• The voltage may have gone down a bit, since you've been using some power to run these tests.

HOLD mode

• HOLD mode will measure the Peak values.
• To turn it on, click the HOLD button.
• Rev your motor and bring it back down a couple of times.
• You will see these peak values displayed. Rearranging the order a bit, they are:
• P 14.3W -- maximum power (wattage).  This is the peak power output of the battery.
• Up 7.71V -- voltage when P was at max.
• Ip 1.9A -- amperage when P was at max.
• Im 1.9A -- maximum amperage, even if it didn't correspond to P above.
  
• Um 7.84V -- the minimum voltage of the time period.
• Click HOLD again to go back to instantaneous mode.

Flight Mode

• If your plane is big enough to carry a couple of extra ounces, you can attach the meter between the battery and ESC in your plane, set HOLD mode, and find out your peak usage aloft.

Manual Calibration Mode

• If you have a good quality multimeter, you can adjust your unit's readings.
• Depress HOLD for three seconds and you will be in adjustment mode.
• Measure an unloaded power source with both the watt meter and your reference multimeter.
• Use the ADD and SUB menu items to make the two units agree.
• SAVE will of course save your calibration.

Hobby King 4-Ch 2.4Ghz Radio and Receiver

This receiver is a pretty nice, low-cost unit.  Here's some notes about setting it up.


WiFi Warning - Laptop interferes with this transmitter!

• I spent about an hour trying (unsuccessfully) to get things working.  Shutting off the  computer WiFi fixed everything!

Installation

• When Plugging in USB, Windows will want to install a driver.  Let it search and install the default.
• Under "Setting", USB will be "COM4".
• Software is here. [add this]
• Better software: Digital Radio by Stefano Grassi
• Another alternative: TurboRix
• Select this to start: System Setting/Stick/Mode 2
• Hobby King video review and tutorial

To Bind

• Bind Plug in BAT
• Power to CH3 (actually, I think it can be any channel)
• Neutral Wire to RIGHT when reading text
• Fast blink: polarity error:
• Slow blink: ready to bind

Channels (note: numbered from bottom to top)

• 6:
• 5:
• 4: aileron
• 3: throttle
• 2: elevator
• 1: rudder

Assignable Buttons

• A: throttle kill (up = throttle off, down = throttle normal)
• B: dual rates (up = ON [100%], down = OFF [50%])
• VR(A): CH5 (VR are for heli??)
• VR(B): CH6