If you plan to use a brushed motor, you will need a brushed motor ESC. If you plan to use a sensored brushless motor (like the X-250-4H) then you can use either a sensorless or sensored brushless motor controller. For the sensorless brushless motor controller, the sensor wires (connector) from the motor will not be connected to anything because the sensors are not required by the controller.
The sensored brushless motors may need to be sent back to the motor factory to reverse the motor direction if your rotor head is spinning in the wrong direction. Therefore, I recommend avoiding sensored brushless motors unless you already know the timing is for the desired direction of rotation.
If you plan to use a sensorless brushless motor, you will need a sensorless brushless motor controller. This motor type is not usable with a sensored brushless motor controller (such as the older Schulze Booster-40b).
An ESC used for main motor control must have the following characteristics are required (or must be programmable):
No low voltage cutoff or programmable very low voltage cutoff. (As low as possible, must be 0.7 volts/cell or less)
Most airplane ESCs are not suitable for helicopters because they have low throttle resolution, include a brake and have a fairly high low-voltage cutoff.
The JETI Micoprocessor (red label series) is not suitable for helis because the throttle control is not smooth and is rather "steppy". The Advance (blue label series) is supposedly better, but nobody I know has tried this. Some ESCs have an optocoupler (usually called OPTO) instead of a BEC. The optocoupler electrically isolates the ESC from the control signal which reduces the possibility of interference from the external BEC.
For the micro helis, the following are poular as main motor ESCs:
Pixie-7P (brushed ESC, 7 amp)
Schulze Future 11.20e (brushless, rather heavy)
Castle Creations Phoenix 10 (brushless, very light)
Piccoboard/Piccoboard Plus/Piccoboard Pro
GWS ICS-100E (brushed main motor ESC, 5 amp)
For the Corona, the following work:
Castle Creations Pegasus 35 (brushed)
Castle Creations Phoenix 35 (brushless)
Hacker Master 40-3P (brushless, do not use the BEC on this ESC because the ESC will overheat on 3 servos?)
For the ECO 8/16, the following work:
Schulze Future 12.46k
Schulze Future 18.46k
Hacker Master 40-3P Heli
Kontronik Jazz 55-6-18
For the Logo 10, the following work:
Schulze Future 18.46K
Kontronik Jazz 55-6-18
Do not use the SMILE 40-6-18 in the Logo 10 - it tends to burn out!!!
The Hacker Masters seem to burn out in the Logo 10 as well due to ESD problems.
The Castle Creations Phoenix works fine in the Piccolos and the Corona but does not work well in the ECO 8/Logo 10 and larger helis. The current version of the firmware has a problem in three areas:
The soft start doesn't work properly. It may kick your heli around 180 degrees and/or tip your heli over.
The governor mode doesn't work properly with a heading hold gyro. The RPMs will go up and down even when hovering, which makes the tail wag back and forth.
The controller seems to have less glitch filtering than other ESCs. When the Phoenix is used in a heli, it requires a receiver which has a fail-safe mode or glitch filtering, such as a PCM receiver or a Berg DSP receiver.
Therefore, the Phoenix is not suitable for larger helicopters until these firmware bugs are fixed.
If you are mounting the Phoenix ESC with double-stick tape, be sure to put the tape on the BEC side and not the FET side. The FET side generates the most heat, so it needs to be exposed to free air.
The FET side is the side with the regular pattern of identical chips. The BEC side has a random collection of chips. Do NOT use a switch between the battery and ESC. Most switches will not handle the current and will become very hot. Also, if the battery is plugged into the helicopter, you should consider it live for basic safety reasons anyway.