Align Electronic Speed Controller (ESC), RCE-BL15X
with integrated Battery Eliminator Circuit (BEC)
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General Information

This page is offering programming tips and information about my experience with this production.

The Align RCE-BL15X from Align is designed for the TREX250 helicopter and ships with the TREX250 super combo package. It is compact versatile and easy to use ESC. The integrated BEC can be programmed to offer:

• 5.0V (default)

• 5.5V

• 6.0V

The ESC in practical use
The RCE-BL15X ESC from Align is an excellent ESC for the TREX250. It is compact, power efficient and offer long life stable operation.
However, I have experience problems with the BEC part of the ESC, this has failed on two occasions -after- a crash. My assumption is that this is caused by all three CCPM servers binding at the crash site, possibly in combination with the tail server also binding. So until I manage to reach the crash site and disconnect the battery large currents surges may have burned out the BEC.

For those of you experienced with electronics the BEC design is based on an UZ1085 Linear voltage regulator from Unisonic Technologies (but don't be surprised if another manufacturer is used in your ESC). In fact the UZ1085 is a complete voltage regulator in one package. So the BEC is the UZ1085. The adjustable variant is used (letters AD on the package), thus it is possible to program the BEC output voltage from 5.0 to 6.0Volts. As can be seen from the photos below, the UZ1085 is easy to replace if you have the energy to do so. A voltage regulator like this is cheap if you buy them from an online or local electronics shop. Linear voltage regulators run hot in combination with large currents and when regulating large voltage drops. The battery is running at around 10Volts on my TREX250. I have programmed the BEC to deliver 6Volts. Thus the drop is 4Volt. Assuming the servos pull, say 1A current when binding, following the crash. The power dissipated by the BEC may be in the range of: 3x1Ax4V = 12Watt. That's a lot, given that the UZ1085 linear regulator is not equipped with a heat sink at all. The UZ1085 chassis is just soldered directly onto the PCB.

The pictures of the ESC also show the ESC FET (Field Effect Transistor) located under the silver metal plate. The metal plate is hest sink for the ESC transistors. The ESC is equipped with a total of 6 FETs.

RCE-BL15X PCB (click thumbs for larger image)
	Unisonic Technology UZ1085 datasheet. Click thumb for PDF copy

Programming the ESC
When programming the ESC there are a few things to keep in mind.

• The buzzing noise used as programming guide and program step confirmation is generated by the electrical motor. (The ESC is sending small audible frequency step forward, step backward charges to the motor, making it buzz). So the electrical motor must be connected on all three leads in order to program the ESC
• The programming input is coming from the throttle stick LOW, MID and HIGH position. Now, the actual data (command) sent to the ESC is a function of the throttle curve programmed into the radio and -not- the throttle stick position in itself. Thus, if you are using the throttle curves I have recommended on this webpage, you have to do as follows.
  - Make sure your radio is in NORMAL mode
  - Look at the throttle curves and you will see that LOW = Throttle stick all the way down, HI = stick all the way up, But, MID position = stick position at about 20%.
  - Click thumbnail for a reminder on recommended throttle curves. Notice the throttle curve for NORMAL model. Hit backspace to continue from here
• To enter the programming mode:
  - Helicopter battery shall be disconnected
  - Ensure that radio is in NORMAL mode (assuming you have programmed the radio the same way as me)
  - Ensure no throttle hold is active
  - Throttle stick at 100%, i.e. fully up
  - Connect the battery
  - ... continue as prescribed in the table below
  - When programming is finished, ensure throttle stick is at 0%. Then recycle the battery power and listen to the configuration status beeps from the ESC. Verify that the ESC is configured as intended.

A note on Governor mode.
The RCE-BL15X ESC can operate in governor mode (constant head speed), however my view is that this is not needed on the TREX250. Governor mode will force the ESC to operate the FET transistors at suboptimal voltage/current levels. I.e. the ESC FETs are dissipating heat (energy). You want this energy in the motor not heating the ESC.  As you will see from the throttle curves the ESC is powering the electrical motor at nearly 100%. The throttle curve is moderated slightly at centre stick (zero blade pitch) in order to avoid rotor speeds that may damage the rotor.
With the standard 15T pinion the head speed is around 4100rpm with this setup, using Align 205mm carbon blades and 40mm tail blades.

Align RCE-BL15X ESC Programming for the TREX250
Step	Throttle stick	Actual throttle command	ESC audible feedback	Description
1	100%	100%	Connect battery	Entering programming mode
2	100%	100%	Buzzing up and down group1	Leave throttle stick at 100%, ESC is calibrating high stick value
3	0%	0%	Buzzing up and down group2	Move stick to 0%, ESC is calibrating low stick value... ESC is  now ready to run through the programming sequence.
3	0%	0%		Brake disabled
4	20%	50%		Midrange timing
5	0%	0%		High battery cut-off voltage protection
6	20%	50%		Helicopter mode with soft start
7	0%	0%		Throttle responds speed: Standard
8	100%	100%		BEC output voltage = 6Volts
7				Programming done.