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E−flite Mini Pulse XT - Brushless ESC Waveform

RF Cafe: E-flite Mini Pulse XT  - Kirt Blattenberger

This is me with the Mini Pulse just prior to its maiden flight. I left the wheel pants off since I was flying from relatively tall grass.

RF Cafe: E-flite Mini Pulse airplane flight - by Kirt BlattenbergerHere is a short takeoff and landing sequence of my new E−flite Mini Pulse XT. This airplane will climb straight up on a full charge, and with a little energy management, will routinely fly for more than 20 minutes on a charge.

RF Cafe: RF Cafe electronics workbench

The official RF Cafe electronics bench setup. 

RF Cafe: Brushless motor ESC waveformThe video below is of the Mini Pulse's an electronics speed controller (ESC) output. Its complex waveform is a composite of a trapezoid composed of pulse-width-modulated rectangular waves with approximately an 80 microsecond period. E−flite EFLA311, 20 A ESC feeding an E−flite 450 brushless outrunner motor. 

RF Cafe: E-flite 450 Brushless Motor and ESC - test clips attached

Here are the test clips attached to two of the three output terminals of the electronic speed control.

RF Cafe: ESC slow speed waveform

This waveform shows the square waves that drives one of the three phases at a relatively low throttle setting (coming from the brushless speed controller). The peak amplitude is constant for all speeds.

RF Cafe: E-flite 450 Brushless Motor and ESC - high speed waveform

Shown is the display for one of the phases at full throttle. The waveform gets really complex at this point, and there are a lot of spikes that cannot be seen clearly in this image.

Much more than just a self-serving video of my new R/C airplane flight agility, this model represents a plethora of modern electronics. Although the radio control system in this plane is a standard narrow band FM variety on 72.170 MHz (as opposed to my 2.4 GHz, spread spectrum system), the motor is a state-of-the-art 3-phase brushless model (E−flite 450)with a sensorless electronic speed control (E−flite EFLA331, 20 A). Power for both the radio and the motor is supplied by a 3-cell (11.1 V) lithium polymer (Li-Po) battery rated at 2,100 mAh with a 15C discharge current capacity. There was a time not so long ago when no one though that electric power could ever provide a equivalent to the nitro methane gulping internal combustion engines, but the time has come. This all-electric setup is fairly small in size, but there are much larger motors and batteries available for large airplanes (and helicopters).

The video at the top right is a demonstration of the ease with which these all-electric models can be operated. Literally turn on the transmitter, plug in the battery, and you are ready to go. The extreme power-to-weight ration for this model is apparent in how quickly it takes off (not even full throttle) and pulls a high-G turn, goes around the short pattern, and then floats in for a perfect landing. Note the near absence of noise - which goes a long way toward keeping people from booting you out of flying locations once you find them.



Air Hogs R/C Helicopter Internals

Here are some photos of the inner workings (aka guts) of one of the Air Hogs remote control helicopters. There's a lot of electronics and mechanical wizardry built into these little $30 wonders!

RF Cafe: Air Hogs electronics

RF Cafe: Air Hogs electronics

RF Cafe workshop - electronics and models

RF Cafe: Air Hogs electronics


RF Cafe workshop - woodworking



Posted May 5, 2020

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About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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