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...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
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.
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.
The official RF Cafe electronics bench setup.
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
Here are the test clips attached to two of the three output terminals
of the electronic speed control.
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.
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!
Posted May 5, 2020
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