Building a better Bitchin' Betty -

Building a better Bitchin’ Betty


Dave Termohlen has accomplished much in his 25 years as an engineer, but he may just be hitting his stride with Bitchin' Betty.

Termohlen, a space engineer in Dulles, Va., took home the grand prize and $3,000 in the NXP Cortex-M0 LPC1100 Design Challenge with his low-weight, low-power temperature-controlled variometer and flight logger for remote-control planes.In flying parlance, these cockpit warning devices are called Bitchin' Betties, named for the often-female voice that warns pilots they're too close to the ground.

Termohlen overcame competitors who used NXP's 32-bit LPC1100 microcontroller to design:

  • A Wikipedia on a chip
  • A Vuvuzela-inspired noisemaker that flashed the NXP logo
  • A faucet sensor/switcher
  • An energy-friendly socket monitor.

NXP sent out nearly 500 LPC Xpresso boards with to engineers and inventors who passed the first step of the contest, submitted a paper design. From those 500, organizers got back 30 project videos and selected 10 of those for the judging phase.

The idea is to showcase what engineers can do with a part that costs less than a cup of coffee.

“What can you do for 65 cents? Plenty,” said NXP Product Marketing Manager Amit Bhojraj. “And that price breaks a big barrier for 32-bits.”

Judges gave Termohlen the grand prize for best use of the MCU, good creativity and reliability. Termohlen’s design allows the remote pilot to review the altitude and performance of the plane to optimize things like launch, lift, and landing.(See his video demonstration and explanation below ).

His design—using parts from NXP, AVX, Maxim, National Semiconductor, Measurement Specialties, Panasonic and Cobra —has a simple elegance to it:The LPCXpresso card polls the variometer for altitude, altitude change (indicating thermal), temperature and battery voltage. It generates speech from .wav data stored in the micro-SD and controls mic-key of (Cobra Micro Talk) walkie-talkie.An included application allows the user to plot all flight data in MS Excel.

Termohlen wrote in his abstract,

“The system might tell you: ‘Up three point five (feet), at one thousand fifty point four (feet), with four point seven (volts).’ This system could be used in Thermal Duration (TD), F3B, F3J, cross country, or any powered aircraft.”

Total cost? $52.84, much of which (see chart ) was the cost of the barometer. Here’s his BOM (check out co-sponsor DigiKey's site for additional information):

ARM Cortex M0 NXP $3.92
DAC National $2.36
RTC Maxim $3.07
Barometer Measurement Specialties $19.50
Battery Cell Any $1.35
RES 4.3K OHM CARBON FILM 1/4W 5% Panasonic $0.08
RES 3.0K OHM CARBON FILM 1/4W 5% Panasonic $0.08
CAP .018UF 50V POLY B SERIES Panasonic $0.08
CAP CERM .01UF 10% 16V X7R 0402 AVX $0.03
CAP CERM .1UF 10% 16V X7R 0603 AVX $0.03
CAP CERM 18PF 5% 50V NP0 0603 AVX $0.06
Set of 2 Walkie Talkies (16 mi range) Cobra $17.00

Termohlen, as you might imagine, is a huge fan of remote-controlled gliders, and therein lies his inspiration:

“I saw something called a Picolario in the early 2000s.  While similar in user features, my design uses an ultra-sensitive temperature-compensated barometer for the altitude sensor. This results in an accuracy of better than one foot compared to 1 meter .  As soon as I saw the Picolario, I started designing my own version.”

Termohlen (pictured ) said the LPC1114 showed him “that microprocessor technology had matured enough to fit my application.  I feel that I squeezed just about all the power that the LPC1114 has to give out of it.”

What's next

He's already laying out a new version of the design:

  • The next version will abandon the COTS walkie talkie, which killed his battery (when transmitting, it pulls more than 10mA).
  • Instead he's designing in a more expensive but practical 2.4GHz transceiver.
  • “Splitting the work-load between the transmitter and the receiver will significantly reduce power.”

Don't be surprised if the NXP champ's inspiration shows up on holiday gift lists one of these days.

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