Monday, February 1, 2010

Control for "Gym for the lungs"

ML Electronics has successfully completed an electronic design for POWERbreathe Kinetic, a respiratory exercise system, which enables the feature-packed device to run comfortably from rechargeable NiMH AAA batteries – including driving a 12V stepper motor.

Advanced power management techniques and power efficient circuit design were key design goals. At the heart of the POWERbreathe electronics a PIC microcontroller takes values from a pressure sensor and uses them to control the stepper motor, ensuring that the ‘resistance’ is constant throughout the breath. ML Electronics leveraged the MCU’s micro-Amp real-time clocks, low power system voltage monitors, and its ability to run the CPU core at a different speed from the peripherals.

Functional circuitry was completed with differential amplifiers to provide inputs from the breath pressure sensor and a stepper motor driver linked to a low-cost off-the-shelf motor. In addition, the design provides a buzzer, LED and LCD displays, a function button and USB2.0 interface. All circuits can be switched in and out to conserve power using software developed by HaB.

Their hardware designers worked hard to minimise voltage drops everywhere, as even a 0.1V drop translates to a significant lowering of battery life. This not only impacted on the tracking and layout, but also necessitated using FETs instead of standard diodes, which resulted in a very compact printed circuit board.

“Our specifications were quite demanding and power management was one of the hardest things to crack. MLE proved to be excellent people to work with, offering a relaxed way of working as well as keen pricing and creative expertise,” said Dave Spurling, product designer, HaB International POWERbreathe trainers incorporating MLE’s innovative design are currently going into volume production and should be on sale in time for the New Year health and fitness peak.

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