Custom Electronics: DC Motor Driven Appliances

Challenge

Update the design and lower costs for DC motor driven laboratory appliances with consideration to aggressive price competition and rising customer expectations for performance.

Solution

Microchip motor control DSP, Austriamicrosystems quadrature encoder, STMicroelectronics IGBT, and Power Integrations switching power supply.

Summary

In a highly competitive global market, it is important to remain the leader in product innovation. Product performance can be a key differentiator, but cost concerns can make it difficult to compete, especially in the Asian market place.

A world leader in scientific laboratory equipment approached Tecnova requesting a critical review of a new product design. The product incorporated a 90 VDC electric motor. The client's initial concept involved an established analog motor controller with a digital keypad and LED display. Concerns over meeting performance expectations lead Tecnova to offer a fully digital solution centered around a Microchip dsPIC30F motor control DSP. The client accepted the proposal and made Tecnova part of the development team responsible for the electronic and firmware portion of the product.

Modern control designs commonly utilize low cost, low pin count DSPs. The dsPIC30F had the correct mix of performance, peripherals, and I/O capability to meet requirements. An Austriamicrosystems AS503A-based quadrature encoder replaced an indirect method of speed measurement with an active design. When coupled with a 22-pole pair magnetic code wheel, Tecnova was able to create a very low-cost 880 pulse-per-revolution encoder. An STMicroelectronics STGB7NC60HD IGBT replaced SCR-based phase control.

The resulting Tecnova design allows the motor to be driven from a 90 to 260 VAC source over a wide speed range through proper control of motor current. The innovative encoder design enables the motor to operate at very low motor speeds. A Power Integrations supply with a custom flyback transformer provides universal power input for the LED display.

The design meets the customer goals of performance and cost and allows them to compete globally.