Versatile PWM Drivers for Diverse Electronic Applications
PWM driver find utility in evaluating, examining, setting up, and energizing various electronic and electrical gadgets. Over the years, Elektor has featured several designs, including the one we introduce here—a ‘deluxe’ version adaptable to a broad spectrum of applications. The project’s software, comprising source code and hex files, can be freely downloaded from the associated pages on the Elektor website [1]. Pre-programmed microcontrollers are offered, and the authors have made Eagle design files for the printed circuit board accessible for download.
Main User Control and Operating Modes
The primary user control for adjusting various settings in the circuit is an Alps incremental rotary encoder, coupled with a mode switch that selects between ‘off’, ‘PWM’, and ‘full power’ modes using a three-position center-off switch. These controls, denoted as K2 and J1, are linked through headers. Current circuit configurations are displayed on a standard LCD panel featuring two rows of sixteen characters. This panel connects to the PCB through a typical connector.
Circuit Core and Motor Drive Capabilities
At the core of the circuit lies a PIC16F628 microcontroller, with an alternative option being the PIC16F628A. The circuit incorporates an output stage comprising two power FETs arranged in parallel, bolstered by heavy-duty flyback diodes. This setup empowers the circuit to drive DC motors up to 30 V and rated currents of 10 A directly. Higher currents are achievable but necessitate careful attention to conductor cross-sectional areas, including tinning circuit board tracks or adding parallel wires.
Special Features: Boost Function and Safety Measures
The circuit design prioritizes motor drive applications, offering a valuable ‘boost function’ ensuring reliable startup for DC motors. This function activates the output at full power for a predetermined boost time, disregarding the PWM duty cycle setting in effect. To enhance safety, the circuit remains off upon power-up until the mode switch is set to ‘off’ and then to one of the ‘on’ settings, preventing sudden motor activation after power restoration.
User Interface and Configuration Settings
During regular operation, the display exhibits the current PWM frequency and duty cycle as a percentage, both adjustable using the incremental encoder. Accessing the setup menu involves setting the mode switch to ‘off’ and holding the incremental encoder for a few seconds. Within this menu, users can configure fundamental settings such as Boost (on/off), Boost time (1s/2s/5s), PWM frequency (1 kHz/2 kHz/5 kHz), and PWM step (1%/2%/5%/10%).
Parameter Storage and Prototype Performance
The circuit’s settings are stored in the EEPROM of the PIC16F628, ensuring data retention even when power is disconnected. The authors’ prototype of this circuit has demonstrated exceptional performance, generating a clean and stable drive waveform even at a frequency of 5 kHz.
[1] www.elektor.com/090856
