Design of a Microcontroller-Based Electrical Stimulator for Physiotherapy Applications at Rehabilitation Centres in Anambra State

Therapeutic electrical stimulators used in physiotherapy for pain management, muscle re-education, and edema reduction are expensive imported devices that limit treatment access at rehabilitation centres in Anambra State, motivating the development of low-cost local alternatives. This study designs a microcontroller-based dual-channel electrical stimulator for physiotherapy applications at rehabilitation centres in Anambra State, providing transcutaneous electrical nerve stimulation (TENS) and neuromuscular electrical stimulation (NMES) waveforms. The system employs an STM32F103 microcontroller to generate programmable biphasic symmetric square wave pulses with adjustable frequency (1 to 150 Hz), pulse width (50 to 400 microseconds), and amplitude (0 to 80 mA peak), covering the standard TENS and NMES clinical parameter ranges. Isolated output stages using transformer coupling and optoisolator circuits ensure electrical isolation of the patient circuit to IEC 60601-1 type BF applied part standards. A rechargeable lithium-ion battery and boost converter provide stable isolated output voltage. A keypad and LCD interface allow selection between preset TENS and NMES programmes and manual parameter entry. Electrical safety testing confirmed compliance with leakage current limits specified in IEC 60601-2-10 for nerve and muscle stimulators. Output waveform characterization on an oscilloscope confirmed parameter accuracy within five percent of set values. Informal usability evaluation with five physiotherapists at a rehabilitation centre in Awka confirmed intuitive device operation. Total fabrication cost was under eighteen thousand naira. The study recommends clinical efficacy comparison against commercial stimulators and long-term reliability testing. Keywords: electrical stimulator, TENS, physiotherapy, microcontroller, Anambra State.