Adaptive multi-channel portable stimulator based on PWM: A tool for micro-stimulation using multi-array electrodes

Electrical Stimulators are widely used in various medical specialties. Depending on the tissue that is going to be stimulated, physicians may adjust the characteristics of the stimulus signals such as frequency, amplitude, length and waveform. Commercial stimulators usually are just capable to generate preloaded waveforms and they cannot be adjusted freely. Moreover, the number of available channels is usually very low. However, not all medical treatments require the same stimulus. Actually, many medical conditions where the electrical stimulation is needed demand specific waveforms with different characteristics. Stimulus can vary in frequency, amplitude, time of application and form. This study describes a portable multichannel and adaptive electrical stimulator. The portable 16-channels stimulator presented in this paper consist of five sections; 1) an interface where the user is able to design the stimulation signal, 2) the transmission modules, one connected to a Personal Computer and the other one to the stimulation device, 3) microcontroller (MCU) that is going to organize the information received from the PC in order to generate the Pulse Width Modulation (PWM) signals (These PWM signals are injected into a set of low pass filters to transform these digital signals into analog waveforms) and 4) an attenuator to regulate the amplitude signal and restricts the current to avoid tissue damage. The presented system permits to design the stimulation signals according to the physician desires. The system was tested with real tissue under different stimulation patterns showing low current consumption and high input to output voltages relationship.