Guide-10 ELECTROSTIMULATION

How does compex electrostimulation work?

Glosarry

Electrotherapy: Uses electrical signals to interfere with the transmission of neural pain signals into the brain. It effectively slows down or distracts the message from the nerve to the brain. From a physiotherapy point of view, affecting one’s ‘Pain Gate’, whether in an acute or chronic pain episode, is crucial area of treatment and electrotherapy is a very useful resource where conventional medicines are not as affective. Electrotherapy can also involve the use of this electric current to speed tissue healing where tissue damage has also occurred.

Current: Is the rate at which an electric charge flows in a conductor. It is the number of electrons passing a given point in a second. This means that if more electrons pass by a given point, the current is greater. The symbol for current is the letter “I”.  Electrical current is measured in Amperes or "amps".

Waveform: Is a representation of how alternating current (AC) varies with time. The most familiar AC waveform is the sine wave, which derives its name from the fact that the current or voltage varies with the sine of the elapsed time. Other common AC waveforms are the square wave, the ramp, the sawtooth wave, and the triangular wave. Their general shapes are shown below.

Some AC waveforms are irregular or complicated. Square or sawtooth waves are produced by certain types of electronic oscillators, and by a low-end UPS, uninterruptible power supply.

The sine wave is unique in that it represents energy entirely concentrated at a single frequency. An ideal, unmodulated wirelles signal has a sine waveform, with a frequency usually measured in megahertz MHz or gigahertz GHz.

How it works EMS?

Results

Electric Desing:

For the implementation of the electro-stimulator, the circuit design was carried out using the Proteus software, where the circuit simulation was subsequently carried out. The components that were used for the construction of the device were: Two integrated C.I 555 in its second astable configuration.

The behavior of this circuit is linked to the load and discharge presented by the capacitor, in the image you can see the signal of this process and the output signal of the circuit.

This configuration allows to use the integrated one as an oscillator. A pulse train was used as an input signal for the first oscillator and a modulator for the second, where the signal from the first integrated will control the pulses generated from the second one.

Speed and frequency control:

A voltage regulator LM7805 was used for the regulation of the circuit, the oscillation is presented in the capacitor, for this reason one of 100uF was used to generate large signals, a resistance of 220 to the output, to visualize in a led the oscillation that is generated. A 10K potentiometer was also used which controls the speed.

Power stage

A reverse transformer was used to generate a voltage and current of small values, which are sufficient to stimulate the muscle. For this part the transistor 2N1053 was fed, which made a switch for saturation, the output of the second oscillator was connected by means of a resistance of 220 to the transistor, a led was connected to visualize the oscillation of the second IC555. Finally, the transformer was connected, where the part of the power where the electrostimulation is received is located. Where a voltage divider was made where one side will have a higher value than the other.

The final design was the following:

Simulation

The yellow signal represents the charge and discharge of the capacitor. The blue signal is the output signal of the first oscillator, the frequency is varied by means of a potentiometer, depending on what the patient requires, the higher the frequency, the better the spectrum of the signal can be visualized. The magenta signal is the one of the second oscillator, while the first IC555 is kept in one the second one will work. The green signal is the output signal composed of the three previous signals, this signal represents the power that drives the circuit.

Alarms:

The alarms that were made were two, the ignition of the device for this was incorporated a led and a resistance to the final circuit and one that was turned on when the time of therapy had ended, an LM324, resistances and leds were used for its correct functioning.

PCB Desing:

Desing of protype:

The inventor software was used to carry out the design of the prototype, where a box was built in a rectangular shape, with perforations for connections to the source, patient, alarms and LEDs. AutoCAD was also used for the construction of the plans of the prototype.

Functioning:

The electrostimulator controlled from the variation of speed, frequency and power by means of the potentiometers, the test therapy was performed with a resistance of 1.5K to avoid damage to the patient, with this resistance was obtained a current that oscillated between 1 and 2mA, when it was found that the current was low, the patient was connected. Subsequently the frequencies were varied to visualize the functioning of the device.

References

[1]B. Healy and B. Healy, "Electrotherapy in Physiotherapy Treatments", Physiotherapy & Sports Injury Clinics | The Physio Company, 2018. [Online]. Available: http://www.thephysiocompany.com/blog/electrotherapy-in-physiotherapy-treatments.

[2]"What is current electricity?", Eschooltoday.com, 2018. [Online]. Available: http://eschooltoday.com/science/electricity/what-is-current-electricity.html

[3]"What is waveform? - Definition from WhatIs.com", WhatIs.com, 2018. [Online]. Available: https://whatis.techtarget.com/definition/waveform.

[4]Webster, J. G.(2006). Encyclodedia of Medical devices and instrumentation. John Wiley & sons, Inc.

Khandpur, R.S. 2014. Handbook Of Biomedical Instrumentation, Third Edition. India. McGraw Hill Education.