Como detectar variação nos sinais EEG na forma de LEDs usando LM3915 (Parte 10/13)

How to detect variation in EEG signals in the form of LEDs using LM3915 (Part 10/13)

June 25, 2024 Roberto Magalhães

How to detect variations in EEG signals in the form of LEDs using LM3915

SOMA MARY

After taking over the relay device control experiment, I'm thinking about analyzing the EEG wave produced by the brain and seeing the variations in the shape of the LEDs. It would be really nice if we could clearly see the variations of our EEG signals in the form of some LED patterns, so as to analyze how much variation is being produced by various thought processes. Let's start.

Imagem mostrando sinais de EEG exibidos como variação de luz LED

Fig. 1: Image showing EEG signals displayed as changing LED light

DESCRIPTION

I decided to use IC LM3915 which can convert analog voltage into digitized form from 1 to 10 and rotate as many LEDs as the digitized value. It can also be called ADC (Analog to Digital Converter). When analyzing our CR wave, we saw that the voltage range is up to 1V. So we set the LM3915 reference to 1V. By doing this, we transmit to the LM3915 that 0v means 0 LEDs and 1V means 10 LEDS. So now let's say 4 LEDs are glowing, that means the voltage is close to 0.4 V. We just send the analog EEG signal directly to the IC LM3915 and connect LEDs at the other end to get the result. Please watch the experiment video.

Fig. 2; Image showing EEG signals displayed as changing LED light

We can conclude that the waves are not very stable in magnitude. I also believe there will be some noise that has been transferred to the 3915 IC. This can also be seen that often the LEDs go to full magnitude and stay there, which is not the case when checked with CRO. This could be due to noise as we just soldered the wire and it is open and long too. Anyway, brain waves are very interesting and I'm still trying to find some patterns in them to carry out more experiments of this type. By this experiment, I discovered the variation in our EEG and the effect of noise. I'm assuming this as noise, but it could be something else.

Diagrama de blocos do indicador LED de sinal EEG baseado no sensor de ondas cerebrais MindFlex

Figure 3: Block diagram of EEG signal LED indicator based on MindFlex brainwave sensor

Hardware: Please find the attached circuit diagram of the connections that must be established. We solder a pin to the EEG pin of the Mindflex sensor and insert the output of the EEG pin into the input of the LM3915. Additionally, we also set the reference voltage to 1V as our EEG signals will not exceed this value. To set 1V, we are using the resistor network. Although we can use 10 LEDs with the 3915IC, here we will only use 4 LEDs just to see the variations and changes of our EEG wave.

Software: There is no coding done in this experiment.

Some points to note: Try shielding this wire and also make sure the reference probes are connected correctly. You can try this experiment and share your feedback with us. In the next experiment we will try to change the color of the RGB LED .

Project source code

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 //Program to

Fading This example shows how to dim an LED using the analogWrite function. The circuit: * LED connected from digital pin 9 to ground. Created November 1, 2008 By David A. Mellis modified August 30, 2011 By Tom Igoe http://arduino.cc/en/Tutorial/Fading This example code is in the public domain. */ int ledPin = 9; // LED connected to digital pin 9 empty configuration { // nothing happens in the configuration //analogWrite(ledPin, 20); // wait 30 milliseconds to see the dimming effect //delay(2000); } empty loop { // fade in from minimum to maximum in 5-point increments: analogWrite(ledPin, 20); /* for (int fadeValue = 0; fadeValue <= 150; fadeValue += 3) { // sets the value (range 0 to 255): analogWrite(ledPin, fadeValue); // wait 30 milliseconds to see the dimming effect delay(1000); } delay(1000); for (int fadeValue = 160 ; fadeValue >= 50; fadeValue -= 10) { // sets the value (range 0 to 255): analogWrite(ledPin, fadeValue); // wait 30 milliseconds to see the dimming effect delay(60); } delay(1000); for (int fadeValue = 50; fadeValue <= 160; fadeValue += 5) { // sets the value (range 0 to 255): analogWrite(ledPin, fadeValue); // wait 30 milliseconds to see the dimming effect delay(60); } delay(1000); for (int fadeValue = 100; fadeValue <= 180; fadeValue += 5) { // sets the value (range 0 to 255): analogWrite(ledPin, fadeValue); // wait 30 milliseconds to see the dimming effect delay(60); } delay(1000); // fade out from maximum to minimum in 5-point increments: */ }

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