Hi guys, this is my first attempt to post a project here.
This is an instructable on how to read a gyro sensor and plot the data using processing software at your desktop. I am using gyroscope model XV81-000 and an arduino. The device is a rough prototype of what will eventually become a self balance robot, this is the first part of the hole thing (read accelerometer and control a motor to self balance).
This is an instructable on how to read a gyro sensor and plot the data using processing software at your desktop. I am using gyroscope model XV81-000 and an arduino. The device is a rough prototype of what will eventually become a self balance robot, this is the first part of the hole thing (read accelerometer and control a motor to self balance).
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Signing UpStep 1: What you need?
You will need:
- Breadboard
- Microcontroller, I used the Arduino board
- Wire
- Jumper Wires
- Gyroscope XV-8100
- Breadboard
- Microcontroller, I used the Arduino board
- Wire
- Jumper Wires
- Gyroscope XV-8100
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o Codigo do arduino_gyro.pde
é o codigo do processing e não do arduino
Vc poderia corigir.
Agradeço pelo tutorial.
Na busca por informações sobre Giroscópio, cheguei no seu tutorial.
Bem, possuo os seguintes componentes:
- Giroscopio0 XV-3500CB PROTOTYPE PCB
- Arduino Duemilanove
- Servo Motor
Estou tentando fazer o mesmo desse link que segue:
http://www.youtube.com/watch?v=xkVRZC0e8Vk
Depois de testes verifiquei que este meu sensor possui um sinal muito baixo na porta analógica
Denominada de ANA0 e verifiquei que você usou dois capacitores para amplificar o sinal.
Meu sensor possui já uma saída de sinal digital compatível com l2c pois assim o sinal fica melhor
Pergunto que capacitores você usou em seu projeto e conectado aonde?
O melhor seria usar o I2C para nao ter problemas de interferencia.
To verify A2D (arduino Analog to Digital) converter I connected analog input 0 to ground. With this configuration the A/D converter is giving me strange values ranging (randomly) from a minimum of 0 to a maximum of 64.
Is that possible? Do you know something about poor A/D conversion with arduino.
What kind of dynamic shows your realization?
Thanks for any comment.
Are you using the same code without modifications?
I fixed the A/D conversion problem on arduiono using a resistive partition on AREF pin on arduino board. AREF is now connected to GND with a 10microF, and with a 10K resistor to Vcc (5V). This give me a reference voltage for A/D of 3.77 V.
Yes, I'm using your sample code.
But I'm still having problem with angular value computation.
The angular value is slowly drifting apart when gyro is kept steady
(no force applied).
But I have just found out that in your code you have this constraint:
if(teta>-1 && teta<1) teta=0; //avoid drift error
teta = teta + ( valor * time ) / 1000;
to avoid drifting.
I would like to change it to:
deltaTeta = ( valor * time ) / 1000; // Angle infinitesimal increment
if(deltaTeta>-1 && deltaTeta<1) {
deltaTeta=0; //avoid drift error
}
teta = teta + deltaTeta;
Probably this would avoid spurious variation is steady state.
But I haven't yet tried this solution.
I would let you know as soon I get tested with new code.
Thanks.
Make a simple code to return the value read from your analog port with your gyro steady. The value show often is yout offset. Just replace this value on the code.
This can help improve the steady problem.
This is what I'm doing. I'm reading teta, the A/D output (from 0 to 1023) which is the gyro output voltage read with the arduino A/D converter.
The gyro output from the A/D has a range from 328 to 330 [count] when gyro is in a steady state ( I do not know if this variability is normal in a gyro or not). So I did use value 329 as offset inside the equation used to compute teta.
This produce, anyway, a drifting value for teta which keeps increasing or decreasing (depending on the value i choose for offset).
Also tuning the offset value using 0.1 resolution (let's suppose 329.4 instead of 329.0) can improve performance in the sense that I reduce the speed with which teta is increasing (decreasing) when gyro is in steady state but i?m not able to stop it.
I do not want to bother you too much with this problem.
Probably I would try with a different gyro with a I2C interface with integrated A/D conversion.
Thanks for you help.
Paolo.
The problem was related to the fact that I was querying the arduino's A/D converter to fast, a was not giving enough delay in between two consecutive readAnalog() calls.
Introducing a delay of at least 50 ms definitively solved my problem.
By the way I did find a solution to increase speed in A/D conversion on arduino.
Here are few lines of "code":
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif
#define FASTDAC 1
#if FASTDAC
#define DELAY 10 // delay in ms
#else
#define DELAY 50
#endif
so you can use less than 10 ms as delay time in between A/D calls.
I tested this with 5 ms delay and A/D conversion worked grate.
Thanks.
http://www.instructables.com/id/Accelerometer-Gyro-Tutorial/
float sens= 0.512;
float offset= 316 ;
float count= 0;
float valor =0;
float first_time, time;
float teta=0;
//####################################################################//
// //
// Gyro //
// Scale Factor 2.5mV/ �/s = 0.512 counts/ �/s //
// Offset 316 counts = 1562mV = 1.562V //
// ADC 4.88 mV/count // 0.2048 count/mV //
// //
//####################################################################//
count =0;
for(int i=0;i<20;i++){
count = count + arduino.analogRead(0);
}
count = count /20;
valor = (count - offset ) / sens;
time=millis()-first_time;
first_time=millis();
teta=teta+valor*time/1000;
if(teta>-1 && teta<1) teta=0; //avoid drift error
cya
Angle=HPF*(teta) + LPF*(arctg( Ay / sqrt( Ax^2 + Az^2 ))
(from your other instructable)
Sorry my bad english and worst explanation.
From the ADC 5V / 1024 = 4.8mV / count(raw value)
( 2.5mV / (º/s) ) / (4.8mV / count) = 0.512 count(raw value) / (º/s)
so, if you read from the adc channel a value like 2, this means 3.9 º/s
2 / 0.512 = 3.9
3.3mV / (º/s) ) / (4.8mV / count) = 0.512 count(raw value) / (º/s)
and if you would wire up 3.3v to Aref pin it would be
From the ADC 3.3V / 1024 = ...
3.33mV / (º/s) / (3.222mV / count) = 1.0333 count (raw value) / (º/s)
316
You will have something like 1.23V. Or 381 counts.
This is your offset.
So, if you extract the value you are reading from the offset you will have ZERO.
Thanks this realy helped a lot because there isnt much about gyros or 6DOF on arduino.cc
im gonna use this for a quadrocoper with a razor 6dof from Sparkfun
Can you provide the manufacturer of the breakout board or the retailer from who you got it? I have only been able to find the Gyro in SMD w/o breakout board. Thanks
i bought that board on ebay, but I didn't found the seller anymore.
cya
Right now I have it set so if I type "T" into my serial monitor, it sends the command out digital pin 9, through my relay, and "presses" a button on my TV controller, thus turning it on.
Can I do something so that pressing a button in my Processing sketch would be like typing "T"?
color fillVal = color(126);
import processing.serial.*;
void draw() {
fill(fillVal);
rect(25, 25, 50, 50);
}
void keyReleased() {
Serial myPort;
myPort = new Serial(this, Serial.list()[0], 9600);
if (keyCode == 'T') {
println("T key pressed");
myPort.write("T");
}
}
Thank you very much.
I'm pretty new to Processing, so I'm not too sure of all it's capabilities.
1)take a cork and insert in the center a long steel stick
2)put your stick in vibration vertical and hold the cork under your palm
3)turn the cork the axe of the stick stay vertical and you feel a force under your palm
in this type of chips they use a double (A,A')=x=(B,B') lyre the extremity (A and A')is put in vibration by a solenoid the other extremity (B and B') will vibrate then generate a current in a receptive solenoid the difference between the current generate by B and B' with a constant vibration A and A' will mesure the anti couple
Would you please explain it mathematically? For I see here:
if(teta>-1 && teta<1) teta=0; //avoid drift error
That the absolute value of teta is less than 1, then teta could not be in degree...right? next I don't see any conversion to degree, and then it is added to 270 and used as a degree. The program works with my IMU and it means that it is correct. I anyway can't understand the math behind this angle offset! do you see where my problem in understanding is? ;)
if(teta>-1 && teta<1) teta=0; //avoid drift error <- when you integrate the signal from the IMU if the IMU doesn't stay still, an error will be summed to the angle, so, this line try to prevent this.
the line() function on processing works in rad, so we have to make a conversion, that's why I use the function radians(270+teta); i really don't remember why i choose this value of 270, but i know it's work fine for me, xD
if you need some other explanation, feel free to ask.
Soon I will post some information about it. http://web.mit.edu/first/segway/ Here you can found some information about sensor merging and filtering. My hole project is based on this. I'm using an accelerometer from a nunchuk to have the acceleration and the angle, that way I have two angles, and avoid the drift error from gyro. I have some documentation but it is on portuguese.
Plz send a PM with your email and I cans send it, and more informations for you.
Good luck