Skip to main content

got the servos, got them working



The servos were delivered today, and I started working on them once I came back home from work. 

The initial set up I had with RPi.GPIO was... a failure. 

When connected, the servo would just twitch and continue to groan with uncertainty about where it should position itself. 

Wanting to see what it should actually do, I fired up my Arduino that's been inactive for quite some time, connected the servo and loaded up the Servo library. It worked like a charm. The difference between a real-time PWM and a soft PWM was very visible. 

For a while, I was thinking about maybe using the Arduino as the servo controller and have the Raspberry Pi just send a single high signal that would trigger the Arduino to move the servo. However, the extra size and power that would be required put me back to my senses.

I have to say I was pretty discouraged. It was probably because I was really expecting whatever I had implemented to work right off the bat. After eating a late dinner, I pushed myself to try more. 

I tried installing the WiringPi library, but after reading about it, it didn't seem much different from RPi.GPIO, so I didn't bother to use it. 

I then thought I should maybe install the Occidentalis OS that is developed by Adafruit, seeing how it comes with servo kernels. Felt like starting from scratch (at least in the Raspberry Pi side) should be a last resort option, so I decided to try to find something else. 

Finally, I landed on ServoBlaster. It relied on writing a duty cycle value to a location in the system, but it worked smoothly, and beautifully. It also did not need to constantly drive the servo a constant signal but activated only when the position was changed (with a timeout value in the initialization parameters). 

echo 5=70 > /dev/servoblaster 

The "70" is the amount of time the signal will be high. The cycles are counted by 10 us (microsecond), making the "70" 700 us, or .7 ms. This would put the servo near the 0 degree position. 

echo 5=230 > /dev/servoblaster

This would put the servo near the 180 degree position.

Had to use system calls through the os module, but once implemented, it finally works.
Labels:

Comments

Post a Comment

Popular posts from this blog

dabbling with cylon

I'm playing around with Cylon JS whenever I have the time. in order to use the leap motion for control, the hand control will need to communicate with the pc that is connected to the leap motion device (leap motion does not provide an arm/linux driver). it seems that Cylon devices can communicate with each other through socket.io or http, and I am currently playing around with that.
Post a Comment
Read more

interfacing alcohol sensor with the led

Programmed the Arduino to have the alcohol sensor play with the LED display. I had the display show either "open" or "lock" depending on the alcohol sensor level. Here is the result: Notice that this has a very notable flaw with respect to its potential use as a "breathalyzer lock": it stays "open" as long as there is alcohol present, which only then "lock"s. This means that currently, if you leave it alone (no breathing into it), it will keep the device unlocked. This is something I will have to resolve. code used for this: int del = 5000; int gasPin = 0; int value = 0; int lastValue = 0; void setup(){ //  Serial.begin(9600);   pinMode(12, OUTPUT);   pinMode(11, OUTPUT);   pinMode(10, OUTPUT);   pinMode(9, OUTPUT);   pinMode(8, OUTPUT);   pinMode(7, OUTPUT);   pinMode(6, OUTPUT);   pinMode(5, OUTPUT);   pinMode(4, OUTPUT);   pinMode(3, OUTPUT);   pinMode(2, OUTPUT);   pinMode(1, OUTPUT);...
Post a Comment
Read more

alcohol sensor (and some patience)

Soldered the alcohol sensor into something that is connectable: I tried to connect this to the Arduino, as I had the appropriate circuitry, but I did not get any legitimate output from it. 5V going in, 5V coming out with no variations. Nothing seems to be awry in wiring, as the circuit seems to be grounded properly (and the 5V current is flowing).  There are a couple of potential factors as to why I'm not seeing any results: - I'm using a 10k ohm resistor, while some guides (and the datasheet for the sensor) asks for 100-200k. However, there seems to be a good amount of people using 10k and getting at least some kind of result. A batch of 100k ohm resistors I ordered is on its way, so I guess I can try with them when they come. - This site  claims that these sensors take 24-48 hours for its signals to be stable. It also tells me that I should not be powering the sensor directly from the Arduino, which I have been doing, out of concern that the power draw of ...
Post a Comment
Read more