HI,
I want to ideally control 8 servo via pwm .but there is only 6 pwm pins.I found Arduino Playground - PWMallPins
this code to convert digital pins to pwm,so do I need to upload this code and then add my own code or is there some other way.
One thing I need to conform .can I run 6 or 8 servo motors from arduino usb connection without any additional component.These are micro servo motor 3 to 5 V ,will I have some current overload problem, do not want to cook my board.It seems difficult that servo motor can draw current more than 40ma, please correct me if I am wrong.
As of arduino 0017, the standard servo library supports up to 12 servos.
PWM hardware isn't really necessary for running servos; since a servo uses a 2ms pulse every 50ms or so, you can run the servos "serially" withing the same 50ms frame, and it's actually "easier" to use the timer without the PWM pin functionality.
You'll definitely need separate power to handle 6 servos, even if they're mico-servos.
What are you making? You might wish to consider using Lynxmotion's SSC-32. Serial Servo Controller that does everything else for you. Worth every cent I paid for it.
I am trying to make a robotic arm.I prefer arduino because of easy language ,flexibility and big community to help.I saw on a website a project who used 4 servo motor via usb.
With 6 servo motor will it be harmful for Pc or arduino.I think using battery will not be a good idea (to much current). the only thing left is a power supply.
With 6 servo motor will it be harmful for Pc or arduino
You must use a separate supply for the servos (don't forget to connect the ground to the Arduino's ground).
Batteries can be used, but it is going to be expensive to run.
That means I cannot use the external power supply of arduino for servo motors .
As I mention in my earlier post I am planning to to make a robotic arm,I am intending to get servo positions from the board to pc via serial and then control the robot arm with some sensor.Something like this. http://robotbrighton.ning.com/video/arduino-servo-5dof-robot-arm
So should I use arduino only or I need to use polou micro servo controller with that.
The issue is not with the controller (the Arduino Servo library should be find for this application) but with the power needed to drive 5 servos. The power from a USB hub will not be enough, you will need an external power supply capable for providing at least 1 amp (perhaps 2 or even more depending on servos and load). See if you can find an old wall wart from some no longer used computer equipment that provides 5 volts at an amp or more. Connect the servo positive power leads to the external supply, connect the servo grounds to the power supply grounds and to the Arduino ground. The USB connection does not need to change, it will power the Arduino but not the Servos.
Hi,
Can I connect the external power supply 5v 1000mA to the ardiuno power pin with the usb connected for pc interface for 6 servo motor or I definitely need a separate power supply for the servoes.
One thing more the datasheet said 40ma 5v or 50ma 3v per pin rating.
But I read after you point out servo motors can draw 150 ma current.
I am bit confuse by this, please explain
The black wire is ground, this must be connected to the ground of the power source and the Arduino Gnd pin.
The center (usually red) is connected to a positive power source, this drives the servo motor and powers the servos electronics. Servos under load can draw much more than 150ma, but this is coming from the external power source, not the Arduino pin.
The wire opposite the Ground wire is the signal line, this is connected to an arduino pin and only requires a tiny amount of current (perhaps a couple of ma)
In other words, the arduino pins are only providing a control signal, they are not providing power to the servo motor and there is no chance of damaging the arduino if you have wired everything up correctly.
Can I use regulated 4amp power adapter for 6 to 8 servos or it will be too much.I read that power supply with high current is fine but it should not be lower then the specification.
The things which is making me confuse is that we use resistors with led as it need 20mA and pin provide 40mA.
So what should I do with power supply.Do I need resistors?
Hi,
I was looking at some projects of robotic arm,many have jitters in servo motor with arduino board.
What is better(smooth) arduino or polou servo controller for robotic arm.I also want to connect some sensors to it.
Please clarify one more thing if I daisy chain servo motors .I can control each chain not each servo in that chain,is this correct
Can I connect two external supplies to the board?I can see two ground pins.
Oh! thanks for clearing the confusion of resistor and power supply.I have read the tutorial,can you please direct me to some other tutorial on this topic.I tried google but could not find any.
I was looking at some projects of robotic arm,many have jitters in servo motor with arduino board.
can you post a few links to those projects.
There are three ground pins on a standard arduino board, they are all connected together. You can use as many external supplies as you need as long as the grounds are connected together.
"You might see the servo jitter a bit as the Arduino temporarily sends out arbitrary electronic signals on the output pin during its startup phase."
And this website claim through pololu the movements are much smoother
I also read usually jitters are due to noise (voltage drop),so for that I should use regulated power supply or I can use unregulated power supply.
I want robotic arm movement as accurate as possible (without the expensive stuff) and also thinking of using some sensor ,so is it a good idea to use arduino or it will become slower due to processing 6 servos and sensors.
I want arduino to send position of servo motor to the pc.
Can I achieve same accuracy via arduino in comparison to servo controllers like lynx and pololu ?
"You might see the servo jitter a bit as the Arduino temporarily sends out arbitrary electronic signals on the output pin during its startup phase."
the code in that link is not using the Arduino Servo Library! The Arduino library does not enable the pin for output until the initialization phase is completed.
I think the second link is showing the difference in servo movement when a capacitor filter is used, I am not clear exactly what code is used in the video.
It is possible to adjust the responsiveness of the pololu board to make servo movements more sluggish and this can smooth out movement. if you want your servos to respond slowly to positional commands then the pololu may be a better choice than the Arduino library.
Why not get the application working with the Arduino library and see how it performs. If you need the capability to adjust the servo speed you can always buy the pololu board later.
"Disadvantages include greater complexity, the generation of high-amplitude, high-frequency energy that the low-pass filter must block to avoid electromagnetic interference (EMI), and a ripple voltage at the switching frequency and the harmonic frequencies thereof.
Very low cost SMPS may couple electrical switching noise back onto the mains power line, causing interference with A/V equipment connected to the same phase. Non power-factor-corrected SMPSs also cause harmonic distortion."
A properly designed switch mode power supply will be fine for driving servos. That maplin one has lots more power than you need for your servos but should be ok.