Hello,
I will be controlling servos with my Arduino and I was wondering how long the wire could be? I need to be able to control the servos at least 8-10 feet away. Will this be to far? Do I need a signal booster like the one posted below? If all else fails I will just use a Xbee to communicate with another Arduino that is closer to the servos. Any info/ideas would be awesome!
I've used three wires of a four conductor cat3 telephone wire to connect a servo to a servo controller over ~12-15'.
I would think there might be power fluctuations at that distance. Inductance in
the cables, eg see
http://www.4qdtec.com/pwm-01.html#cap
I just ran a test comparing a servo with a 1 foot wire to one with a 9 foot wire. I used the sweep example to test it out. Both servos ran fine. So having a long wire did not seem to cause any problems, but when I add the other 6 servos on the Arduiuno all with long wires would anything change?
Thanks!
Don't be a wizz, try it and see.
Experimentation is fun !!
if you are trying to power them off the Arduino (especially under load) & not a separate/direct battery source,.. I would think you'll have a problem.
They do have quite a bit of load on them but I have a separate power supply for the servos.
I will check and see if anything changes with the rest of the servos. I normally agree that experimenting is fun but not when I have to waste wire if it does not work. 
Also, how far can an analog sensors be placed from the Arduino until the signal starts to be distorted?
Thanks!
You can put a capacitor on the supply at the end of the wire with the servo to compensate for any voltage drops due to fast, high power pulses. 10uF should be fine.
I have attached photo of what I think you want me to do. Could you confirm it is correct. The blue wires are the signal wires and they will travel the 9 feet to my Arduino. The power supply will be near the servos but will have a common ground with the Arduino.
Thanks!
How do you intend running the circa 1kHz signal cables from the arduino to the individual servos. If all in the same bundle you might get cross-talk - there again you might not. Although the pulse frequency is relatively low the pulse edges are supposed to be square which implies frequency components much higher than pulse frequency, so there may/will be degradation of the pulse shapes if you use poor quality cables, resulting in the servos not performing as expected.
I'd also be a little concerned about using only one common reference cable from all servos to the arduino. You might be better using a twisted pair for each servo - but then you might come up against ground circulation currents. Alternatively make sure the common ground cable to the arduino is a lot heftier then the signal cable.
This is where the lack of project detail leads to speculation as to possible problems.
Sorry for the lack of details I thought this would be a simple... yes it will work or no buy another Xbee.
Anyway here are the full details. I'm building an interactive robotic display so that the crowd can get involved in the competitions that I go to. The host has requested that I do this. This is not what i'm using to compete so don't think i'm cheating.
Basically it has 3 main parts: A robot arm, A robot "car", and a control station with live video feed. It moves in a cycle that will take about one minute. After each cycle a new person will step up to control it. The cycle starts with a loaded car. The person will unload the blocks off the car via the arm. Once the blocks are off the car, the arm will autonomously build a small structure with the blocks. After that the arm will autonomously put the blocks back in the car. The car will then navigate to the end of the track and back autonomously. The next user will repeat the process.
The control station will be a about 8 feet away from the robot arm. The robot arm has six servos and I was just going to run 2 multi-wire cables to the arm to control it.
I have everything worked out except the servo wire issue.
Thanks,
Drew
Any idea on servo motor manufacture and model - or better still do you have a data sheet. What is their working current when loaded. Are they low voltage (4.8). Will the common servo power supply be located at the control system (8feet away from the robot) and will this power supply also power the arduino.
Link to the robot arm (it uses many kinds of servos)…
http://www.robotshop.com/lynxmotion-al5d-robot-arm-combo-kit-4-dof.html
As far as current goes all I know is that it uses 2 amps or less.
Also, the power supply will be located right next to the arm not the control station. Thus I will run a ground wire to the Arduino from the robot arm, and signal wires from the Arduino to the arm. They will be powered with 5v. The power supply will not power the Arduino. The Arduino will most likely be powered off of my computer.
Thanks!
Shouldn't be any major issues - it's really a case of suck it and see. If you're running two screened multicores it might be better to have the common reference wire in one bundle only; this will prevent the possibility of circulating currents. Also ensure both screens are connected to the common reference point at one end only; I'd suggest the robot end; again to prevent the possibility of circulating currents.
They will be powered with 5v. The power supply will not power the Arduino.
If the servos are standard types, you need to run them at near 6v (or upper voltage limit) instead of 5v.
zoomkat:
They will be powered with 5v. The power supply will not power the Arduino.
If the servos are standard types, you need to run them at near 6v (or upper voltage limit) instead of 5v.
Not true. For most of the time RC servos have been in use, people have been running them from four AA NiCd batteries, then four AA NiMH cells, both running about 4.8V full charge. Now you buy a brushless ESC and it takes 2 or 3 cell Lithium input and puts out 5V for the receiver and servos.
polymorph:
zoomkat:
They will be powered with 5v. The power supply will not power the Arduino.
If the servos are standard types, you need to run them at near 6v (or upper voltage limit) instead of 5v.
Not true. For most of the time RC servos have been in use, people have been running them from four AA NiCd batteries, then four AA NiMH cells, both running about 4.8V full charge. Now you buy a brushless ESC and it takes 2 or 3 cell Lithium input and puts out 5V for the receiver and servos.
I'm just making a suggestion if the OP wants better performance from his servos. From my testing servo performance is somewhat mediocre at 4.8v as compared to 6v. YMMV
Hello,
I would be happy to run them at 6v, however, I could not find a 6v Voltage Regulator. Do you know wear I could find one? I know if you apply more voltage to a dc motor it spins faster. Is that the same for a servo?
Also, I have wired up one wire (with 4 little wires inside). One of the wires is used for ground and the other three are signal wires. Everything seemed to behave correctly. Tomorrow I will add in the other three servos and ground connection and report back.
I'm using the capacitor like KeithRB suggested so that probably helps.
Thank you so much for all the help!
I would be happy to run them at 6v, however, I could not find a 6v Voltage Regulator. Do you know wear I could find one?
Below is a UBEC voltage regulator that might be of interest.
Looks good and it is cheap but before I buy it how will 6v make the servos run better? I have always powered servos with 5v.
Thanks,
Drew
