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I have a problem to handle more than one servo. I have three servos, if I connect only one at any pin OWN work properly. But when I try to connect more than one servo simultaneously (each pin in his OWN) the source is shorted and everything stops working. What can be the problem. Thanks for everything.
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If you are connecting the servo power wires to the Arduino 5V pin you may be drawing more power than the Arduino has available.
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A basic standard 3.5Kg.cm servo may easily draw 0.6A when under some load (0.8A almost stalled).
Besides this, a servo pulls spikes of a lot of current when starting to move, and that can easily bring the power supply's voltage down enough to cause resets on arduinos and microcontrollers. Sometimes it helps alot to put a generous capacitor (100uF or more) at the (+) and (-) servo power pins, on each servo.
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The servos are connected to an external source, and share the mass with arduino. Arduino handles only single pulses to move the servo.
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So what is the current rating of your power supply, it sounds like it is too small.
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Is a PC power, more than 20A for 5 volts. thanks
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Well 20A should be enough.
When you say:-
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the source is shorted and everything stops working
Are you sure it is shorted, what evidence do you have for this. Have you measured the output from the power supply when this happens.

It could be that interference generated by the servos is resting the arduino or even the power supply. If so you need to add some large capacitors across the servos, something like 100uF or larger.
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thanks Grumpy_Mike , but another question, how do I connect these capacitors?
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You may need to paste your code for review. Below is a basic servo power supply setup, note the servo power supply and arduino grounds are connected. The notion that the servos are generating noise causing a problem requiring capacitors is probably wrong.  

« Last Edit: December 11, 2011, 07:05:14 pm by zoomkat » Logged

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not the servo power supply and arduino grounds are connected.

should say:-

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note the servo power supply and arduino grounds are connected.

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how do I connect these capacitors?
Do you mean how or where? The are connected from the + voltage source to the - voltage source (ground) as close to the motor as you can get. You connect them by soldering them at the servo terminals if possible, or the end of the wires if not.
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It could be that interference generated by the servos is resting the arduino or even the power supply. If so you need to add some large capacitors across the servos, something like 100uF or larger.

There may be noise from the power supply if it is a switching unit. I have servos connected to my arduino and don't seem to have noise issues. I don't think servos make much electrical noise, otherwise thousands of RC hobbiest would be using capacitors on their servos. Large brushed motors might cause electrical noise.
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I don't think servos make much electrical noise,
Yes they do, we get this all the time on this forum. In a RC situation the reviver is adiquitly protected by the manufacturer, an arduino has only minimum supply decoupling.
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I don't think servos make much electrical noise,
Yes they do, we get this all the time on this forum. In a RC situation the reviver is adiquitly protected by the manufacturer, an arduino has only minimum supply decoupling.
Not to mention that R/C guys usually use big lipo bats and arduino guys sometimes use just NiMH AA cells and other power sources that don't react that fast to sudden current demand. Good and big AA NiMH cells actually aren't that bad (we're talking 2 or 3 servos here), but adding the capacitors still has advantages at lower states of charge, actually making the cells' charge "last longer".
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Hi,

I have several projects in progress that involve radio controlled cars and interfacing between the receiver and speed controller or servos. I have built test rigs which work however I was also aware that there was too much noise running around the system.

It's a bit of a Mission to source components and as there seem to be a few people responding here who know a good bit more than I do and as this request is still within topic, could anyone help with compiling a parts list to reduce the noise in the environment of a radio controlled model.

My list so far is -
1) ceramic capacitors in 10,1,.1 and .01uF across servo signal and ground
2) 47uf across arduino supply pins which are supplied by the same lipo battery used to power the car, esc, motor and servo
3) 6800uf capacitor across the supply pins of the ESC

I would like to go with this approach, however if I can get the parts I am just as happy to optically isolate the input and output signals between the arduino and car. I am guessing  that if I want to share power this doesn't really effect the need to decouple noise so any and all help with the shopping list is very much appreciated.

Thanks
Duane.






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