How to find out the needed amp for the servo motor without damaging it ?tyvm.

Projects General Guidance
1

I am building a robotic arm for my rescue robot and I have used this servo in my project (DS3115-Metal-Digital-Servo-20kg-High-Torque).

At the given website's Product Description, it writes like this and I shared a picture from there to here too and it says a little different info.

Size:40*20*40.5(servo)

Weight:60g

Wire length:320mm

Speed: 0.14sec/60 degree at(6v)

           0.16sec/60 degree at(7.2v)

Torque: 18kg.cm.at(6v)
            20kg.cm.at(7.2v)

Voltage: 4.8v-7.2v

Dead Zoon setting:4 Microseconds

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What I want to ask is, is there a formula to find out how much amps do I need to use these hobby servos with using an external power supply / lipo or NiMH battery ? I will use a 6v lipo battery but how much amps do I need ? I will be very happy if you friends help me to understand this subject much clear. I don't want to damage my servos and understand this subject better too.

Currently, I am using a 6v,1600mah NiMH battery to power the servo; so is this battery is good enough or do I need a different one to power up every servos for my robotic arm ? thank you very much.

2

The currrent (Amps or milliAmps) won't burn out the motor - it's just a measure of how much is available from the supply - or needed by the motor.
It is also often used to identify the rating of a conductor (wire), but then we get into a new area. POWER

Your datasheet shows the motor will run at 6 or 7.2V - with slightly diffeent current requirements at each voltage.
(The table is weird, because in most appolications the voltage x current in any given situation would typically level out to the same power delivered.)
Power (W) = Voltage (V) x Current (A)

To be honest - I don't believe that table at all.
Based on experience and the indicated run current - I'd expect the stall current to be a thousand times as high as they listed! 4000mA vs 4mA

The only way you'll be sure is to find someone that has one you can test - or buy and measure the load & stall current youself.

At this point - my only suggestion woudl be to allow at LEAST 2A stall current PER MOTOR. It could well be more, but unlikely to be less.

3

Yes, unfortunately that table is useless. It is impossible for the stall current to be less than the running current. So we're left guessing what the real specification is.

And we can't even guess at the current needed to "power every servos" unless we know how many servos there are.

Steve

4

lastchancename:
Your datasheet shows the motor will run at 6 or 7.2V - with slightly diffeent current requirements at each voltage.
(The table is weird, because in most appolications the voltage x current in any given situation would typically level out to the same power delivered.)
Power (W) = Voltage (V) x Current (A)

No that isn't how things work. It is perfectly normal for something to take more current when the voltage is increased...even a resistor will do that. Motors certainly do it. Increase voltage, the motor speed increases and so do the current and power required.

Steve

5

lastchancename:
Based on experience and the indicated run current - I'd expect the stall current to be a thousand times as high as they listed! 4000mA vs 4mA

The image of the datasheet states 4 MA and 80 MA; mega amps :slight_smile:

I think that the OP needs to contact his/her electricity provider 8)

6

MEKACI:
What I want to ask is, is there a formula to find out how much amps do I need

..........

I don't want to damage my servos and understand this subject better too.

As long as you are powering the servo with the correct voltage having "too many" amps available will not cause any problem. The servo will only take what it needs. (If you want one cup of coffee it does not matter what size coffee machine it comes from).

The bigger problem is a power supply that can deliver too few amps. Then the servo will demand what it requires and overload, and maybe damage, the power supply.

...R