How would I go about connecting two high speed servo's to my mega2560? Would I need a separate battery and some sort of transistor or a more complex circuit? How do I control them?
The normal hobby servos need their own power supply with the power supply GND connected to the Arduino GND. Then the signal wire is connected to the appropriate Arduino pin. A Mega can control many more than 2 servos. See this diagram
If you don't mean hobby servos then post a link to the datasheet for the servo.
Don't draw power for any motor THROUGH the Arduino board.
...R
What power supply would you recommend for these guys?
Why does the power need to be connected to the arduino ground?
What do I send through the digital pins to control them?
pawelzaborek:
Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - HobbykingWhat power supply would you recommend for these guys?
Perhaps a pack of 6 AA NiMh cells or a 6v or 7v wall-wart with at least 2 amps output.
Why does the power need to be connected to the arduino ground?
To make a complete electrical circuit
What do I send through the digital pins to control them?
Use the Arduino Servo library
...R
Wouldn't the 'complete electrical circuit' send like 2A down the arduino?? Or is it like a parallel circuit with different currents?
Would there be any chance of having a LiPo instead? The servos are meant to go in a model rocket and it needs to be as light as possible.
Thanks 
An electrical circuit only draws as much current as it requires. It is voltage that "pushes" current through a circuit.
The circuit that is completed is the signal circuit, not the power circuit.
In any case if you only have the battery GND connected to the Arduino how can the battery positive connection put power into the Arduino?
Google will find lots of tutorials for you about the basics of electricity - volts, amps, watts, resistance etc.
A single LiPo (3.7v) may not have enough voltage for a servo and 2 LiPos (7.4v to 8.4v) may have too much. Otherwise they should be fine You can buy small voltage boost circuits that may allow you to use a single LiPo.
...R
Yeah I know the basics of electricity, therefore I was wondering if the current going to the servos would pass through the arduino. Now I see the parallel circuit. Also, would't I need to multiply the voltage by two since there are two servos? The pd across each servo would be half of the emf??
"Also, would't I need to multiply the voltage by two since there are two servos?"
No, the two servos are in parallel, so you add their currents. Example: 1 servo, 1 amp; 2 servos, 2 amps. Both see the 5 or 6 volts of the power supply.
pawelzaborek:
Yeah I know the basics of electricity, therefore I was wondering if the current going to the servos would pass through the arduino. Now I see the parallel circuit. Also, would't I need to multiply the voltage by two since there are two servos? The pd across each servo would be half of the emf??
The blue bit is not consistent with the red bit, and neither were your earlier questions.
...R
Robin2:
Google will find lots of tutorials for you about the basics of electricity - volts, amps, watts, resistance etc.
I was just confused because I didn't see the parallel circuits.
I know what voltage, current, power, resistance, capacitance, internal resistance, and resistivity are.
How does the resistance of a servo change as the arm moves?
It doesn't. The servo draws about an amp to start moving (overcoming motor inertia (also known as stall current)), then may draw that much also while holding position against a load. If moving and with no load, current draw will be less.
pawelzaborek:
I know what voltage, current, power, resistance, capacitance, internal resistance, and resistivity are.How does the resistance of a servo change as the arm moves?
When in a hole the first thing is to stop digging
Do you know how a servo works? Google will have lots of info about that also.
...R
pawelzaborek:
Yeah I know the basics of electricity, therefore I was wondering if the current going to the servos would pass through the arduino. Now I see the parallel circuit. Also, would't I need to multiply the voltage by two since there are two servos? The pd across each servo would be half of the emf??
Yeah....... I know what you mean. Motors need to have enough input power to get them to move and operate properly. The arduino outputs aren't designed to output the needed power levels to drive motors. But if you did try to drive motors with an arduino output, the arduino could become damaged while trying to output power that exceeds its own design limits (and the motor probably won't move since not getting enough current due to the low power output capability of the arduino). Normally, some protection features are usually added to try stop the device from operating too long out of it's comfort zone. But .... the amount of power that the arduino can output is usually not enough to drive motors. Your question is.... if you do try to get the arduino itself to directly drive the motors with its own output ... then does the current go through the arduino? Yeah... it does. It will. And that current must obviously get to the motor via the arduino's output stage. And if the stage can't handle the power (ie.... can't cool down sufficiently), then arduino components could fail.... due to heating effects.
To avoid making the arduino do the heavy lifting..... the arduino can call upon the services of its buddies....the power amplifiers and/or h-bridge/switch modules.... that allows the arduino to order the big guns to do the heavy duty work.
Southpark:
Yeah....... I know what you mean. Motors need to have enough input power to get them to move and operate properly. The arduino outputs aren't designed to output the needed power levels to drive motors. But if you did try to drive motors with an arduino output, the arduino could become damaged while trying to output power that exceeds its own design limits (and the motor probably won't move since not getting enough current due to the low power output capability of the arduino). Normally, some protection features are usually added to try stop the device from operating too long out of it's comfort zone. But .... the amount of power that the arduino can output is usually not enough to drive motors. Your question is.... if you do try to get the arduino itself to directly drive the motors with its own output ... then does the current go through the arduino? Yeah... it does. It will. And that current must obviously get to the motor via the arduino's output stage. And if the stage can't handle the power (ie.... can't cool down sufficiently), then arduino components could fail.... due to heating effects.To avoid making the arduino do the heavy lifting..... the arduino can call upon the services of its buddies....the power amplifiers and/or h-bridge/switch modules.... that allows the arduino to order the big guns to do the heavy duty work.
Standard hobby servos don't need any form of additional driver, H-bridge or otherwise. A servo has a built-in driver, and only needs a low-current signal from the Arduino, (but a separate power supply is necessary, as mentioned by Robin in reply #1).
No need to confuse @pawelzaborek with the information needed to drive other motors. His are standard hobby servos, albeit high-torque/high speed.
Thank you very much guys.
These servos are to control a rocket and you got me worried for a second that the arduino might break mid flight and send the rocket on a wrong course XD.
Hi,
What is your electronics, programming, arduino, hardware experience?
It looks like you are embarking on a pretty substantial project, what is the full scope of the project.
Thanks.. Tom....
pawelzaborek:
I was just confused because I didn't see the parallel circuits.
I know what voltage, current, power, resistance, capacitance, internal resistance, and resistivity are.How does the resistance of a servo change as the arm moves?
The servo is a complex load, it will draw a varying current, upto some maximum, you
provide a power source that can handle at least that maximum current without overloading.
You can think of it having a resistance that veries, its not really useful to do so, what is
useful is ensuring it has adequate power for the worst case.
Those are high speed high torque servos, I'd expect their peak current requirements to be 2 to 3A each,
not 1A.
Thanks,
The project will be very difficult. I am a 17 year old studying maths, chem and physics at college. I have model rocketry experience but not at this level, the main difference being the PID controller. I think I will be fine with the maths side, but I'm new to arduino so might have problems programming and stuff.
It was intended to be a 'EPQ' (Extended Project Qualification) for application to university, however my school doesn't want to sign it if I use explosives to propel the rocket. 