External Power Supply to Servo

Hi,

I am currently developing a project that now needs a servo to work along with the rest of the already built in instruments.

I am using a external power supply of 12V to juice up a pump, the current of it allows me to connect the servo since the arduino itself can not supply enough amps for it. Though the servo only goes with 7.8V max.. Since the power supply I have has 12V I built a voltage divider to get around 6V, but everytime I plug in the servo or the arduino the tension relation drops to mv's. Why? Should this behave like described?

Is the voltage regulator the only better solution?
Any solution?

Thank you!

you do not say how many amps.

if you are under about 2 amps, you can buy a variable voltage unit.

http://www.ebay.com/itm/160995621268

it has to have about a 2 volt drop, but you can adjust it to what you want.

for the voltage divider, you need massive power as the resistors are always pulling power to ground.

Hi, if you are using a resistor potential divider to get your 6V, then the voltage will drop when you attach the servo, because it does not regulate its output with load current.
You need to regulate the 12Vdc to 6Vdc, using a regulator, either a linear reg or a small efficient switch mode power supply.
A simple resistor network is not going to work.

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png or pdf?

Tom..... :slight_smile:

look at teh circuit, a pair of resistors. between them, you have a voltage.

when you connect anything to the circuit, you alter the circuit and create a new path. the voltage will change with the new circuit.

the power supply may dip with the new load.

the only reason to use voltage dividers is for signals of low power.

Sorry for not being so present on my own post, but I did not have much time to spend on the project till yesterday. ;/
Since I do not know much about electronic I have tried to find some guidance among people more use to work with this kind of stuff.

I understood your opinion about the voltage divider. As so I manage to build a voltage regulator with a LM7806. Though, had an issue about overheating due to the unknown amps needed! Measuring the high torque servo consumption found that I needed to allow the flow of more current in the circuit, so I found this LM2678 that goes up to 5A with the circuit developed in the datasheet.
As so I am waiting for the components to arrive. After this holiday I will post the results! :wink:

Thank you for the support!
Merry Christmas!
Hope you enjoy a good evening in family!

You might want to try one of these if your home-made switching regulator doesn't work out.
Similar switching regulator to LM2678.

Using a UBEC might be a good way to go.

Hi all,

I found the solution I mentioned to work pretty well. I have also installed a massive heatsink in order to deviate the heat from underneath the lcd I have installed on top layer of the circuit. But the circuits works just fine that I can't really feel it getting hotter. So, or the heatsink is really effective with the size it has or the circuit is working really fine. Did not waste time measuring any temperature, but the current is getting up to 4.8A easily and without any voltage drop.

Again, used the LM2678 with the circuit on the data sheet! Works fine to me!

Thank you for the help anyway!

@CrossRoads - I did buy some buck converters like that! Adjustables and fixed voltage ones. As this works I will just use it, but in any case that would be my next solution.
@zoomkat - did not know about UBEC but I am going to take a look into it!