Arduino Forum

Using Arduino => Motors, Mechanics, and Power => Topic started by: ButchCaelum on Feb 11, 2019, 03:06 pm

Title: Powering 2 high-torque servos
Post by: ButchCaelum on Feb 11, 2019, 03:06 pm
Hi there,

I am new to the entire Arduino and electronics world and got some questions regarding a project I am currently working on.

I want to control two high-torque servo motors using a Arduino Nano. I already figured out, that I cannot use the Arduino to power the servos. Instead I have to use a external power source. I worked on a setup that hopefully works - but as I am a bloody rookie in those topics I'd like to get a sanity check from you guys :-)

For my project I have some very specific requirements, one of them is that I need a very easy to switch and reloadable power source. I also need to use the entire torque of my servos.

Here is what I came up with:



I tried to use this circuito.io to roughly draw my circuit - unfortunately I did not find a larger battery as well as a DC-DC converter in it. So please replace the battery pack with the one mentioned above (18V, 5Ah) and the L7805 with a proper DC-DC converter:

Drawing of the circuit (https://www.circuito.io/app?components=10334,10334,11022,783868)

The parts I am planning to use are the following (plus the two capacitors as seen on the circuit):



Will that work to run both servos off of one battery as well as the Arduino and is the circuit correct in that case when I use a DCDC-Converter instead of the linear one and the mentioned battery?

As I said, I am absolutely new to this entire topic, still try to get my head around it and read forums and blogs the last three days to get everything above somehow together.

Thank you all already for your valuable feedback and for helping me starting my first project :)

Best,
Jules
Title: Re: Powering 2 high-torque servos
Post by: vinceherman on Feb 11, 2019, 03:57 pm
Quote
The servos will be powered directly
Can those servos run on 18V?

hmmm, I could be wrong, but it looks to me like you are applying the full battery voltage to the VIN pin.  Is that what you intend?
Title: Re: Powering 2 high-torque servos
Post by: ButchCaelum on Feb 11, 2019, 04:05 pm
Can those servos run on 18V?

hmmm, I could be wrong, but it looks to me like you are applying the full battery voltage to the VIN pin.  Is that what you intend?
Hi,

thank you for your answer!

No, I am planning to put a DC-DC-Stepdown Converter (https://www.amazon.de/dp/B00HV4EPG8/ref=cm_sw_em_r_mt_dp_U_eZxyCbSP47XNP) between the battery and the Arduino, as well as between the servos and the battery. So the battery will connect to the DCDC-Converter and from that I gonna connect the servos and the VIN of the Arduino Nano. The DCDC-Converter can be adjusted and I would set it to 6V and 5A as the servos run on 6V and 2500mA each.

I hope I understood DCDC-Converters correct ;)

Best,
Jules
Title: Re: Powering 2 high-torque servos
Post by: MarkT on Feb 12, 2019, 12:28 pm
Not very convinced by that that stepdown converter, looks cheap and nasty.   At the very least it would need to be tested on a dummy load before allowing it near your expensive servos.
Title: Re: Powering 2 high-torque servos
Post by: ButchCaelum on Feb 12, 2019, 12:42 pm
Hi @MarkT,

Yes the converter is one of the points I'm unsure with. Do you probably have a good recommendation for a converter that I could use instead?

Any opinion to the rest of the game? Does it sound valid to you?

Thanks a ton,
Jules
Title: Re: Powering 2 high-torque servos
Post by: MarkT on Feb 12, 2019, 12:45 pm
Why not go to an electronic component distributer's website and search for suitable converters?
Title: Re: Powering 2 high-torque servos
Post by: ButchCaelum on Feb 12, 2019, 01:33 pm
Hi MarkT,

Sure. But as I said I am new to this entire topic so I thought you probably got a good recommendation for me.

Am I right with assuming that for 2 servos with a stall current of 2300mA I gonna need a DCDC converter that allows for 5A?

Thank you,
Jules
Title: Re: Powering 2 high-torque servos
Post by: vinceherman on Feb 12, 2019, 03:07 pm
Hobby King (https://hobbyking.com/en_us/power-systems.html) has a large selection of affordable switching converters.  In the radio control hobby these are referred to as BEC (battery elimination circuit) since you do not need a main flight battery AND a battery to run your electronics.

This one (https://hobbyking.com/en_us/5v-5a-ubec-2-5s-lipoly-7-2-21v.html) looks like a good fit.