Choosing a power supply for servos

I am looking to use more powerful servos on a project I am working on that will provide me with more torque. I have looked at a few different ones-

Option 1:
Servo - HSB-9380TH
Max Torque - 472 oz-in
Max Voltage - 7.4 V
Max Current - 2,100 mA

Option 2:
Servo - HS-M7990TH
Max Torque - 611 oz-in
Max Voltage - 7.4
Max Current - 9,800 mA

Option 3:
Servo - MKS HV777A+
Max Torque - 561.1 oz-in
Max Voltage - 8.2V
Max Current - 10.3 A

I am going to pick one servo from the above list and get 2 of them for what I am doing. I can't just do servos that are bigger because I do not have the space for them. My personal favorite is the HS-M7990TH simply because of how much torque I can get from it.

The things I am confused about are:

How does one go about picking a power supply?

Do I simply find a power supply with 7.4 Volts that can supply the around 20 amps of current?

Is it fine to choose a power supply that provides 7.5 Volts? Like this

I know that servos should use a separate power supply from the Arduino but if I have a 5V arduino pro micro do I need to also make sure the logic going to the servos is the same voltage as the servos take?

You do not tell us what your project is. But in case it matters, be aware that the speed of these servos is relatively slow.
If that does not matter in your application, then you are good to go.

This battery can provide 20A for about 8-10 minutes.

These servos are designed to run off of 2s batteries like I linked to. These batteries start out a charge cycle at about 8.4v. That supply, at 7.5v, would not be a problem.

Edit: 20A for those 2 servos assumes they are stalled all the time. Typically, the current draw will be much less, depending on your application.

In servo-speak 7.4V means a 2S Lipo battery and they will be over 8V fully charged so a 7.5V supply will be fine.

All servos use an input signal of 3-5V. DO NOT try to put 7.5V on the signal connection. The standard output from a 5V Arduino will be what it needs.

Steve

vinceherman:
You do not tell us what your project is. But in case it matters, be aware that the speed of these servos is relatively slow.
If that does not matter in your application, then you are good to go.

I am using them for a robotic wrist. From what I could tell the speed would be fine. Unless I am reading the speed incorrectly.

slipstick:
In servo-speak 7.4V means a 2S Lipo battery and they will be over 8V fully charged so a 7.5V supply will be fine.

So from this is sounds like I am okay to use the 7.5V 20Amp supply?

Another random question about power supplies... I have noticed that sometimes a power supply will list an output voltage as 6 to 8 V...... 6 to 12 Volts.... exc... Does this mean if I plug in a device that needs a voltage somewhere in that range the supply will be regulated to give the device the voltage it requires without affecting the current?

nathan0929:
Another random question about power supplies... I have noticed that sometimes a power supply will list an output voltage as 6 to 8 V...... 6 to 12 Volts.... exc... Does this mean if I plug in a device that needs a voltage somewhere in that range the supply will be regulated to give the device the voltage it requires without affecting the current?

I can't see what you've been looking at but a range like that usually means that the output voltage can be manually set to a voltage within that range by you adjusting a control. NOT that it will automatically adjust the voltage for you.

Steve

Similar to the adjustment screw on this regulator I have used.

I hooked up my supply, hooked up a load and a DMM, and adjusted the screw until the output was what I wanted.

vinceherman:
Edit: 20A for those 2 servos assumes they are stalled all the time. Typically, the current draw will be much less, depending on your application.

And typically if you stall your servos continuously they will soon be cooked and burnt out. But if you
fail to provide that 20A when the servos need it they will reset and go haywire.

First time I've ever heard of titanium gears - sounds like marketing gimmick, hardened steel is
likely much better.

MarkT:
First time I've ever heard of titanium gears - sounds like marketing gimmick, hardened steel is
likely much better.

But heavy. Most of the design considerations for these are with the radio control aircraft hobby in mind.
But, yes, buzz words. Marketing loves to be able to say that their product is made from 100% unobtanium.