I have an Arduino Uno R3 with an I/O expansion shield that I'm going to be using to control 7 JX PDI-6221MG servos. My power source is a 7V DC battery and the servos run at either 4.8V or 6V. I'm creating my setup based on a similar project, and in their electronics flow diagram they show a voltage regulator between the arduino and the servos. Unfortunately, they do not elaborate on it anywhere.
My question is, is the voltage regulation something I can achieve via code in the arduino, or do I need a physical component? And, if the latter, what would be some good components to fill that role? I've found a standalone voltage regulator module board on CZH Labs, but there's just over 100 varieties so I didn't want to buy one until I knew what I wanted.
My question is, is the voltage regulation something I can achieve via code in the arduino, or do I need a physical component?
You need a physical voltage regulator. Or if you want a "shortcut", a couple of regular diodes in series will drop about 1/2 volt each.
Voltage regulators and regular* power supplies have a fixed voltage and the current (Amps or milliamps) is determined by the load. So, your voltage regulator (or diodes) has to be rated for whatever the servos will "draw", plus some safety margin.
If you make your own voltage regulator note that linear regulators (like the LM78xx) are usually rated for 1 Amp, but in the real world they will often overheat and shut-down at much lower currents. Switching regulators are much more efficient (very little energy converted to heat) but they are not as easy to build.
There are special constant-current power supplies used for high-power LEDs.
That's very helpful so far, Doug, thank you very much!
Unfortunately I can't seem to find any documentation on the current load for the servos, so I'll have to test that somehow.
Follow-up question, if I were to buy a premade regulator, would I want one with a fixed output or adjustable, and would I want one with a positive output, negative, or both?
You will need a high current DC-DC converter for those large servos. For 7 servos about 15A would be reasonable and I hope your "7V DC battery" is a good one able to supply that much current and that your "I/O expansion shield" can handle the current.
slipstick:
You will need a high current DC-DC converter for those large servos. For 7 servos about 15A would be reasonable and I hope your "7V DC battery" is a good one able to supply that much current and that your "I/O expansion shield" can handle the current.
Steve
Those sure are some neat quotes you put there, but thanks for the 15A number and the phrase "high current DC-DC converter", those're actually pretty useful.
slipstick:
Just a gentle hint that if you don't give any real details of your components we can't comment on their suitability.
BTW I'm willing to bet you don't really have a 7V battery.
Steve
Oh! Well, so long as we're offering critique, you can more easily and directly ask for details on my components by: asking for details on my components. Here, I'll give you an example: "Hey, I'm concerned about the suitability of some of the other components you mentioned that aren't directly related to your question. Could you give me some more details about them?" Try that going forward, I'm sure you'll do much better!
