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Author Topic: Powering Arduino on 5.5V via USB  (Read 652 times)
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The ESCs I am using for my quad copter have a 5.5V regulator on them for all the electronics. 5.5V is out of spec (10%) from the USB standard (5%) and I was wondering if it would work, or if it is too much. I can use diodes or something to drop it down if necessary.
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What are the ESCs?
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What are the ESCs?

Electronic Speed Controller. They are a type of motor controller that are controlled with a servo type signal (you use the servo library to interface with them. The ESC then wires to a motor either a 3 wire DC brushless type or there are two wire output types for standard DC motors. These ESC usually have a built in voltage regulator that outputs 5-6vdc to power the stuff you normally use in a R/C airplane like the R/C receiver and control servos.

Lefty
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5.5V is fine to operate at.
Using a high current diode, like 1A rated 1N4001 wouldn't hurt to get you down to ~4.8V
Or a Schottky diode with 0.3V or 0.4V rating.
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5.5V is fine to operate at.
Using a high current diode, like 1A rated 1N4001 wouldn't hurt to get you down to ~4.8V
Or a Schottky diode with 0.3V or 0.4V rating.

I know that a diode needs that 0.7V to "turn on" so to speak. Excuse my ignorance here, but am I right in thinking that this approach to voltage regulation relies on that 0.7v being dropped across the diode?

(That said, I tested a 1N400x just yesterday with my new Fluke which has a diode test position, and it indicated a voltage closer to 0.5 than 0.7... or is that diode test testing yet another characteristic of a diode?)
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5.5V is fine to operate at.
Using a high current diode, like 1A rated 1N4001 wouldn't hurt to get you down to ~4.8V
Or a Schottky diode with 0.3V or 0.4V rating.

I know that a diode needs that 0.7V to "turn on" so to speak. Excuse my ignorance here, but am I right in thinking that this approach to voltage regulation relies on that 0.7v being dropped across the diode?

It would not be consider 'voltage regulation' but rather just a constant voltage drop at whatever the source voltage provided (but of course higher then Vf rating of the diode) and load current draw might be. You just have to make sure your maximum circuit current draw is less then the maximum forward current rating of the diode, and there are diodes available for most any current requirement you might need. The 1N400x series is rated at 1 amp max continuous current.

(That said, I tested a 1N400x just yesterday with my new Fluke which has a diode test position, and it indicated a voltage closer to 0.5 than 0.7... or is that diode test testing yet another characteristic of a diode?)

The Vf value is a pretty 'loose' spec and will vary from batch to batch and will vary with temperature and to some small effect by the amount of current flowing through the diode. Most silicon diodes will be somewhere in the .5 to .7 range, and germanium and Shockley diodes with have a lower Vf value.

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Thanks Lefty... yep I was going to put regulation in quotes for that reason....

Now that I have a nice meter that measures current, I can use it in conjunction with my old one to set up a little experiment to measure the simultaneous currents through and voltage drops across (eg) LEDs and resistors in series and verify all this stuff I read about!

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Thanks Lefty... yep I was going to put regulation in quotes for that reason....

Now that I have a nice meter that measures current, I can use it in conjunction with my old one to set up a little experiment to measure the simultaneous currents through and voltage drops across (eg) LEDs and resistors in series and verify all this stuff I read about!



One hint on measuring current with your new fluke. Right after you take a current measurement and at that time change the meter leads back to the voltage position. The reason is if you leave them in the current position and the next day go to make a quick voltage reading you will set the function switch but more times then not you won't think about the meter lead position and as soon as you place the leads across a voltage source, pop goes the current protection fuse and those suckers get expensive when having to replace again and again just because of a brain fart. My fluke model 87 DMM make a beeping noise if the function switch is in volts position but the meter lead is in the current jack, but my fluke model 45 bench meter doesn't and not sure what your new one does?

Any time your taking current measurements pretend you are out hunting bear with only a Bowie knife, keep alert.

Lefty
« Last Edit: January 12, 2013, 12:24:01 am by retrolefty » Logged

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Perfect! thank you very much. I will but a diode in series just in case. got lots of rectifier diodes laying around anyway.
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