Powering Arduino Through 5V

Other Hardware General Electronics
1

Hello all,

As a beginner to arduino, I'm starting to move past the basics of sensors and lcd screens, and moving on to stuff that require more juice (aka external power). So I've been doing a lot of reading, and wanted to get some opinions from you guys on whether my schematics are on the right track.

First of all, I read that arduino uses an AMS1117 linear regulator which is not very efficient (can't find its efficiency graph anywhere though), so I was wondering if just putting feeding it 9V through a 7805 would be more efficient, like this:

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I know, I know, 9V batteries are crap. This is more of a proof of concept, using parts that I already have on hand. In reality I'd probably be using a stronger battery and a more efficient step-up converter. I just want to hear what you think about powering an arduino directly through the 5V port. I know it's officially "not recommended" because there is no reverse voltage protection, and lots of people recommend hacking apart a usb cable and giving the regulated 5v through the usb port, but that's rather bulky, and I like the compactness of just powering it through the 5v port if there are no adverse effects (as long as the wiring is right).

Anyway, moving on, the second image in the album is using one of those breadboard power supplies to power both the arduino and a esp8266:

[Album] Power through 5V

Once again, straight through the 5v port. The breadboard PSU has two AMS1117's on it and can supply both 3v3 and 5v, at up to 800mA. The wall-wart itself that feeds the breadboard PSU is a 9V 1A regulated supply. With all that in mind, does this schematic look okay?

  • I know that I'll have to disconnect the breadboard power from the arduino before I plug in a USB to program it.

  • The ESP will be connected to the arduino (through a logic level converter) once it's programmed with the FTDI board.

  • Should I connect the grounds of 3v3 and 5v together on the breadboard? I heard that having a common ground is important, but I'm not sure in this case.

  • Some guides use a 100uF capacitor for the ESP8266. Is that applicable in this case?

  • Anything else I'm doing horribly wrong? :slight_smile:

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obuw:
Hello all,

As a beginner to arduino, I'm starting to move past the basics of sensors and lcd screens, and moving on to stuff that require more juice (aka external power).

I'm thinking that ..... the components that the arduino will control are going to be powered by their own external supplies already. So the onboard regulator on the arduino shouldn't be a problem.

Just use the DC power jack (eg. 9V regulated supply, with adequate power output) to supply the arduino if needed.

3

The 7805 is the bigger inefficient brother of the inefficient 11117.
They are both lineair regulators, and convert "in-out voltage difference * current" into heat.

A "breadboard power supply" uses the same 1117 regulators.
800mA (total in for both) can only be achieved with ~6volt regulated in.
Expect ~300mA max with 9volt in.

All grounds are most likely already joined on a breadboard supply.

A Nano has a weak 3.3volt pin.
~50mA for an official one with FTDI chip, much less for a clone with a CH340 serial chip.
A 3.3volt breadboard supply solves that problem.

Maybe wise to supply the breadboard supply with a 5volt phone charger (if it has a USB socket).
That bypasses the 5volt regulator.
Leo..

4

Southpark:
I'm thinking that ..... the components that the arduino will control are going to be powered by their own external supplies already. So the onboard regulator on the arduino shouldn't be a problem.

Just use the DC power jack (eg. 9V regulated supply, with adequate power output) to supply the arduino if needed.

That is precisely what I want to avoid. Having to plug in multiple supplies (one for the breadboard, one for the arduino, one for whatever else, etc) seems bulky, counterproductive and almost certainly unnecessary. It's not like when you buy an appliance from a store you have to plug in 6 different adapters to make it work, so I'm sure there is a way for the arduino as well, and powering it from the 5V seems to be the the most sensible way to accomplish that.

Wawa:
The 7805 is the bigger inefficient brother of the inefficient 11117.
They are both lineair regulators, and convert "in-out voltage difference * current" into heat.

A "breadboard power supply" uses the same 1117 regulators.
800mA (total in for both) can only be achieved with ~6volt regulated in.
Expect ~300mA max with 9volt in.

All grounds are most likely already joined on a breadboard supply.

A Nano has a weak 3.3volt pin.
~50mA for an official one with FTDI chip, much less for a clone with a CH340 serial chip.
A 3.3volt breadboard supply solves that problem.

Maybe wise to supply the breadboard supply with a 5volt phone charger (if it has a USB socket).
That bypasses the 5volt regulator.
Leo..

Interesting. I did not realize the 7805 was also a linear regulator, I must have confused it with something else. So that's why I couldn't find any efficiency graphs. It's a freaking linear regulator. >:(

I also did not realize the nano had an even weaker 3v3 pin than the regular arduino. Well I wasn't planning on using it anyway, the 3v3 port on arduinos seems to be useless in general.

The problem with supplying the breadboard with usb power is that it can't convert it to 3v3 which I need for the ESP8266. Besides, I don't understand the math behind 9V being converted to 300mA. This is ridiculous, it seems like no device on earth can power the ESP8266. The linear regulators waste most of the current only outputting a fraction of it, and the more efficient regulators seem to usually have a max output of around ~200-300mA anyway. Any chance I can use The FTDI chip which is rated at 3v3 800mA? Would that also somehow mean it can only output something like 80mA for some obscure reason?

Sorry, I'm just frustrated, I have been trying to get this damn thing working for the past three weeks, each time I have a plan, someone points out that it won't work, and I need a different part. Then I have to order that, wait another 3 days, rinse and repeat. I think what I need to do is just smash this with a hammer, throw it in the bin and order a NodeMCU Lolin (that's the only esp8266 devboard available around here). But who knows, maybe I'll find out that one also actually needs a bunch of special components to work. :roll_eyes:

5

obuw:
Well I wasn't planning on using it anyway, the 3v3 port on arduinos seems to be useless in general.

The problem with supplying the breadboard with usb power is that it can't convert it to 3v3 which I need for the ESP8266.

Besides, I don't understand the math behind 9V being converted to 300mA.

This is ridiculous, it seems like no device on earth can power the ESP8266.

the more efficient regulators seem to usually have a max output of around ~200-300mA anyway.

Any chance I can use The FTDI chip which is rated at 3v3 800mA? Would that also somehow mean it can only output something like 80mA for some obscure reason?

Sorry, I'm just frustrated, I have been trying to get this damn thing working for the past three weeks, each time I have a plan, someone points out that it won't work, and I need a different part. Then I have to order that, wait another 3 days, rinse and repeat. I think what I need to do is just smash this with a hammer, throw it in the bin and order a NodeMCU Lolin (that's the only esp8266 devboard available around here). But who knows, maybe I'll find out that one also actually needs a bunch of special components to work. :roll_eyes:

  1. Depends on how you look at it.
    The Uno/Mega has a dedicated 3.3volt/150mA regulator.
    It provides a stable voltage for sensors and low power 3.3volt devices.

  2. The 3.3volt regulator on that breadboard supply does run off the USB socket.
    Look at the schematic diagram. Small voltage difference (5-3.3), so current shouldn't be a problem.

  3. The regulator has to bridge the voltage between in and out.
    Heat/power is voltage difference times current.
    An 1117 can only handle ~1watt (warm) to 1.5watt (stinking hot) on a small circuit board like that.
    Do the maths. 9volt in - 5volt out = 4volt difference. 4volt * 0.3Amp = 1.2watt.

  4. Breadboard supply (on USB power) should be ok.

  5. The very small ones do. Normal ones are >2Amp

  6. An FTDI chip can output 3.3volt/50mA max.

  7. First time I've seen you post here. The net is full of "experts". Instructables is a place to stay away from, unless you have the experience to spot the many errors.
    Leo..

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  1. The 3.3volt regulator on that breadboard supply does run off the USB socket.
    Look at the schematic diagram. Small voltage difference (5-3.3), so current shouldn't be a problem.

I have specifically read that the usb port bypasses the regulators and if the jumper is in the 3v3 position, there will be no output. Admittedly I haven't actually tested this. But I have also read on some sources that the USB port on the breadboard supply is supposed to be for output, not input, so plugging it into a computer could potentially fry the device. Some of the comments state that it depends on the variant, some of them variants support both input and output and would work, some only do output. No way to know other than plug it in and wait for fireworks.

  1. The very small ones do. Normal ones are >2Amp

Can you give me the name of one of these fabled "normal" ones? I have been searching and haven't been able to find anything above 600mA.

  1. An FTDI chip can output 3.3volt/50mA max.

Ah, there we go again. The goto chip that is meant to be used with the ESP8266 provides 1/15 the power ESP8266 actually needs. Why am I not surprised.

However, I have officially stopped caring. I just connected the 8266 to my computer's USB port directly through the FTDI board I have, and it works perfectly fine. I ran several examples and connected to webpages without any issues. If it melts within a day, good riddance. Otherwise, I'm now done caring about mA ratings. Whatever happens, happens.

  1. First time I've seen you post here. The net is full of "experts". Instructables is a place to stay away from, unless you have the experience to spot the many errors.
    Leo..

I'm new to arduino. I've been lurking around for the past few weeks, occasionally posting questions. Everyone here keeps telling me to stay away from instructables. But I take whatever I can find. Most of the time it's from people's blogs, sometimes it's stuff from adafruit, sometimes it's an instructable. Whatever I read, I take it with a grain of salt, and compare multiple tutorials and read all the comments before starting to experiment on a breadboard. But so far the tutorials have been invaluable. Without them where am I even supposed to learn from? Books? :roll_eyes:

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obuw:
I have specifically read that the usb port bypasses the regulators and if the jumper is in the 3v3 position, there will be no output.

But I have also read on some sources that the USB port on the breadboard supply is supposed to be for output, not input,

so plugging it into a computer could potentially fry the device.

  1. This YWRobot diagram shows that the USB connects to the input of the 3.3volt regulator.

  2. Output and input. It's connected to out of the 5volt regulator and in of the 3.3volt regulator.

3)Yes, true. But only if you have a supply plugged into the DC socket.

Many clones on ebay.

I don't know which FTDI board you're talking about.
I only said that the 3.3volt output of the FTDI chip of an official Nano has this limitation.
Your bourd could have a separate 1117 3.3volt regulator.
The Uno/Mega with FTDI chip does not take 3.3volt from the FTDI chip either.
Post the link to your board.
Leo..

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obuw:
That is precisely what I want to avoid. Having to plug in multiple supplies (one for the breadboard, one for the arduino, one for whatever else, etc) seems bulky, counterproductive and almost certainly unnecessary.

Yeah....true. I guess it depends on what devices the arduino is controlling. External supplies (separate from the arduino's own supply) are usually recommended for motor systems being controlled by arduino - to cut down on supply voltage fluctuations that could affect the arduino's operation. Depends on application I guess. In your case, yeah..... if you are able to replace the onboard regulator with a more powerful one, then that should do the trick for you.

Eg.... bolt the arduino board onto some other board, and then add the regulator system to the larger board, and link to the arduino.

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1-2) That is assuming the diagram is correct and matches the one I have. :stuck_out_tongue: Anyway, I found a male-male usb cable and decided to give it a try, and yep it works, no smoke! 5v on one side, 3.2v on the other. Hurray! I guess these guys are wrong then.

So let me see if I got this right... 5V from USB gets converted to 3.3V, 1.7V difference. The 8266 goes all-out and draws 750mA. 1.7*0.75 = 1.275W, which the 1117 can handle (for brief periods). Am I on the right track?

Also, this means the USB port outputs 5V 750mA for the 1117 to generate 3.3V 750mA, right?

  1. Umm, confused, what is this in response to? The breadboard frying if I try to supply it power through both the usb & dc sockets at once?

Pololu: Oh wow, I've looked at a few products on their website, but I had no idea they had super handy tables like that. Nice!

Yeah....true. I guess it depends on what devices the arduino is controlling. External supplies (separate from the arduino's own supply) are usually recommended for motor systems being controlled by arduino - to cut down on supply voltage fluctuations that could affect the arduino's operation. Depends on application I guess. In your case, yeah..... if you are able to replace the onboard regulator with a more powerful one, then that should do the trick for you.

Eg.... bolt the arduino board onto some other board, and then add the regulator system to the larger board, and link to the arduino.

Yeah, separating the supplies might be safer for stuff like motors. Even then, I think I'd rather prefer to make a system that has a single cable going in, then separate voltage regulators supplying each motor & arduino independently. Possibly doing some magic with capacitors too. (I have a feeling they are supposed to be useful for alleviating power spikes, but I don't know how to use them yet. :P)

Edit:

I don't know which FTDI board you're talking about.
I only said that the 3.3volt output of the FTDI chip of an official Nano has this limitation.
Your bourd could have a separate 1117 3.3volt regulator.
The Uno/Mega with FTDI chip does not take 3.3volt from the FTDI chip either.
Post the link to your board.

Sorry, it's one of these.

before my last post I tried to find the model name and whether it has a separate regulator, but could not find any info, other than the fact that it has a fuse/shunt/thing that turns it off if the current goes above 500mA. The fact that it only protects it past 500mA, and the fact it has a switch that allows it to output 3v3, gives me a feeling it probably has a regulator hidden somewhere on it, but I couldn't find it. :stuck_out_tongue:

10

obuw:
So let me see if I got this right... 5V from USB gets converted to 3.3V, 1.7V difference. The 8266 goes all-out and draws 750mA. 1.7*0.75 = 1.275W, which the 1117 can handle (for brief periods). Am I on the right track?

Also, this means the USB port outputs 5V 750mA for the 1117 to generate 3.3V 750mA, right?

  1. Umm, confused, what is this in response to? The breadboard frying if I try to supply it power through both the usb & dc sockets at once?

Yes.

Yes. You have to supply the USB port with 5volt and 750mA minimum.
A PC/laptop could have a limit (polyfuse) of 500mA. A 5volt/1A tablet/smartphone charger could work.
At those currents, USB leads are important. Thick and short is best.

Don't know what a PC/laptop will do if you backfeed 5volt into it's USB socket.
Could be ok, but better to avoid.
Most Arduinos have a backflow stop diode or fet circuit.

Don't see a regulator on that side of the board.
A 1117 regulator should be clearly visable. Without is, assume 3.3volt/50mA from the chip only.
Leo..

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I'll leave your other questions for the others in this thread. What I can tell you is that ft232 module has no external regulator. The 3.3 volt supply is in fact from the low current 3.3 volt output pin on the ft232. So, there no way it can power the 8266.

Another thing to watch for is on Uno clone boards. Many will eliminate the 1117-3.3 to save a few cents and especially those with clone ft232 chip, the ch340, will use the 3.3 v output from the ch340 which for all practical purposes, is useless.

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AFAIK an Uno clone with CH340 has a dedicated LP2985 3.3volt/150mA chip.
A Nano with CH340 has not.

The chip is labled U5. Small, 5-pin, and 1/4 of the size of a 1117.
Leo..

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:-[ well I'll be :-[

Wawa, thank you for the education. I thought that I had once upon a time traced out that circuit on a CH340 clone. I guess my memory ain't what it used to be.

BTW: Wawa- any connection to Wawasset PA?

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No connection.
60 years ago a toddler called me Wawa for some weird reason before he could speak.
Leo..

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Interesting.

Edit: Oops, looks like I did an accidental submit.

So I tried to measure the current the 8266 draws, but all I got was a bluescreen from my computer. :stuck_out_tongue:

Either way it's working perfectly fine right now with power from the FTDI board, so either the board has a hidden regulator, or the 8266 is scraping by on 50mA power, or it's drawing 10-15x the max load of the FTDI chip and will fry it at some point. But it's been fine for the past couple hours.

Either way, thanks for your help! (And this must be the 4th-5th time I write up a post in quick edit, then accidentally click "reply" instead of "save", and lose it all. Argh!)

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Thanks. Now I know. I don't want to hijack the thread but we have a chain of privately held gas and convenience stores here in the East called "Wawa". They are based out of Wawaset PA. They've now spread as far south as Florida and north to New Jersey, all up and down the I-95 corridor. The they're pretty much on everywhere you look here in southeastern PA. Not bad for a small dairy that started selling milk via direct retail in the fifties.

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obuw:
(And this must be the 4th-5th time I write up a post in quick edit, then accidentally click "reply" instead of "save", and lose it all. Argh!)

Click on your avatar/picture.
Click on Show drafts.
Leo..

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Just tried, sadly that doesn't seem to work with the quick edit interface; only works for new messages.

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obuw:

  • I know that I'll have to disconnect the breadboard power from the arduino before I plug in a USB to program it.

Can you clarify this for me?

When I have an Arduino hooked up to a 256 LED matrix that is separately powered by a power brick, I can hook up a power line from the matrix back to the Arduino's 5v to power the Arduino and the whole shebang works with just the one wall plug.

But I can also plug in a USB between Arduino and PC to change the patterns without unplugging any of the power stuff. What harm am I risking for doing this?

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A breadboard supply has no USB backflow protection circuit.
Most Arduinos, like an Uno, Mega, and Nano do.
Leo..