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Raspberry PI power source
AMCerasoli
Member #11,955
May 2010
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Hello There!!

Sooooo many time since I made my last post... I was just a kid...

I want to ask a short question:

I have connected one of those 3G USB modems to my Raspberry PI when it was turned on and the RPI shut down. I immediately thought "Oh, the RPI charger doesn't have the enough power to supply the 3G modem". But then I realease that it didn't shut down completely but it was a reset! :o. It booted normally and all that...

So... I was trying to use Sakis3G to configure and connect to the internet using the 3G modem, but the setup always failed... So I thought "Oh, this must have something to do with the current and voltages an all that crap".

So I borrowed an external USB hub from a friend to see if that could solve the problem. And it actually did, I could configure the 3G modem using Sakis3G and everything worked fine...

The thing is that reading on the web I came to the conclusion that the problem could be that the amperes of the charger I was using wasn't enough (700 mAh). When I saw the amperage of my friend's USB hub it was of 2000 mAh, so I cut the wire and connect the microUSB connector to it and connect that directly to the RPI to see if I could now use the 3G modem without the USB hub. The surprise was that I couldn't... So what the fuck?

I also noticed that connecting the USB hub to the RPI (Using a normal USB port) I don't need to use the power MicroUSB connector of the RPI... Somehow the USB hub through the USB port feeds the RPI... So the MicroUSB port is useless.

So my current conclusion is that maybe the USB hub has a capacitor (I don't know if that is the correct name) that when the 3G modem sucks too much energy the USB Hub is able to provide that energy for a short period of time while the RPI shuts down due to the low voltage of that moment...

What do you think?

Thomas Fjellstrom
Member #476
June 2000
avatar

Normal USB can't properly power a Raspi, especially if you're plugging regular usb devices into the usb ports (except powered usb hubs).

Your best bet is to use a 1.5A or higher AC adapter, and a powered usb hub.

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

jmasterx
Member #11,410
October 2009

I tried 1A and I cannot even have ethernet with that, nor keyboard, or anything. With 2A everything works great for me.

AMCerasoli
Member #11,955
May 2010
avatar

I was using a 0.7A charger and my ethernet connection and keyboard worked fine. I think the problem in this case is not related directly to the charger but the circuit of the RPi. I'm supplying enough energy but there must be some part of the RPi that can't provide that amount of energy that the 3G modem needs when it's connected.

I'm wonder if there is no problem to power the RPi using the normal USB port. It seems to work fine.

Thomas Fjellstrom
Member #476
June 2000
avatar

The real problem is the Rpi takes 700mA on its own. Adding more usb devices like a 3g modem is going to pull even MORE power. wifi and 3g modems tend to want 200-500mA on their own.

Like I said earlier, you want at least 1.5A if you're plugging additional stuff into the raspberry pi directly. You can get away with less if you're only using a powered USB hub.

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

Like I said earlier, you want at least 1.5A if you're plugging additional stuff into the raspberry pi directly. You can get away with less if you're only using a powered USB hub.

I also said earlier that I used a 2.0A charger and it's the same. My current theory is that even if I had a 3.0A charger I will have the same problem. I have just bought one to see if it's true. I purchased from China, though... :(

Thomas Fjellstrom
Member #476
June 2000
avatar

Watch out for cheap chinese ac->dc adapters. They like to cause shock hazards and fires.

It is also possible that your hub is a cheap pos as well! ;)

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

No, I first bought this, then I found this one with the MicroUSB and I bought it too. Those are pretty CHEAP but... Whatever... DC to DC btw.

Thomas Fjellstrom
Member #476
June 2000
avatar

You're powering it from a car? Or another 12v source?

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

Yhea I will be using a 12V battery.

Thomas Fjellstrom
Member #476
June 2000
avatar

Interesting setup. You're going to need a rather large 12v battery.

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

Yhea, this is a project for cars.

Arthur Kalliokoski
Second in Command
February 2005
avatar

You're not going to surf the interwebs while you're driving, are you? >:(

“Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded — here and there, now and then — are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty. This is known as "bad luck.”

― Robert A. Heinlein

Thomas Fjellstrom
Member #476
June 2000
avatar

I hope your dc->dc converter has some beefy voltage regulation. power in a vehicle is incredibly noisy.

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

You're not going to surf the interwebs while you're driving, are you?

Of course not............................

I hope your dc->dc converter has some beefy voltage regulation. power in a vehicle is incredibly noisy.

Yhea it has! You see, when the voltage goes down my DC to DC converter also goes down! and the same when the voltage goes up! Isn't that great!?

Thomas Fjellstrom
Member #476
June 2000
avatar

You see, when the voltage goes down my DC to DC converter also goes down! and the same when the voltage goes up! Isn't that great!?

Assuming I'm understanding you properly.. No, thats bad. That's exactly the opposite of good. The output voltage from a good regulator should be steady, even if the input is noisy. Of course there will be certain thresholds that the will cause the regulator to not work properly or at all (input too low or too high).

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

Ahhhh... Poor Thomas... Man, you're a computer. Where is your sense of humor? I told you to not program so much, do you see what happens?

Thomas Fjellstrom
Member #476
June 2000
avatar

I dunno, its hard to tell sometimes what's supposed to be a joke or not :P

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

Oh BTW. All these years I have been asking you for your furnace. So tell me Thomas, is your furnace working? I want to remind you that you live in Canada a country most known by its maple syrup and its long long loooonnggg winter... Have you replaced your furnace?

Here in Spain we're at 12º more or less. Not that bad so far. :D

Arthur Kalliokoski
Second in Command
February 2005
avatar

All these years I have been asking you for your furnace. So tell me Thomas, is your furnace working?

I heard the movie version comes out next year. :o

“Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded — here and there, now and then — are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty. This is known as "bad luck.”

― Robert A. Heinlein

Thomas Fjellstrom
Member #476
June 2000
avatar

Oh BTW. All these years I have been asking you for your furnace. So tell me Thomas, is your furnace working? I want to remind you that you live in Canada a country most known by its maple syrup and its long long loooonnggg winter... Have you replaced your furnace?

Heh. Yeah. Over a year ago now. And boy is it nice. It's actually able to keep my bedroom warm now. Used to be when it got to -20 and below, my room would be ice cold, and I'd need like 4-6 blankets to keep warm at night. Now one is more than enough.

We hit somewhere around -40c within the past couple weeks. With windchill it was probably -50c. For that one day we were the coldest recorded place on the planet. Even colder than the Arctic or Antarctic.

--
Thomas Fjellstrom - [website] - [email] - [Allegro Wiki] - [Allegro TODO]
"If you can't think of a better solution, don't try to make a better solution." -- weapon_S
"The less evidence we have for what we believe is certain, the more violently we defend beliefs against those who don't agree" -- https://twitter.com/neiltyson/status/592870205409353730

AMCerasoli
Member #11,955
May 2010
avatar

I heard the movie version comes out next year.

Oh nO! What! Where!... I didn't get it... :P

Heh. Yeah. Over a year ago now. And boy is it nice.

Good to hear that.

Quote:

Used to be when it got to -20 and below, my room would be ice cold, and I'd need like 4-6 blankets to keep warm at night.

Not good at all to hear that :o... MAN!

Quote:

With windchill it was probably -50c. For that one day we were the coldest recorded place on the planet. Even colder than the Arctic or Antarctic.

Man, I didn't know Canada could be so cold. Compared to that here it's summer all year long.

Arthur Kalliokoski
Second in Command
February 2005
avatar

Used to be when it got to -20 and below, my room would be ice cold, and I'd need like 4-6 blankets to keep warm at night.

I've ruined computers by storing them in a room that may have gotten as low as +7 C (+45 deg F).

“Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded — here and there, now and then — are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty. This is known as "bad luck.”

― Robert A. Heinlein

MiquelFire
Member #3,110
January 2003
avatar

High humidity?

---
Febreze (and other air fresheners actually) is just below perfumes/colognes, and that's just below dead skunks in terms of smells that offend my nose.
MiquelFire.red | +Me
If it doesn't resolve the issue, we'll evaluate whether the latest round of anti-speculative-execution patches we've had to apply could somehow be responsible. (The performance impact of this fix is estimated to be just a couple of percent, but a banana on a football field isn't even that much and yet woe unto the quarterback who steps on it.) Gonna have to start looking at AMD CPUs. ~Owner of Nearly Free Speech.net

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