Hi everyone, I am having big problems trying to power my arduino Mega.
Right now I need to power: Arduino Mega + Ethernet Shield + High intensity led + RTC clock + 20x4 lcd + computer speaker.
All these sum up to about 0.45 Amps.
Power Jack
I have tried using 12 V and 7 V from a computer power supply, also normal power supplies.
This means internal regulator must disipate P = (12-5)*0.50 = 3.5 Watts or (7-5)*0.50 = 1 Watt Which i belief is too much without heat sink.
In all cases, the regulator gets hot or the micro, and 5volts start going down to 4 and arduino finally shuts down.
I am also fearing if i have damage the built in regulator as before it could handle more powering time, but know voltage drops much quicker.
Also, is it normal that powering using USB the regulator gets really really hot?
I really dont know which way to go, internal regulator gets too hot, and using an external regulator does not give clean 5 volts so micro and regulator get very hot and shutdown.
Please can you help me out?
I really used 2 days trying to find a solution and im lost.
Thanks
btw, how can i know if i have damage the built in regulator? can i replace it with a normal 7805 I have in the shelf?
An external regulator on a heatsink is the way to go. Certainly take the LED's off the 5V pin, the ethernet shield presumably plugs into the 5V pin anyway and you'll have to live with that (about 150ma??)
That switchmode power supply should be giving out 5.0V +/-0.1V if it was any good at all - looks like its cheap dangerous junk: bin it. You may have damaged the Mega (6V is the abs max for the ATmega microcontrollers).
Give the seller negative feedback if that supply really is giving out 6.6V...
MarkT:
An external regulator on a heatsink is the way to go. Certainly take the LED's off the 5V pin, the ethernet shield presumably plugs into the 5V pin anyway and you'll have to live with that (about 150ma??)
That switchmode power supply should be giving out 5.0V +/-0.1V if it was any good at all - looks like its cheap dangerous junk: bin it. You may have damaged the Mega (6V is the abs max for the ATmega microcontrollers).
Give the seller negative feedback if that supply really is giving out 6.6V...
Thanks Mark, unfortunately i already voted time ago for the item.
The Mega is alive as if I plug it through the USB port it starts up and starts working, however the built in regulator starts to heat up, and voltage starts dropping till it gets to around 4,2 and lcd dimms and arduino stops working.
might it be that i have fried just the regulator? is it possible to replace it for a 7805 just soldering it on top? (removing the old one)
the led is only 20mA, but i really dont understand why all this is happening i have seen plenty of projects running from the arduino power without so much trouble. and even I have a very similar components proyect running from the arduino regulator.
any further help is much appreciated.
(at the moment the regulator is reading:
Vin = 7.6 V
Vout = 1.6 V
so i guess it is damaged? as i said, replaceble with a 7805?
MarkT:
That switchmode power supply should be giving out 5.0V +/-0.1V if it was any good at all - looks like its cheap dangerous junk: bin it. You may have damaged the Mega (6V is the abs max for the ATmega microcontrollers).
Give the seller negative feedback if that supply really is giving out 6.6V...
I am starting to think that maybe my multimeter may be wrong also, I have put together a 7805 and using 12V-5V from a computer PSU to give 7 Volts.
and the output of the 7805 is also 6,87 V without anything connected to it.
so maybe the switchmode power supply is working correctely?
but then, the MEGA micro should not heat up!
So im confused.
MarkT:
The on-board regulator has the board as its heatsink - it can probably take upto a watt or a little less - 3.5W is way beyond safe.
Most regulators detect over-temperature and shutdown automatically, which is probably what you see.
Add an external regulator with enough heatsinking?
I had a external regulator with heat sink semi-ready.
but the problem now is that if I connect using the power jack, nothing lights up.
if i connect using USB, arduino starts and all works but regulator gets really really hot. (but it shouldnt, right? cause usb is giving 5V directly, not going through the regulator.
Mark any guess of what can i try?
thanks a lot
I guess i will have to give it a try. as maybe my regulator is short circuit. I have measured it and it does not do a continuous beeeep, but each time i tap it i get a short beep. so something might be wrong.
So what powering solution would you recommend, a 7805 with heat sink or a switchmode power supply?
and then feed through the 5V pin ?
There are much better linear regulators than the 7805 these days (with low drop-out-voltage particularly, the 7805 needs about 2V above the output).
Switchmode regulators save power but can produce a lot of noise (this may affect the analogRead() values).
You can probably find a directly pin-for-pin compatible replacement linear regulator. I can't remember what regulator the Mega uses (mine is inside a metal box on one of my projects, hard to get to!).
MarkT:
There are much better linear regulators than the 7805 these days (with low drop-out-voltage particularly, the 7805 needs about 2V above the output).
Switchmode regulators save power but can produce a lot of noise (this may affect the analogRead() values).
You can probably find a directly pin-for-pin compatible replacement linear regulator. I can't remember what regulator the Mega uses (mine is inside a metal box on one of my projects, hard to get to!).
Thanks Mark.
For now I have it working again I had to desolder the regulator of the arduino mega.
Now using an external 7805 + heat sink is working again.
Although i dont seem to like very much this setup as its not that elegant and tight. Its running at 51ºC right now on the heat-sink. bit better than before where it was doing nearly 80ºC and voltage droppind down.
Is the regulator I mention in my first post a good option? It is nicely packed, and should coupe with 3A and 12V input is quite convenient.