I accidentally fried my board and the highlighted component in the attached pictured got burned and smoked.
I was connecting it to my self-made rectifier circuit which transforms 220v AC to 24v DC, I have connected the output DC voltage to 2 voltage regulators (7824 and 7805) in parallel and supplied the Uno with the 7805 one with no loads on it (just powering it up), I left it on for a few minutes and suddenly this component got burned.
I assume it has something to do with the current limits as the regulator got extremely hot just before the incident, is it the regulator who got the board fried or something else?
That is a 47uF 25V aluminum electrolytic capacitor. PC1 is the designation. It is on the Vin side of the onboard 5V regulator.
Were you feeding 24V into the Uno, or 5V? 24V is pretty close to the max voltage of that capacitor. Is that a picture of your board, or an image you found online? I ask because the Uno R3 image on Arduino.cc has only a 16V capacitor there.
That would explain the capacitor blowing up. The Uno recommended input voltage is 7 to 12V, 20V maximum. If it really has 16V caps, then I'd call it 12V max.
24V would also cause an awful lot of heat burning up the 5V regulator.
By paralleling the 24V and 5V regulator, I hope you mean input and ground together, but the outputs separated.
polymorph:
It is also possible the ground connection to your 7805 wasn't good enough, so it put out a lot more than 5V.
How are you confirming these voltages? Where did you put the output of the 7805?
About that picture, no I found it online and it is not my board.
I confirmed them by the AVO meter and it was 4.97v exactly, and I put the output to the Vin pin on the board.
It worked fine for a while but after few minutes the 7805 got really hot like burning my finger, I thought this is because I supplied the regulator with a direct 24v source but after that it fried that capacitor on board.
Could the regulator pass more voltage if its input is too high?
The 7805 is supposed to shut down if it overheats, but s**t happens. Heatsink? The 7805 is good for less than a watt without a heatsink, and at about 20V drop, that's only 50mA. Yes, 50mA. 20x0.05 = 1W
The Vin barrel socket is not supposed to get 5V, anyway, it is for 7 to 12V input. There is an onboard regulator.
MohSalah:
I was connecting it to my self-made rectifier circuit which transforms 220v AC to 24v DC
why is it 24V? [you happened to have 'one of those' laying about?]
I suggest a series regulator between the 24V and the Uno, dropping volts below 12VDC, 9V being a good choice.
ALSO, Adafruit sells very inexpensive switching power supplies that will plug right in. They're VERY inexpensive. I've got a few of them (the older versions). It should work anywhere in the world.
you won't need 1000ma for your Uno unless your shield draws more power, in which case it should have separate power input since the Uno regulator probably can't handle that much current anyway.
Hi, can you post a picture of your power supply, and a CAD or picture of the circuit diagram please.
Have you fitted 10uf and 0.1uF capacitors around the regulators as is suggested in the data sheets.
ALSO, Adafruit sells very inexpensive switching power supplies that will plug right in. They're VERY inexpensive. I've got a few of them (the older versions). It should work anywhere in the world.
you won't need 1000ma for your Uno unless your shield draws more power, in which case it should have separate power input since the Uno regulator probably can't handle that much current anyway.
I need a 24v output source in my project to activate a hydraulic DCV and I want to use an unified AC power supply.
I don't care whether it is expensive or not, it is my first time to use a rectifier circuit and just wanted to learn something new.
That DCV needs 1A to function and as I heard a rectifier circuit is more efficient when it comes to current drawing.
TomGeorge:
Hi, can you post a picture of your power supply, and a CAD or picture of the circuit diagram please.
Have you fitted 10uf and 0.1uF capacitors around the regulators as is suggested in the data sheets.
Tom....
If you mean the rectifier circuit, it is just a simple one with 220v to 24v transformer, bridge rectifier after the secondary coil output and a 1000uf smoothing capacitor.
I have been using regulators for years and never added those capacitors, are they mandatory?
polymorph:
24Vac transformer? So about 32.5V on the capacitor. Just barely under the max 35V rating of the 7805. But if that is really 25.2Vac, then 34.2V.
You've not said if there is a heatsink.
Those capacitors are highly recommended.
Are you feeding 5V into the Vin?
I am about done with this. I am not going to work hard just to get you to answer my questions in order to help you.
Yes about 34V on the capacitor, but they are supposed to drop down to 24V when loaded I think
No heatsink for now but I'm planning to add one in the future, I already have it, and I will try those capacitors as well.
Yes I'm feeding the 5V into the Vin.
Hi, can I suggest, you feed the input of the LM7805 with the output of the 24volt reg, that way you will be sure that the LM7805 is not overloaded on its input.
You need to do some math too, I think that you will definitely need heatsinks, work out the volt drop across each regulator and the current that is going to flow through it.
Yes about 34V on the capacitor, but they are supposed to drop down to 24V when loaded I think
Wrong. Measure it.
No heatsink for now but I'm planning to add one in the future, I already have it,
Wrong. As I said, a TO-220 package like the LM78xx series are good for about 1/2W. You can't just say you'll add it later. Add it now, or forget it.
and I will try those capacitors as well.
Add them now. Insufficent bypassing can cause voltage regulators to burst into oscillation.
Yes I'm feeding the 5V into the Vin.
Wrong. What is your Arduino rated for on Vin? What have I been saying? 7V to 12V.
It will help if you power the 7805 from the 7824, as TomGeorge suggested. However, this does mean more power dissipation in the 7824. Again, heat sink! I cannot stress this enough, HEAT SINK!!!
Check your grounds. Always measure the output of your power supply. Not just without a load, but with a load. Obviously something went wrong.
Check your grounds. Not just how they look. Measure them. Is pin 2 of the 7805 at ground when it is powered with a load? Use a big resistor to load it down for testing, not an expensive Arduino.
polymorph:
Check your grounds. Not just how they look. Measure them. Is pin 2 of the 7805 at ground when it is powered with a load? Use a big resistor to load it down for testing, not an expensive Arduino.
Yes pin 2 is on ground.
Anyways Thanks for your help, I will try these new actions and see.
fungus:
Lesson: Next time spend those "few minutes" looking at the voltage with a multimeter.
I don't want to know if you looked at it, I want to know if you -measured- it. Preferably with power applied and a resistor drawing a few hundred mA. and check the other voltages while you are at it. Is it soldered? Protoboard? Clip leads? Wires twisted together?
It is very bad to just assume things are what you think they are without measuring.
For "ground going to external power supply" I prefer to solder a wire to the USB housing like this.
Poking wires into the Arduino connectors is far too risky. Even if the wire doesn't fall out it only takes a moment of bad contact to destroy all sorts of components.
