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Author Topic: Externally powering LEDs so Arduino doesn't fry  (Read 4147 times)
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Eugene, Oregon
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I have mentioned that I think the LEDs are not getting 5v (probably closer to 4.5v, and that maybe the other reversed LED in the circuit is having some current limiting effect.
I thought so you don't have a clue about what is limiting the LED current.

Let me tell you then, although given your track record you will probably not understand this.
The peak current is limited by the source impedance of the arduino output pins. This in effect is your resistor. The bad bit about this is that from my experiments I have found that you can get about 240mA from a single arduino pin. See this, these are real measurements and they surprised me as well.
http://www.thebox.myzen.co.uk/Tutorial/LEDs.html
So that is more than the limit for a whole 328 chip going through one pin. I have pointed you at this web site before.
Oh an while we are on the topic of you not understanding things having read my decoupling tutorial:-
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
You come to the conclusion
I looked over mikes decoupling page, and things are still rather complicated and hard to understand everything, but its good to have that as a reference. As I understand it, if the caps arent quite right, there can be a lot of RF noise, and I guess its common for folks to just throw some caps at it, and be unaware of the noise issue. I dont like solving problems by making other problems, which is what im trying to avoid, while learning...
How on earth any one can come to the conclusion that using caps that are not quite right will GENERATE RF noise. That is a totally wrong conclusion and further underlines your credentials for giving advice to anyone about anything electronic.

As usual, you are just looking for ways to try to make me look bad. I did not say that caps will "GENERATE RF noise", but rather that I have read that if you dont have the right size cap, the result can be a noise issue, and I have also read that designers will just guess and stick a cap in, not notice any problem, and move on, but they may have a noise issue that is not being dealt with properly (like it would be with the correctly part). That post was over a week ago, are you digging through my post hoping to find some bit of dirt? LOL.

My "track record" as you put it, is only in your mind, its a fake construct that you have made to try to convince me that Im stupid and reckless, it only serves you, projecting it on me is just you being grumpy mike. I accept none of your projection, you get to keep that one.

But while we are on the topic of decoupling, Why dont the arduino tutorials have decoupling caps? It seems to me they should have a tutorial on decoupling caps, and include them in the tutorials that need decoupling caps.
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whats your point ? sry im not english so i maybe missed this.

using no resistors in that construction is within specifications or beeing above max ratings is a fun place to be?
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Manchester (England England)
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@Hippynerd
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As usual, you are just looking for ways to try to make me look bad.
I am trying to illustrate to you that you don't know enough to offer anyone any advice because you do not know what you are doing.

Quote
I did not say that caps will "GENERATE RF noise", but rather that I have read that if you dont have the right size cap, the result can be a noise issue,
The noise issue already exists without adding any capacitors. When you add capacitors you reduce this. If you do not use the right type then you will not reduce it enough.
Your comment
Quote
I dont like solving problems by making other problems,
Is totally nonsensical, even more so if you are saying you don't believe it will generate noise, so what other problems were you referring to that you think is caused by the wrong type of decoupling capacitor. You seem to understand even less that I thought, which is going some.

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My "track record" as you put it, is only in your mind,
Odd that, so I can copy an paste from my mind - cool. Your track record is just that, a record and it is on the forum for all to see, I don't have to make anything up.

Quote
I accept none of your projection, you get to keep that one.
No I don't expect you do, it is a trait of the self delusional.
I expect these suppliers were impressed when they posted those parts to
Hyppynerd Institute for Tech and Science - how many employees do you have in that institute then.
And why post a picture showing what a little boy you are?

Quote
That post was over a week ago, are you digging through my post hoping to find some bit of dirt? LOL.
The group 'Radiohead' - the song 'Just', work it out.

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Why dont the arduino tutorials have decoupling caps?
A very good question and one that I do not know the answer to. See I don't claim I know everything.
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Valencia, Spain
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In your car analogy, do you drive half the speed limit, because its safer? it is safer isnt it, so why dont you drive half the speed limit. Are you unconcerned with safety? Are you a reckless person driving the maximum speed limit, or are you interested in safety, and drive half of the recommended maximum speed limit?

I always felt the safest speed to drive at is the same speed everybody else is doing. Driving half speed causes unexpected circumstances for other people.

OTOH you just broke the original analogy by taking it too far.

PS: You still didn't answer about the 'cloud' guy, he resembles you in many ways. Yes he's lighting up some LEDs, but his 'designs' are going to break people's parts. What's your opinion on that?

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No, I don't answer questions sent in private messages...

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Have you noticed he is more interested in peoples perceptions of him than the actual technical aspects of electronics.
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Eugene, Oregon
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Have you noticed he is more interested in peoples perceptions of him than the actual technical aspects of electronics.
This is a pretty ironic thing to say. from a guy that just wants to attack anyone that doesnt agree with him. My interest is mostly dispelling the crap that you write. Its not about perceptions, its about strategic systematic abuse of people that dont agree with you. You seem to think its ok to insult and berate people that disagree with you, because thats the only way you can win, and winning is paramount, since you are on a mission to save the LEDs.

In your car analogy, do you drive half the speed limit, because its safer? it is safer isnt it, so why dont you drive half the speed limit. Are you unconcerned with safety? Are you a reckless person driving the maximum speed limit, or are you interested in safety, and drive half of the recommended maximum speed limit?

I always felt the safest speed to drive at is the same speed everybody else is doing. Driving half speed causes unexpected circumstances for other people.

OTOH you just broke the original analogy by taking it too far.

PS: You still didn't answer about the 'cloud' guy, he resembles you in many ways. Yes he's lighting up some LEDs, but his 'designs' are going to break people's parts. What's your opinion on that?

I dont know how the original analogy is broken, but it doesnt really matter, its not really relevant.

P.S.
I did answer your question about why im not going to respond to someone else project (no matter how popular it is), it is not relevant to the discussion here, and I am not the author of that document, if you have a problem with it, you should address them, not me. Do you understand now why I am not trying to discuss something that has no relevance, and has nothing to do with me.


I should change my signature again, I changed it just for you, using your quote, but I guess there is nothing I can say that will ever make any difference.


@Hippynerd
Quote
As usual, you are just looking for ways to try to make me look bad.
I am trying to illustrate to you that you don't know enough to offer anyone any advice because you do not know what you are doing.

Quote
I did not say that caps will "GENERATE RF noise", but rather that I have read that if you dont have the right size cap, the result can be a noise issue,
The noise issue already exists without adding any capacitors. When you add capacitors you reduce this. If you do not use the right type then you will not reduce it enough.
Your comment
Quote
I dont like solving problems by making other problems,
Is totally nonsensical, even more so if you are saying you don't believe it will generate noise, so what other problems were you referring to that you think is caused by the wrong type of decoupling capacitor. You seem to understand even less that I thought, which is going some.

PoopyMike, This is something you dragged from a completely different thread, it has no relevance here. You are making all the wrong assumptions TO attempt to make an argument just to discredit me, its not accidental, so there is no need for me to clarify, its intentionally being abusive to me. To clarify, it is not relevant, it is a intentional mischaracterization, and it is harmful behaviour, and that your only intention is to shut up someone that doesnt agree with you.

I would like to take this moment to point out to you that you are happy to abuse people, if you think that they may be abusing some LEDs. Thats a pretty disturbing thought.


Quote
My "track record" as you put it, is only in your mind,
Odd that, so I can copy an paste from my mind - cool. Your track record is just that, a record and it is on the forum for all to see, I don't have to make anything up.

Im sure that I could copy and paste lots of examples of you being abusive to people if I wanted too waste time on unhappy stuff. From my personal anecdotal experiences, I remember a time when you called me names like 5 times in one paragraph. That isnt really relevant to this discussion though, but since you bring up peoples track record, Im compelled to point out your track record with me.

I have posted a few threads, and you have posted in them, you could have been very helpful, being that you are and electrical engineer, with lots of knowledge, and experience. Your posts have ranged from being detrimental(like angry name calling) to slightly helpful, but unclear or ambiguous. sometimes you just post "no" which usually just doesnt help.

All in all, you could be very helpful, but instead you chose to be the defender of LEDs by castigating anyone that dares use an LED without a resistor. You seem to feel like your mission is so important that you feel its ok to ignore evidence, and it also allows you to be abusive to people, since you know you are right, and they are wrong, they deserve what they get.

That being said, those posts dont have anything to do with this thread, and are not relevant, and they dont change anything in this thread.


Quote
I accept none of your projection, you get to keep that one.
No I don't expect you do, it is a trait of the self delusional.
I expect these suppliers were impressed when they posted those parts to
Hyppynerd Institute for Tech and Science - how many employees do you have in that institute then.
And why post a picture showing what a little boy you are?

Its Hippynurd, or Hippynerd, but not Hyppynerd. People make mistakes, its ok, but you should at least try, when it comes to personal names. I have noticed that you have had some spelling and grammar errors in your posts, I dont point them out, because that wont really help, and it may make you self conscious. I could use it to try to discredit you, being that to get a degree in engineering, you usually have to pass basic writing classes and all... but once again, that isnt helpful, its just curious.

As far as the shipping label is concerned that was just me having a little fun, the order form had a line for company, so I put something funny in, you know, kinda like your "solder is electric glue" tag line under your avatar... its just fun. If someone seriously thought that solder was glue, then maybe that would be worth questioning, but its understood that its just a joke (even if it isnt funny, its still just an attempt at humor.)

Its also important to note that this is just another desperate attempt to discredit me, by taking something that is not relevant, from a different thread, and mischaractorized as an attempt to castigate me.  You seriously believe that my funny shipping label is a valid excuse to call me a little boy, or delusional? That is pretty pathetic I dont know how anyone can support that behaviour.


Quote
That post was over a week ago, are you digging through my post hoping to find some bit of dirt? LOL.
The group 'Radiohead' - the song 'Just', work it out.

Quote
Why dont the arduino tutorials have decoupling caps?
A very good question and one that I do not know the answer to. See I don't claim I know everything.

My point about the tutorials is that you should spend your time and effort getting that stuff straightened out since that is something that you have some expertise, it shouldnt be too difficult for you, and it should benefit many people, This IS what i call helping, and IS the sort of thing that you should be doing.

Because the tutorial doesnt have the caps, I built my circuits without them (I need to get back to that one soon...) I looked through the tutorial, and the datasheet and found nothing about capacitors. A guy on the internet has a webpage (made with a mac, LOL!), and he says I should use a 47uf cap with my TLC chip. Even though his page is made with a mac, it could be that the information is legitimate, but being made with a mac really reduces my confidence.
So, PoopyMike, who should I trust, some guy with a mac, or the official documentation?

P.S. I get to call you PoopyMike, because its the only way to learn you that name calling is bad behaviour. I would like to petition that forum user Grumpy_Mike should get his forum name changed to Poopy_Mike, until he learns to stick to the facts.
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Eugene, Oregon
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I also wanted to point out that, if you had been more helpful in my threads, i may not have found the charliecube. I found it while I was looking around for different LED cube designs, because the one I was working on was being so difficult. Its still not done, I have some parts to test out, to see if they will do what I need, but meanwhile, the charliecubes have been built, documented, measure (to the best of my abillity), and I've even modified one to be a "safe" version.

In a strange sort of way, your lack of help, has contributed to the development of this resistorless RGB LED cube. Thanks buddy!
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Repsonse received from Atmel regarding power/pin and total consumption in reply to my question:

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Dear customer,

Thank you for contacting Atmel Technical support.

The 200mA is the absolute maximum current rating of the power supply pin. Whatever may be the power supply voltage (The power supply voltage should be within the specification), the current through the Vcc pin should not exceed 200mA.

Also the 200mA specification under the absolute maximum rating is for individual Vcc pin. And the AVCC pins should not be considered along with the VCC pins for the total absolute maximum rating. Hence, for the device ATmega1284P, for the DIP package, the maximum current rating will be 200mA, whereas for the TQFP package, the max. current rating will be 600mA.

For 328P, the max current rating is 400mA for the TQFP package. For ATmega2560, the max current rating is 800 mA. Also, please note that this is absolute maximum rating and exposing the device to absolute maximum conditions for longer duration of time could possibly cause damage to the device.

Hope this clarifies. Please get back to us in case of further queries.

Best Regards,
Ineyaa N
Atmel Technical Support Team

And my question to them (posted earlier also)
Quote
   Hello Atmel technical team,
   I have a question regarding power utilization in ATmega328P,
   ATmega1284P, ATmega2560 devices.
   
   
   The ATmega328P, ATmega1284P, ATmega2560 data sheets all show:
   
   Absolute Max for DC current VCC and GND pins
   .................................. 200.0mA.
   
   The Electrical characteristics all show greater then 200mA total being
   supported by the ports with various current limits per port:
   
   Notes on allowed currents:
   
   ATmega48A/PA/88A/PA/168A/PA/328/P:
   3. Although each I/O port can source more than the test conditions (20mA
   at VCC = 5V, 10mA at VCC = 3V) under steady state conditions
   (non-transient), the following must be observed:
   1] The sum of all IOH, for ports C0 - C5, D0- D4, ADC7, RESET should not
   exceed 150mA.
   2] The sum of all IOH, for ports B0 - B5, D5 - D7, ADC6, XTAL1, XTAL2
   should not exceed 150mA.
   If IIOH exceeds the test condition, VOH may exceed the related
   specification. Pins are not guaranteed to source current greater than
   the listed test condition.
   4. Although each I/O port can sink more than the test conditions (20 mA
   at VCC = 5V, 10 mA at VCC = 3V) under steady state conditions
   (non-transient), the following must be observed:
   1] The sum of all IOL, for ports C0 - C5, ADC7, ADC6 should not exceed
   100 mA.
   2] The sum of all IOL, for ports B0 - B5, D5 - D7, XTAL1, XTAL2 should
   not exceed 100 mA.
   3] The sum of all IOL, for ports D0 - D4, RESET should not exceed 100
   mA.
   If IOL exceeds the test condition, VOL may exceed the related
   specification. Pins are not guaranteed to sink current greater than the
   listed test condition.
   
   ATmega164A/PA/324A/PA/644A/PA/1284/P:
   3. Although each I/O port can sink more than the test conditions (20mA
   at VCC = 5V, 10mA at VCC = 3V) under steady state conditions
   (non-transient), the following must be observed:
   1.)The sum of all IOL, for ports PB0-PB7, XTAL2, PD0-PD7 should not
   exceed 100mA.
   2.)The sum of all IOL, for ports PA0-PA3, PC0-PC7 should not exceed
   100mA.
   If IOL exceeds the test condition, VOL may exceed the related
   specification. Pins are not guaranteed to sink current greater than the
   listed test condition.
   4. Although each I/O port can source more than the test conditions (20mA
   at VCC = 5V, 10mA at VCC = 3V) under steady state conditions
   (non-transient), the following must be observed:
   1.)The sum of all IOH, for ports PB0-PB7, XTAL2, PD0-PD7 should not
   exceed 100mA.
   2.)The sum of all IOH, for ports PA0-PA3, PC0-PC7 should not exceed
   100mA.
   If IOH exceeds the test condition, VOH may exceed the related
   specification. Pins are not guaranteed to source current greater than
   the listed test condition.
   
   ATmega640/1280/2560:
   3. Although each I/O port can sink more than the test conditions (20mA
   at VCC = 5V, 10mA at VCC = 3V) under steady state conditions
   (non-transient), the following must be observed:
   1.)The sum of all IOL, for ports J0-J7, A0-A7, G2 should not exceed
   200mA.
   2.)The sum of all IOL, for ports C0-C7, G0-G1, D0-D7, L0-L7 should not
   exceed 200mA.
   3.)The sum of all IOL, for ports G3-G4, B0-B7, H0-B7 should not exceed
   200mA.
   4.)The sum of all IOL, for ports E0-E7, G5 should not exceed 100mA.
   5.)The sum of all IOL, for ports F0-F7, K0-K7 should not exceed 100mA.
   If IOL exceeds the test condition, VOL may exceed the related
   specification. Pins are not guaranteed to sink current greater than the
   listed test condition.
   4. Although each I/O port can source more than the test conditions (20mA
   at VCC = 5V, 10mA at VCC = 3V) under steady state conditions
   (non-transient), the following must be observed:
   1)The sum of all IOH, for ports J0-J7, G2, A0-A7 should not exceed
   200mA.
   2)The sum of all IOH, for ports C0-C7, G0-G1, D0-D7, L0-L7 should not
   exceed 200mA.
   3)The sum of all IOH, for ports G3-G4, B0-B7, H0-H7 should not exceed
   200mA.
   4)The sum of all IOH, for ports E0-E7, G5 should not exceed 100mA.
   5)The sum of all IOH, for ports F0-F7, K0-K7 should not exceed 100mA.
   If IOH exceeds the test condition, VOH may exceed the related
   specification. Pins are not guaranteed to source current greater than
   the listed test condition.
   
   My interpretation of these notes is that:
   
   for the '328P the sum of current across the VCC/AVCC pins can support
   the current thru the ports, with 400mA max thru the VCC/AVCC & Gnd pins
   and 300mA thru the ports, (altho SMD parts have an extra VCC& Gnd pin,
   so 600mA could be taken in)
   
   for the '2560 the sum of current across the VCC/AVCC pins can support
   the current thru the ports, with 1000mA max thru the VCC/AVCC & Gnd pins
   and 800mA thru the ports,
   
   and for the '1284P the sum of current across the VCC/AVCC pins can
   support the current thru the ports, with 400mA max thru the VCC/AVCC &
   Gnd pins and 200mA thru the ports (altho SMD parts have 4 each VCC/AVCC
   & Gnd pins, so 800mA could be taken in) So the '1284 seems to be under
   supported for IO current. But a nice chip none the less that I will
   continue to use.
   
   Can you confirm that for 328s & 2560s that the higher currents in the
   notes are supported and the 200mA Absolute Max is for each individual
   VCC/Gnd pin and Not for the entire device?
   
   Thank you.
   Robert
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Eugene, Oregon
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It looks like (with the 328) if you have a dip or a 28 pin chip, you only have 1 VCC, and are limited to 200ma sourcing, but 400ma sinking (proving that you dont do more than any one port or any one pin can handle.) It still looks like you could source 150 and sink another 200, if you are careful.
If you have a 32 pin chip or any non-dip chip, you have 2 VCC pins, and 400ma depending on how you handle the other limits. You could source 300, or sink 300, or source and sink for 350.

I guess its also safe to say that the AVCC pin should be ignored, but it would be nice to know what the heck it is, and why, ...

What gets me, is that the big DIP package is the weakest, but the tiny QFP packages can handle a lot more current. That is the opposite of what I would assume.
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