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Author Topic: Doubling PWM voltage (For LED Driver)  (Read 1698 times)
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I know this is covered other places, believe me, I've been reading for hours, but I guess i'm just dumb.

I need to control dimming on 3 led drivers. 2 Mean Well ELN-60-27P and 1 Mean Well ELN-60-48P (DATASHEET: http://www.meanwell.com/search/eln-60/default.htm) I want to use the fewest components possible, of course. I have an Arduino UNO R2.

The thread that I understand best is this one(http://arduino.cc/forum/index.php?topic=20632.0) from a few years ago, but I didn't wanna raise the dead to ask questions there. Post #8 has a diagram that I think I understand, and I could use that, but I think there's a better solution further down.

So, for starters, on post 8; how do I figure out what resistors to use?
How do I figure out which pins on the NPN go to which places? (Really, I think that's shown, I really could also use a good resource on the meaning of the symbols)

Further down, the ULN2801/2/3/4/5, ULN2001/2/3/4 chips are recommended. I've been looking at their spec sheets, but that's not helping me figure out how to wire them. Can anyone give me some insight, or point me in the right direction? (Also, just for now, can someone tell me which ones to buy? I want to order them ASAP, even though I dono what they even are yet)

I think i'll build and test the first solution, and once that's working, also build and test the second solution. I have a bit of time before I'm ready to cough up the $300 for the other parts of the build. (Which is REALLY cheap, by the way, looking through old threads, people were spending $2000 doing the same thing I'm doing now only a few years ago... I'm sidetracking...) If I power the Arduino with a 10v, does that 10v come out of the board somewhere (Vin?)? If I can't find a good 10v supply (seems they're hard to come across) and i need to use 12v, how would I work that out? I guess I really don't know how to power this, and I could ask a billion questions right here, but I'm sure one of you geniuses just knows the answer.

I know this is a lot for my first post, but I'd be really thankful for some help. I've been having a ton of fun messing with this board ofr the past few days, it's so easy to use, and there's so much documentation. Thanks a ton!



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So, for starters, on post 8; how do I figure out what resistors to use?
Use the ones the post.

Get a 12 V supply and a 10V regulator.

Vin has the voltage on the power barrell minus 0.7V because of the seriese diode.

That controller data sheet says the control is either 0 to 10V for the D-type or PWM for the P type, no where does it say the PWM has to be 10V, check that it has to be, it could work off 5V PWM.
« Last Edit: March 21, 2013, 09:00:33 am by Grumpy_Mike » Logged

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You're sure the posted resistors are correct? The poster says they might not be.

Okay, I thought that the data sheet did indicate 10V (I'm not familliar with drivers, assumed that since the 10V is the only one listed, that it was assumed that PWM was also 10V.) I would think that something taking PWM shouldn't need a whole 10V, but I dono. Everyone online seems to agree that it does need 10V for the PWM. I guess with a 5V PWM it maxes at half brightness (Which doesn't seem to make sense to me, PWM is digital, right? Others who are more knowledgeable than me also don't understand, and I guess it has something to do with the driver not being 'true PWM' I dono how that works.) I should probably pick up a driver anway, and start testing. Maybe everyone else is just confused, and the 5V works fine. Thanks for the prod!

So I get a 12V supply, the Vin pin will put out 11.3 ideally? And a 10V regulator is a magical thing that will drop that to 10? Sounds beautiful. now to go research how a regulator works.

Thanks for the reply!

(EDIT: How do you give Karma?)
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to give karma click on the little green plus sign next to karma
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Hmm, it's not showing. Maybe I need more posts or something.


EDIT:

I'm on the right track here. Gonna head to the local electronics shop after work (Hopefully they have what I need 'cause god knows da shak won't) to pick some transistors, 10v (and variable, why not) regulators, and a 12v power supply.. and I guess some kinda board. Maybe some wire... and new tips...

I'm still interested in using some kind of IC to make this project smaller, so if anyone has any guidance, I'm still all ears.
« Last Edit: March 21, 2013, 11:52:09 am by Longarms » Logged

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I guess with a 5V PWM it maxes at half brightness (Which doesn't seem to make sense to me, PWM is digital, right?

As you suspected that is not right, PWM works on the ratio of on to off, read this page of mine:-
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

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I thought that the data sheet did indicate 10V
For analogue only, it said nothing about the PWM. If you get the analogue input controller you will have to smooth the PWM into DC after the collector of the transistor.

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Hmm, it's not showing.
Thanks for trying, try again later if you like.

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I was looking at the data sheet later, and maybe it was an updated version, but lower on the sheet it goes into more detail about the PWM and it does call out 10v on the PWM.

Quite a few people claimed that running from the arduino board with a 5v PWM halved the output of the driver, and I was really confused about it. I thought (and still do think, but this made me question myself for a little) that PWM was on or off, digital... output is determined by the time between on and off. (skimming your link, the gif seems to indicate that it's actually the difference between time on and time off, but the principal is the same... I still have to assume that half of this "electronics" stuff is black magic)

Reading further, I saw a lot of people saying 'that's not how PWM works' but there were enough people saying that it happened to them that I think it's true. I don't know if they were getting half power, and it was going from on to off, or what, people with the problem didn't go into much detail, they just sailed right by it to "need to boost the voltage." I dono, something must be going on there. Some people had thoughts that the circuitry used some kind of work-around, maybe to lower costs for both models, and that's where the unexpected results came from, sounds plausible.

I'll keep trying. smiley-wink

EDIT: Yeah, I'm going with the PWM drivers for now. I think some day I might try switching them to analog drivers, or maybe on my next build. I'm interested in trying it out. I think they're a little more useful, 'cause you can override (With a switch, or modify in line) the arduino's signal with a pot. Also, they cut off at 5% power, whereas the PWM ones cut off at 15%. PWM just seems a lot easier for now though.
« Last Edit: March 21, 2013, 01:26:29 pm by Longarms » Logged

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cause you can override (With a switch, or modify in line) the arduino's signal with a pot.
Be careful how you do that so you don't feed a voltage greater than 5V back into the arduino, that will damage it.

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but there were enough people saying that it happened to them
None technical people are normally a bit rubbish as actually knowing what is going on.

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I'm going with the PWM drivers for now.
You make that choice when you buy the controller. There are two types, one is for PWM and the other for DC.
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Yeah, I think that the PWM drivers are the simplest set-up, that's why I'm starting out with them. Arduino puts out a PWM already, what could be easier? I'm aware of the fact that they're physically different drivers, but thanks for the tip.

I'm definitely worried about improvising (adding an override) because I'm not knowledgeable enough to do that. I'm sure a pot between the arduino and the driver would be fine, but I'd have to think hard about a switch and pot, probably another power source, to completely override it.

Thanks a bunch for sticking this out, and giving me such good advice. Much appreciated.

Told my girlfriend she won't be seeing me much this weekend. Will report back!

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I'm sure a pot between the arduino and the driver would be fine,
I am not sure.
Post a schematic of what you want to do before you try it.
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Yeah, I definitly won't be doing anything without consent from this forum, haha. It should be a ways off, I'll crass that bridge when i come to it. In other news, after only slight frustration, I got my RTC working!

Time to breadboard this voltage limiting/boosting thingy!
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Was just looking back through this thread, and noticed you said not to feed more than 5V back into the arduino board.

Does that include the ground? I've been using the ground on the board during my experiments, and been feeding between 2V and 11.7V into the ground on the arduino.

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How can you do that? It dosn't make any sense to me.
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Maybe I don't know what I'm talking about...

In the circuit I'm using for the voltage regulator, http://imgur.com/cDZIY9a , Vout goes through a resistor to ground, and to measure voltage I've been putting the leads of my multimeter to Vout and Ground.

I've had Vout over 10 volts at some points.
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Yes but that is not putting a voltage into the ground pin it is referencing your power supply to your arduino's supply. No only is that OK it is essential you do it.
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