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Topic: Doubling pwm output voltage. (Read 13522 times)previous topic - next topic

Vancouver Reefer

Apr 21, 2009, 07:32 pm
I understand the pwm output on the arduinos is 0-5V. Is there a way i could make this voltage go from 0-10V?

Would a king of voltage doubler circuit work on the end of the output. Similar to a voltage divider, but a multiplier instead???

VR

estranged

#1
Apr 21, 2009, 07:54 pm
See if this playground article is what you're after:

http://www.arduino.cc/playground/Main/RegulatedPositiveVoltageBooster

Vancouver Reefer

#2
Apr 21, 2009, 08:00 pm
I was looking at keeping things something simple. So would something like this work:

darudude

#3
Apr 21, 2009, 08:06 pm
this voltage doubler would work for something that is on or off for long periods of time, cause it takes some time for the caps to charge. Therefore you will never get a full resolution pwm to work with this circuit.

You are better off working with active components like transistors or op amps? but you need a source of 10+V. Do you have that source available?

Vancouver Reefer

#4
Apr 21, 2009, 08:09 pm
Getting the +10v source is not a problem. Just figuring out a way to control the pwm linearly is the problem!

koyaanisqatsi

#5
Apr 21, 2009, 08:24 pm
You need a transistor driver like the following:

This will give you up to 500mA at 10VDC (minus about .7v drop of the transistor)

Vancouver Reefer

#6
Apr 22, 2009, 01:51 am
koyaanisqatsi:

i cant see any diagram and it asks me for a password everytime i open up the page.

VR

koyaanisqatsi

#7
Apr 22, 2009, 02:12 am
Ugg!  Sorry, I do that all the time.    Fixed now.

Vancouver Reefer

#8
Apr 22, 2009, 02:29 am
im trying to dim a flourescent light driver that has pwm and 0v pin, so how would i attach it to that circuit???

Is there a way to have just the doubled voltage outputted?

ie:

I know that circuit you showed would work for a fan etc, but how would i connect the ballast?

koyaanisqatsi

#9
Apr 22, 2009, 05:08 amLast Edit: Apr 22, 2009, 05:19 am by koyaanisqatsi Reason: 1
In that case, the load resistor in my diagram becomes a pull-up resistor and the connection to your ballast input comes off of the circuit between the pull-up resistor and transistor.

This will invert the PWM signal, so you'll have to account for that in software.  When the PWM signal is high, the transistor will conduct to ground and put a low on the ballast input.  When the PWM is low, the transistor will be off and the pull-up resistor will put a high on the ballast input.

The values of the resistors can be higher in this case too.  You could probably use 10k resistors for both, depending on how the ballast reacts.  You may need to test with different values to find the best setup.

EDIT: I modified and reuploaded the diagram, which I realized is not the best thing to do right after doing it.  I should have put up a new image instead.  Oh well...

Vancouver Reefer

#10
Apr 22, 2009, 05:20 am
You mean like this:

Then arduino pwm 0 - 259 will dim from on to off ( 100% - 0% brightness) and vice versa, if im reading you correct??

koyaanisqatsi

#11
Apr 22, 2009, 05:24 am
Yep, that's it.  I am a slightly concerned about tying the Arduino ground to the ballast 0V input.  Be sure that's an OK thing to do before doing it.  It should be explained in the ballast documentation.

Vancouver Reefer

#12
Apr 22, 2009, 05:27 am
This is the kind of thing im looking at:

http://www.1000bulbs.com/images/PDF/Mark7-0-10V-brochure.pdf

Just scroll down a little to the diagrams and let me know what you think.

VR

koyaanisqatsi

#13
Apr 22, 2009, 07:00 am
Man, there just isn't very much information on what the "Mark 7 0-10v" signal should look like.  A few docs I found through Google all said something like "supports 0-10v dimming" but none of them spec'd the actual signal.

So I'm not sure what you're going to get when you hit it with a PWM signal.

Vancouver Reefer

#14
Apr 22, 2009, 07:14 am
Yeah i know what you mean. I know you can hit it with a POT. looks like more research is involved, but at least now i now how to get the pwm signal to it.

Thanks for all your help.

VR

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