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Topic: PWM Signal to 10v (Read 7925 times) previous topic - next topic

numlock10

Hello,

I have a pretty basic problem and I also think I have a solution, but I just want to run it by some people that might know a bit more about this then me.

I need to up my PWM signal from 5v to 10v.  I will be using the signal to drive a PWM controlled Meanwell driver.
 
It states that it needs a low = 0v high = 10v PWM signal.

My plan is to use a uA741 Op-Amp to boost the signal to 10v.

I don't need any heavy load on the circuit as it is only a signal to the driver and will not be powering anything.  Is this going to accomplish what I need done?

Thanks for your help,

Jason

daveg360

a 10v supply, a transistor and some resistors is all you need :)
If your system involves lethal voltages/life critical/flamable elements - you probably shouldn't need to ask.
The Arduino != PC.

numlock10

#2
Oct 28, 2010, 02:39 pm Last Edit: Oct 28, 2010, 02:40 pm by numlock10 Reason: 1
I plan to use a 12v supply with a LM317 to drop the voltage to around 10.3v.  The supply would then feed to the uA741 Op-Amp to achieve the 10v signal to pass on to the drivers.

http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/opampvar.html#c3

I just need to know if this is going to accomplish what I need.

Cheers,

Jason

daveg360

i think a simple transistor (2n2222) would suffice for this.  The 0 - 5v PWM signal from the arduino controls the base of the 2n2222 that in turn controls the 10v going to the Meanwell driver.
If your system involves lethal voltages/life critical/flamable elements - you probably shouldn't need to ask.
The Arduino != PC.

Graynomad

#4
Oct 28, 2010, 02:51 pm Last Edit: Oct 28, 2010, 02:52 pm by graynomad Reason: 1
I don't see the need for an opamp.

To elaborate on what daveg360 said, feed your 5v signal through a resistor to the base of a transistor. Emitter to GND, collector to 10v through another resistor. Then tap your 0-10v PWM signal from the collector.

This will invert the duty cycle of the PWM so handle that in software.
______
Rob

Rob Gray aka the GRAYnomad www.robgray.com

numlock10

So, if I am reading it right, use the transistor to open and close the ground on the 10v circuit that is connected to the drivers?

Graynomad

#6
Oct 28, 2010, 02:59 pm Last Edit: Oct 28, 2010, 03:00 pm by graynomad Reason: 1
Umm, I think so. I prefer to look at it this way.

The collector resistor pulls the meanwell input high, and every now and then the transistor overrides that and pulls it low.

______
Rob

Rob Gray aka the GRAYnomad www.robgray.com

numlock10

I know it's a bit of an ask but would someone be able to knock-up a little drawing for me?  It might make a bit more since to me if I have something to look at.

Graynomad

#8
Oct 28, 2010, 03:50 pm Last Edit: Oct 28, 2010, 03:51 pm by graynomad Reason: 1
No problems,



Resistor values may vary but that's the idea.

(oops, VCC should be 10v)

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

numlock10

Thanks mate looks good,

You mentioned that I would need to invert the PWM signal in the software.  I imagine that will be a little more complex than just reversing the values.  I'll have a bit of a dig around and see if I can find anything on the website about it.

Thanks again,

Jason

Graynomad

Quote
I imagine that will be a little more complex than just reversing the values.

I don't think so, if you invert the value that would do the trick.

analogWrite (pin, value); // B00000011 or 3

becomes

analogWrite (pin, ~value); // B11111100 or 252



______
Rob


Rob Gray aka the GRAYnomad www.robgray.com

numlock10

I'll give that a try once I get all the pieces together.

Do you know of an IC that would contain multiple 2n2222 or similar transistors?  I need to have 6 different channels and would like to try and combine them into the smallest package that I can.  I don't have a problem putting together 6 individual 2n2222's but would be much easier as one larger package.

What is the best way to determine the resistor values?  Is there a formula or a calculator that i can use, or is it just trial and error?

Thanks again,

Jason

Graynomad

Quote
Do you know of an IC that would contain multiple 2n2222 or similar transistors?

Have a look at ULN2801/2/3/4/5, ULN2001/2/3/4.

Even better these chips don't need base resistors so you will lose 6 components.

_____
Rob
Rob Gray aka the GRAYnomad www.robgray.com

apollo21

Hi
There are drawbacks uA741 slow.

This is my favorite circuit.
Supply Voltage 2 / 3 to determine the voltage.
Voltage of the power / trigger 2 3 / 3 return, and window discrimination.
(Hysteresis circuit)
The output can be expected to drive a powerful totem pole.



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