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Topic: Drive a 12V, 16W LED stripe via turning PWM (Read 744 times) previous topic - next topic

jakmu

Hi forum,
I'm working on a interface to controll a special LED stripe via PWM.
Special cause they're 2700 K and 6400 K on the stripe, one with a reserved polarity.

You can controll the lightcolor via the frequenz that you use to switch between the polarity.

For the tested a classic motor driver circuit with an L293 H-Bridge.

It works out fine, but the working range of the L293 so to small (just up to 600 mA...)

So i'm looking for another H bridge or maybe a better way to controll the LED Stripe.

At the end I would like to use DMXControl to controll the stripe, so will need the right
DMX Driver, too.

Hope you can help me out, thx


artisticforge

Hi forum,
I'm working on a interface to controll a special LED stripe via PWM.
Special cause they're 2700 K and 6400 K on the stripe, one with a reserved polarity.

You can controll the lightcolor via the frequenz that you use to switch between the polarity.

For the tested a classic motor driver circuit with an L293 H-Bridge.

It works out fine, but the working range of the L293 so to small (just up to 600 mA...)

So i'm looking for another H bridge or maybe a better way to controll the LED Stripe.

At the end I would like to use DMXControl to controll the stripe, so will need the right
DMX Driver, too.

Hope you can help me out, thx


A link to the LED please.
Which Arduino board are you using?

I am surprised that you do not burn the L293 up by overheating it.
With that much current required you should be using Power MOFETs.

I know nothing about DMXControl.
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jakmu

http://www.ls-light.com/products-cn/residential/emotion-cn/strip_led_flex-cn-detail

It's hard to find more details about it. My version is working with 7,8w per meter.

I conneted the L293 just with one pair of LEDs on the stripe for testing.

I'm not really into mosfets tech. I know that they can easily controll RGB LEDs but is it possible to
rotate the polarity in a really high frequenz?

thx for your help!

Grumpy_Mike

Quote
but is it possible to rotate the polarity in a really high frequenz?
Yes, many orders of magnitude greater than the eye can see.

PaulRB

#4
Jan 20, 2018, 11:46 am Last Edit: Jan 20, 2018, 12:11 pm by PaulRB
Quote
You can controll the lightcolor via the frequenz that you use to switch between the polarity.
I suspect you are wrong. The frequency will have no effect on the colour. It is the duty cycle or mark-space ratio which will allow the strip to mix colours.

Take care choosing a motor driver to do this. Many motor drivers generate their own ac frequency & duty cycle waveforms and will not allow you to mix the colours in the way you want. You need to control the duty cycle separately for both forward and reverse current and interleave them. This is something that would not be done with DC motors, so many motor drivers will not allow it. You need a more powerful H-bridge driver with a simple logic interface, so that the Arduino can generate the required waveforms.

Code: [Select]

Forward current
+----------+
!     t1   !
+          +    +--------------- Zero Current
           ! t2 !        t3
           +----+
Reverse current

jakmu

so I've found the Si9986 from vishay: https://www.vishay.com/docs/70007/si9986.pdf
it's not to expensive and has got a 200khz switching rate (for my LEDs 175khz is perfect)

and I found this project: https://stratifylabs.co/embedded%20design%20tips/2013/10/15/Tips-Motor-Control-using-PWM-and-PID/

So normally a arduino can not handle more 200khz ...

Any ideas?

Wawa

#6
Jan 23, 2018, 01:15 am Last Edit: Jan 23, 2018, 01:17 am by Wawa
...for my LEDs 175khz is perfect
?
That PWM frequency generates 22ns wide pulses when dimmed to 1 or 254.
The equivalent of a frequency of almost 25Mhz.
Better use a PWM frequence < 1kHz.
200Hz PWM is already enough for general LED lighting.
Leo..

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