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Author Topic: PWM Dimming non dimmable led drivers.  (Read 1119 times)
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Hello to all,
I'm new to the arduino world an i would like to ask some questions about a project i'm planning.

I want to dim my led fixture which i have over my 90g reef tank using the pwm signal from arduino to control a n chanel mosfet.
The problem is that i don't know if i can do that with the drivers i'm using right now.
The drivers are 2x meanwell lpc 60-1400 and 2x lpc 60-1050.

The way i'm planning on doing it is by using the pwm signal from arduino to operate the gate of the mosfet.
Will this work, or should i do something more?

 
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Valencia, Spain
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The problem is that i don't know if i can do that with the drivers i'm using right now.
The drivers are 2x meanwell lpc 60-1400 and 2x lpc 60-1050.

If it doesn't have a pin labelled "PWM" then probably not.

The way i'm planning on doing it is by using the pwm signal from arduino to operate the gate of the mosfet.
Will this work

No. Those drivers watch their output voltage closely. Interfering with that voltage will cause problems.

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If the drivers are analog constant current then they won't be amenable to _high-speed_ digital PWM,
but all drivers can be powered off and on, its just a question of how fast you can do this and still
have them work - perhaps they can be PWM'd at 100Hz or so simply by using a p-channel MOSFET on the
supply - you may have to move decoupling from the driver to before the MOSFET though.

A constant-current driver should probably have something in the datasheet about how fast it can
power up and power-down - if that is 100us then you will get away with PWM at a few 100 Hz, if its 10ms
you won't...  Most electronic devices are fast enough I would suggest.  Just don't try PWM'ing at
100kHz, that's not likely to work.

Also check out all the application circuits in datasheets, sometimes there will be an example circuit
for just what you want (manufacturers are keen to show off their devices at their most flexible)
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Valencia, Spain
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If the drivers are analog constant current then they won't be amenable to _high-speed_ digital PWM,
but all drivers can be powered off and on, its just a question of how fast you can do this and still
have them work

The input to those drivers is A/C mains so it won't work.

Even if it wasn't, applying any kind of PWM to a switch-mode device (input or output) is unlikely to end well.

To make this work he needs different drivers, ones with a PWM input.

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First of all i would like to thank everyone for the quick response.
I managed to find and download the datasheet of the drivers from the manufacturers site http://www.meanwell.com/search/lpc-60/default.htm.
If anybody could read it and give me a hope... smiley-confuse
Or else i'm afraid that probably i have to replace the drivers with dimmable. smiley-money

Thanks!
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As fungus mentioned twice, it won't work. If you're looking for the spec that states that look at the "SETUP, RISE TIME" which is stated as 500ms and 120ms  for a total of 620ms before the LED will turn on completely when you give it power.
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Well after all seems lika i will have to search for new drivers. Any recomendations for pwm dimmable drivers will be much appriciated.

Thanks once again everyone for the informations.
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what about building one of these? http://www.tbideas.com/blog/build-an-arduino-shield-to-drive-high-power-rgb-led/
Just got my RGB leds and I am onto that.
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what about building one of these? http://www.tbideas.com/blog/build-an-arduino-shield-to-drive-high-power-rgb-led/
Just got my RGB leds and I am onto that.

Seems very interesting but i have to drive 52 power leds and a solution like this I thing it won't be very cheap. Although i can imagine a lot of dimming potentials through this.

Thanks anyway!
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