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Topic: Powering 200W LEDs (Read 2914 times) previous topic - next topic

pito

#15
Oct 18, 2011, 09:11 pm Last Edit: Oct 18, 2011, 09:23 pm by pito Reason: 1
..the power mosfets have usualy a large gate capacitance, so you might need a "driver". The driver has to be put between arduino's pwm output and the mosfet's gate.
When not using the driver, the mosfets will be operating in a "linear region" (because the arduino's low output current will charge/discharge the mosfet's gate capacitance rather slowly when switching between logical 1 and 0) and the mosfets might become quite hot. The power dissipation of the mosfets is proportional to on/off switching time (influenced mainly by the gate charge/discharge speed) and the U*I between mosfet's source and drain.
P.

burgos

hi
Im not understand what you really want, but if you dont have an Electronic knowloge I recomend you to use power supply whit PWM included.
The image are in spanish but you can deduced


You can increase the PWM voltage range whit this IC


I can you you more option but I need to undertan better your proyect if you draw you led configuration maybe ease to help you.
you can use the IC ULN2003 to drive a led dependig how many milli amp consume.

Connected one 9.8W strip directly to the Arduino (connected to 12VDC) tonight. Green and Blue are responding as they should, red is static.... why is that? Why isn´t the PWM-signal sufficient for the red, but for the blue and green? Guess I need that MOSFET, could you please give more specific details about what to buy... https://www.elfa.se/elfa3~se_sv/elfa/init.do?item=71-147-17&toc=19199??

Magician

MOSFET linked above is o'k, 7A x 12 V = 84 W maximum control power, if you connect it directly to arduino.
there is alternative:
http://www.sparkfun.com/products/10213

Grumpy_Mike

@burgos
There is no resistor on that LED on pin 13. Pin 13 does not have an internal resistor, you are endangering your arduino.

Could this driver https://www.elfa.se/elfa3~se_sv/elfa/init.do?item=73-296-26&toc=19777 be an alternative to the MOSFET? Any gains by doing that?

Magician

No,
Quote
The UCD7231 high current driver is specifically designed for digitally-controlled,
point-of-load, synchronous buck switching power supplies.

It would complicated things far above your comprehension.

Ok  :smiley-sweat:

What kind of driver chip do I need between the Arduino and the MOSFET? Mentioned by Pito

Grumpy_Mike

If you get a logic level FET then all you need is a 100R resistor to limit the current from the arduino pin. There is no need for a driver at these sorts of currents.

When you do need a driver there are lots available see:-
http://uk.farnell.com/jsp/search/results.jsp?N=0&Ns=P_PRICE_FARNELL_UK%7C0&Ntk=gensearch&Ntt=fet+driver&Ntx=mode+matchallpartial&suppressRedirect=true

The power FETs and resistors are now in place and it runs perfect. The LED-stripe is working just as it should. Thank you for all help.

For you who intend to use MOSFETs I can recommend this shield i found: http://www.robotshop.com/eu/productinfo.aspx?pc=RB-Spa-505&lang=en-US
I´ve ordered one of those for "integration" of the FETs to the Arduino.

I also bought a Cupperhead WiFi-Shield. Next step ahead.

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