LEDs not full bright through mosfet

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malichite
 
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Joined: Fri Oct 31, 2014 12:48 am

LEDs not full bright through mosfet

Post by malichite »

Forgive me this is one of the first things I have ever done with a microcontroller. I am trying to simulate sunrise/sunset with a strip of LEDs much like these http://goo.gl/ehK7Ng. Hooking them up directly to 12v they are very bright. I then wired them through a mosfet (IRF510) like this.

Image

If I jump the gate to positive, the LEDs light up full bright so I know the mosfet works. Once I hoook the gate to a GPIO on my raspberry pi, They never seem to get full bright. I am able to dim them using PWM, but even with the duty cycle at 100%, or they are not full bright. I will admit, and I dont know if this is the reason, that I do not have the 10k resistor between the gpio pin and ground. Any thoughts?

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malichite
 
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Re: LEDs not full bright through mosfet

Post by malichite »

Wanted to add an update. The small strip of LEDs is only for testing. Ultimately I am hoping to be able to run 300ish Watts at 12v worth of lights off of this.

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adafruit_support_bill
 
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Re: LEDs not full bright through mosfet

Post by adafruit_support_bill »

Sounds like your MOSFET Rds at Arduino signal voltage is too high to efficiently drive that load. From the datasheet, it looks like it wants a control signal closer to 10v.

These are designed to be driven directly from 5v TTL logic: https://www.adafruit.com/products/355

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