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Topic: MOFET selection to run 12v (Read 1 time) previous topic - next topic

anderscrib

I tried it without and no go.  I diconnected the gate and kept the source and drain connected to the projects grounds and power was getting through and I wasn't sure why..

fungus

what's the voltage difference between source and gate when it's turned on?

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

anderscrib

I'll have to check and post tonight.. Thanks for the input

MarkT


You don't need limiting resistors for MOSFETs. Try it without them.




What?  You shouldn't recommend this - a power MOSFET gate can be in range 1nF to 20nF, that's like a short-circuit load to an Arduino output pin on short timescales - they can only take 40mA abs max so a gate resistor of 150 ohms or so is recommended.  The datasheet seems to lack max load capacitance figures, but typical values are around 100pF or so for logic outputs in general, well below nanofarads.
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MarkT


I am trying to control some LED strip lights (12V, 2 AMP) with the arduino and am trying to select the correct MOSFET to handle the load. I thought this one (http://www.vishay.com/docs/91325/sihlz14.pdf) might work but it does not. When connected with all the pull down and limiting resistors, the lights are dim. Then I noticed when I connected the Drain to Source without the gate power was getting through and dimly lighting the lights...I have researched several sites and similar projects but they do not have the same conditions.
Any thoughts? Thanks community!


That MOSFET has a rather high Rds(on) of 0.2 ohms, so it will dissipate 800mW for a 2A load - it will run very hot - small heatsink highly recommended.  Its perfectly upto the job though as it is logic level and will only lose you 0.4V in voltage drop - clearly you have it wired up wrongly.

If you connect drain to source then you completely bypass the device, and if in that state the LEDs aren't lighting up properly its clearly nothing to do the the MOSFET!
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