MOSFET IRF840 DRIVER DOWNLOAD
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Here is the part of the code where the delay mosdet not working, I set it up to eliminate any outside factors: I found that "analogWrite 9, " worked better. The water pump is rated at 12V and 2. I'm having some very weird issues with using PWM analogWrite and the delay function.
Tying the gate to the source with a high value resistor is a good plan as people have mentioned, such as 1Mohm, so that its safely off until setup has run. I'd suggest a 1K from 12V to a capacitor to ground.
I've attached an actual picture of what I'm working with. If so, what are proper components to use? Here are some examples, to illustrate what is available http: You simply need to drive its gate from a NPN transistor with pull-up to 12V - however the pump might be putting spikes onto the 12V rail which might be an issue.
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My problem is that it never seems to be in an off state, as soon as I connect the power, mosget pump turns nosfet and the MOSFET gets really hot. I looked at the spec for a the IRF, and it looks like it needs 10V to switch it on. This is its listing on Ebay: Once I did these things, the resistance seemed to drop to zero when I applied 5V to the gate.
Both lowered resistance, but still kept maybe 2k ohms.
Remember MOSFETS have an effectively infinite input resistance so if the gate is left floating it will pick whatever ions are floating around in the air, respond to any slight leakage currents that might be present.
You alo need to check the data sheet to see how well it performs with only 5v on the gate. The last problem that I had was that the thing would overheat pretty bad after a just a few moments mosfdt the motor being on.
So my next question is what is the proper method for giving a motor more and less power? I went to Radio Shack today and picked up a few things that I thought would be helpful and help get me ahead of where I was yesterday: Also, I have no idea how to properly use a PNP transistor, I attempted to run the 12V through the PNP and use the Arduino's 5V to turn it off an on, however this did not seem to work and I ran into all kinds of crazy issues such as power seeming to run back through the gate from the collector.
Do you do what I did and turn the power on and off really fast?
Trouble with MOSFET
I didn't have any luck with the transistors that got from Radio Shack, I actually just ended up getting the original IRFs that I had to work by using 4 in parallel to prevent irf84 from overheating. Use Google Search box in upper right side of this page. This is the source code that I used: I maybe could have solved this with proper use of diodes, but after a few hours of messing around, I was still stumped.
This happens even if I don't even have the Ardunio hooked up.
IRF840 MOSFET
I combed over the code because oftentimes problems like this are mosfeet to coding errors, but I have not been able to find any problems in the code.
Another problem you have is that the IRF has an enormous Ron of 0. Then try supplying the NPN base from the arduino pin.
And Arduino doesn't have high-voltage tolerant output pins. Something rated V and A and with logic-level drive would be much more useful to you Also of note is josfet the delay function seems to work just fine if I remove the PWM pin so that it is not connected to anything.
MarkT Brattain Member Posts: You might need something to increase the gate voltage for lower internal resistance.
Have you got a potentiometer to hand, maybe 1K?
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