MOSFET IRF840 DRIVER

You alo need to check the data sheet to see how well it performs with only 5v on the gate. If so, what are proper components to use? 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 them from overheating. I maybe could have solved this with proper use of diodes, but after a few hours of messing around, I was still stumped. 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. This is the source code that I used:

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This is its listing on Ebay: I solved this by simply adding 3 more IRF’s in parallel. I’d suggest a 1K from 12V to a capacitor to ground.

So my next question is what is the proper method for giving a motor more and less power? You might need something to moafet the gate voltage for lower internal resistance. This happens even if I don’t even have the Ardunio hooked up.

IRF MOSFET Datasheet pdf – Equivalent. Cross Reference Search

I thought I’d post an update since everyone was so helpful. Another problem you have is that the IRF has an enormous Ron of 0. Use Google Search box in upper right side of this page.

I combed over the code because oftentimes problems like this are due to coding errors, but I have not been able to find any problems in the code. I found that “analogWrite 9, ” worked better.

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I’m having some very weird issues with using PWM analogWrite and the delay function. Here is the part of the code where the delay is not working, I set it up to eliminate any outside factors: This is the source code that I used: Do you do what I did and turn the power on and off really fast? Remember MOSFETS have an effectively mosfef 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.

Vishay – MOSFETs – IRF, SiHF – Power MOSFET

Once I did these things, the resistance seemed to drop to zero when I applied 5V to the gate. 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.

I’ve attached an actual picture of what I’m working with. If so, what are proper components to use? This apparently produces a 1V signal.

Then try supplying the NPN base from the arduino pin. You alo need to check the data sheet to see how well it performs with only 5v on the gate.

Perhaps I should post this in a separate topic, but it is a continuation of the project addressed above and may relate to the way that I am using power. My problem is that it never seems to be in an off state, as soon as I connect the power, the pump turns on and the MOSFET gets really hot.

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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. 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. I maybe could have solved this with proper use of diodes, but after a few hours of messing around, I was still stumped. And Arduino doesn’t have high-voltage tolerant output pins.

IRF840, SiHF840 product information

I looked at the spec for a the IRF, and it looks like it needs 10V to switch it on. MarkT Brattain Member Posts: Something rated V and A and with logic-level drive would be much more useful to you Here are some examples, to illustrate what is available http: The last problem that I had was that the thing would overheat pretty bad after a just a few moments of the motor being on. 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 them from overheating.

Have you got a potentiometer to hand, maybe 1K? Both lowered resistance, but still kept maybe 2k ohms.