Hello
I'm using a n chanel mosfet to drive a p chanel one with arduino and 12 volt power supply.
The circuit works fine when usin only arduino and it's power supply (+5v).
But when i make some change according to the images listed below it dose not work or just pass small out put voltage.
Sorry for my Bad English, i'm not a native one.


https://ibb.co/kq4rBv


https://ibb.co/ccAEWv


https://ibb.co/hX704F


https://ibb.co/jx06Bv


Mods Note:
Please upload the images and circuit to our forum as 800x600 *.jpg.

 

Welcome to AAC!

Posting pictures on this website is preferred. As is using images of an appropriate resolution to keep size small.

You indicate the Arduino and 12V power supply have a shared ground. Does that mean they're connected? Where does the load get connected to ground?

What voltage do you measure on the gate and drain of the P MOSFET when it's supposed to be on?

 

Hi dl324;
Thanks for your attention.

Yes , all ground pin included load ground , Arduino ground , and power supply ground are connected together.
The load could be a simple LED for test.
As in the photo below drain of the P MOSFET is less than 1 volt, and i did not measure gate voltage but according to the photo it was less than enogh for turn on the first led that is between N mosfet drain and P mosfet gate.

https://ibb.co/jx06Bv

 

i did not measure gate voltage but according to the photo it was less than enogh for turn on the first led that is between N mosfet drain and P mosfet gate.

Measure the gate voltage and describe the nature of the load.

 

( with separate 12 volt power supply and basic blink sketch for Arduino )

The voltage of P mosfet gate was 0.00 wen it supposed to be on and also drain was 0.00
I measured 0.00 to 0.20 from N mosfet drain and it directly goes to the P mosfet gate.

But i found something more wired
i connect the positive probe of multimeter to the positive side of the circuit and the negative probe to the grand
then when the Arduino send High signal the multimeter measure near the zero volt and when it send Low signal the voltage rise up to 12 volt.

Note: this thing doesn't happen when i use Arduino power supply (5 volt).

 

Is the load the same when you test with 5V and with 12V? If it's an LED, you probably need a different size resistor when testing with different voltages.

When you're testing with 12V, can you check other points in the circuit and confirm that your 12V supply is still working? If something were shorted, or even just drawing more current than your supply is meant to deliver, the power supply might be shutting down temporarily.

 

I change the circuit to above image

Q2 = s9012
Q3 = s9014
12v power instead of 9v in image.

And the result was same as before.

The power supply is 12v 20amp switching.

And yes i think there shold be some kind of short circuit when the logic pin ( npn base) becomes high.

What do you think is the cause ?

 

In your earlier tests, you've got a diode going from the drain of your n channel MOSFET to your power supply.

• What kind of diode is it?
• part number?
• Datasheet?
• Is it still present in your new circuit, based on bjts instead of MOSFETs?