IRLZ44N odd behavior

Projects General Guidance
1

I have a small project where I will control a 12VDC motor with IRLZ44N MosFet and measure the output. Individually, they work perfectly. But when I connect the minus pole to the voltage measure, the MosFet goes high, how come?
Hope to get some help.

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2

I don't understand what you're saying, can you rephrase it clearer?

Oh, and you have A0 tied to ground.

3

It would help us understand if you could redraw your schematic in a more conventional way, with ground at the bottom, +12V at the top? I'm trying to mentally rearrange it in my head...

4

Sorry for the wrong diagram, here is the correct one.
The circuit with the MosFet regulates the motor perfectly as long as I do not connect the 7K5 resistor from the voltmeter to the negative terminal of the motor. This results in the IRLZ44N regulating the motor to full speed.

DCReg
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5

No, the IRLZ is there irelevant.

You have path

12V+ - motor - GND - GND - 12V-

and it simply connects motor to the 12V battery.

6

Hi, @pela1402
Welcome to the forum.

Can you show us with some inages what your project looks like and where you are connecting the voltmeter?
The gnd connected to the 7K5 resistor is causing your problem, why is gnd connected there?
You do have your DMM in voltage mode and not current?
Is the 30k and 7K5 acting as a potential divider to measure battery volts.
If so this is what you should have;

motordrive
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Thanks.. Tom.... :smiley: :+1: :coffee: :australia:

8

Hi, @pela1402

What model Arduino controller are you using?

Thanks for a clear schematic, here is it redrawn in a more standard layout with the A0 potential divider correction, measuring the battery voltage at A0.

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If you want to measure the voltage at the motor;

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Tom.... :smiley: :+1: :coffee: :australia:

9

Some other schematics are already shown. I did redraw your schematic from post #4 in KiCad to show you some principles; they might be personal. I hope I did not make mistakes.

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Power at top.
GND at bottom.
Inputs at the left.
Outputs at the right.

Note:
I can't quite follow your schematicf

10

I have a Arduino Uno R3 ATmega328

11

now you have R3 -grnd-grnd , R4 - A0 - 12VOLTS ..........YIKES :unamused_face:

@TomGeorge GOT IT RIGHT !

12

The output of what?
Maybe if you explain exactly what you want to measure, you may receive some more useful suggestions.

13

Maybe if you explain exactly what you want to measure, you may receive some more useful suggestions.

First of all, I am a beginner with Arduino and English is not my native language, but I can understand that you are very skilled, so I will ask you to bear with my lack of skills.
That said, I think TomGeorge has solved my problem and I will test it when I get home.

14

OK, no hurry.

15

Hi,
I think you mean D9 not A9 as the PWM output pin.

Tom.... :smiley: :+1: :coffee: :australia:

16

Yes of course stupid me :slight_smile:
Thanks TomGeorge

17

Now connected according to TomGeorge drawing and it works of cause perfectly - thanks!

18

Hi, @pela1402
Good to hear.

What are you aiming to measure with A0, battery voltage or motor voltage?

Tom.... :smiley: :+1: :coffee: :australia: