What is the voltage at the MOSFET Gate, Source and Drain when it is OFF, and the same when it is ON?

That will let us know if the MOSFET is being switched ON fully or not.

 

What is the voltage at the MOSFET Gate, Source and Drain when it is OFF, and the same when it is ON?

That will let us know if the MOSFET is being switched ON fully or not.

Hi,
1- OC input = -.8 to 1.25
2- With only OC connected no Mosfet, OC pin #4&5 is -.4 to 14.60
3- Other DC source 14.6v
4- Gate -1.5 to 5.5
5- with all connected, L1 left = 8 to 12v
6- L1 right 7 to 11v
7- Q2 #2 = 9 to 13.5v
8- Q2 #3 = -1 to 2
Q2 #2 & #3 = 12.5

what seems to be wrong is the L1 pins not falling to Zero and hence a delta of only about 3 volts which explains the solenoid week actio. It functions just fine according to instructions from Arduino but very week due the low voltage or whatever.

I also disconnected the LED since it never lit anyways, we can get to it later.

thanks again for your help

p.s.
I don't think the Mosfet is functioning properly since the #2 pin does not drop to 0 hence the L1 problem?

 

I'm confused by the measurements, as you have negative voltages.

If the black lead of the meter is connected to ground as shown in the previous schematics, there shouldn't be any point in the circuit (measured with the red probe) that is a negative voltage.

 

Is the ground of the +5V supply from the arduino connected to the ground of the other DC source? It is on the diagram but is it on the board?

 

Is the ground of the +5V supply from the arduino connected to the ground of the other DC source? It is on the diagram but is it on the board?

Hi,
No it's connected to the Arduino ground. Will try using the other Ground and see.

 

I used the other DC ground for the Arduino and Mosfet pin #2 voltage stayed constant at about 12!

 

I'm confused by the measurements, as you have negative voltages.

If the black lead of the meter is connected to ground as shown in the previous schematics, there shouldn't be any point in the circuit (measured with the red probe) that is a negative voltage.

Hi,
My meter must be messed up due low battery, since with nothing connected to it/s probs shows negative voltage.
I'll report back tomorrow after changing the batteries. But I stll think the Mosfet pin #2 should fluctuate between zero and 12 or not?

thanks

 

how long time does the Mosfet need? I,m only giving it 3 seconds on time! Is that enough?

 

3 seconds is plenty of time for it to switch on. And, when working correctly the drain of the mosfet, pin 2, should fluctuate between 12 and close to 0.

What are the two grounds you were using from the Arduino board? One from the power connector and the other from the digital connector?

When you get new batteries in the meter, re-check all of the voltages that thatoneguy asked about. You may also want to spend a couple of minutes checking all of the connections in the circuit to make sure it exactly matches the diagram.

 

how long time does the Mosfet need? I,m only giving it 3 seconds on time! Is that enough?

It will switch instantly from the point of view of a voltmeter.

Make sure the grounds are connected as shown in the schematic, and all other components are connected as shown in the schematic before applying power to the system again. Something may be touching/crossed which is causing the errors.

 

Hi,

The fact that this is a logical Mosfet and I'm giving it power rather than a logical 1 or 0 has nothing to do with it? It's a IFRZ4NN.

 

This has nothing to do with IRFZ44N being a logical Mosfet or something?

 

The Logic Level means that it will switch 18 amps with only 5V at the gate.

A standard mosfet needs close to the drain voltage at the gate to turn fully "on".

 

The Logic Level means that it will switch 18 amps with only 5V at the gate.

A standard mosfet needs close to the drain voltage at the gate to turn fully "on".

Hi,

This seems like the kind of problem I'm having?!

Could it be that my Mosfet is not a logical one? How can I test that feature?

thanks

 

Hello,

What type mosfet are you using?
In your schematic you state IRLZ44N, wich is a logic gate mosfet.

Greetings,
Bertus

 

Hi,

This seems like the kind of problem I'm having?!

Could it be that my Mosfet is not a logical one? How can I test that feature?

thanks

If the 5V and 24V supply grounds are separate, or other reasons causing the negative voltage readings, that is causing the issue.

What I'm trying to find with the measurements on the MOSFET while it is supposed to be on and supposed to be off will answer quite a bit.

While on, the voltage at the Drain should be very close to the voltage at the Source. If not, the gate voltage must be less than 5V.

When the black lead of the multimeter is on the Arduino ground, what does the +5V of the Arduino show? Without moving the black lead/ground, what does the +24 volt supply read?

Without meaningful voltage measurements, it is very difficult/impossible to troubleshoot.

 

Noooooooooooooooooooo, My Mosfet is IRFZ44N and NOT IRLZ44N!!!!
Is that why?
No wonder they were cheap like $0.25 each!

Please Confirm!

 

Hello,

The IRFZ44 is a "standard" gate mosfet, and not a logic gate mosfet.
I attached the datasheets for both types for comparisson.

Greetings,
Bertus

 

Hello,

I have adopted the circuit for IRFZ44.

Greetings,
Bertus

 

Bertus,

Thank you so much for the advice. Please recommend a type of Zener Diode also let me know if a IN4007 would do or not? Also any good readz on what a Zenner Diod does?