I am attempting to create a 24V PWM signal using an arduino and an external 24V power supply.
To do so, I am using a VMA411 Mosfet module ( https://www.velleman.eu/downloads/29/vma411_a4v01.pdf ). When I try to create a signal the PWM in arduino works well (Getting around 2.5V of effective voltage at 127 bits). But the output of the module stays at 24V. I am measuring effective voltages with a tester because I don't have access to an oscilloscope.
Checking the specs of the mosfet of the module (IRF520) I have seen that it is not a logic level mosfet but it should be working for <2A load current (It is about 100mA).
I am not familiar with mosfets so i don't know if I am doing something wrong or the module is not suitable for my set-up.
Can you post a circuit diagram showing exactly how you have the 24V power supply and motor connected and how the Arduino is powered and connected to the module.
slipstick:
Can you post a circuit diagram showing exactly how you have the 24V power supply and motor connected and how the Arduino is powered and connected to the module.
raschemmel:
Are you saying the mosfet is always ON, or always OFF ? (WHAT is the Drain to Source voltage ?)(0V, or 24V ?)
It is always ON, for whichever PWM I apply the voltage between V+ and V- is always 24V. The Drain to Source voltage is 24V.
raschemmel:
Have tried testing the mosfet with a meter on diode scale (with power off of course) ?
(can you confirm it is not shorted ?)
I will confirm tomorrow because now i don't have access to the prototype. But i tried the same setup in two brand-new modules (I got them out of the box) and it doesn't work in none of them.
raschemmel:
I don't see a schematic for your setup.
The link for the mosfet doesn't tell us enough about what you are doing .
I posted one just above.
raschemmel:
According to this thread , that
breakout board seems to work , even if it is not a logic level mosfet.
Yes, I've read about people who uses this mosfet without problems and others don't. Maybe in my case i don't have the conditions for the mosfet to work.
Yes, I've read about people who uses this mosfet without problems and others don't. Maybe in my case i don't have the conditions for the mosfet to work.
Yes, I've read about people who uses this mosfet without problems and others don't. Maybe in my case i don't have the conditions for the mosfet to work.
Seeing as the only thing you have told us is your mosfet V+ voltage (24V), there not much I can say
about conditions. It might help if you told us your load current .
raschemmel:
Seeing as the only thing you have told us is your mosfet V+ voltage (24V), there not much I can say
about conditions. It might help if you told us your load current .
That being the case, my initial response is to ask you what possessed you to order a mosfet module
rated for 5A to handle a 100mA load ? Does that not seem like overkill to you ?
It is not good practice to use a switching device that is rated for 50x your load current. (for a number of
reasons, starting with "it makes no sense".
I would recommend you "rethink" your design and find something rated for 500mA to 1A maximum.
I will leave it to others to explain why using a device rated for 50 times your load current is not way to
go.
As far as why your mosfet doesn't seem to be working , your comment:
I am measuring effective voltages with a tester because I don't have access to an oscilloscope.
raschemmel:
That being the case, my initial response is to ask you what possessed you to order a mosfet module
rated for 5A to handle a 100mA load ? Does that not seem like overkill to you ?
It is not good practice to use a switching device that is rated for 50x your load current. (for a number of
reasons, starting with "it makes no sense".
I would recommend you "rethink" your design and find something rated for 500mA to 1A maximum.
I will leave it to others to explain why using a device rated for 50 times your load current is not way to
go.
I know, but these are the only mosfets I have as spare parts and if I can't avoid it I won't purchase more. Which MOSFET would you recommend driving that load?
raschemmel:
That being the case, my initial response is to ask you what possessed you to order a mosfet module
rated for 5A to handle a 100mA load ? Does that not seem like overkill to you ?
Not in the slightest, you never choose a MOSFET by current rating, always by on-resistance. Running anywhere
near the current max requires huge heatsinks, never contemplate it.
I submit that if you actally looked at the datasheet and actually know the pinout of the device and measured 24V from Drain to Source with a meter then you must conclude the mosfet is always OFF , not always ON because if it was on the voltage would be close to zero and there would be current flowing . You have not reported Drain Source current and I don't see your load nor have you stated what your load is or where it is (it's not in the schematic.
