I am using a irlz44n mosfet to control a small heating element (load) using direct current. I have included a simple circuit as a picture to show how I am connecting the mosfet, arduino, and load.
When I measure voltage through the load when connecting directly to power supply, I read roughly 6 V. When I measure voltage through the load when using mosfet, I read about 4.3 V.
I believe this is too high of a voltage drop and I don't know why? Please help
Also, Arduino ground is connected to ground of power supply.
If looking at the mosfet where the specs are written, I have the right most leg connected to the negative terminal of the load, and the center leg of the mosfet connected to power supply ground.
If I swap the connections between the right most leg and center leg, I get no voltage through the load.
cmore082:
If looking at the mosfet where the specs are written, I have the right most leg connected to the negative terminal of the load, and the center leg of the mosfet connected to power supply ground.
Definitely backwards. You were conducting via the body-diode of the MOSFET, hence a diode-drop
was seen.
Drain is the centre terminal for MOSFETs in TO220 package - this is always the case since the drain
is the substrate in a power MOSFET and the substrate goes to the tab (which is also the middle leg).
MarkT:
Definitely backwards. You were conducting via the body-diode of the MOSFET, hence a diode-drop
was seen.
Drain is the centre terminal for MOSFETs in TO220 package - this is always the case since the drain
is the substrate in a power MOSFET and the substrate goes to the tab (which is also the middle leg).
You are right, I fixed the connections. Therefore having the negative terminal of the load to the middle leg, and ground to the right leg. However, I am getting a drop voltage of 1 V.
MarkT:
Unless your load is 45A(!), something is very wrong with a 1V drop.
The MOSFET should be 0.022 ohms when switched on. You haven't said how much current
the load is supposed to take.
I have two loads connected in series, and each load takes about 3 V and 1.5 A. So total load is roughly 6 V and 1.5 A. I am using a power supply of 7.4 V and 5 A.
I think I found the problem. When connecting the wires to the breadboard, connections seem to be not that strong. I found this when I would press down hard on the connections voltage would increase.
You're using solderless breadboard? No wonder! Solderless breadboard is only suitable for low current applications - the connections have non-negligible contact resistance, and the internal conductors aren't meant to take high current either (I've seen breadboards where the plastic melted from the heat when an excessive amount of current was run through part of it)
DrAzzy:
You're using solderless breadboard? No wonder! Solderless breadboard is only suitable for low current applications - the connections have non-negligible contact resistance, and the internal conductors aren't meant to take high current either (I've seen breadboards where the plastic melted from the heat when an excessive amount of current was run through part of it)
