Hello,
I am working on a project which involves using an Arduino Mega, and I am trying to use an NMOSFET (BUZ101S) and an NPN BJT(2N3904) to drive the 5V output from the MCU back and forth between 0V and 12V across "SOL".
At the moment, the problem I have is that Vgs always stays high, thus driving SOL on all the time, and I cant figure out why this occurs.
Here is my circuit diagram:
Firstly images can be included inline using the Insert Image button....
You have the load on the source side of the MOSFET - no good, it must be on the drain side.
However that doesnt account for Vgs never reaching 0V, and I can't figure out what the second
connection to the base is - a 1k to ground would be sensible if using PWM to speed up switching,
otherwise nothing is needed there.
Check you've got the NPN pinout correct?
Everything MarkT said .... plus: That's not a logic level MOSFET, you can't turn it on with 5V.
(The datasheet gives Rds value with gate at 10V...)
Thanks for the replies, I will try switching SOL to the other side and see how that goes. I believe my NPN pinout is fine, as well as the NMOSFET.
I am using the NMOSFET due to the supplies I have available, and I was hoping that I could make it work with these parts
focspike:
Thanks for the replies, I will try switching SOL to the other side and see how that goes. I believe my NPN pinout is fine, as well as the NMOSFET.I am using the NMOSFET due to the supplies I have available, and I was hoping that I could make it work with these parts
Ignore that. It might work with the pullup to 12V....get rid of the 100k/50k resistor.
fungus:
focspike:
Thanks for the replies, I will try switching SOL to the other side and see how that goes. I believe my NPN pinout is fine, as well as the NMOSFET.I am using the NMOSFET due to the supplies I have available, and I was hoping that I could make it work with these parts
Ignore that. It might work with the pullup to 12V....get rid of the 100k/50k resistor.
I was unable to make it work by removing the resistor, and also removing the resistor+moving SOL to connect with the drain.
So....get your multimeter out and start measuring voltages. See if they're what you expect.
I wasn't really sure what to look for in the DMM, but here are some measurements.
Vgd .7v-0v
Vgs .6v-0v
Vds .7-0v
Vec.7-0v
Vbc .6-.8
Veb .7-0v
I am currently running a configuration of moving SOL attached to drain and +12V
Edit: I want to also note that from the advice from some others I am using a diagram almost identical to this, with the exception of removing the 4N35 in place of my NPN BJT
http://forum.allaboutcircuits.com/attachment.php?attachmentid=68823&d=1400757981
Edit 2:
Sorry, I realized I didnt have the image displaying properly
