Mosfet suppression diode
- Thread starter ac21
- Start date
Hi,
Certainly the diode (cathode) should NOT go to any PICaxe pin (which would be pulled to +12 volts and very probably "release the magic smoke").
As bill says, the diode is not strictly necessary for a purely resistive load such as an incandescent (filiament) lamp. But bear in mind that even the connecting wires have some inductance, so if they are "long" then the diode might still be beneficial (connected on the FET/circuit board, not near the lamp).
What is the purpose of the 100k ohm resistor? It only appears to be "leaking" about 120 uA out of the battery. Shouild it actually be on the gate to prevent the FET conducting if the PICaxe output is "off" (no power applied and/or output pin not switched as an output)?
Cheers, Alan.
Certainly the diode (cathode) should NOT go to any PICaxe pin (which would be pulled to +12 volts and very probably "release the magic smoke").
As bill says, the diode is not strictly necessary for a purely resistive load such as an incandescent (filiament) lamp. But bear in mind that even the connecting wires have some inductance, so if they are "long" then the diode might still be beneficial (connected on the FET/circuit board, not near the lamp).
What is the purpose of the 100k ohm resistor? It only appears to be "leaking" about 120 uA out of the battery. Shouild it actually be on the gate to prevent the FET conducting if the PICaxe output is "off" (no power applied and/or output pin not switched as an output)?
Cheers, Alan.
Not too sure about the source of your research , but the 100K resistor should go from the gate of the FET to ground to prevent the FET from turning on while the Picaxe is powering up and the output Pin is floating. This prevents the lamp from blinking on power up. I see no reason at all to have a 100K resistor across the load.
Below is an example of a more acceptable and less confusing schematic layout. Red is hard on the eyes and is almost never used for schematic traces unless the schematic is primarily a wiring diagram showing the actual colors of the wires.
Below is an example of a more acceptable and less confusing schematic layout. Red is hard on the eyes and is almost never used for schematic traces unless the schematic is primarily a wiring diagram showing the actual colors of the wires.
Attachments
Example.........Read from left to right...input to output
