I am trying to convert a 3.3V logic signal to 5V logic signal. I am using a p-channel MOSFET and I can not get it to send the full 5V signal through. Below is the circuit I am using.
Electrical – 3.3V to 5V logic converter using p-channel mosfet
3.3v5vconvertersignal
Related Solutions
The Sparkfun logic level converter outputs voltage, not current. It can output a maximum of 220 mA to an output that is drawing that current, but will not "push" a current anywhere. It should probably be safe to use for this task.
That being said, a more appropriate part for this task would be a buffer IC, like the 74HC244 (octal tristate buffer, 3.3V CMOS compatible inputs when running at 5V). There's nothing wrong with the Sparkfun level shifter, but this part should be easier to source and use in a professional design.
You have 2 options:
1) Use a 3.3V logic level MOSFET designed to be interfaced with 3v3 systems.
2) Tie the MOSFETs gate to +5V using a 10k pull up resistor, and use a NPN transistor to ground the MOSFET via the NodeMCU when required. This is not going to give you spectacular switching characteristics but will work in low speed switching.
It should be easy enough to understand how this works: The 10K resistor is used to turn the MOSFET on when the transistor Q2 is off. To turn the MOSFET off you turn the transistor on, which shorts the MOSFET gate to ground.
See image below (Image not mine, rather googled "NPN MOSFET driver"), replace +12V with +5V
Best Answer
Use an N-channel MOSFET, or swap the 100k resistor and the P-channel MOSFET.
Also, it'll work a bit better with a lower value resistor. Say, 10k. And both circuits will invert your logic. If you cannot deal with that, then you need a few more components (another MOSFET, for instance).
See the below diagram for two ways that work.
simulate this circuit – Schematic created using CircuitLab
The MOSFETs in the schematic are merely symbolic, the part numbers may or may not be appropriate.
Because of your 3.3V input, you must choose a MOSFET with an appropriate low turn on voltage. That is, \$V_{gs(th)}\$ must be sufficiently below 3.3V, otherwise your MOSFET will not turn on or be barely on.