I need help to draw a diagram of this picture the project include an Arduino nano, dht11 sensor, power module IRF520, 12V power supply and a fan
See Rules and guidelines for drawing good schematics on electronics.stackexchange.com.
I'm no expert but perhaps some of what I have found will be of help.
To produce a clear easy-to-read useful schematic it doesn't really matter what tools you use. This website has a reasonable schematic editor so I suggest you could try that to start with.
Other tools I have tried include KiCAD, EasyEDA and Fritzing. KiCAD is maybe a bit hard to start with and Fritzing I find is very troublesome - It's good for the kind of breadboard layout diagram it was originally designed for. I have really enjoyed using EasyEDA. Other notable tools include Eagle. All these are free or have free versions for hobbyists. Beyond that are more capable and sophisticated professional tools.
Drawing a good schematic is an art and taking care of small details makes a big difference to how useful the diagram is.
The main features that I find make schematics for me to read are
- Ground connections at bottom edge of diagram.
- Positive voltage connections at top edge of diagram.
- Left to right flow for signals and power (e.g. battery at left, microprocessor in middle, LEDs, motors etc at right)
- Avoid having wires cross. Adjust the pin positions on an IC symbol to make this possible.
- Label everything clearly but don't let text overlap with anything else.
The way you appear to be powering these modules seems a bit eccentric but this would be how I might draw that as a block-level schematic.