Inconsistent temperature and light readings.

Hello guys.

I have a project with 4 7 segment displays, 1 pc fan and 4x LEDs. Depending on whether fan/led/display is on, reading from temperature and ambient light sensors are different. For example I turn the leds on temperature reading reduces by 15%. What ways are there to stabilize the voltage? I have a 5V 300mA adapter that I connected to the breadboard instead of arduino’s 5V pin. And when it is connected everything goes wild (displays segments are randomised when I press a button). Anybody have an Idea why?

Show us a schematic please. Hand-drawn is OK.

A photo of the setup might be useful too. Try to show all of the wires where they connect to the breadboard and the other devices.

I think I've captured everything. I home You can distinguish everything.
Sheme

Picture. Thick red wires lead to two sensors and 4 LEDs.
Picture

You appearing to be powering the motor from the same supply as everything else. Don't, it always causes problems.

I've connected the motor's +/- leads to the power adapter and it don't seem to work. What am i missing? What is the difference between arduino's and power adapter's 5V/GND?