Powering components using various sources

Projects General Guidance
1

Hi, I'm relatively new to this and trying to figure out what exactly is going on when we power components using the arduino board, or introduce other sources of power as well.

I was playing around with a 9in1 sensor shield (with the DHT11, LM35, buzer etc), seeing if I could still run a previous project with this shield attached. [the original project: 0.96inch adafruit oled (3.3v) that report distance from HC-Sr04 range finder (5v)]

I discovered that this didn't work using power from shield pins, as this shield board operates at 5V and the oled requires 3.3v. I then tried using a buck that could provide 3.3v from a 9v battery, by attaching vcc & gnd from the oled to the buck. This also didn't work.

However, when I attach the power ports from both the sensor and the oled (to 5v and 3.3v respectively) to the buck, then the system works again and the range is displayed on the oled (after a reset). Why is this?

2

Impossible to say without seeing clear, hand drawn (pencil and paper) wiring diagrams for each case, with pins and parts labeled. Post links to the modules.

3

Welcome to the forum

This topic raises a number of questions both explicit and implicit so here are some facts

  • when components of an Arduino project are powered by different power sources all devices and power sources must have a common GND connection
  • the 3.3V and 5V requirements of components must be observed and respected to avoid damage to components due to overvoltage
  • whilst it is acceptable to use a 3.3V signal connection to control a device that uses 5V the results may be unpredictable, but not damaging
  • it is never acceptable to use a 5V signal to control a 3.3V device
  • the common 9V batteries (I know them as type PP3) are generally useless as power supplies as they cannot supply enough current for a sufficient period
4

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.