Noise on the voltage rail?

Forum 2005-2010 (read only) Hardware Troubleshooting
1

I have a basic setup, arduino LCD, i2c rtc, lm35 temp sensor, i2c keypad using an mcp23008, i2c dosing pump using mcp23008 / transistor setup.

there are two problems. the arduino locks up and has to be reset, or the rtc spits out bad data and diplays an alert on the lcd.
it is still built on protoyping breadboard, and not in a case so may be part of the issue.

the effects happen usually when something is switched on florescent lights or small aquarium heater, it used to e triggered by the pump activating but i changed to an old wire wound psu and that removed that problem.
the arduino is powered by a 9v regulated switch mode psu.
im guessing its a power issue but not sure wheres its being introduced.

  1. through the psu.
  2. through the proto board and it mass of wiring
  3. through the short but unshielded i2c wire going to the dosing pump unit.

any ideas? or do you require a bit more info

2

You need proper decoupling and power distribution:-
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

3

il have a good read throught the decoupling.

on another note the florescent lights or heater are not controlled via the arduino. the arduino used to be next to my fish tank as eventually it will control it. the heater and tank lights were on standard timers and caused the issue. so i move the arduino into the kitchen and now the kitchen lights cause the same effect.

4

Yes it's all part of the same effect. Your system is susceptible to interference because of lack of decoupling.