I’m building a solar powered arduino Mega-based system and using ArduinoConnect ipad App for remote control.
One of the things I do is turn on and off a fan from my iPad (with the app above) in addition to graphs and meters (pic below).
Since it is a solar powered system, I’m very concerned about current draw and have put INA219s through out the system so I know just where the power is going.
Here’s some information:
Arduino Mega 2560 - 100ma typical.
5V computer fan - takes about 80ma when it is on.
I was very concerned about current draw from the relays so I bought a selection and measured the currents. Here are the results:
Name / Measured Current Draw with Relay On / Specification
SainSmart 2 Signal Relay / 30ma / 8.7ma
SainSmart 2 Relay / 70ma / 20ma
Evil Mad Scientist Relay Shield / 70ma / 72ma
I’m using the SainSmart 2 Signal Relay as it saves me 40ma. Note the huge difference in spec to measured on the SainSmart 2 Relay and the big difference between the spec and measured for the SainSmart 2 Signal Relay. 30ma is better than 70ma however.
A picture of the control panel is attached.
Note that while I am reading the currents from INA219s connected to the Arduino I2C bus, I put the data in a MySQL database on a Raspberry Pi to crunch the data and build the graph using matplotlib in python. So in the picture below from my iPad, the graph is connected up to a Raspberry Pi and the meters and buttons are connected to the Arduino directly (across the internet of course). ArduinoConnect allows me to mix end computer devices on the same page.