newbie question

Hello folks, this is my first time posting on this forum.

I'm currently taking a embedded system class and my project invokes making a automated garden bot.
I'm still in the prototype phase and have a couple of questions.

If I buy a fish tank heater (use to heat the tank when it gets too cold), how do I power it? I assume that the 5 volts from the arduino wont be enough.
Can an external battery be use to power the heater?
and if so how do i set it up? (Do I strip the wire, hook it up to the power supply and arduino?)

If this is a heater you plug into an AC outlet use this:

No. The Arduino operates at 5 volts DC. It is capable of providing about 0.3 watts of power at 5v.

An aquarium heater of moderate size operates at 110 volts AC. It requires about 100 or 200 watts of power.

To control the heater you will need a 5V 2-Channel Relay Module for Arduino. Actually, it works for all 5v DC computers.

This will allow you to control 2 devices. 2 heaters or heater and light, etc.

The computer, through programming, provides 5v to one of it's output pins and a ground pin. This voltage causes the relay to connect two wires. This operates in the same way that a wall switch operates. It connects and disconnects to interrupt the flow of electricity.

110v flows out one of the wall plug wires, through the aquarium heater, and back into the other wall plug wire. You cut one of the wires in two, and connect one of them to the common connector of the output side of the relay and the other to the NO (Normally Open) side of the relay, you can then use the Arduino to turn on and off the heater.

It's relatively simple, but I can tell from your question that you will need help or you will make lots of blue flash sparks, destroying equipment or yourself.

Arduinos and other computers work in the realm of low voltages and low current (amps).

There are some excellent youtube videos that explain volts, amps, and resistance. Look through a few.
DO NOT do any wiring without live supervision. You could end up with curley hair.

Or use what LarryD suggested.

A battery won't work. It would have to be HUGE and you would have to run it through an AC/DC power inverter.


No. The Arduino operates at 5 volts DC. It is capable of providing about 0.3 watts of power at 5v.

You've never think of it like this - the absolute limit is 40mA, and in practice 25mA is a
more sensible upper value, enough to power an opto coupler which is what is needed here.

Remember simple questions like this are covered in the "Learning" section of the Arduino
website - OP: you have read this? Arduino Playground - InterfacingWithHardware