Beginner needing advice.

Hello,

I have taken up the Arduino Uno R3 to design a setup where I can connect 4 space heaters to an Arduino-controlled relay board, and have the Uno alternatively turn on 2 space heaters at a time for 300 seconds, after which they would turn off and the other two would turn on, and endlessly loop in that manner.

This is my first ever experience with electronics and programming, and I am learning on my own as I go. I have been following Jeremy Blum's YouTube tutorials creating simple projects with the Uno, and learning how the programming language works. I want to get as extensive of a knowledge as I need to create this project prior to starting, because I understand the risk with working with high voltage appliances.

Can anyone recommend some smaller projects/educational materials that will help me in achieving this goal? Any help would be greatly appreciated !

I offer a relay card that can switch up to 5A on & off.
http://www.crossroadsfencing.com/BobuinoRev17/


Simple to use, just shift in some data.

In your case:

// setting up variables & setup() left as an exercise to the reader ...

void loop(){
digitalWrite (ssPin, LOW);
SPI.transfer(0b00000011);
digitalWrite (ssPin, HIGH); // data turns on 2 relays
delay (300000); // dumb 300 second delay as a starting point
digitalWrite (ssPin, LOW);
SPI.transfer(0b00001100);
digitalWrite (ssPin, HIGH); // data turns on 2 other relays
delay (300000); // dumb 300 second delay as a starting point
}

With some devices such as heaters and fans it is often better to let them "tickover".

That often has a few benefits in the there is often no surge load for a re-start much the same as many modern appliances also work.

Even if you don't fire the burner keeping the fan at a low speed will keep air movement going

And with heaters you could always incorporate temperature monitoring to keep a much more even environment allowing you to use less fuel or overall electricity.

Thanks for the advice CrossRoads! However the heaters that I will be using are 1500W 120V, so about 12.5A. I would need a relay that is rated for a much higher current. Is that code example you provided specific to the relay board that you mentioned?

And ballscrewbob what exactly is "tick-over"?

Thanks again!

The same code will work for shift registers controlling larger relays.
Sounds like you need something like one of these

and a TPIC6C595 or TPIC6B595 shift register to sink the coil current and energize the relay.

"Tickover" is the ability to run something at minimal power in a ready state until it need to perform its function fully. Also known as IDLE state.

Think of a car engine that has started but not yet revved up or gear engaged but in a state of readiness.

Its something I also do in some of my projects where I may keep a fan rotating at minimal speed until a higher duty cycle is called for.

Many home water heaters will keep a pilot burner running and a fan on minimal revs until a hot water cycle is needed at which point more gas may be called and ignited and the for additional fans may be called to expel the Carbon monoxide gas.

In your case if they are electric heaters then keeping the fans on tickover would keep an airflow moving and with a low value set for temperature you would keep a minimal value of heat in the area unless a higher value was called for.
Then your system would run just long enough to make up the heat difference plus a margin of extra to allow for heat dissipation over an amount of time.

I took a very similar approach but used a gas sensor instead of a thermostat in this project.

The code is here and you can see the tickover used here in lines 49,50, 113,114, 123 and 144

I used MOSFETS for my project but there would be no reason not to modify the code to account for relays and two stages of fan speed with a similar approach using the NC/NO side of a relay to switch to a lower power or state when not in full cycle.

Something like Crossroads board would be great for that approach.

Thank you both very much for the detailed and thorough explanations! I'll look into that relay Crossroads, and see how I can incorporate a tickover as ballscrewbob suggested. Thanks again!