controlling flourescent light fixtures

I'm currently building a uv lightbox consisting of three fixtures connected in parallel.

Now, I've decided i want to have a countdown timer to automatically turn the lights off.

I'm going out to purchase the arduino tomorrow and plan on doing all of the beginner blinking led tutorials. But since im going to the store what would I need to connect the lights to the arduino then to a wall plug? Do I need relays?


Relay would be the most straightforward. Look for one primarily that has contacts rated for the voltage/current required by your fluorescents, then ideally one that has a 5V, <20mA coil. If you can find one with those coil requirements, you can wire it directly to an Arduino pin. If the coil voltage/current is higher than those values you’ll need to use a transistor to switch the relay coil.

thanks. I went to a store where the guy told me what to, but i forgot the schematic he drew. Let me post the parts later so you guys could help me figure out what he was saying.

Need to sort through all the goodies!

btw I bought some arduinos that had different coloured pcbs. I didnt know that it came in different colours!

i got this lcd 16x2. Very basic. I'm following this guide

They have 14 eeerrrr inputs but mine has 16. So what goes where now?

As for the lighting fixture, you may want to look into a transistor type of device called a "Silicon Controlled Rectifier" or SCR, these are the devices that take a small signal and switch on 115VAC or more with a much smaller voltage. and It's solid state, so you have no standby current or relay contacts.

as for the LCD, you need to look online for a pinout and locate the pins u need to make it work.

If you use the LCD4Bit Library courtesy of the geniouses on this site (i use it all the time) you can drive the LCD with only 4 bits, a Register Select (RS) and Enable (E).

so the pins U need are

D4, D5, D6, D7. Enable (E) Register Select (RS) Read/Write (RW)

***Just ty the RW pin to GND, or a Digital Low signal from anywhere else.

Oh yeah, and download the library for it too, it's not hard to find,

Problem with an SCR is that you only get half the wave so what ever you power with it will only get half the power. I would go for a Triac, that is like two SCRs back to back.

As you are dealing with mains voltages I would also precede it with an opto isolator.

If you are not experienced with construction I would very very strongly recommend you got it all in one package as a solid state relay.

While I think SSRs are a brilliant encapsulated and isolated solution for switching mains from an Arduino, could I ask a question or two, specifically about fluorescent lighting?

SSR's are said to be a bit vulnerable to current surges. Does switching a fluorescent tube produce any troublesome transients on the mains supply? If so, would specifically choosing a zero-crossing-switching SSR be helpful?

Does switching a fluorescent tube produce any troublesome transients on the mains supply?

Not so much transients but they can look like an inductive load, this puts the current and voltage out of phase and makes it difficult to do phase control. But lucky you don't want to do this.

A zero crossing switch cuts down on the amount of radiated interference FROM the solid state relay, which is always a good idea but not essential. I have switched florescent lights from ordinary solid state relays without issue.

Thanks for that! :)

I think this is what i want done.

I also went to a store where the owner told me to purchase these to do what i wanted: Relay, 1k resistor, 1N4001diode, and a PN2222… have any ideas what to do with these?

any ideas what to do with these?

Is there not a full explanation of what to do with these on the page you posted?

yes. Maybe I should rephrase the question. The diode and the PN2222 I have are different from the tutorial. Can they be substituted with what I have?

Yes they can.

ok thanks

If you are in the US, these cases are handy for keeping you safer from all the “hot” parts.

I use the version that has provisions for a snap-in outlet.

i planned on having all the electrical parts and arduino inside the project im making, which is a uv exposure box. Then have the plug and cable to the wall outlet.

Much tidier.


I have my lcd attached to my arduino using the ground inputs. The wiring for the lights require me to ground as well. Can i place multiple wires in the same ground input?

The wiring for the lights require me to ground as well.

No they don't, that's a safety earth (or ground).

That is not the same thing as a ground or common signal on the Arduino. Don't connect the Arduino's ground to the mains ground.

yea sorry. I think it is the grounding for the relay?

Something is being grounded in the picture.