Arduino Indoor Garden

Hello all!

Skip this part if you don't want the long version

I'm excited to be part of this community, I purchased my first Arduino a few weeks ago. I built some blinking light circuits, clicked some buttons, and then put it all down for a bit while I decided on a winter project I could integrate my Arduino into. I stumbled upon hydroponics as a result of our basil consumption. We cook a lot of Italian food, and basil is one of our favorite flavors. We have been trying to tend (keep alive) the live basil plants from Fred Meyer, but they are hydroponic (and thus nearly to transplant to soil) and already pretty shocked when you get them. They also cost about $4 a plant, and if you are making a meal that requires 1 cup of chopped basil (not uncommon for us) you have used most of the plant. We could probably chew our way (haha) through a plant and a half a week, no problem.

My girlfriend and I live a pretty busy lifestyle. We both are full-time students, and we both have nearly full-time jobs. We try to eat as healthily as possible, buying less processed, more natural foods when possible. Regular maintenance of plants isn't something we have perfected. So an automated hydroponic garden seemed the natural choice for cost, and ease of maintenance.


I know many have gone before me, and some of them even have passable (if only partial) documentation of how they accomplished different parts of the project.

Right now I am looking for a recommendation of a solid state relay to switch my lights (2 compact fluorescents, 27 watts @ 110v apiece) and pump (I do not know how much the pump draws, but it is tiny. Less than the light, I'm sure).

I wanted get the puck-type (with screw-down terminals on all four corners) because I feel like they will be easiest to integrate. I'm using an Arduino Uno, and would like to be able to switch the relays directly from a +5 VDC digital pin on the Arduino.

This stage of the project will be complete when I can switch my lights on and off automatically on a schedule.

Eventually, I would like to be able to monitor pH, water temp, electrical conductivity of the nutrient solution, etc. Beyond that, I want to be able to add more nutrients and cycle fresh water into the reservoir.

I have to start small as this is my first project with my Arduino and writing my own software (I know, it barely counts).

So, with all that out of the way, can someone recommend a reliable (and reasonably priced) SSR? If I left out any details, let me know.


My only experience with SSRs has been traffic light systems systems where the zero-crossing switching capability was important. They can get quite expensive though. I haven't used low current ones myself, but a helpful suggestion here sent me to JeeLabs for something else, and while I was there I noticed that they do have a 'relay plug' which gives you two relays capable of switching a couple of amps at mains voltages.

For what it's worth, I'd consider combining mains voltage with electronic controllers and water to be extremely dangerous. If I were you I'd be very cautious about touching anything connected directly or indirectly to mains voltages, and make sure you use an RCD.

Just some inspiration i came across...

Thanks guys!

I'm not too concerned about using mains voltage with dc control electronics and water. All you need to prevent a dangerous situation is a little common sense. The reason I am planning to use SSRs is their opto-isolation.

Everything will have a drip loop, and all the mains circuits will be GFI circuits.

You might want to check out 80% red/20% blue LED mix as grow lights. Plants only need those colors, you waste less electric on eye-friendly lumens and heat with R&B LEDs.

Allelectronics sells 5mm LEDs with built-in resistor for 12V operation, around 50 cents each though. Still they can be run off common 12V and ground with no worry that a few quit and the rest overload. Needless to say, you'd need MANY of them. LED pins do fit rather well in cheap chip sockets. :)

Thanks for the tip, GoForSmoke!

LED grow lights are definitely on the project list, albiet a ways out.

My current lighting is just Daylight ecosmart (brand) CFL bulbs in a work light. I will be working to maximize light containment shortly, as I am currently losing a lot of the light I'm producing (1750 lumens, according to the package).

I'm open to any sort of tips any has got!

And of course, I'm still looking for SSR brand/model recommendations.

Flat white is 51% reflective but does spread the light. Silver mylar OTOH....

Just remember to deal with the extra heat you trap.

Looking to future, check out aquaponics. But that's not something you'd want to try in an apartment. they might have what you are looking for

Zack: That is exactly the type of relay I'm looking at. Do you have any experience with Opto-22 relays? They seem to be on the more expensive range, but typically you get what you pay for.

No sorry I'm just starting my first Arduino Project and I don't have any experience with relays

SSR not opto-isolated for $11

SSR-25DA 25Amp 380V Solid State Relay

Easily driven from Arduino digital output pin.

As for opto-isolation, that's simple and cheap chips with typically 5000+V isolation:[m]=pattern&id[q]=Optoisolator&x=17&y=7

All Electronics is a clearance-type house. You can't get everything but they have lots of parts for low prices.

It's much cheaper to use switch relays, 120V x 10A = 1200W... how much you need?:

Dual opto-isolated relays on a little Arduino-ready board with other parts for $6.50:

Opto-Isolated 2 Channel Relay Board for Arduino

See more details, applications on our WIKI here:

With high-current relays, AC250V 10A ; DC30V 10A Size: 12.3cm X5.3cm X1.8cm high

Quad opto-isolated relays on a little Arduino-ready board with other parts for $12.00:

Opto-Isolated 4 Channel Relay Board for Arduino

See more details, applications on our WIKI here:

With high-current relays, AC250V 10A ; DC30V 10A Size: 12.3cm X5.3cm X1.8cm high

A single relay on a little Arduino-ready board with other parts for $2.90 and Seeed Studios has good shipping rates:

The Relay Twig is a digital normally open switch that controls a relay capable of switching much higher voltages and currents than your normal Arduino boards. When set to HIGH, the LED will light up and the relay will close allowing current to flow. The peak voltage capability is 250V at 10 amps.

Just for fun:

DHT11 Humidity and Temperature Sensor SKU: EC-010401 Our Price: $2.50

[quote author=Ezra Moore link=topic=77291.msg584539#msg584539 date=1320082269]Do you have any experience with Opto-22 relays?[/quote]

I do. In my experience, Opto-22 makes very high quality hardware. I have seen it endure through horrible conditions.