Advice needed on fully automatic greenhouse schematic

Projects General Guidance
1

Hello All,

This is my first post on this forum, thank you for reading this far.

In all seriousness, I am new to electronics and have done a lot of reading, learning, googling up to this point in designing my 3rd project: A fully automatic greenhouse to produce some radishes.

My end goad in learning Arduino, and general electronics is to make my paludarium (aquarium with land inside) fully automatic.

For this I have to learn a lot, thus the greenhouse project, to learn as I go.

My final problem with the greenhouse now is that I doubt my idea/ schematic is correct.

I would like someone to have a look at it who has more experience.

My biggest doubt is: Is it possible to drive my pump,DC Fan and 20W LED module from 1 power supply, without any special components etc. to protect it, so as it is shown in my schematic (att).
The PSU will be able to handle the load (it is 6A 12V). My doubt is from how I am going to connect everything.

I cannot find the answer after 1 hour of googling.
My assumption is that it is okay because I wired them parallel from eachother.

Please see the attachment for my schematic.

Good, now some notes on the schematic and components I am using:

my Arduino board is of the Uno R3 taste.

Relay Module Link

The relay module used is the single module from the link.
on this board there is a transistor, which is why I included it on the schematic.

For the 12v DC fan I am using a generic 3 pins type from an old PC, and I do not want to control the speed. I am controlling when it turns on via a transistor (on the low side). Is this okay?

For air hum and temp I am using a DHT22 sensor.

AlsoI use 2 generic waterproof resistor type temp sensors: 1 temp sensor for the lamp temperature and one for the soil temperature.

The 20W LED module is and old SMD LED Aquarium light I have re-purposed for this project.

The Pump is an high pressure irrigation pump, which will be used to control the soil humidity.
Soil humidity wil be checked via a seperate sensor, that I have not included in the schematic.

Finally I would like to thank you in advance for any replies and looking at my schematic.

Alex

Radish Paradise_schema.jpg
Radish Paradise_schema.jpg2445×1683 201 KB

2

No problem at your schematic, if your led is working with 12V.
12V × 6A = 72 Watt
Your led is 20W, your pump is 12W and your fan is less than 2W.

3

First thing i notice...
Move Q2 and Q3 to the low side of the driven device(like Q1), and add a current limiting resistor in the base from the Arduino... 1K should be a reasonable value. (you used 220R on Q1... may be a little bit low to protect the output pin)
Edit: IMPORTANT- look into flyback diodes across the relay coils.

Good work on tying all the 0V together.
Also good work pulling the loads from a separate supply point than the cpu.

If you redraft, read up how to put the JPG inline with your post.
Some will appreciate being able to see it without opening separately.

4

Inductive loads(fan,pump,relays) need "flyback" diodes across them so they don't backfeed power when turning them off. The relay modules probably already have them but you'll need them for the pump and fans.

5

Hi guys,

Thanks a lot for reading about my project and giving your advice.

Based on your feedback I have just produced the 2nd draft of my schematic (inline this time :slight_smile: )

EDIT:
Something went wrong with adding the image, this is the link to it:
Imgur

I have checked the relays: they all have a diode on them: I assume these are flyback diodes.

I am happy to hear that you guys are positive about the first draft.
in the 2nd draft I have replaced the one resistor with 3 1kohm resistors.
Also the transistors have been moved to the back ends of the relay module. I must say that the transistors are a part of this module, so I assume this is true.

i look forward to your messages.

6

Those relay modules have the driver circuit on board. Connect to 5V power (derived from a 5V power supply, not the Arduino). You can drop the transistors to switch the relays.

In fact you can also drop the relays, and have the transistors switch the various devices directly. Just make sure that the transistors you selected (a MOSFET type is best, the symbol you used implies BJT type) can handle the current of the things they switch.

7

Since you already have a 12V supply, I would use relays with 12V coils, no need for a separate 5V relay supply.

Also, the output from the LM35 must go to analog input pins (A0 ~ A5), not digital.