This code shows how to control an "Ebb and Flow" (Also called "Flood and Drain") hydroponic installation using an Arduino Mega controller.
Ebb and Flow is a very simple process where nutrient is sprayed into the growth medium and allowed to drain back to the main reservoir. A typical duty cycle is 2 hours flood, followed by 15 minutes drain.
Timing does not require anything in the way of precision (within a minute is fine), so we simple accumulate time with delay() calls. If this is a problem, and perhaps it will be for future functions, we could add some real-time device to get us better control, but for now it just is not justified.
- Arduino Mega 2560 (if debug information is removed, it is possible to fit into a Uno, but it's very tight for memory)
- WiFi or Ethernet Shield (or equivalent built-in functionality)
- DHT11 or DHT22 sensor
- Dallas 18B20 sensor in waterproof housing (also a 4K7 resistor)
- Homebrew Ec probe (See References)
- Relay Module(s)
- SSD1306-based display
First, decide which features you wish to use, because there are dependencies. For example, you can't use ThingSpeak without a network connection, and you can't measure Ec without the 18B20 sensor. Enabling and disabling a feature is a matter of updating sysconfig.h
DO NOT enable multiple network interfaces, as it won't compile (for now). GSM is a stub only for now, and when I get my hands on some proper hardware I will give it the attention it deserves.
There are some assumptions around ThingSpeak. The channel should be set up as follows
| Channel | Name | Variable |
|---|---|---|
| 1 | External Temperature | airTemp |
| 2 | External Humidity | airHumidity |
| 3 | Fluid Temperature | fluidTemp |
| 4 | Fluid pH | pH |
| 5 | Fluid Ec | eC |
| 6 | Not Used | None |
| 7 | Not Used | None |
| 8 | Battery Voltage | vBatt |
- You can only have a single network technology enabled. Later I will get smart and figure out how to deal with better. But for now, just don't do it.
- GSM support is non-existent at the moment.
- All temperatures are given in Centigrade. It would be easy enough to change this.
- Only a single DS18B20 device is supported. If you have more than one installed, only the lowest ID device will be used, and this might not be the device you were expecting.
If you'd like to help out, drop me a line via GitHub. Or just fork the repo