Urban Survivalists

Sorry for the long delay in posts! Life intervened and we had to take care of issues, clean stuff up, and get ourselves back in order to do this blog. We may be undergoing some drastic changes here in the near future so we will keep you posted as to future post schedules. Again, sorry for the delay and here we are back to the builds!

We have been working on the aeroponics system this weekend. An Arduino is being used to control the fogger and fan right now. We have a video for you guys demonstrating the set up and how we envision everything working.

The things that we have done since the last post are a little hard to describe the process of. First of all, we wrapped the frame in plastic so that any water will drain back into the fog bucket. We have some images of it, but would really rather not have to tell you how to use duct tape and plastic.

Here is a list of the materials we used to wrap the frame, and we will leave it to you to figure out a wrapping procedure that works best for you.

Frame Wrapping Materials:

1. Duct Tape
2. Scissors
3. Clear plastic sheeting for wrapping windows in the winter. 3mil

Here is an image of us taping the plastic to the inside of the frame. This is to make sure that the water drips inside the bucket and not on our floor.

Here is a picture of the finished frame with its plastic sheeting.

In order to test how well the control software and our tape job was working , we ran the foggers all night with the Arduino.  We didn’t see any leaks and the fogger was still on the next day, so everything appears to be running smoothly. With your own projects, we recommend finding a taping method that prevents the water from trickling outside the plastic onto the floor. This will vary based on the frame that you are using, so we can’t really give you step by step instructions on how to make it.

Materials for the Switching Board:

1. Arduino
2. 2- TIP120 power MOSFET
3. 2- 1K resistors
4. 1- 240V Solid State Relay
5. 4- Two position stackable terminal blocks, Filmore part # TB132
6. Velleman 3164 strip board
7. 3- 0.1inch header pins
8. 18ga stranded wire

Here is the strip board layout, you can use this to make the board:

The three pins marked at the bottom indicate connections to your arduino. We choose to use the 0.1″ header pins and plug the strip board directly into the Arduino so it is piggy-backing. This works okay but isn’t really all that stable with only three points of connection. A better method would be to use a couple terminal blocks and run wires to the Arduino which would be kept separate. In any case, this is the wiring we are currently using with the power supply we built previously. The 2 amp transformer is a bit undersized but it does work. If you choose to build all this yourself, I suggest getting a 3 or 4 amp transformer. That will significantly reduce the heat produced by the power supply. Gives you piece of mind.

Control Software

The control software for the arduino–which we will use until we get the Tower up and running, could be awhile–is very simple. Just a couple of variables, a coupe of if-then statements and some pin control. We simply switch digital pins 2 and 3 on and off to control the fan and foggers. Simple as that. Here is the code:

/*Initial program to control the timing of our aeroponics system.*/

int fogger_pin = 3;
int fan_pin = 2;
int fogger_on = 0; //Non-zero true.
int fan_on = 0; //Non-zero true.
int fan_on_time = 4000; //Fan on time in miliseconds.
int fogger_on_time = 15000; //Fogger on time in milliseconds.
int fogger_delay_time = 30000; //Time between foggings in milliseconds.
unsigned long current_off_time;
unsigned long current_on_time;

void setup(void){

Serial.begin(9600);
pinMode(fogger_pin, OUTPUT);
pinMode(fan_pin, OUTPUT);
current_off_time = millis();
}

void loop(){

if(fogger_on){
//Our foggers are on so we need to see if we need to
//turn on the fans, turn off the fans and foggers, or do nothing.
if(fan_on){
if(millis()-current_on_time>=fogger_on_time){
digitalWrite(fogger_pin, LOW);//Off.
digitalWrite(fan_pin, LOW);//Off.
fogger_on = fan_on = 0; //Off/False.
current_off_time = millis();
} //if(millis()-current_on_time>=fogger_on_time){
} else if(millis()-current_on_time>=fogger_on_time-fan_on_time){
digitalWrite(fan_pin, HIGH);//On.
fan_on = 1;//On/True;
}//if(fan_on)
} else { //foggers were off so we see if they need to be turned on.
//If our current off time is greater than fogger_delay time then
//we need to turn the fogger on.
if(millis()-current_off_time>=fogger_delay_time){
digitalWrite(fogger_pin, HIGH);//On.
fogger_on = 1;//On/True.
current_on_time = millis();
}//if(millis()-current_off_time>=fogger_delay_time){)
}//if(fogger_on)
}//void loop()

You’ll notice that we have three variables at the top of the program that control the timing of the three main components. fogger_delay_time is the time (in milliseconds) between when everything is turned off and when the foggers are turned on again. fogger_on_time is the time (in milliseconds) between when the foggers are turned on and when they are turned off. And finally, fan_on_time is the time (again in milliseconds) between when the fan is turned on and when everythign is turned off. Let me give you a bulleted list of how things run.

• Program starts…everything is zero.
• We wait fogger_delay_time milliseconds and then we turn the foggers on.
• Once the foggers are on, we wait fogger_on_time-fan_on_time milliseconds and then turn the fans on.
• We then wait fan_on_time milliseconds and shut everything off and begin again.

Obviously everything about this setup is simple. The times we have in there currently are for experimental purposes only. The scientific literature we’ve read about Aeroponics suggests that we need 7 seconds of fogger time to every ten minutes of off time. That seems like a huge stretch of no-water time to us so we are going to start out with a much more agressive fogging schedule. Maybe 10-15 seconds every miniute or two with a fan on time of 4 or 5 seconds.This really depends on how much fog we are producing in the nutrient water and how much root blockage we have in the root chamber. The fog must penatrate all of the roots so we need good circulation which means more fan on time. Experimentation will show us what we need to do.

Other Stuff

So, we now have an essentially functional system–sans lights but those were always icing on the cake and not required for immediate functionality–and we want to get right down to business. To that end, we’ve started sprouting some string-beans, peas, leaf lettuce, and chives. We hope to see substantial roots in 2-3 days and have them in the aeroponics setup before next weekend. With the possible growth we’ve read about and seen for ourselves, we have high hopes that we could be eating some of our own produce soon.

As mentioned before, we will be attempting to use trench-cloth, the stuff we used on the sand filter, as a support medium for the plants once they have been rooted on a wet cloth. If that works out, we will have a substantial aeroponics system for well under $200 US. And that’s without scavenging parts! If we had been more frugal and used some scrap lumber for the frame, this could have been a sub $100 US build. Well within the price range of your average apartment dweller in need of some sustainable food.

That’s all for now, be safe and sustainable

Pam & Stan