arduino
Internet Christmas Tree is a Hit
I’ve modified the fireplace blower controller to control the Christmas tree lights.
At first, I wanted to get the Christmas tree lights to flicker like a candle flame. However, at about the time I programmed in the random function my Particle Photon stopped responding. None of the googled “flashing red light” solutions worked on my Photon. Hmmm, I’ll have to investigate this after Christmas, because trying to get the Photon unbricked was turning into a real time suck.
So, in order to keep moving ahead, I down rev’ed to my Spark Core, which is the previous generation of the Particle Photon. I got it working just in the nick of time. I wanted to show off my IoT Christmas Tree to my nephews and the rest of the family during the Christmas Skype call. Indeed, everyone at the far end of my Skype connection has fun turning the Christmas tree on and off, and changing the flickering characteristics after I gave them my secret web page.
The circuit consists of a Spark Core or Particle Photon, a homebrew optocoupler and a less than $2 AC motor controller from eBay. The optocoupler consists of a green LED which shines on a Light Dependant Resistor (LDR). The LDR is soldered in parallel with the motor speed controller control. The LDR has a lot of capacitance, so it smooth out the pulse width modulation (PWM) output from the Photon. I got the GL5537 Photoresistor from eBay and I had a 10 mA green LED in my junk box. I butted the green LED up against the LDR and held them together with a couple of layers of heat shrink tubing. A resistor of 680 to 1.5K in series with the LED limits current. Comercial versions are made by Vactrol or Silonex. The transfer function is very linear when graphed on a log/log scale.
Hardware costs should be less than $25, most of which is for the Photon.
The software consists of a short program for the Photon that receives commands from the control web page. Follow the links for the code. Make sure to put your own deviceID and accesscode in the beginning of the javascript.
Beyond NEST – Wood Fireplace Insert and Pellet Stove Controller
Previously, I had experimented with an Arudino Uno based fireplace insert blower controller. That experiment evolved in having two displays – one for the time and temperature, another for a graph showing temperature over time.
But, it makes sense to combine the two displays in the previous design into one display. A common, inexpensive display available are 240×320 TFT LCD displays based on the ILI9341 chips. The one I got from Banggood (I couldn’t make up a name like that if I tried!) plugs directly on an Arduino Uno. However, this makes it difficult to find pins for the thermocouple interface. So, I upgraded to an Arudino Mega, which gives me more memory, and oodles of spare I/O ports.
Wood Fireplace Insert Blower controller with graphic display – double click to enlarge.
Note in the picture that the display the time is shown on the first line, temperature on the second line, and then time vs temperature graph below that.
Temperature is graphed once a minute, which makes it easy and entertaining to see the temperature hump created by throwing in a log. A grid with blue dots every 10 minutes and white dots every hour further helps give structure to the graph. Horizontal dots are 50 degrees Fahrenheit intervals. I personally find this graph quite useful for figuring out when, and how big a log to throw on the fire. However, I’m sure I’m going to be dinking with the user interface for quite a while to come.
The DS3231 real time clock (RTC ) from the previous design continues to be on the I2C bus, which is also more accessible with the Mega because the I2C pins are brought out in a second location that is not blocked by the LCD shield.
A few months ago, I did a survey of digitally controlled fan controllers. All the designs seemed more complex and expensive than I though necessary. When I found a AC motor speed controller on eBay for about 2 bucks, I ordered one. In the mean time, I saw a post about using a LDR (Light Dependent Resistor) to complement the variable resistor (Pot) and thought I’d give that a go. By the way, I left the pot in the circuit, so I can bypass the Arduino if I want.
I came up with an Arudino interface consists of a green LED shining onto the LDR , both of which cost about a nickle on eBay. What I don’t understand is why a commercial version (Vactec or Vactrol) of this type of opto-coupler cost $6, when I can build one myself for 2 parts costing a dime, plus a bit of heat shrink tubing. It did not hurt that I already had these parts in my “junk” box. The transfer function my home brew unit is also quite linear if graphed on a log/log scale. The opto-coupler is the nearly vertical black cylinder on the upper left of the picture. However, it’s taking a bit of experimenting to get a good dynamic range and resolution when coupled with the $2 motor speed controller. Selecting the right series resistance for the LED is the key. The LDR has a lot of useful smoothing capacitance and can handle a higher voltage than your typical opto-coupler. The lDR capacitance is useful because the so called Arduino “analog” output is actually pulse width modulation at 750 Hz.
My other reason for creating a second prototype is that I have a pellet stove with a blown controller board in the basement. What it takes to fix it is a blower speed controller – and I now have two working prototypes.
I did a bit of market research and it appears that the market for pellet stoves and fireplace inserts are on the order of hundreds of thousands of units sold in the USA per year. Perhaps there is a path to commercializing my design? I’m going to have to give the design of a demo worthy case some thought.
Wood Stove Fireplace Insert Controller – Beyond NEST
Wood Stove Fireplace Insert Fan Speed Controller with Graphic Display
There are some home temperature control situation that don’t work with a NEST.
In my example, I am controlling the fan speed for the blower of my wood fireplace insert.
I want to be able to control the fan speed depending on stove temperature as well as time of day. In addition, it’s helpful to have a display that graphs the stove temperature for the last couple of hours.
In the prototype, I am showing the time, and blower exhaust temperature in Celsius and Fahrenheit. This forced air is used to heat over 1000 square feet from my fireplace insert.
Modules visible are the arduino UNO, AC fan speed controller, DS3231 real time clock module, 2×16 LCD display, thermocouple interface and 128×64 OLED graphic display. Usually, the graphic display shows a gradual curve as a piece of wood burns.
My next step is to combine the two displays into one 320×240 display (code already written) and put the historical temperature data in the cloud.
Arduino Utility Circuit to Set/Modify DS3231 RTC
I’ve become quite a fan of the DFRobot LCD keypad shield. I’m finding all kinds of little uses for it.
One frequent issue I have is needing to set or modify the DS3231 I2C modules.
So I popped the LCD keypad shield on a Arduino Uno, hooked up the DS3231 module. Then using the simple button interlace to select year, month, day, hour, minute and seconds, I can us the up/down buttons to quickly set or modify the RTC time.
Set the DS3232 RTC clock with a simple Arduino LCD keypad interface.
Here’s the Arduino DS3231 wiring code.
Case Study: Off-The-Shelf Parts Make for Rapid Prototyping
Off the shelf components make for a quick prototype
My client wanted to be able to monitor a number of environmental parameters and then respond by turning pumps, fans and heaters on or off. The end result was a optimal plant growth environment in a mini-greenhouse.
I had previously experimented with a odroid Show2. This Arduino Uno type device features a 2.2 inch, 240 x 320 pixel display, 3 switches, 3 LEDs, LiPo battery charging circuit, and a I2C breakout header. There was also a daughter board that turned the Show2 into a weather station.
I realized that this could be the basis for a simplified version of the controller that my client was looking for. By adding additional I2C sensors, and a I2C to 8 bit output, I could take the required readings and turn up to 8 relays on and off.
The client had been working on getting a Beaglebone Black programmed as the brains, but progress was slow. By implementing this “quick and dirty” off-the-shelf prototype, we got a test bed that allowed for faster design considerations. This then gave the project the momentum needed to then make rapid progress.
Arduino IDE and open source rocks!
Refer to the above picture for described function:
Not numbered is the “octopus” I2C patch board in the middle. It distributes the I2C bus which is controlled by the display board to the various sensors and outputs.
1. The odroid Display2 is running the (slightly modified) weather program. In this example it is powered by a battery that is glued to the back of the display.
The display is showing the current values from the 3 weather board sensors. Those readings are the “indoor” temperature & humidity, ultraviolet & visible & infrared light levels, temperature (again in both Celsius and Fahrenheit) & pressure & equivalent altitude in feet.
2. Real time clock (RTC) module with button battery. I add this so that the Arduino specs are consistent with Beaglebone specs. Note that the RTC battery typically has a life of 2 to 5 years – at which point it needs to be replaced.
3. The weather board has been relocated from it’s designed position as a daughter board to the display board to a leg of the I2C patch panel. It has the sensors that are currently showing on the display board. The fact that the sensors read correctly indicates that the I2C bus is working properly with the approximately 11 feet of wiring shown in the picture. Although the I2C buss was originally intended for communication between different corners of a PCB, it appears it can be used for longer distances too. At some point I may go back and see how far I2C can practically reach.
4. “Water” temperature sensor. Note that it needs to ruggedized. My intent was to mount it to the outside of the water storage bladder that is in the base of the greenhouse and cover it with a spot of insulation.
5. “External” visible and IR light sensor. As an alternative, this could be the internal sensor because it does not measure UV. The weather board light sensor DOES measure UV. This is significant because the UV will not penetrate through plastic, but it may be helpful to know the UV level “outside.” Personally, I use the UV sensor as guidance for how long to stay out in the mid-day sun.
6. Relay board. The I2C port extender board connects to the relay board with 10 (8 signal + 2 power) wires (not shown.)
7. Ruggedized soil humidity and temperature with 3 foot cable. Adafruit cautions that this $50 sensor should not be immersed in water for more than an hour.
8. Ruggedized “External” air temperature and humidity with 18 inch cable. This is a $30 sensor.
A Quick and Dirty PCB Production Technique
Back in my teens, I experimented with etching my own PCBs. I would draw the circuit with a permanent marker. The thick ink traces acted as a etch resist.
The 21st century upgrade to this technology is the toner transfer method. You print your PCB on a piece of paper. Then you use a clothing iron to transfer the toner from the paper to a copper board. The toner acts as a etch resist and you etch away the rest of the copper using the same chemical process I used decades earlier.
So, how well does this work?
I joined a class given at the Solid State Depot to find out. The instructor was John English and he has the project on github at
https://github.com/johnisenglish/ssd_blinky
We built up the board, but could not get it programmed within the time limits of the class. So, it sat, collecting dust for months until I had the time to have another go at it because I wanted a Christmas mood light project.
It turned out that in order to get the ISP (In System Programmer) to work, I need to fix a trace routing mistake. Specifically, I cut the trace show below the “e” of “Cut Trace” in the picture. In place of the cut trace, I ran a fine green wire from point 1 to point 2. By the way, the wire is made with special insulation that melts cleanly when heated with solder. I’ve not been able to locate more of this handy wire in over a decade.
Once I got board debugged, I decided that the RGB light would make a great mood light. Sure, you can get mood lights cheaply from eBay, but I wanted to program a mood light with my own artistic flair. Specifically, I wanted to explore the balance between randomness and predictability for the perfect hypnotic effect.
Fortunately, the Arduino IDE has been extended to work with the blank chip used in this project. Programming was done over the ISP interface once the board was debugged
Because the Atmel 2586 AVR chip only had two timers and a RGB LED suggests the need three timers, I decided to do the pulse width modulation entirely in software.
I wish that I could show the arduino wiring code with all the pretty color enhanced highlights from the arduino IDE. I was aiming to create a hypnotic, flickering mood light.
/*
RGB Mood light using SSD Blinky board – Mike Seiler
*/
#define GREEN_LED PB0 // Green LED
#define BLUE_LED PB1 // Blue LED
#define RED_LED PB4 // Red LED
#define UP 1 // Increase pulse width
#define HOLD 0 // keep pulse width the same
#define DOWN -1 // decrease pulse width
// randomly choose to increase, hold or decrease pulse width.
// this creates flickering fades of one color into another.
unsigned short color_direction( unsigned short direction){
long val;
val = random()%8;
if (val==0) direction = UP;
if (val==1) direction = HOLD;
if (val==2) direction = DOWN;
// Serial.println(direction);
return (direction);
}
// standard arduino function
void setup() {
// initialize serial and wait for port to open:
Serial.begin(9600); // for testing code
DDRB |= (1 << GREEN_LED); // LED green Pin set to output
DDRB |= (1 << RED_LED); // LED red Pin set to output
DDRB |= (1 << BLUE_LED); // LED blue Pin set to output
// send an intro:
Serial.println(“\n\nMood light test:”);
Serial.println();
}
void loop() {
unsigned short red_direction=1, green_direction=1, blue_direction=1;
unsigned short red_level=40, green_level=1, blue_level=20; // initial values
char teststring[20];
while(1) // do forever
{
red_direction = color_direction(red_direction); // randomly change red pulse width
red_level += red_direction;
if (red_level > 252 ) red_direction = DOWN; // “bounce” off limits
if (red_level < 3) red_direction = UP;
green_direction = color_direction(green_direction); // randomly change green pulse width
green_level += green_direction;
if (green_level > 252 ) green_direction = DOWN; // “bounce” off limits
if (green_level < 3) green_direction = UP;
blue_direction = color_direction(blue_direction);// randomly change blue pulse width
blue_level += blue_direction;
if (blue_level > 252 ) blue_direction = DOWN; // “bounce” off limits
if (blue_level < 3) blue_direction = UP;
sprintf(teststring, “%d %d %d”,red_level,green_level,blue_level); // for testing
Serial.println(teststring);
delay(100);
}
}