This Christmas, my brother-in-law gave me the best gift: a MintyBoost v3.0 construction kit and associated small electronics components. I set to work right after the holiday rush died down putting it together; my thoughts on the project follow.
While looking for something to use a gift card on, I stumbled across the Radio Shack 3D LED Cube Kit for Arduino. It'd been awhile since I'd tried building an electronics board project from scratch, and I'd seen some clever demos of "3D pixel" displays; I thought I'd try my hand at putting this together. What follows is my experience with it.
The essence of user-friendliness is feedback. I won't be rivaling Apple with my little creation, but having more than zero indication that the IR receiver is actually picking up signal is probably wise. So the next step in the project was to mount some LEDs to the case to give me a bit of status indication.
A quick trip to Radio Shack netted me three red LEDs (2.6v, 28mA, 10mcd), one green LED (2.1v, 25mA, 6.3mcd), and a quad of 220-ohm resistors (and some 1K-ohm resistors). One thing I've learned during this process is to verify everything before busting out the permanent-connection hardware; before soldering or gluing anything, I bread-boarded the LEDs and used a slight modification on the Arduino "Fading" demo to confirm that all four LEDs would light. This turned out to be wise; my initial plan had been to use a 1K-ohm resistor between all four cathodes (in parallel) and ground, but I discovered that allowed too much back-current to leak across the LEDs---not desirable at all.
Final configuration for the LEDs and resistors on the testing breadboard.
Once I'd verified the configuration, it was time to get to work. Trimming the anode leads a bit on the LEDs, I soldered one resistor to each anode. I then grabbed my Dewalt and 3/16" bit again and bored four parallel holes in the upper half of the case, then glued the LEDs in place. Due to a slight mix-up on my part, the green LED ended up with its resistor on the cathode, but no harm seemed to be done. I soldered all the cathode leads (including the resistor lead from the green LED) into one, and left the anode leads to be connected to the Arduino.
I ran into a bit of a conundrum at this point: with the LEDs living on the top shell, I wanted some flexible wire with some nice, solid end plugs to connect the LEDs to the Arduino control pins, but nothing in my kit really fit the description. Fortunately, I discovered that Radio Shack sells a SideKick basic kit that includes what the kit calls "breadboard jumper wire." It turned out to be the perfect tool for the job if I cut them in half and soldered the loose wire to my LED leads.
With the jumper wires in place, I connected the LED anodes to Arduino pins 6, 9, 10, and 11, and the cathodes to one of the two GND pins. I then wrote a couple of short LED test functions:
// LED control library, by Mark T. Tomczak // Public domain // To use: // * Call SetupLedControl with an array of LED inputs IDs // (-1 terminates the array as a sentinel value) // * Call functions in the library to control the LEDs. // Control LED firing patterns // -1 used as sentinel value int *g_led_control_leds; int g_led_control_num_leds = 0; // *leds is the arraay of LED pin IDs, terminated with a sentinel value of -1. void SetupLedControl(int *leds) { g_led_control_leds = leds; g_led_control_num_leds = 0; while(*leds != -1) { g_led_control_num_leds++; pinMode(*leds, OUTPUT); leds++; } } // Blink several times (off-on-off). // - times: number of times to blink // - flash_delay_millis: Number of milliseconds to wait // before toggling the light on or off.void FlashLights(int times, int flash_delay_millis) { for(int i=0; i < times; i++) { for(int i=0; i < g_led_control_num_leds; i++) { analogWrite(g_led_control_leds[i], 255); } delay(flash_delay_millis); for(int i=0; i < g_led_control_num_leds; i++) { analogWrite(g_led_control_leds[i], 0); } delay(flash_delay_millis); } } // This is a fun little function that delays a specified // number of milliseconds, while showing the time remaining as the // intensity of several LEDs. // // When all the time is remaining, the LEDs all glow at maximum brightness. // Elapsing time is shown as the LEDs slowly going out one-by-one.void CountDown(long time_to_countdown_millis) { unsigned long start_time = millis(); // TODO(mtomczak): Arduino millis() function rolls over to 0 after // about fifty days. You should account for this rollover... // possibly build a timer library with some structs to hold that state. for( long time_elapsed = 0; time_elapsed < time_to_countdown_millis; time_elapsed = (long)(millis() - start_time)) { float percent_remaining = (float)(time_to_countdown_millis - time_elapsed) / (float)(time_to_countdown_millis); float led_fraction = 1.0 / (float)(g_led_control_num_leds); for (int i=0; i < g_led_control_num_leds; i++) { // The logic is exciting here, but it basically boils down to: // * consider the time remaining to be divided into a series of "ranges" // (one per LED). // * If the time remaining is more than my range, glow maximum intensity. // * If time remaining is less than my range, shut off completely. // * Otherwise, glow proportional to how much time is left within my // range. int output = 255; if (percent_remaining < led_fraction * (float)(i + 1)) { if (percent_remaining < led_fraction * (float)(i)) { output = 0; } else { // percent remaining is in range led_fraction * (i, i+1) output = (int)((percent_remaining - (led_fraction * (float)(i))) * 255.0 / led_fraction); } } analogWrite(g_led_control_leds[i], output); } } }
I combined this library with the recognition code from my Arduino IR bridge project so that it would blink twice and then count-down over five seconds when it recognized an IR pattern. Overall, I'm not unhappy with the results!
What I learned
This is the part of the project where the insulating properties of hot glue were especially helpful. I basically glued over the forest of wired-together cathodes so that they couldn't short against anything, and I'm pretty pleased with the results.
Pay more attention to output ratings on LEDs. There's a noticeable visual difference between the green LED and the much brighter red LEDs (I'm guessing that my eye is reacting logarithmically to the difference between 6.3mcd and 10mcd). If I wanted to back this part out and try again, I'd go with four red LEDs.
Part three will wrap things up by adding the IR emitter and the code to drive the entire project.
I've had an Arduino UNO board kicking around my house for about a year. My original plan was to create an input switcher for the TV that would run off the cable remote (it would maintain a bit of internal state and fire the commands to switch TV modes from the current one to the desired one instead of needing to fish around for the TV remote). This was pretty successful, and I published both the IR decoder and the input changer itself on GitHub. But I never got around to enclosing the project and making it "clean."
So this week, I finally purchased an enclosure and power supply for my UNO board. Trying it out, I immediately discovered that the enclosure doesn't really fit my Ethernet shield (which the reviews will tell you gladly; that's what I get for not reading the reviews before purchasing). Since I didn't need the shield, I shed it (I'll probably get another UNO to plug it into later).
Then, I got out my kit and got to work. It's been awhile since I had occasion to solder anything, and I've never done hot glue for an electronics project before. Overall, I'm not unhappy with the results.
I made a hole in the enclosure using a 3/16" bit on my Dewalt drill, angling it diagonally back-and-forth to get a good wide slot (I wanted to make sure the receiver had a nice, wide field-of-view to catch IR signals). I then seated the Arduino board in the enclosure and glued the IR sensor in place with my wife's glue gun (note to self: I've stolen my wife's glue gun and owe her a new one). My gluing technique is hellishly wasteful, but I figure I'll get better with practice. One thing I love about working with glue is that it doubles as an insulator; no more wiggling my fingers in between tiny wire runs to get the electrical tape on there!
IR decoder visible through the drilled slot in the side of the enclosure.
Once the glue solidified a bit, I did a quick soldering job and was all set. I wrapped the signal and power wires around the posts in the enclosure also and threw some hot glue on there for mechanical stability (I want to make sure any jostles the wires might take are being supported by the posts and not the Arduino's female pin coupler or the IR sensor's leads).
I then fished a sticker out as a finishing touch. :)
I'm very happy with both this sensor and its range. I ran some quick tests with the full enclosure at different ranges using my old remote signal decoder program, and found it was able to sense a good distance away (about 15 feet; plenty for my needs).
What I learned
This IR sensor is more temperature-resistant than I'd feared it might be; I ran the soldering without any heat sinks, and no harm was done.
Hot glue is actually pretty safe to work with; I'd worried I would get burned, but discovered that it appears to shunt its heat pretty quickly as it transitions to a solid state. solid strands can be touched within a few seconds of being emitted from the nozzle (though blobs should be given about thirty seconds to a minute to gel cleanly; they change opacity a bit on solidification, which is convenient).
Hot glue is messy; spiderweb-strands everywhere, needed to go in with pliers to clean it up. Also, I'll be more careful in the future about letting the glue find its way into the seam of the enclosure itself; my enclosure no longer seats quite correctly because one blob of glue bubbled over the top and got into the joint.
Part 2 will discuss extending the software and adding status indicators.
and associated small electronics components. I set to work right after the holiday rush died down putting it together; my thoughts on the project follow.
