Now I’m playing with high voltage.
Well,12v DC which is much higher than the 5v I’ve been dealing with. And to increase my chance of hurting myself I’ve been dealing with higher current in the 2+ amp scale, which is much higher than the 60mA I’ve been working with. So I’ve been careful not to cross the streams like Egon.
The circuit is really simple: power, MOSFET to switch on the current, and a pull-down resistor. Now that I have an idea of how to get higher-intensity lighting with Arduino, I can reevaluate how the main lamp will be constructed.
Lots of movement on the logic board today.
Instead of printing and assembling 16+ LED boards plus a logic board, why not just put it together (like PB&J) onto one board? Then I only need to attach one PCB to the enclosure, and the less things I need to do myself, the better.
Below you can see a Fritzing printout taped to a 1/2″ piece of foamcore inside a prototype enclosure. I expect that the base will be thicker in order to house more stuff, and by stuff I mean at least a battery and charging mechanism, and so that I can hold the Lamp without touching the glass.
As I was showing this around the office, a gauntlet was thrown down: why use an Arduino Uno r3 when I could use a smaller version without any penalty in processing or functionality, with the added gift of miniaturizing the stack? I didn’t have an answer to this, except, “Umm.”
So challenge accepted!
I have now integrated an Arduino Pro Mini 5v into the PCB stack. I also added some power flexibility by adding a power mounting block and an external 5v voltage regulator, even though the Pro Mini can accept up to 12VDC and has a built-in voltage regulator. I wanted to split out that function so that the Arduino doesn’t have to do any additional work. Also, I don’t know exactly how much power the main light will take, and I want some headroom to attach the largest battery I can safely source.
You might remember, dear reader, that I originally started this experiment using an Arduino Pro Mini 3v3 board (oh how we go round the bend again). I decided against reusing the 3v3 board because the GPS module which I found to be most stable needs 5v and I don’t want to go around shifting voltage where I don’t need to. I’m all about reducing complexity now.
With that in mind, I am certainly thinking about removing IC3 & IC4; IC1 & 2 run the 16 compass LEDs, while IC3 & 4 are two additional shift registers which are legacies from my original idea to build my own LED lighting array. I am now considering using an LED string such as this one sold by Adafruit or a single point source I can vary in intensity (yet to be sourced). Moving my main power supply from a 3v3/5v LiPoly source to a high voltage battery would open up more lighting sources I could use efficiently.
Adafruit and Sparkfun orders placed, let’s play with it when they arrive.
Sketchup is a wonderful prototyping tool – it is cheap (mostly free) and has a huge 3d warehouse you can populate your model with. It also has lots of plugins to render the model out to, most notable VRay and Maxwell. I wanted to learn Maxwell, and while the curve appears steep, here are a quick series of renderings I did in less than 10 minutes.
These renderings aren’t good at all, but this blog is about sharing progress and prototypes.
Building on the Compass PCB prototype 01 I’ve updated the PCB so that I can install the 16 boards easier, along with doing some little things to reduce the amount of wires which will need to run this array.
I created a Ground Bus which I can solder to Board 01 from the Arduino GND and then daisy chain the next 15 together, so I get rid of 15 unnecessary wires. I then moved the +5v feed (which will come from the shift registers) to the top, so I can solder wire, straight, or angled headers depending on what I decide. Lastly, I moved the support holes to the center so that I will be able to flip the board one way or another to install it. This will allow me to manage the 16 wires which go back to the shift registers in a logical way. How I will do that is for another day, at least I know I have options, and I’m giving myself some flexibility here.
The Lamp is a portable object which communicates with the satellites in order to find important (or not) places in the world, and then shine a light.
Pretty simple. But the details are important.
The important part of the above sentence is the concept of portability. I can’t tether the lamp to mains power, or require a giant car battery.
Of all the limitations this project has, is the battery. Right now I’m specifying a 3.7v 2000mAh Lithium Ion Battery with an alternate being the 3.7V 6600mAh Lithium Ion Battery Pack, and connecting it to the system through an Adafruit PowerBoost 500 rechargeable 5V power shield. I guess I could design my own charging system, but lithium-ion batteries scare me. They pack a lot of power per cubic centimeter, but don’t play well with others, tending to melt or blow up if they are shorted, bent, crushed or punctured. So, I will have to create a cage for it so it doesn’t hurt me.
Let’s look at what the system draws without lighting the lamp at all:
So I have 2,000 mAh at worst case battery to play with, but let’s assume a 10% reduction due to recharging, storage loss, etc. This gives me 1,800 mAh to work with. I also am assuming worst-case scenario where the lamp is fully lit (for example at a center of population). In reality, most of the time all the LED’s will be lit. I’m sure there I can use calculus to find the slope and areas of illumination to derive the typical power consumption.
|Item||1 hr ops||2hr ops||3hr ops||4hr ops
|Lamp power remaining||1689.89||1579.78||1469.67||1359.56
|WS2812 LED @ 60mA|
|28 lamps||26 lamps||24 lamps||22 lamps
|Luminous Intensity @ 233 (mcd)3||6524 mcd||6058 mcd||5592 mcd||5126 mcd
|84 lamps||78 lamps||73 lamps||67 lamps
|Luminous Intensity @ 600 (mcd)3||50400 mcd||46800 mcd||43800 mcd||40200 mcd
Besides the total power available, the real limiting factor of the battery is the standard discharge of 500mA which can peak at 1000mA. I don’t want to go toward peaking, because see exploding, above.
I have some options: I could source alternative batteries, use multiple batteries to run different systems or parts of systems, or find a better illumination system so I can get the maximum luminance per mA.
Building on yesterday’s Compass LED PCB prototype, I wanted to get the compass actually working so I could drive some LED’s.
Using Adafruit triple-axis accelerometer & magnetometer LSM303 and NeoPixel Ring – 24 x WS2812 RGB LED, I was able to get a functioning digital compass fairly quickly utilizing the Adafruit_LSM303 library.
I don’t know if I will use off-the-shelf LED’s for the compass as shown in the Compass PCB prototype 01 or use a Neopixel version via SparkFun, the WS2812 RGB LED Breakout. I save about 1.3 mA per LED versus my chosen through-hole LED if I use the WS2812 with a single channel of the RGB on, but to get white it costs me 60 mA! If I use this breakout board I won’t have to assemble or test out the components and boards or test out a self-designed board, which is a huge time saver and reduces the change of me messing up, but I don’t think I can afford the power for the compass.
If I use the Neopixel for the compass, I’m stuck using the Neopixel library for the compass and my home-brew shift registers to drive the lamp subsystem. Which might not be a problem since they both do different things. In the end it might come down to aesthetics: which system do I want more control over the color of light, the lamp or the compass? I think I would want more control over the lamp colors via the Neopixel than control the color of the compass.
Until I get a handle on my power consumption, I won’t be able to choose one system over the other.
I’ve been thinking a lot about the Lamp’s compass. Creating a Lamp with built-in dowsing rod capability will both increase complexity – a major headache is dealing with all the shift registers and the accompanying 16 LED’s – not to mention the added power load required to drive an accelerometer and magnetometer continuously. But it will be cool. And that’s the whole point, right?
Why do I need both an accelerometer and a magnetometer. The magnetometer is self explanatory: I need to know which way is magnetic north and compare that to the local Lamp heading so I can turn on the correct LED to point me in the right direction. I don’t have perfect balance. The accelerometer is essential to compensate for a non-flat magnetometer reading. I can also get fancy and begin to compensate for magnetic declination by both reading the accelerometer and the GPS location. If I want to get fancy.
I’ll deal with the power consumption and compass later, but right now the thought of custom making then soldering 16 LED housings to make a hexakaidecagon (hexadecagon) makes me want to run down the street. Luckily, I’ve been messing with Fritzing Fab and designed my own little LED PCB which will hold the LED, a resister, pins to go to ground and to the proper shift register, and mounting holes. At US$2.15 per board each one isn’t exactly cheap, but I will have a consistent and rugged board to mount the electronics to and then to an internal housing. Kit-bashing my own would both be more time consuming and I would have 16 times to foul it up.
I tried to fabricate my own LED harness with MakerBot, but it just was a pain in the butt to fab and then I still had all the electronics to deal with anyway. I might have to fab one anyway to hold the PCB’s but that will just give me another factor of safety with the electronics.
As it is, this board might win as the most simple board produced by Fritzing, but you try to create a run of 16 (or 32 in case I mess up) boards yourself. I’m going to rely on mass production on this one.
Another day, another module. This time a compass, well, a magnetometer. In this case a triple-axis Accelerometer+Magnetometer (Compass) Board – LSM303 from Adafruit. This module will allow the lamp to know which direction (nominally) it is pointed.
Besides the lamp becoming brighter the closer it gets to a center of population, there is a compass ring which can point you in the correct direction. Prototype 3 with the shift registers is an early concept of the 16 LED’s, albeit in a straight line.
Conceptually it should work this way: the GPS module will calculate the distance between the Lamp and the closest Population Center, and get the numerical direction in degrees. The LSM303 will calculate the local orientation of the Lamp. Then we can compare the two, do some math, and light one of the 16 LED’s. Here is a great example (code) using Adafuit’s NeoPixel’s (warning, loud music):
Right now, the compass module is orienting what appears to be fairly close to precise measurements (using my trusty compass) and the trust sharpie + post-it combination. I just need to build the LED array, but that shouldn’t be too bad, but that is dependent on evolving the case design an additional step.
I am a bit concerned about magnetic interference from the other components, so I will have to find a place for it far away from the battery and the GPS module just in case.
Now that both the GPS subsystem is at a good place and there is some material exploration going on, it is time to look at how to turn on a large amount of LED’s.
Shift Registers are fun little digital circuits where all they do is continually cascade bits, shifting in the data present at input and shifting out the last bit. The nice result is that you can drive multiple items – such as large array of LED’s – with only three pins: a clock pin, a latch pin which stores the data, and a data wire. I don’t know the upper limit, but at some point there becomes too many IC’s to sync at the right speed and you have too many LED’s to run off of the given power.
So now I can drive a n = (∞ − 1) amount of LED’s for the lamp itself, with power being the limiting factor, and have room for other items. The upshot is that I can now easily drive the Compass subsystem – an array of 16 LED’s which correspond to the 16 cardinal directions. Combining the GPS output from Prototype 1 with two shift registers was easy – with the help of Serial to Parallel Shifting-Out with a 74HC595 from Arduino. Mostly it is a lot of wiring and making sure that you have the clock, latch, and data wires connected properly. The hardest part was finding enough resisters to connect all the LED’s so they wouldn’t short out.
Here’s a photo of the prototype board, on the roof once again since the GPS module is having a hard time acquiring a signal from the satellites.
After successfully getting the GPS subsystem to a respectable place, I wanted to see what kind of size and shape of container would work.
I’m interested in the lamp being sandblasted/frosted with the light bright and diffuse with the electronics hidden inside. I want to encourage people to touch the lamp, so the palette feels right to be a wood and glass combination, so where a human would grab the lamp, they would be touching a natural fibrous material. I don’t know what type of wood to use. Maybe a burl Maple or a Cherry carbonized. Right now, I’m interested in the base to be darker and more solid that the light emitting top.
The wood base will be an open item for a bit, so I took a large mason jar we have in the office, some tracing paper, an Arduino with a blink program running, and I soldered a bunch of LED’s on a stick.