I’m so crazy that I went ahead and bought some op amps (LM741) and other stuff from Jameco before actually planning anything (typical late-night purchase).  Jameco seems to beat Digikey in price for most things I’ve been looking for.  And I usually get everything the next day or in two days at the latest.  Pretty good.  Anyway, I figure I’ll use an op amp to amplify the signal from LED photosensors like Tanya does.

Then I just need a circuit to enable the motors (through my SN754410 h-bridge) to turn over some voltage range, discharging from like 16V to 8V or something.  I don’t know the first thing about how to do that, but hopefully can adjust the voltage regulators I got to use hysteresis or whatever to get that effect.  I’ll try using various motors to operate it at various voltages to check the performance.

I’m thinking I can use a 74HCT245 and some capacitors to make a simple/easy charge pump so the tracker can run intermittently off a tiny, low voltage solar cell.  I figure with a duty cycle of 2.5%, I should be able to run the motors for 12 minutes of an 8-hour sunny day.  If I use my 0.3W solar cell, that comes to over 100 ft-lbs (maybe lift 20 lbs 5 feet, eh?) of energy per day, with power used at 12W when on.  Super-rough numbers, but makes some sense.  It’ll be fun to experiment.

Of course I need to build a thing to mount whatever it is that will be pointed toward the sun (like a tripod/pole, hinges, and some the threaded rod and bolts as a linear actuator).

Here I restate the goal of this endeavor both to motivate myself and prevent this from becoming a mere time and resource-wasting selfish hobby:

I am in the research and development phase of a project to identify products that we can manufacture locally for profit or to offset local cost of living/business.  The goal is economic development in the form of local jobs, influx of money from outside our community,  or reduction in expenses for locals.  The project has the side benefits of being extremely fun and potentially helping out my family in the same way I hope to help out my community.

We’ll see how it goes, eh?

Spiritual Need

03/02/2011

For what profit is it to a man if he gains the whole world, and loses his own soul? —Jesus (Matthew 16:26)

I don’t wanna gain the whole world and lose my soul!  —Toby Mac

Got me thinking about real change, the transformation that comes with folks fully giving their hearts to Jesus.  Following Jesus means repentance, a 180 degree change in direction.  Sometimes my social justice drive gets me hyper-focused on trying to “gain the whole world” by fighting poverty and advocating for social programs.  The key issues keeping people from full life are really soul issues, maybe complicated and intensified by social issues.  I felt a bit of negative reaction to the Daily Bread (devotional reader thing) the other day because it spoke to how no matter what socioeconomic position you find yourself in, you’re either saved or not.  I felt like it neglected to mention our responsibility to fight injustice and oppose oppressive systems that trap people in poverty.  But then realized the thing was really totally right.  I found my frustration betrayed my misguided thought.  I have been placing my faith in physical remedies, rather than spiritual, which is really the central issue for most.  This doesn’t mean I’m not into promoting a better way of doing things, but my perspective needs some refocusing!

Vocation

02/20/2011

A friend of mine at work shared with me how he was recently challenged with the task of writing a mission statement for his life.  He smiled as he told me it caused a lot of trouble for him because it made him question why he was doing what he was doing.  Now he’s passed the trouble on to me.

I wrote a mission statement for my life this morning.  It goes like this:

My mission is to use my life as a conduit for Christ to bring persistent hope and holistic transformation–in me, my family, my community, my job, and the world.

Lately I’ve committed to act on what I perceive to be God’s strong tugs on my heart.  I’m taking a class that’s essentially a primer on social entrepreneurship from a Kingdom perspective.  I started a group trying to get poor folks into homeownership.  I bought an Arduino Uno to explore manufacturing and other job-creating business opportunities.  As I flounder around trying things, I get the sense that I could waste a lot of my energy if I don’t focus, set goals, make plans, and generally apply some discipline to the process of doing things.  The tricky thing for me seems to be that I have trouble balancing the high value I place on not letting structure and routine interfere with creativity and this new idea that structure and routine (discipline!) can be the key to making a creative effort successful.

I like how the Wikipedia article on vocation describes Christian vocation as “the use of one’s gifts” for the sake of the common good.  I’m convinced that putting gifts to use requires intentionality.  I plan on making some goals consistent with my mission statement for each of the different areas of life over which I have influence (mentioned above:  me, family, community, job, and world).

Success!

02/15/2011

Success indeed!  I controlled a DC motor through an Arduino UNO and a SN754410 h-bridge chip.  I can’t say I totally understand what my problems were before.  I think what happened is that I didn’t have a common ground for the Arduino, SN754410, and the motor power supply.  At one point, I measured 32V between the ground for the motor power supply and the Arduino!  That voltage went away when I plugged my power supply into the power strip as my computer connected to the Arduino – at that point I felt safe to connect all the grounds together.  I also neglected to connect 5V power (pin 16) to the SN754410 at first.

I used a 12V lead from an ATX computer power supply for the motor supply (SN754410 pin 8) and the Arduino 5V output for SN754410 pin 16.  With the enable pin (pin 1) of the SN754410 at 5V, the output (across pins 3 and 6) was about 10.5V, I think.  I put some resistors (like 2 ohms) between the motor and the SN754410 to try to protect from voltage spikes induced in the motor (back EMF?).  I didn’t want to have a voltage drop of more than a couple of volts or the motors might not turn much.  Anyway, it worked great!  I got a screaming motor that tried to run off the table instead of a near-ultrasonic whining and a slight twitch.

This is really exciting.  Not only can I now make a robot that the Arduino can control, I’m sure I can control the SN754410 (motors!) with a simpler/cheaper circuit with digital output!  I think the output from the suspended bicore circuit may be just right for connection to the direction pins (2 and 7) of the SN754410.  A small, solar cell could charge a capacitor with a circuit to energize the enable pin (pin 1) of the SN754410 when it’s ready to power the motors.  Then we’ll have short bursts of solar-powered sun tracking!  I honestly don’t even fully understand what the suspended bicore is, but it looks like an easy way to get a digital signal telling my circuit which direction to turn toward the sun.

Aging

02/10/2011

Dear Diary,

I enjoy the feel of the sun on my face and love to see blue sky after a long winter, but sometimes that all gets overshadowed by frustration about how little my community and I take advantage of the abundant, free power pouring down on us.  Actually, pretty much my longest-running, most nagging, nearly most exciting dream has been to concentrate solar energy to do amazing, awesome things.  I recently had my 5th anniversary, my daughter and son turned 4 and 2, and I turned 30 years old.  I can’t help but reconsider what’s important to me and what I have done and plan to do with my life.  I embrace the life God has called me to, including the passions I have for so long dismissed as selfish ambition and indulgence.  I commit to buckle down and really do something rather than only dream.

I bought myself an Arduino UNO electronics prototyping board to facilitate the process of developing science/tech ideas into some real stuff.  I don’t want to get stuck on Arduino, but if you don’t know already, the Arduino is incredibly awesome – so much so that when I consider its outrageous opensourcedness and what the Arduino enables us to do it triggers a near-cataclysmic avalanche of happy/creative/hopeful neuron blasts in my brain that effectively white out my consciousness for significant periods of time.  I’m sure it’s not healthy for me to linger in that exploded-mind state for two long, so let’s get down to the first efforts toward doing something.

Below is a list of things I’ve collected recently to experiment with basic suntracking circuits and maybe doing some experiments.  Most of the stuff is commonly referred to on hobby robotics and DIY solar websites (primarily this BEAM website).  At first I hoped to save a bunch of money by buying the most basic components and assembling all my circuits from scratch.  Then I realized that my patience and spare time don’t allow me to work that hard.  Anyway, here’s what I’ve got:

  • Arduino UNO SMD
  • a breadboard
  • lots of NPN/PNP transistors (2N3904 / 2N3906)
  • CMOS 1381J Voltage Detectors
  • SN754410NE quadruple half H-bridges
  • Some 74HCT240, 74ACT240, 74ACT245
  • a bunch of resistors, capacitors, potentiometers, LEDs, etc.
  • lots of different kinds of rechargeable batteries
  • some supercapacitors and various regular capacitors
  • a 3W (24V/0.1A) solar panel
  • some little 3V solar panels
  • cadmium sulfide photocells
  • lots of DC motors from TINY to big honkin’ scooter-types
  • lots of junk electronics I can strip for parts

I struggled for a couple hours last night just trying to get my Arduino to tell the H-bridge to drive some motors.  At first I didn’t think it worked at all.  Then I realized there was a high-pitched squeal surging on and off at the frequency I told the Arduino to change the motor direction.  When I looked more closely at the motor, I noticed it was moving very slightly.  The voltage across the motor was as I had expected (around 12 V), but it drew a current of only about 45 mA.  That’s similar to what you might get from the output of an Arduino directly!  What the heck is going on?  I couldn’t figure it out.

Here’s a series of smaller goals I hope to attain along the way to the larger goal of tracking the sun in order to concentrate tons of light into a tiny spot:

  1. Learn how to protect the circuit components from crazy inductive load (motor)
  2. Get H-bridge to work w/ Arduino
  3. Set up phototropic suspended bicore (BEAM robot concept) to see what it does (test output)
  4. Try to run a motor using the H-bridge w/ bicore output – might need amplification (transistor)
  5. Try to run two motors on the one H-bridge chip, signals from pair of suspended bicores (2 on one chip?)
  6. Solder it together!
  7. Build a thing that can rotate toward the sun under the direction of the motors.

Starting the Blog

01/31/2011

I’ve found myself getting pretty frustrated about not being able to organize my thoughts or remember what I’ve been working on lately. I realize I don’t have time to waste. I hope this blog helps me record ideas, explore new possibilities, prioritize my work, and even just vent a little bit. I’m currently in zombie state – a typical late-night level of function characterized by persistent restlessness and zero productivity. I choose to sleep now! Woohoo! I slay zombie-Steve for the sake of tomorrow-Steve!