Under Control

My Turbulent Electronics Seem to Work!

Because my "studio" is a bit cramped -- i.e., cluttered with tools and detritus -- I've had to fly the fan box in the rafters and try to find a clear-enough area to put the sensors to test them:

fans at the top, sensors at bottom (see arrows if you can)

Here's the control board (the driver transistors are underneath the silvery heat sink which actually seems to work, and the little black rectangle just to their right is the PIC microcontroller):

Controller

On the left are the fan connections, each with an individual fuse and indicator LED. On the right are the sensor connections -- see more below. At bottom right is my failed attempt at a remote ON/OFF cutout relay. It works fine, however any bouncing around -- say driving over a bump -- makes it bounce around-ON, so I think I'm going to have to replace it with a regular switch. Which means we'll have to crawl under the ramp in the truck to turn the thing on and off. But only for a couple weeks...

I tested the sensors and each one seems to be correct. On top is a "PIR" motion detector which should see people milling around 30 feet out. Below are three IR distance sensors (Sharp GP2Y0A00K0F) which are supposed to work to 5 meters (15 feet), but will be reliable within 10 feet at least, so if anyone has the temerity to actually aproach the truck, we'll know about it:

Sensor Block

The fact that the PIR sensor works is amazing considering how much trouble it is to get a "Motion Detector" to work the way I want... The problem being that all of the easily battery powered Passive InfraRed (PIR) sensors that I had upon my hands didn't work very well in the sunny-windy outdoors (I'm looking at _you_ Parallax). This led me to futzing with various Porch Light Motion Sensors, where some did a reasonable job of not false-triggering outside [...remember your (or at least my) damn proch lights going on and off all night when it's windy? That's the problem, along with the bright lights of Santa Fe in general...]. Some of the porch sensors could be hacked to run on 24v DC -- which meant more power supply complications -- and some can't (easily). Then, the one I though I got to work croaked on me as soon as I assembled it with all the other bits'n'pieces. So it was off to the hardware store again (speaking of which, if you haven't read Neil Stephenson's description of Hardware Store Foraging, it's a must at this point.)

I swallowed my pride and bought a Heath/Zenith "Wireless Command" module (#SL-6030-BZ-A) for $28 smackaroos which runs on two AA batteries (power problem solved!), but only communicates by radio. After testing it outdoors and finding it to be very reliable I opened it up to find that I could connect across the built-in LED indicator and get a good 0-3v signal out. So with a bit of drilling and grinding it's mounted up top there.

Which leaves us with Power. I got a 100AH Sun Extender 12v battery for your basic off-grid use and added a 55A PowerMax three stage charger to top it up:

Power Central

I ran this whole kabodle for 5 hours yesterday at about 40% of peak load -- each fan sucks about  2.5A, so all eight use 20A -- by sequencing fans on and off in a multi-pattern. The transistors did not overheat and the battery did not die. In fact it didn't even make it to half-charge, so I think there'll be enough juice to go around.