I obviously knew it wasn't the computer animation, I was just trying to point out that you were less than clear what you were doing. 
Since a couple of microswitches did it, you obviously didn't need a processor. That's not a universal solution to every problem however, and I'm sure you know that as well.
rtr12 posted:I like that one!! Another one I believe I read here on the forum somewhere went something like:
"I am retired, I get up every day with nothing to do and when I go to bed I'm only half done."
(Sorry, but I don't remember who the original poster was to give proper credit?)
How about:
"I am still alive because I have yet to find something worth dying for."
I like that one too!!
You mentioned the 7805 running near its limit without a heat sink. It would add $2-$3 to the overall cost but you could use an R-78 switching regulator, they are a drop in replacement for the energy wasting, heat producing 7805. You can charge extra and people will happily pay it because your product is "green"!
I use the Recom R-78E5.0-0.5 on the Super-Chuffer, neat little product and drops in to replace the 5V regulator. It's $2.51 at Digikey if you buy 100 or more.
This gets really far off the path here, but is fun anyway:
I've kicked around some other power supply options and may end up with a switching regulator later on. The heat isn't a super big deal, as a heat sink only costs around 15 cents. I'm not drawing a ton of current, actually much less than I expected. The data sheet for the Songle relay on the module says it should take over 70mA to power. That works out with a measured reading of the coil resistance (68 ohms) as well. When I throw an amp meter into the power line to the relay module, however, I'm only reading a 45mA current draw. All told we have about a 95mA current draw from the relay module, Arduino, optocouple LED and trigger signal LED all running. I'm figuring 100mA for the math. If we have a 20 VAC input voltage, thats gonna be around 28.3V going into the regulator, maybe a little less when we consider the voltage drop from the doides in the bridge, but I'm not going to bother with that. so, we're dropping 23.3 volts in the regulator at 100mA, or 2.3 watts of waste heat. The LM7805, if I am understanding the math right, will rise about 55 degrees C over ambient temp which will be well under the 125 degree cut-off even on the hottest of days... but still plenty hot enough to burn yourself on the regulator.
All told, to run just one relay, as in this particular project, a heat sink isn't quite required, but 10 or 15 cents is good insurance.
Also, keep in mind that the heat production will drop quit a bit if this thing is running off of a more typical accessory voltage of, say, 14VAC. We only have to dissipate about 1.5 watts then.
In any case the total current draw is around half that of a typical light bulb found in many O gauge products.
For more complete systems of sensors and triggers such as that discussed in my thread on a multi-function unit the power consumption could grow quit a bit, but for a one-off unit it's not a big deal. For the other project I am looking at more efficient power supplies, but tend to gravitate toward the option of powering the modules through a separate, cheap, ATX power supply instead of track power. On those modules I think a design feature may be a jumper that allows direct 5VDC input to remove any power loss in the unit it's self.
JGL
