Motors and computers

[jdhurst]

The discussion on servo motors was interesting. The motor in this post is not a servo motor but it is still interesting (to me).

I have had a timer inside the front door of my house running the outside lights for many years. A number of these timers broke after a relatively short period of time.

About 5 years ago, I saw an Intermatic timer that claimed to be able to run a 15-amp load including motors. That, thought I, will not wimp under the load of three outdoor lights. And it did last very well.

Several weeks ago in Home Depot, I saw the same timer, and beside it was a newer Intermatic timer that claimed to be "set and forget" (auto sun up time, auto sun down time, auto Daylight Savings and so on). I purchased it, installed it, and it runs just fine (totally automatic as to on and off times for the lights).

So then I decided to dismantle the old timer to see what makes it tick. This was (to me) the interesting part.

The timer fits in a standard electrical outlet in place of a standard on-off switch and is about two inches deep.

In the front half, there is a circuit board with a display, and I discover it has been running on a single AA battery for the last five years with no connection whatever to the house wiring. I didn't even realize there was a battery in it when I installed it five years ago. I thought any ability to retain settings through a power failure was due to a large-value capacitor in the unit.

In the back half, there is a very large microswitch rated at 15 amps inductive with 14 guage wires welded to the terminals and exiting the case.

Then I see the motor. A really tiny little motor less than a half-inch long and less than 1/4 inch in diameter. It is connected to a triple gear set to raise the torque and slow down the end speed which in turn runs a simple cam that switches the microswitch on and off. The motor is much, much smaller than the motor in any 3.5 inch floppy disk drive unit.

So this design truly isolates the control circuit from the house wiring and permits very large inductive loads to be handled by the unit with no danger. All this in the same space as a standard light switch.

The new unit is a marvel. It is tiny circuit board that runs a display and a motor. Additionally, it is a many-year calendar (it doesn't say how many years), manages DST, contains a table of sun up and sun down times for 3 latitute zones (north (Lake Superior), central (Chicago), and south (Florida), and manages up to seven programs per day.

... JD Hurst

[marcos]

The US and Home Depot in particular are always a source of amazing technology for public use. I found the timer and the remote controlled valves of the sprinklers in my California home quite interesting. I ended having a quite functionaly timer altough I always choosen the most economical model. Upgrading to a rain-sensor was quite an achievement.

Now I live in an European flat with a terrace, and irrigation is pain in the [censored] even with the tiny tubing and valve I installed.

Sometime I miss California and the days spent at Home Depot.

[christopher_wolf]

Wow, pretty impressive for a timer; although I guess it is kinda the logical, and simple ( eletromechanical solution if you don't want chunky amps running through the control circuitry.

I haven't seen something like that, in most consumer equipment, at all. Maybe I should take a look at what they are selling in Home Depot now.

[Domain]

This thread makes me want to take apart my old Teddy Ruxpin from 1993!

"My name is Teddy Ruxpin, can we be friends? Well, first, why the hell are you destroying me! Ahhhh!"


There was a servo motor I believe in the mouth of the bear.