“I'd rather regret the things that I have done than the things that I have not.”
― Lucille Ball

Thursday, April 14, 2016

Safety light timers

A couple of weeks ago I decided, as part of a still ongoing project to replace our safety lights, to install timer switches, as to automate the scheduled on and off times of these lights.

It took me some time to make a design that would have minimal impact on the existing electrical and physical installation.

The security lights are arranged in two groups, called East- and West-fence for the electrical wiring in the fences, as part of four groupings in total for all lights including the house ground- and first-floor. In case of a brownout or blackout, these groups are switched to the on-site generator.

We have three switches for each fence to select the lights we want to be activated: 1) front gate, 2) front fence, 3) side and back fence.

The final design is as follows:
Between the feed from the fence group to the switches I installed a timer-switch with sufficient capacity to support all the lights on that fence. So in total I have two timer switches, one for East and one for West. The maximum number of lights per group is 12 (West) and 10 (East). An 18 Watt energy saving light draws a current of  (theoretically 82mA) depending of the brand up-to 112 mA. This means that the maximum current to switch is 12 * 112mA =  1.34 A. I used a timer-switch that is capable to switch up-to 18A, so more than 10 times the requirement.
In this way the manual switches can still be used as we like, so no changes at all. If the light switches are unattended, we only have to be sure that the lights we want to be switched on by the timer-switches are manually pre-selected.

The timer-switch I used is an electronic one (Sassin 3SH18A) with a small digital display to program the switching times and an internal clock with battery backup, such that when there is a brownout, the clock will continue to run and the switching times are remembered. So after the brownout everything is functioning as usually again, without the need to program everything again.

You can with a single push button put the switch in manual mode. In case we don't want the timer-switches to take control of the lights, the switches can be easily put in manual mode, and hence they are not in control.

The advantage of having two (or more) timer switches is that you can program the on/off times differently such that it seems for external viewers that switching is done manually.

I was able to find the best place to install the two switches, such that I didn't have to install a new junction-box and or to dig holes in the wall. The chosen place was in the existing Circuit Breaker box for the four lighting groups, by adding two new slots for the timer switches.

Here are some pictures of the installation project.

East and West trio switches

Front panel of the CB box, to be adapted for installation of the timer switches

Drawing the perimeter for the timer switches and drilling small holes to copy the corners to the backside

Big holes drilled to allow the jigsaw blade to be inserted

Using the jigsaw to cut out the slots from the backside

Slots are made, only some polishing of the slots is required before installation and drilling 4 small holes for cable ties to fasten the switches
Adapting the wiring and connecting the timer switches
Installing the front panel and programming the timer switches


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