how to insert relay into circuit to add a backup lamp for 240VAC 50 Hzs veranda light

Thread Starter

JohnSSRSWITCH

Joined Sep 3, 2017
5
Good'ay, I currently have a 60 Watt incandescent bulb (230VAC 50 Hzs) on my verandah. It is switched via a motion sensor, and only operates at night due to the incorpoation of a photoelectric cell. My problem is that, when I am away from home, if the bulb element blows I then have no verandah light. Please help me to work out a relay circuit (with or without additional items such as Rectifier Bridge, Smoothing Capacitor, etc.) which will operate in the event that the filament in the primary bulb blows, so as to energise the back-up one. T.I.A.
 

WBahn

Joined Mar 31, 2012
24,854
One thought would be to put another photocell aimed directly at the first light (and shielded so that only a much smaller fraction of light from the second light reaches it). Have the system provide power to both bulbs, but use a relay or circuit in the path of the second bulb but that prevents it from coming on if light from the first bulb is hitting the sensor.
 

philba

Joined Aug 17, 2017
960
Simplest idea - add a second light in parallel to the first one. Replace the bulbs with lower power ones. Both will come on. When one burns out you will still have the other and will know to replace the burned out one. The odds of both burning out at the same time is very low. Also, move up to LED bulbs for a much longer life.
 

WBahn

Joined Mar 31, 2012
24,854
I would agree with philba's suggestion unless there is some reason that you need a single light (seems unlikely). This is one of the reasons why so many motion-activated floodlights come with two sockets (though, I admit, I tend to wait until the second bulb burns out -- but that's completely on me).

I'm not positive (haven't looked into it much) but if you live in a particularly cold climate then you may need to pay attention to the recommended ambient operating temperature for the LED bulbs you use -- the electronics in them may not like the cold.
 

WBahn

Joined Mar 31, 2012
24,854
Based on his greeting, I'd say he's dow-nunder. Probably more have to worry about ambient heat...
That's how one of my neighbors greets everyone. Of course, he's from downunder. ;)

But if he is located down there, I would definitely agree.
 

Thread Starter

JohnSSRSWITCH

Joined Sep 3, 2017
5
Based on his greeting, I'd say he's dow-nunder. Probably more have to worry about ambient heat...
You're correct philba, Creswick Victoria Australia. 5-6 months 0°C - 40°C (32F - F); 6-7 months -3°C - 12°C (F - F).
RE: LED's ambient temp. Maybe both heat and cold would be of concern. Need to investigate manufacturer's tech data sheets

Thank you philba and also to WBahn for your wonderful suggestions. I you were to see my trial schematics, I'm sure you'd go mad.
 

dendad

Joined Feb 20, 2016
3,084
I'm a couple of hours North of Melbourne myself :)
A change to LED lamps may be in order. And run a couple in parallel too. The power saved will be worth it as the running costs are a lot lower.
 

k7elp60

Joined Nov 4, 2008
555
If you still wanted to use a relay you could get a low voltage ac relay and connect the coil in series with the normal light bulb. Wire the replacement bulb with the contact common and the normally closed contact. When the original bulb burns out the relay will deenergize and the closed contacts will turn on the spare bulb.
 

philba

Joined Aug 17, 2017
960
If you still wanted to use a relay you could get a low voltage ac relay and connect the coil in series with the normal light bulb. Wire the replacement bulb with the contact common and the normally closed contact. When the original bulb burns out the relay will deenergize and the closed contacts will turn on the spare bulb.
What is the coil wattage for a relay like that?
 
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