PIR with Photocell

[Dr. Compynei]

Hi all,

Our house has a PIR with Photocell fitted in a Hi/Lo format. Basically, when dusk comes, it switches the outdoor lighting on at a dimmed level, and if the PIR picks anything up then it gets turned onto full power.

The unit has failed, and I can't seem to find a suitable replacement. I will soon be installing soffit downlights (12v with transformers, 3 of) and possibly 5 brick lights when the wall is rebuilt, at 40 w each. Couple this with two 60w spotlights on the garden to sit on the patio with, and three more 60w lights around the sides of the house then I think I will need something with a higher rating than the 150w that the existing unit can control. The exisiting unit has also failed anyway.

So just wondering if there was anything suitable that I could replace with? Or will I have to settle with either a simple PIR or Photocell?

Cheers, Neil

[Chewbacca]

Sounds like you want about 600w of lights, which sounds a lot to me. Have you considered LED lights, cool with a very long lamp life and cheap to run.

[Andrew Gabriel]

I've used a number of LED lights outside. Trouble with them is that good ones are completely silly prices, but if you make up your own, the individual parts are not at all expensive. I have been using the Luxeon

3W LEDs, and often found I can run them at 2W and get enough light, even using the warm white ones (which are less efficient than the blueish white ones). 2 x 3W LEDs in a brick light works very well, and the bricklight case makes a good enough heat sink even running at 3W each.

Must get round to posting some constructional pictures of the lights.

[Martin]

That would be brilliant - including where you source the component parts?

TIA

[cj]

[Andrew Gabriel]

Mostly from

I try to use only about 3 electronics suppliers, and of the 3 I use, Rapid have the best selection of power LEDs and optics to use with them. I haven't actually checked to see if there are cheaper suppliers, but note that the LED industry is flooded with poorly performing fakes, so if you find 3W luxeons on eBay at a price too good to believe, the price probably really is too good to believe for genuine parts.

The other key part is the power supply. You can buy LED (constant current) switched mode PSU's, but again, they are silly prices. I buy generic switched mode power supplies for a few quid, and add current foldback to the existing voltage foldback circuit. If you aren't up to modifying a commercial switched mode PSU, you could use a standard voltage stabilised one, with a current limiting resistor in series with the LED(s), although this will be less efficient (power is wasted in the resistor, so make sure you calculate and size the resistor for the expected power dissipation).

Another advantage here is that you can have the power supply indoors, and route a series cable around outside which is limited to extra low voltage, so you have no outdoor mains wiring. I have run up to 5 LEDs in series on one PSU - it was a 24V 1A PSU, but with my current limiting added driving the LEDs at about 500mA, it normally folds back to around 19V output, and total power consumption of the 5 LEDs and PSU is 10W (nearly all going into the LEDs - PSU barely warms up at all).

[Martin]

That's really helpful - thank you Andrew.

I'm obv well behind you on this - so will take time to digest it...!