outdoor pir and positioning question

[steveo3002]

ive got a couple of outdoor lamps fitted with built in pir , they dont really work as id hoped

if i was to buy a decent quality pir to control them , does anyone know if they can be fitted close to the lamp? had planned to have it slightly above the lamp but fear the bulb might trigger it? dont really want it under the lamp

and...anyone got any thoughts on a okay quality pir

 

[madkayaker]

above is not much cop as it will detect the light when on. pir work better when target crosses detector

 

[steveo3002]

any ideas how far away? im thinking the 500watter jobs are only a couple of inches below

 

[madkayaker]

true but there behind the front of the fitting so stay dark

 

[brightspark]

above is not much cop as it will detect the light when on. pir work better when target crosses detector

pir work on heat so the light wont affect it .photocell works on light

 

[brightspark]

just get one of these http://www.screwfix.com/p/140-standalone-pir/11291

 

[steveo3002]

yeah thats the kinda thing i planned to get ...without sounding clever wont it sense the light bulb heat?

i know it might take a bit of trial and error but just trying to avoid 100s of holes in the house

 

[brightspark]

yeah thats the kinda thing i planned to get ...without sounding clever wont it sense the light bulb heat?

i know it might take a bit of trial and error but just trying to avoid 100s of holes in the house

as long as its not bang on top of a 500w halogen fitting it will be ok. leave a foot between it and dont have it near or facing a gas boiler heating flue

 

[steveo3002]

ok yeah will have a foot between where ive planned , and pointing away from the light a bit

and only normal 60 watters

 

[madkayaker]

yeah thats the kinda thing i planned to get ...without sounding clever wont it sense the light bulb heat?

i know it might take a bit of trial and error but just trying to avoid 100s of holes in the house

My advice ditch halogen fit led the payback time is very short in energy alone before you factor in bulb changing effort. Don't entertain the Fluredrnt equivalent there rubbish

 

[wheresmejumper]

Robus are a good reliable brand of sensor

 

[brightspark]

Robus are a good reliable brand of sensor

some are ok there ocupancy ceiling sensors are crap ive changed 4 in under a year under waranty in a school now to another make

 

[Fintray]

Steinel are good, I have put in quite a few different types over the years and never had to replace a Steinel.

 

[wheresmejumper]

I meant bloody steinel!
robus for downlighters, steinel for sensors

 

[rich r]

PIR sensors work by detecting a change in the amount of infrared (ie heat) radiation. I've made a few from scratch using IR phototransistors. So the light turning on makes no difference, as once it's on, it's no longer changing. The detection level is reset when the load is turned off so it doesn't retrigger immediately. But if the light has a metal body that gets hot when it's on, you want to avoid the PIR being able to sense that as it cools down. You can always mask off part of the sensor with tape if it's not possible to position it so no heat sources are in view. Better sensors come with plastic or foam sticky bits to selectively 'blind' the sensor like this.

I would go for Steinel too - I've used all kinds of PIR sensors (including some quite nice self contained units salvaged off cheap halogen security lights), but very few are as reliable or sensitive as the Steinel ones. The ones with two sensors with overlapping fields of view are very good - much better at detecting things moving towards them than single sensor units.

 

[steveo3002]

right steinel it is

i was playing about with the existing ones ...i found unmasked they worked only when its dark as expected , so i tried a bit of black tape to cut down the distance and it must have made the sensor think its dark so they trigger in daylight lol

rich..its only a 40 odd watt halogen = 60 w normal bulb , i doubt its going to get that hot in a few mins

 

[steveo3002]

right ..got one set up and no fires or burning smells etc heheh

can anyone offer any advice on masking off sections to blank bits off , ive got a triangle of lawn out the front then the road , im trying to get max coverage without picking up the cars

 

[brightspark]

right ..got one set up and no fires or burning smells etc heheh

can anyone offer any advice on masking off sections to blank bits off , ive got a triangle of lawn out the front then the road , im trying to get max coverage without picking up the cars

use some insulation tape and blank a small section off then walk test. if it works as required either paint that bit out black or leave the tape on if it will stick

 

[steveo3002]

yeah ive been playing tape , seems to be hard work getting it right

any ideas if curved shapes or hard angles make any diffo?

 

[brightspark]

its dificult to get them to cover a good aeria if there fairly low down .the higher the better as u can tilt them down to miss the road and still cover your garden. the tape would be fitted either side of censor if coverage was 2 wide