I recently began doing some maintenance on a small apt complex that has eight 250w metal halide shoe-box fixtures controlled by one stem mount (1/2" KO) photocell (and presumably a relay somewhere). Unfortunately the original electricians placed this photocell in a location that causes the lights to come on well before dusk and stay on until the sun is well up. It would be costly and unsightly to move the photocell, so my question is this. Is there an adjustable photocell unit commercially available that would allow me to adjust the sensitivity for later turn on and earlier off? The shutter on the existing unit is completely removed. What I want is to INCREASE the sensitivity of the unit. Any help would be appreciated.

Best solution: Go with a timer that's tied to sunrise/sunset. It's on and off times are computed.

Photocells ave way too many variables.

KISS,

The timer idea is fine except on really overcast days. I need the flexibility of the photocell to get the illumination before/after sunset/ sunrise. Also I would have to install a timer INSIDE the electrical panel that the photocell is mounted on. You know, vandals and all... I don't think I can do that.

Anybody else?

EPM

Wrong country. Wrong voltage, but it looks like your looking for something like this: http://www.roycethompson.co.uk/pdf/V16.pdf

Yeah, I saw that one. Can't find anything like it around here. I think the lights are 240v though. US source of supply anyone?

This is interesting: Hadco , PC1, Photocell (ADJUSTABLE FINGER) (PC1) :Lighting Superstore (http://www.louielighting.com/product/149484.html)

This isn't it either, but getting close: http://www.leviton.com/OA_HTML/ibcGetAttachment.jsp?cItemId=WSwQk9sPGBckBsEJDNajq Q&label=IBE&appName=IBE&minisite=10025

That Hadco link looks something like the one on there now. The other ones are 24v units for daylight harvesting systems.

Still looking.

What I have done in similar situations is utilize a time clock with the photocell. The timer basically allows the photocell to function when you decide by the times you set. It's not a fix all, but it may get you closer to what you want to do.

Yeah, we've used timeclocks with photocells too. Unfortunately the electrician wired the timeclocks BEFORE the photocells, so when the timer cut in, the MH light would strike and then go out only to come back on at dusk. Eats bulbs extra fast. I've disabled most of those by now. Also that only works if you are careful to keep the trippers adjusted just right, in which case the photocell isn't needed anyway. NOT something I have time to do. Around here it could be every 2 weeks if you wanted tight regulation. Remember, this is a parking and public area. If it gets dark, no matter what the time, I need light. But not BEFORE it gets dark.

I found this: ILC-USA :: Products (http://www.ilc-usa.com/products/ps_photo_sensor.asp)

I found this: ILC-USA :: Products (http://www.ilc-usa.com/products/ps_photo_sensor.asp)

That's close too, but all low voltage. I would need a separate enclosure on the side of the building which would be a bit difficult to make aesthetically pleasing. It would be possible though, but sounds like too much money. I need a direct drop-in line voltage unit.

Thanks for trying though.

One more issue you may have with an increased sensitivity photocell is false triggering from headlights at night. With high intensity lamps any interruptions would create a re-strike situation and there could be a few minutes of darkness. I think that I would find an electronic time clock, perhaps chronological and eliminate the photocell completely. If some of the lights need to be on when others do not, consider installing photocells in each fixture.

MB:

The datasheet seems to have all of that nonsense built in. For a robust environment, your going to need a robust solution.

Averaging sensor inputs would make it more robust. It has to have time delays too for clouds and headlights too.

I recently began doing some maintenance on a small apt complex that has eight 250w metal halide shoe-box fixtures controlled by one stem mount (1/2" KO) photocell (and presumably a relay somewhere)

This may not be as difficult as you think. Eight 250 W lamps have to be on a relay somewhere. Find the relay. Find how it's fed.

Lets go from there.

You may be able to pull some low voltage wire using the wire that's there. It has to go to the contactor, right?
Although odd, you may be able to use the existing wire for the sensor. If you can, then your basically home free.

Been away from this computer for a week. Sorry, but the schedule is tight. Thanks for all your input. Unfortunately it still doesn't come up to a solution that will work easily.

Missouri Bound: False triggering is no problem where this unit is located. The built in hysteresis of a photocell/bimetal switch will take care of that. Even at slightly changed trip point.

KISS: If it's on a relay, my guess is that it is a line voltage coil. Unless there is a dedicated xfmr right at the relay just for the coil. I'd have to find that though. It is nowhere on the panel where the current photocell is mounted.

Eight 250 W lights isn't going to happen on a single photocell. There has to be a lighting contactor somewhere or even a lighting panel.

Is the photocell 2 wire? Any make/model numbers? What do you actually have in the photocell box?

And just for giggles, anyway you can think of to go wireless?
Can you replace/add any of the wires if they are presumably in conduit?

I will have to check on the model of photocell. The photocell is mounted in a KO on the bottom of a big 200A panel with one breaker for the lights. It is just an adjustable stem mount unit a bit like the Hadco unit you linked to before. The whole place is wired with Romex, I don't recall exactly, but I think the light conduit would run out of the bottom of that breaker panel. I would have NO idea where there would be a contactor or lighting panel. There is no mechanical area inside any of the buildings except the sprinkler controls under one stairway in one apartment in each building. At least you give me something to check out now.

There are breakers that can be opened/closed with a contact closure. Rare, but possible.

Just like there is shunt trip and status contacts available for breakers as well such as this one: http://flamecorp.com/ETA/PDF/ETA,4930.pdf

I'd consider the breaker as the contactor idea.

Call me goofy but I had a similar problem with where my photocell was located. I elected to buy some fiber optic wire/cord about 1/2" thick and ran it about 10 feet onto my deck on the south side. It worked "better" . The next day I decided to add a reflector to get a bit more light. I tried a flashlight mirror and then ended up using a mr-16 halogen spotlight bulb. Broke off the end and put my fiber optic into that, towards the sun on my deck. The lighted end then got taped/glued to the photocell. Cheap. Works good. No electrician.
Goofy? Yes. $15 of fiber optic off eBay it may be worth a shot. Maybe there is an existing product, but I couldn't find one.
My next idea is to take apart a solar garden light and bypass the battery/charging and let the LED light up during the day next to the photocell. Maybe 2 lights/ 2 panels 1 light? Add 20 feet of tiny wire?? Again, goofy but damn near free.