Photocell and dimmer on same circuit bad?

[hurk27]

Just thought of a new design for a light controller, eliminate photo resistor, and heater, mount a magnifying lens over the bi-metal plate, make controller adjustable to aim at sun, let the sun do all the work?


Never mind, dumb idea, can't always have it mounted in the sun, and or it would come on when cloudy

guess I will have to go to work tomorrow, no million dollar patient this time.:roll:

 

[rattus]

Maybe:

Maybe:

The load current should not affect the operation of the photocell and thermal relay.

Could be though that in your experiment, the light from the lamp causes the photocell to open the relay.

 

[hurk27]

The load current should not affect the operation of the photocell and thermal relay.

Could be though that in your experiment, the light from the lamp causes the photocell to open the relay.

sure but it wouldn't keep the lamp on? wouldn't that turn the lamp off?

 

[ELA]

Nice diagram, but I have one problem, how does the heater cool off when the load is removed with power still applied to the photo cell?

hurk27,
I was careful to state that I had examined "one such device". There may be different flavors. It seems undesirable to have the load involved in the heater circuit though.
Maybe you could dissect your unit and diagram it?

 

[kwired]

Here is a link to one such a device that I took apart:
http://forums.mikeholt.com/showthre...a-photoeye-stop-working?p=1185675#post1185675

see post #18.

Here is the circuit as I traced it out:

I think that an upstream dimmer in series may affect the switching time since the heater power is changing.

Nice drawing, I tried to submit basically the same schematic yesterday but for some reason the forum would not let me upload it. Yours looks better than mine did, but contains all the same components.

An upstream dimmer would reduce the voltage to not only the load but also the heater and will effect the operation of it.

Nice diagram, but I have one problem, how does the heater cool off when the load is removed with power still applied to the photo cell? I have replaced hundreds of burned out lamps in post lights (popular around here) and every time the new lamp will light and go out after about 2-5 minutes, the photo cell I took apart had a resistor between the load terminal (red wire) and the point between the heater and photo resistor, it looked kind of like another part of the heater as it was wire wound, but wasn't close enough to the bi-metal plate to be part of the heating to open the contact.

So ok to make sure my mind is not going berserk on me, I just went out to my garage and hooked up a temporary lamp holder and a button photo cell I have for a job I'm doing tomorrow, (Kid's don't try this at home) I screw in a 60 watt lamp let it cycle off, unscrew the lamp wait 2 min's screw it back in, it stayed off, unscrew it again this time wait 10 min's screw it back in it comes on and 2 min's goes back out? all the time power wasn't removed from photo cell, next I hook up a two wire dimmer load side of photo cell, I turn it full bright lamp goes out, turn it off wait 10 min's turn it back on but leave it 80% dimmed barely glowing, lamp never goes out, last test, screw in a 4 watt (25 watt equivalent CFL) photo cell never shuts off? try a 7 watt (40 watt equivalent CFL) this one did shut off, but I have had problems with a 7 watt CFL before, 13 watt's CFL's work just fine, but if LED's only pull a few watt's they might be a problem, never tried them yet.

Output contact should not be dependent on the connected load, but instead the input voltage and quantity of light hitting the photo cell, will directly vary the amount of heat applied to the bimetal strip. How much light was hitting the cell when you changed the lamp.

If the load were needed in the circuit to create heat in the bitmetal strip then I would think connecting different loads would effect the operation of the unit. Not enough load may never turn off, too much load may cycle on and off. Each unit would have to be designed for a specific amount of load.

All of them I have seen have a maximum load rating but it is likely the contact rating and I can't recall ever seeing a minimum load rating on one.