IC Identification

[johnsmith123]

Hi everyone.

I am trying to re-construct a VERY SIMPLE circuit that turns on a lamp once darkness is detected. The idea came from a small night light that plugs into an AC outlet. There is a small photo sensor in the unit that turns on the small 4 Watt night light when darkness is detected and turns it off when there is light in the room. The beauty of this circuit is its simplicity, and the fact that it does not require external power to drive a relay or some other components. It takes the power right from the AC outlet.

There is one component that I cannot identify, I was wondering if anyone can give me some help?

Here is a quick drawing of the circuit found inside the night light. I have also attached a photo of the Unknown IC. The IC comes in a TO92 package. I am sure it is not an NPN or PNP.

As it is now, the circuit does not work. The light stays on all the time. I suspect that the unknown IC is not functioning properly.

The photo resistor measures roughly 130 ohms in the light and around 2K ohms when the photo resistor is covered up.

 

[crutschow]

The unknown circuit is likely not an IC (integrated circuit) but a triac. It allows switching of an ac circuit with just one device. You just select the appropriate voltage and current rating for your application. For 120vac and a 4W bulb, a 200V, 1A triac should be more than adequate. They often come in different sensitivities. A higher sensitivity unit will turn off at a lower light level.

 

[kchriste]

You are not showing us the entire circuit. ie: the "bulb" is not shown. A quick search shows that the part is a SCR:
https://www.datasheets.org.uk/pdf/3750575.pdf
Is this for a LED night light? It would still work with a regular bulb but it wouldn't reach full brightness which is fine for a night light I guess.

 

[johnsmith123]

yes, thank you.

I figured out that it was an scr. I am trying to make the circuit work with an outdoor light (100 Watts or so)

I am not completely familiar with how these work so please bear with me.

What spec should I be looking for, in order to increase the amount of current/voltage the light bulb will receive?

In the datasheet I see the following:

On-State Current IT(RMS) = 0.8A
Peak Gate Current (IGM) = 0.1A
Gate Dissipation PG(AV) = 150W
Repetitive Peak Off-State Voltage = 400V

Any help is appreciated.
(I am mostly software guy)

 

[kchriste]

First off, building circuits that use AC line voltage which are to be operated outside, is very dangerous and not recommended for the beginner. You use a TRIAC to dim/switch AC lights:
https://www.epanorama.net/documents/lights/lightdimmer.html
I don't recommend that you build this yourself. Your hardware store should have something that will work.