I just got home from Home Depot and could not find these. Do you have a link or more info? Thanks.FWIW, I have outdoor light sockets that have adjustable light sensitivity and adjustable turn-off times. They do this function exactly and are less than $10, I think.
I use these to turn off my "gaslights". They used to be on all night long and that seemed like a waste to me.
I did find one for about $10, but the minimum on time was longer than I wanted.See the links I posted here. I had trouble finding it, so I hope you have more luck.
I have attempted to build the circuit you posted, as reflected in the schematic below. In order to make testing of my breadboard easier, I replaced C3 with a 10uF electrolytic, and added an LED/resistor to the output of U1; I have not built the optocoupler/triac portion of the circuit.Consider this:
As expected. Isn't that what you wanted? You need to screen the LDR so that it's not illuminated by the night-light.When LDR1 is dark, U1, pin 3 is high, but as soon as LDR is illuminated U1-3 goes low
No, that's not what I wanted. See post 1.As expected. Isn't that what you wanted? You need to screen the LDR so that it's not illuminated by the night-light.
At dusk, LDR1 goes dark, so U1 is switched on by Q1 and will start timing. Pin 3 goes high immediately and the night-light gets switched on via the opto-coupler. You said "When LDR1 is dark, U1, pin 3 is high". So far, so good. But you must ensure that the light doesn't shine on LDR1 otherwise, as you said, "as soon as LDR is illuminated U1-3 goes low."I want a light inside my chicken coop that comes on at dusk, and stays on long enough for the chickens to get on the roost, and then goes off and stays off until the next evening.
There is no light that comes on with my breadboard. All that comes on now is one 5mm LED to indicate that U1-3 is high. The only time U1-3 is high is when the LDR is dark. In other words, the one-shot isn't working.Post #1:
At dusk, LDR1 goes dark, so U1 is switched on by Q1 and will start timing. Pin 3 goes high immediately and the night-light gets switched on via the opto-coupler. You said "When LDR1 is dark, U1, pin 3 is high". So far, so good. But you must ensure that the light doesn't shine on LDR1 otherwise, as you said, "as soon as LDR is illuminated U1-3 goes low."
When U1 times out, pin 3 goes low and the light goes off. So far, so good.
At dawn, LDR1 goes light. This causes Q1 and U1 to switch off. The light was already off at the end of the timed period.
That actually crossed my mind, but I didn't try it until you suggested it. It works!! and reduces the part count by 2. As you can see from the posts in this thread, I have been struggling with this for quite a while. Thanks much.Why not remove the coupling capacitor C4 and directly couple? I think a slow swing at the op-amp (which you might overcome using a comparator instead) causes R2 to hold the trigger high. The coupled pulse across C4 never pulls the trigger low enough to start the timer.
At one point, I had a rudimentary understanding of op-amps; alas, that (like a lot of other things) has slipped away from me.We seem to be having a discussion about what happens to the resistance of the sensor when, "dark" happens. Did I get it backwards?
So, reverse the positions of the sensor and the pot, or reverse the inputs of the op-amp. Hint: The two transistors I drew are a simple op-amp! You can make a feedback circuit to either input of the differential pair if you put some resistance between the voltage reference and the base. Then about ten times as much resistance from something that goes high or low when the proper output happens. Am I going right over your head? Maybe I should shut up because you have a working circuit.
by Jake Hertz
by Jake Hertz
by Jake Hertz