Hi guys would like to know if this circuit is good cause I am trying to make ldr more sensitive without success.
Any help please?
Thanks
Any help please?
Thanks
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Component values, please.Hi guys would like to know if this circuit is good cause I am trying to make ldr more sensitive without success.
Any help please?
Thanks
Quite correct, as it should be. So ...LEDs to mains are a restricted topic, as per the Terms of Service.
Couldn't resist. I built it.View attachment 106875
Quite correct, as it should be. So ...
Will it work? Probably. Adjusting sensitivity? Not knowing anything about the light sensitive component all I can suggest is to adjust resistances until you get what you want.
Now that we have the voltage down, the transistor can be just about any NPN you have on hand. 2N3904 is cheap.
R1 - 150 or so
R3 - 220 o 1K, adjusted for desired brightness
R2 - depends or RT1
RT1 - ???
Zener - 1N751, or what ever you have on hand
Transformer - At least 50 mA, or so, what ever you have on hand or can find. Or ...
Base voltage will be V LED, + V R3 + about 600 mV = ? V
As light decreases RT1 resistance increases until "? V" is reached and the LED turns on.
What is the resistance of RT1 at that point? That gives you a value for current. Add 1 mA or so for base current. Then you know voltage and current and resistance for R2.
adjust for sensitivity.
I didn't bother to simulate or build it, but it should work.
Just a tad overkill for a night-light? .a LED headlamp (12x 5mm white LEDs)
Hi circuit is exact. That cds is an ldr I imagined yes?View attachment 106875
Quite correct, as it should be. So ...
Will it work? Probably. Adjusting sensitivity? Not knowing anything about the light sensitive component all I can suggest is to adjust resistances until you get what you want.
Now that we have the voltage down, the transistor can be just about any NPN you have on hand. 2N3904 is cheap.
R1 - 150 or so
R3 - 220 o 1K, adjusted for desired brightness
R2 - depends or RT1
RT1 - ???
Zener - 1N751, or what ever you have on hand
Transformer - At least 50 mA, or so, what ever you have on hand or can find. Or ...
Base voltage will be V LED, + V R3 + about 600 mV = ? V
As light decreases RT1 resistance increases until "? V" is reached and the LED turns on.
What is the resistance of RT1 at that point? That gives you a value for current. Add 1 mA or so for base current. Then you know voltage and current and resistance for R2.
adjust for sensitivity.
I didn't bother to simulate or build it, but it should work.
Try a smaller pot.1K or 5K.Hi circuit is exact. That cds is an ldr I imagined yes?
Is the zener important? what is it's function?
I did a 1meg pot instead of the 150k but still ldr not sensitive enough.
Any clue?
Thanks
Thanks for response. Yes but zener is controlling the voltage then of the circuit cause when I removed it leds stayed on.Try a smaller pot.1K or 5K.
The working range of the LDR is down in the hundreds to thousands of ohms. No, the value of the Zener is not important. It just sets the operating voltage of the rest of the circuit. 5.1 V is just a suggestion. Actually when I built the circuit I just used a 5 V power supply. No Zener or R1.
Yes, removing the Zener throws operation off unpredictably. It just doesn't have to be 5.1 Volt. A little higher would still work. You just need to adjust calibration for the changes.Thanks for response. Yes but zener is controlling the voltage then of the circuit cause when I removed it leds stayed on.
If you connected the post #1 circuit directly to the mains that's not surprising . Didn't you heed the post #3 warning and use a transformer as per post #5?Today this circuit made an explosion when connected it to mains :0
Do you mean you're using a cap as a voltage-dropper, instead of using a transformer? If so, that's a circuit contrary to the Terms of Service!I did not connected direct to BR. There is a 224j cap before br.
This was made like that; a chinese nightlite circuit with a capacitive transformer. I am trying to fix it.Do you mean you're using a cap as a voltage-dropper, instead of using a transformer? If so, that's a circuit contrary to the Terms of Service!
Well, capacitor as an AC resistor. They use the capacitive reactance to drop the voltage.This was made like that; a chinese nightlite circuit with a capacitive transformer. I am trying to fix it.
Yes one of the problems is the 5k resistor ; I think it was too low so that was a sort of short.Well, capacitor as an AC resistor. They use the capacitive reactance to drop the voltage.
by Duane Benson
by Duane Benson
by Aaron Carman
by Duane Benson