LED night light

[shadykassem]

need help

I know there have been discussions on these forums of LEDs as light sensors, but I don't remember seeing one used like this.
Fig. 1 **broken link removed** is a night light that uses the same LED for sensing and for illumination. I breadboarded it, and it worked. I'm not sure how useful it would be, but it demonstrates the principle nicely.
Fig. 2 supposedly works in the opposite fashion, but I didn't test it.

EDIT: Here is a more complicated, earlier version of the same idea.

First I want to thank you very much for that bright idea...
I want to make it but I face some problems I hope you could help me:
1- I could not find in my country ICM 7555 its not available at all so I searched and find normal 555 so I want to ask you will it fit instead of the 7555 and when I use 555 do I need to change any values of the resistance?
2- Also I could not find 1N914 and they told me 1N4148 H is the same...what do you think?
3- concerning the resistance values I want to be sure from R1 and R2 you mentioned R1 820 do you mean ohm or kilo and R2 390 Ohm or kilo just to be sure as I know values are very critical in that circuit
4- As for the red LED light in the night is it good I mean one can see from it? Or we need stronger light source and how could we implement it in the circuit?
Thanks again and sorry for disturbance...

I've modefied it to use less power.

Now it should only use 257.44µA.

I haven't tested it but it should work.

Thanks also for that nice modification but I need some clarifications:
1- You used R1 820 Kilo and R2 390K and collector resistance 390 Ohm am i right?
2- The transistor you used, which model or any one can fit; please recommend one for me
And if you have any comment on the above questions your advice is appreciated
Many thanks to all of you

 

[shadykassem]

I know there have been discussions on these forums of LEDs as light sensors, but I don't remember seeing one used like this.
Fig. 1 **broken link removed** is a night light that uses the same LED for sensing and for illumination. I breadboarded it, and it worked. I'm not sure how useful it would be, but it demonstrates the principle nicely.
Fig. 2 supposedly works in the opposite fashion, but I didn't test it.

EDIT: Here is a more complicated, earlier version of the same idea.

Dear Roff,
I want to thank you very much for that very nice idea and I want to make it my self...
But I’m facing some problems I hope you could help me
1- I could not find in my country ICM 7555 and after I searched I found only 555 is available so can I replace the 7555 with the 555 with out changing the circuit values?
2- The values of R1 and R2 I want to be sure about them are they R1= 820 ohm and R2= 390 ohm and not kilo ohm?
3- Also the diode 1N914 not available in my country so could I replace it with 1N4148 H they told me they are the same what do you think?
4- For the red LED light in the night is it ok, I mean one can see from it? And can we add more powerful light source in that circuit?

Many thanks again and sorry for the disturbance....

I've modefied it to use less power.

Now it should only use 257.44µA.

I haven't tested it but it should work.

Dear Hero999,
Thanks for your support and nice modification but I need some clarification from you
1- The transistor you used is which type or mode could you recommend one for me
2- The values of R1 and R2 I want to be sure about them you used R1= 820 Kilo ohm and R2= 390 Kilo ohm and collector resistance 390 ohm right?
Also if you have any comment on my above question your advice is appreciated...
Thanks to you all

 

[audioguru]

1- I could not find in my country ICM 7555 and after I searched I found only 555 is available so can I replace the 7555 with the 555 with out changing the circuit values?

The ICM7555 is a Cmos 555 made by Intersil. As I said earlier in this thread, the LMC555 is exactly the same made by National Semi and the TLC555 is exactly the same made by Texas Instruments. The old original 555 is completely different and would need to have the resistor values changed to work if it works in this circuit.

2- The values of R1 and R2 I want to be sure about them are they R1= 820 ohm and R2= 390 ohm and not kilo ohm?

The values are shown on the schematic.

3- Also the diode 1N914 not available in my country so could I replace it with 1N4148 H they told me they are the same what do you think?

The 1N4148 diode will work fine. Both the 1N914 and 1N4148 are affected by light so put black tubing around it.

4- For the red LED light in the night is it ok, I mean one can see from it? And can we add more powerful light source in that circuit?

RED LEDs do not produce much light. I don't know if a white LED will work since it has a phosphor.

4- The transistor you used is which type or mode could you recommend one for me

Any little NPN silicon transistor is fine. 2N3904 or BC547.

 

[shadykassem]

[/COLOR]
The ICM7555 is a Cmos 555 made by Intersil. As I said earlier in this thread, the LMC555 is exactly the same made by National Semi and the TLC555 is exactly the same made by Texas Instruments. The old original 555 is completely different and would need to have the resistor values changed to work if it works in this circuit.


The values are shown on the schematic.


The 1N4148 diode will work fine. Both the 1N914 and 1N4148 are affected by light so put black tubing around it.


RED LEDs do not produce much light. I don't know if a white LED will work since it has a phosphor.


Any little NPN silicon transistor is fine. 2N3904 or BC547.

Many Thanks audioguru you really helped me a lot