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Anyone can help me wire LED night light?

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Forum topic by mahdee posted 09-20-2014 04:57 PM 895 views 0 times favorited 14 replies Add to Favorites Watch
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mahdee

3553 posts in 1232 days


09-20-2014 04:57 PM

Topic tags/keywords: traditional

Hi and thanks in advance,
I am trying to figure out how to wire 4 LED lights in series to a 9v outlet and using a photo sensor so it can turn on automatically at night. I don’t know how to read electrical diagram. These are the two ways I’ve tried:

This one worked sorta opposite; when I cover the photo sensor. it got lighter from being deem.

I was told to do it this way, but nothing happens.

-- earthartandfoods.com


14 replies so far

View wseand's profile

wseand

2754 posts in 2507 days


#1 posted 09-20-2014 05:56 PM

I believe when those are in the dark they get brighter. So it did exactly what it was supposed to do. It looks like a Cadmium Sulfide Photocell. So when it is light it turns itself off basically and in the dark it turns itself on. If that makes sense. Or did I read that wrong I am assuming it got brighter when you covered it.

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

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mahdee

3553 posts in 1232 days


#2 posted 09-20-2014 07:38 PM

Hi, thanks for the response it actually got darker when I covered the photo sensor.

-- earthartandfoods.com

View Slemi's profile

Slemi

103 posts in 1006 days


#3 posted 09-21-2014 06:12 AM

If You can post photo of the diagram we can surely help You. I hope You didn’t broke any of the material in process because it is very simple to do that.

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bodark

11 posts in 856 days


#4 posted 09-21-2014 07:37 PM

What is the part number for the transistor? Need to know if it’s an NPN or a PNP, and also the pinout.

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exelectrician

2327 posts in 1892 days


#5 posted 09-21-2014 08:07 PM

You are doing pretty good for ‘someone who can’t read wiring diagrams’, Keep plugging away you are well on the road to becoming very good at ‘electronics’
Oh! and there is a wealth of information at http://www.elektor.com absolutely the best hobby electronics magazine in the world. This magazine is where I got my start in electronics. Fond memories for me.

-- Love thy neighbour as thyself

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mahdee

3553 posts in 1232 days


#6 posted 09-21-2014 10:48 PM

bodark, it is an NPN switch transistor (2N4401).

exelectrician, I hate to be ignorant, although I realize if I knew everything I could be some sort of god. Nevertheless. I am going to spend the next few weeks to at least read a simple electrical diagram.

-- earthartandfoods.com

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mahdee

3553 posts in 1232 days


#7 posted 09-21-2014 10:56 PM

I used this website as a reference:
http://www.evilmadscientist.com/2007/a-simple-and-cheap-dark-detecting-led-circuit/

Then I looked at this which I didn’t get:
https://www.youtube.com/watch?v=_dcjzJfQZHk

-- earthartandfoods.com

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bodark

11 posts in 856 days


#8 posted 09-22-2014 12:13 AM

It looks like you’re on the right track – bear with me and I’ll try and step through it.

The pins on the transistor all do different things depending on the type. On this particular package, if you hold the transistor with the pins pointing down and the flat side of the body towards you, then the pins from left to right are the emitter, base, and collector. On an NPN transistor, the way it works is that when you apply a voltage to the base the transistor allows current to flow from the collector to the emitter, just like a switch.

So first, take the red wire from your power supply and connect it to the red wire on your LED, and to one end of the resistor (doesn’t matter which end). Next, connect the black lead of the LED to the right hand pin on the transistor (the collector). Then, connect the other end of the resistor and either end of the photoresistor to the middle lead of the transistor (the base). Finally, connect the other end of the photoresistor and the left lead of the transistor to the black lead from your power supply. Then, go sacrifice a chicken, cross your fingers, and try it. Hope it works.

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mahdee

3553 posts in 1232 days


#9 posted 09-22-2014 01:30 AM

bodark, thank you so much for your help. I almost set the couch on fire trying to figure your solution and my wife informed me that this experiment was not going to happen inside the house. I will try your solution as soon as she is out of the house (lol) and report right away. Thanks again.

-- earthartandfoods.com

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Grandpa

3256 posts in 2140 days


#10 posted 09-22-2014 01:43 AM

Tuned for minimum smoke….LOL

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mahdee

3553 posts in 1232 days


#11 posted 09-22-2014 10:19 PM

O.K., bodark. the wife is out of the house and it now partially works. When I cover the photo sensor, the light dims but does not turn off. Should I be using a second diode? Current one is 100k:

-- earthartandfoods.com

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mahdee

3553 posts in 1232 days


#12 posted 09-23-2014 12:09 AM

Never mind, I got it and it works! although not as strong as a beam I hoped for… Thanks again.

-- earthartandfoods.com

View bodark's profile

bodark

11 posts in 856 days


#13 posted 09-23-2014 03:09 AM

Cool! Glad you got it going!

View exelectrician's profile

exelectrician

2327 posts in 1892 days


#14 posted 09-23-2014 06:08 AM

Now go and buy a ‘bread-board’ you will be flying through different circuits like a pro in no time, no soldering required.

-- Love thy neighbour as thyself

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