12 V night sensing adjustable photo switch circut

Thread Starter

RemoWest

Joined Feb 9, 2015
33
I think this will work.

Photo transistor
http://www.mouser.com/ds/2/427/bpw96-222639.pdf
LM339N
http://www.mouser.com/ds/2/149/LM339-186212.pdf

50K pot 3362P-1-503LF
http://www.mouser.com/ds/2/54/3362-55248.pdf

Fet NTD4906N-35G
http://www.mouser.com/ds/2/308/NTD4906N-D-97762.pdf

Edit:
add schematic.
I think the led strips come with built in resistors.

Yes, the resistors are installed on the LED strip. They are 12 V ready.

Thanks , much clearer to understand when actual components are actually listed from the Mouser website. And much easier to put a parts list together, since I don't know enough about this to pick what I need.

On the "LM339N". Do I need one with "Open Collector, Open Drain or just Open Drain". Does it matter?
 
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Thread Starter

RemoWest

Joined Feb 9, 2015
33
Look on this site:

http://ee.old.no/library/

Most of the electronics construction kits include at least one light/dark detector, they all use the Cd-S LDR which is not RoHS compliant - but eBay still has plenty from China.

Some time ago; contractors did the emergency lighting and alarms in the flats where I live - I managed to rescue one of the twilight sensing outdoor lights they ripped out, the circuit I traced used a regular photodiode which is better suited to IR wavelengths - but it evidently worked. Maybe I can find the scan of that schematic if you need it.

Thanks for the info, appreciate it.

Sure. I would look at the schematic, if you could find it. Always ready to learn.
 

Thread Starter

RemoWest

Joined Feb 9, 2015
33

#12

Joined Nov 30, 2010
18,224
The mosfet in the schematic has thrown me for a loop. I cant really tell how it's wired in. it doesn't really look like any wires actually go to it.
From the drawing in post #38
I can't see a problem there. The gate is connected to a 51 ohm resistor, the source is grounded, and the drain awaits your LED load.
 

Thread Starter

RemoWest

Joined Feb 9, 2015
33
From the drawing in post #38
I can't see a problem there. The gate is connected to a 51 ohm resistor, the source is grounded, and the drain awaits your LED load.
Thanks for making that clear. I don't know why I cant actually see that from the schematic.:confused::cool:
 

ronv

Joined Nov 12, 2008
3,770
I'm not sure which one you are talking about. But the FET on the right has the source to ground, the gate to the 51 ohm and the drain to your led strip.
 

Thread Starter

RemoWest

Joined Feb 9, 2015
33
I'm not sure which one you are talking about. But the FET on the right has the source to ground, the gate to the 51 ohm and the drain to your led strip.
Ya. Thanks Ron. I think I got it now. I just didn't see it, don't know why.
 
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Thread Starter

RemoWest

Joined Feb 9, 2015
33
Parts should arrive an a few days. I'll let you guys know how it goes from there.

Thanks again to all who assisted, or offered to help. :)
 

Thread Starter

RemoWest

Joined Feb 9, 2015
33
It's been a few weeks. Got a lot going on and trying to get this thing going...:confused:
OK. I have the parts, tried to sort it out, but having a couple issues understanding the schematic.

On the LM339, there is a line going through the chip. Is that a branch of the circuit? I don't see it on the chip data sheet. I only see "3" legs of the chip I can solder on the LM339 on the chip data sheet. I assume the vertical line/leg on the schematic reflects the polarity under operation?, but I don't know. can you explain.

Also on the schematic on the photosensor I see a label that says "+ light". What exactly does this mean. could you explain that as well.
 
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ronv

Joined Nov 12, 2008
3,770
I'm not 100% sure I understand your question, but I think you are talking about the vertical lines coming out of the IC. If so those are power and ground that the chip needs to work. In the data sheets they are often called Vcc+ and Vcc-. Vcc+ goes to the + on your supply and Vcc- to ground.
The + light on the schematic is just there to indicate that that point goes more positive when light is shining on the transistor. Nothing hooks to it.
 

Thread Starter

RemoWest

Joined Feb 9, 2015
33
Thanks Ron. I'll try again to sort this out.

I only remember seeing 3 leads on the LM339... Your schematic shows 5.

Guess I'll look again at the data sheet.
 

ian field

Joined Oct 27, 2012
6,536
Thanks Ron. I'll try again to sort this out.

I only remember seeing 3 leads on the LM339... Your schematic shows 5.

Guess I'll look again at the data sheet.
The LM339 is a quad comparator - each functional block has 3 leads, then 2 more pins serve all 4 units with supply rails.
 
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