LDR LED spotlight

334

04:39:36

Light Dependent Resistor (potentiometer) decreases resistance (turns to ground) when exposed to light, shutting the spotlight off, when darkened the resistance of the LDR increases, thus stoping the shunt on the base, triggering the relay to power up and turn on the spotlight, 19.4kOhm is my latest test and starts just before sunset and ends just after sunrise

This starts with sun up, noon time light levels, lamp off

New:
I made a tree (looks more like a telephone pole) that shows the LED "mounted" to the tree with circuit laid out just about how it is in reality, circuity with relay and transistor is near the battery under the hood of the truck and the LDR takes a little trip to just Infront of the grille of the truck, as to capture daylight information without interfering with itself.

UPDATE:

Switched from a BJT to a MOSFET and upped gate/base resistance to 19.4k Ohm. Added a diode reverse biased across coil to protect the MOSFET from surge through the coil when switched, blew my BJT's this way, hence a MOSFET now.

published 9 years ago

BillyT

9 years ago

Here is a circuit that I did a couple of days ago, I did away with the relays to decrease the current consumption. Feel free to use as you like. http://everycircuit.com/circuit/4559448240816128

ETJAKEOC

9 years ago

I was going to use a more passive circuit but the LED I'm using is actually a 12V turn signal blinker LED replacement, these were just spare parts I had laying around so this is what I ended up building, the relay's just because I didn't want to drop 3W across the transistor

2ctiby

9 years ago

Can be done without the relay http://everycircuit.com/circuit/5988286820777984

ETJAKEOC

9 years ago

Yes, I know that as I previously stated though it didn't suite my needs, my circuit also has to disable the positive flow to the LED otherwise the ground loop through mounting it to a tree would keep the light on at a dimmed state, hence why I went with a relay for my build

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