Friday, March 10, 2017

48 LED Infrared Spotlight Schematic ... bought on eBay

This is the schematic for a spotlight available on eBay as of 2017m03d01 ....

Purchased qty 4 from eBay      ~ $3 each    with CdS photocell  12VDC

When dark , spotlight should turn on.  When dark , CdS in series with 345K resistor causes voltage to base of Q2 ( PNP ) to drop below voltage at emitter which is approximately 6v  ( using forward drop of IR LEDs as voltage reference )   ...Q2 turns on current flows into the base of Q3 ( NPN ) through a 1K resistor.     The emitter is tied to ground.  Q3 turns on and
Q1 is a power transistor that connects to 8 Strings of LEDs with a 27 ohm resistor in series in each string.  Q1 has a 2.2 ohm resistor between it’s ?? and ground.  This is used for current sensing.  

There are 11 resistors, 3 transistors , no capacitors , no inductors.  IRC can turn Spotlight on and off.

The coating on this PCB is very dark and hard to scratch ... so following the traces was difficult.

The 27 ohm resistors typically have 1V across them when the spotlight is on. This means 36 ma is flowing through each string or about 288 ma for 8 strings. the voltage across R3 is about 0.6V which is 272 ma. My DMM is a $5 cheapie .... so these readings are approximate.


I measured one diode chain as 11.66 VDC , 10.22 , 8.75 , 7.30 , 5.86 , 4.43 , R10 , 3.45 , 2.01 

tags:   #48IRLEDSpoghtlight   777IRLEDSpotlight             99guspuppet

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