- Jan 14, 2019
- Reaction score
I basically took apart my smart cord and started reverse engineering it...
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The red box is a +12V supply filter consisting of a 100uF Electrolytic cap and a smaller ceramic cap to filter ripple voltages(not sure the size without removing it from the board, likely 1-10uF).
The blue box consists of basically a +5V power supply and some resistors for the USB charger. The chip, U1, is an HC8813 DC-DC step-down(buck) voltage regulator. R8-R11 are resistors that tell your device, such as a phone, to start charging when it's plugged in.
The rest is what most of you are going to be concerned about. K1 is the momentary push button used to mute the detector. It has a capacitor, C5(1nF), to dampen it. The LED is fed by +12V and has a 6.8K ohm resistor. There's also an NPN transistor that is used by the detector to enable the LED when it's powered on and also flash the LED when there's an alert. I used a BC547 in my schematic below because its a TO-92 package and easy to solder or breadboard.
Below is a quick schematic of how the push button and LED are wired.
A = Alert which is the white wire in the Uniden cable
S = Switch which is the green wire
GND is black
+12V is Red
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