Repurposing an old laptop power supply (18vdc) and dozens (actually - hundreds...) of white LEDs from old solar powered Christmas lights, to build an illuminated 'Merry Christmas' sign (a la Big Clive's Arcade sign).
The LEDs are made into strings of 5, each with a current limiting resistor, and a switching transistor to control the string. The transistors are switched from the outputs of multip...
This PCB allows you tu use a 74HC595 switch register an 8 TIP120 transistors.
That allows you to switch on and off 8 dc devices (up to 60V) with a microcontroller.
They can be daisy-chained to increase the nuber of DC outputs at will while using only 3 GPIO pins.
12V 50Ω solenoid driver. Can be chained to control more than eight solenoids.
The solenoid driver uses a shift register with a latch to control its outputs such that a singe microcontroller (e.g. Arduino) can control large amounts of solenoids whilst only requiring 3 output pins.
- Too big thermals reliefs on; U1-pin8, R12..R15, R24..R27 (they cool too quickly while solder...