The connections are as follows:
- [+5 V from arduino pin] => 680 Ω resistor => C1815 transistor's base pin (3)
- [+14 V from variable power supply] => C1815 transistor's collector pin (2)
- [C1815 transistor's emitter pin (1)] => Load => [Negative from variable power supply].
Oscilloscope probe connected at C1815 transistor's emitter pin (1).
Oscilloscope probe's ground connected at negative from variable power supply.
The arduino PIN in outputing 5v for 1 second, and then 0v for another second in a neverending loop, producing a square-wave pattern on the oscilloscope.
The problem is as follows:
When the variable power supply is turned off, the oscilloscope displays alternating voltage between 0 and 1.5 V.
However, when it's turned on, it displays alternating voltage between 0 and 5 V.
My understanding it that it should alternate between 0 and 14 V, since the collector voltage is 14 V.
Where am I wrong?