Example project · Analog & circuits
5 V regulated supply
A 7805 turns the 12 V barrel jack into a clean 5 V rail. Watch the voltmeter hold 5 V as you change the input.
How it works
The most common power stage in hobby electronics: a 12 V barrel jack into a 7805 linear regulator, 5 V out. The regulator holds its output at 5 V as long as the input stays roughly 2 V above it, burning the difference as heat: honest but inefficient (compare the buck converter in the fume-extractor build). The voltmeter reads the regulated rail live, and the LED runs from it through a 220 Ω resistor as a load.
What's on the bench
- 7805 Reg
- DC Jack
- LED
- Resistor
- Voltmeter
How it's wired
- hole B+4→hole a10
- hole a11→hole B-4
- hole a17→hole B-8
- hole d14→hole B-13
This project runs prebuilt firmware on the emulated board; open it in the simulator to watch it work and inspect every part live.
Try this
- Watch the voltmeter: ~5.0 V from a 12 V input.
- Raise the barrel jack to 15 V in the Inspector: the output does not move. That is regulation.
- Now lower it below 7 V and watch the rail sag: a 7805 needs ~2 V of headroom.
- Hover the IN and OUT pins: the 7 V difference is being dropped inside the regulator as heat.
