But if I want the LEDs to actually be bright, I probably need to use the sensor to activate a relay, right?
I know this is basic as shit, but I'm having a blast
Update: first trial with the planned number of LEDs and pillow stuffing, looks fantastic!
Ah it's always satisfying when a project starts showing signs of ~~correct operation~~ life
You don't need a relay, you can either buy an LED driver IC or some discrete transistors and resistors. Unless you want the satisfying clicky-clicky sound (yes that is a technical term).
How do I calculate which transistor to use?
Bc 547 should be in your spare box so buy a dozen even if it's not the best fit now.
I don't remember Mosfet codes but you may want one. However this is for many milli amps, I'm concerned on things catching fire without proper ventilation. A quick search gave me IRF540N. It's the TO-20 package that gives the hint of operating power, that metal back is for screwing a heat sink. Watch your fingers when it works properly.
I still need to run the numbers to figure out exactly which transistor fits this application, but I feel like anything getting that hot isn't properly matched to 8 LEDs