perhaps you can help out.
So, I'm making a prop replica and light is a big part of it. To this end, I picked up three cheap LED torches, which have arrays of 9 LEDs in each. Cheaper than I could buy the LEDs separately!
Firstly, to power them I was thinking I'd use a transistor to switch them on and off, as the microcontroller couldn't handle the load if it was to switch them directly. Can you recommend a transistor that'll happily switch enough current for the 27 white LEDs when I give it a low-level signal from the microcontroller?
Secondly, as I dismantle the torches I notice they don't have any resistors in series with the LEDs. The LEDs themselves are connected in parallel, and run from three batteries (providing 4.5V) and I was thinking I'd connect the three arrays also in parallel -- so 27 LEDs in parallel, effectively.
I'm using a 5V power supply for all this, and I'm thinking the extra half volt shouldn't worry the LEDs too much, right? But do I need to add any series resistors in here, given that there weren't any in the torches?
Thanks in advance for all your advice!