I want to order a few of the Velleman MK102 kits. Any idea what resistor would be needed to power this kit with 12vDC?
The BC547 is rated for maximum 45V. With the 1K current limiter, you’ll increase the LED power from about 7mA to 9mA. My guess is that they are just fine at 12V. If you want to be 100% safe, exchange R1 and R2 with 1K2 resistors.
Regards,
Jan