PUT LED flasher V1

The next circuit is based on the PUT relaxation oscillator to make a LED flasher that generates a flash approximately every second when the power supply voltage is about +12V DC.
R3 (10K) determines the ON-time of the LED and thus the pulse width of the flash. With R3 = 10K, the pulse width is about 11ms.
The value of R5 in the schematic was chosen for a power supply voltage of about +12V DC.
Increase R5 when higher power supply voltage are used, so the current through the LED is about 15mA for high efficiency LEDs.