LED Beat Frequency Video

LED Beat Frequency module is ready and working. Pictured is the new version with FlatKeys FK50240 top octave generator. Right side is the 2MHz crystal clock that is divided by 16 with 4520-counter to get the 440Hz A. Left side is the LED Beat Frequency circuit that I found here: www.tradeofic.com/Circuit/3962-HI_L0_LED_FREQUENCY_DISPLAY.html
I changed it to CMOS-logic and added a 4.7k resistor from NPN-transistors (2N3904) collector to +12V. Both the reference and external inputs have this transistor circuit. I also added output-jack for the reference frequency so this module can also be used as a traditional tuning-reference. The video shows this module in action. L-channel is the tuning reference and R-channel is the external VCO that is tuned. First I switch the tuning reference to C. Then I tune the external VCO to unison. After this I tune the external VCO to perfect fifth G (notice the different LED-beat pattern). Then I tune the VCO to perfect octave. If you look at the LED's carefully you can also tune to other intervals but unison, perfect fifth and the octaves are the easiest. Notice also how the LED's show precisely the slow beating of the frequencies when tuning is almost done.


BeatFreq1 from Mauno Tuominen on Vimeo.