Creating Strobe FX on a 7Segment

[Mosaic]

Hi all:

I made a mistake while doing the PWM for dimmer control with a 4 digit 7 seg. display and I got an interesting effect.

I believe it can be useful as a highlighting technique.

Rather than run the PWM dimmer from the same timebase as the strobe routine, you can run it from a slightly different time base or from a dynamic time base once the time bases are within say 20-50% of each other.

What happens is u get a modulating beat (wave) pattern occurring , this shows up as a bright band passing across the digits. If u have a sensor feeding the PIC u can actually have the band change speed based on the sensor value, by using the sensor value to alter the timebase.

I think it could be useful for alarm functions as peripheral vision is disturbed by this odd wave effect on the display. It attracts attention even if u r not looking directly at the display.

BTW, u can't simulate this....it's gotta be done on a real prototype.

It's also a useful way to show that data is changing rapidly (fast moving band) while displaying 1/2 sec legible readout snapshots on the 4 digit display, eg RPM.

 

[Mosaic]

Strobe Update:

While achieving a better than 50Hz refresh rate for all the LED digits is required to avoid flicker, you have to consider the PWM dimmer as a direct modifier of this.

If u have a refresh rate of 5 ms per digit for a 4 digit display that totals 5x4 for 20ms which is 50Hz. BUT if u introduce pwm dimming you must compensate with a faster refresh rate.

If u use a 50% DC PWM your refresh rate needs to be 2x as fast etc. A 25% PWM dimmer requires a refresh rate 4x faster than the minimum. So that means 1.25ms/digit rather than 5 ms.

 

[Mike - K8LH]

please disregard....