Arduino Forum

Using Arduino => LEDs and Multiplexing => Topic started by: masavone on Aug 28, 2012, 10:24 am

Title: Dual frequency and PWM
Post by: masavone on Aug 28, 2012, 10:24 am

I would like to control and visualize my home-made piezo (drop-on-demand) printhead with arduino. I have tested it with simple 555 timer with pulse width and frequency tuning. Also I did add a led in parallel with printhead so that it lights the drops synchronously. It works flawlessly but I want something more.

My idea was to use one timer for controlling the firing pulses. One potentiometer is for pulse length and another for period. Proper firing pulse is approx 0.05-5 us (depending on the liquid properties) and period 10 us - 5000 us. Probably this needs two timers, one for interrupt which starts firing pulse timer. Am I right?

Also I want to have another timer for LED(s). If this runs at frequency slightly (1 Hz) below the firing pulse frequency, the result can be seen as slow drops (moving at 1 Hz). The pulse duration for this can be fixed. If it is possible, even led pulses are then used for one coloured led and odd pulses for another led. For example blue and red. So it looks then like there are red and blue drops dropping slowly. This would be a great help for tuning the firing pulses (collisions of drops could be seen easilly). This two coloured thing is option and it can be easilly done with discrete logic.

So how to do this kind of pulse generator, where the frequency and pulse duration are controlled and another frequency (depended on the first freq) with fixed pulse duration (several us) is generated? Is it even possible with arduino?