The "Autos Dias" Project.

JavaCo said:

You didnt by any chance take it lower then a 100Hz did you. Just wondering what would happen to a meanwell if you ran the frequency lower then specs

Click to expand...

I did go lower than 100 Hz ...
I tested 50 Hz ..(@ 10 % , 30 % , 50% & 80 % duty cycle )
It works as it is supposed to work .
It flashes the COBS 50 times per second .
Still ,there's a disturbing buzzing sound coming from the drivers ,when they go "OFF" .
( i.e. DIM- & DIM+ shorting for 500 ms per second ,when duty cycle = 50% )

I 'm guessing that the coil windings ( wire wraps ) are getting some serious magnetic "slaps" ,over there ...
50 Hz falls in the audible range ...
I can hear the coil windings being " beaten up " .

Cheers.

Is there a practical application to say increase to 100 hertz [doubling your clock] and reducing duty cycle increments?

Just curious as a I had a very recent practical application conversation of PWM in general, not necessarily for a led drivers..... Although, they referred to it as wave change initially.....

Abiqua said:

Is there a practical application to say increase to 100 hertz [doubling your clock] and reducing duty cycle increments?

Just curious as a I had a very recent practical application conversation of PWM in general, not necessarily for a led drivers..... Although, they referred to it as wave change initially.....

Click to expand...

case 1 : frequency 50 Hz ,duty cycle = 50%
drivers will be flashing the cobs 50 times per second .
1 sec = 1000 msec . 1000 / 50 = 20 msec .

Each on/off cycle will have a period of 20 msec .
Since 50% of the 20msec is "on" state ,then for every cycle of 20msec ,10 of them cobs are off & the rest 10 msec
cobs are on .

50 Hz * 10 msec = 500 msec per second @ "On " state ..

case 2 : frequency 100 Hz ,duty cycle = 25 % (= 1/4)
1000/100=10 msec
10 *0.25 = 2.5 msec

100 Hz * 2.5 msec = 250 msec per second @ "On " state ..


case 3 : frequency 100 Hz ,duty cycle = 50 %
1000/100=10 msec
10 *0.5 = 5 msec

100 Hz * 5 msec = 500 msec per second @ "On " state ..



So you see ,even if clock doubles ,as long Duty cycle remains the same ,overall on/off times(duration) ,
remain the same .

if duty cycle changes ,then the ratio ON/OFF time change too,no matter the frequency .

The frequency sets the period of an "ON/OFF" cycle .
The duty cycle sets the time ratio between ON & OFF states,of a full cycle's period .

I wonder if it will damage the driver going below 100 Hz. Might write Meanwell a email asking them. See what they have to say about it.