Table LED Matrix, Weeks of debugging, column problems

[nomad]

i'm not a C programmer but it looks like the line that says 4ms delay is your delay between rows. you could try making 259 a smaller number. i think that would get rid of your flicker but may make it even dimmer.

[mekohler]

i'm not a C programmer but it looks like the line that says 4ms delay is your delay between rows. you could try making 259 a smaller number. i think that would get rid of your flicker but may make it even dimmer.

There is no visible flicker in person. It only showed on the camera because of the fast framerate it captures at. The only problem is brightness.

Update: I tried increasing the delay...that helped brightness a little but made the flicker noticeable to the human eye

[Ioannis]

Yes, that's the price one has to pay, I 'm afraid. You cannot scan the matrix without a little flicker.

On the other hand, you may increase the current that LED's draw. Do you have the data sheets about that LEDs? Are they capable to withstand more than 20mA?

On a recent project I used Kingbright LED 5mm @ 20mA. They were really bright! They are 10000mcad and may replace car lamps (that's what I intend to do soon).

Ioannis

[mekohler]

Yes, that's the price one has to pay, I 'm afraid. You cannot scan the matrix without a little flicker.

On the other hand, you may increase the current that LED's draw. Do you have the data sheets about that LEDs? Are they capable to withstand more than 20mA?

On a recent project I used Kingbright LED 5mm @ 20mA. They were really bright! They are 10000mcad and may replace car lamps (that's what I intend to do soon).

Ioannis

Here you go! http://superbrightleds.com/specs/r3_specs.htm

Looks like it's 50 mA, what would your solution be?

Just connected to a 9V battery with the appropriate resistors they are too bright to look at directly. In my table, however, that is not the case :[ . There isn't any way to account for the scanning/duty cycle?

Thanks to all of you for the help so far

[Ioannis]

If you take a closer look at the spec's you presented, you will notice that the 1/10th duty cycle current is 200mA. That is, your ON pulse must be 100usec and the OFF width 900usec. Little tough, but you can do it. No flicker then!

So, choose the approrpiate timing to be that 1/10th ON and the resistors to give that 200mA and ... wear your sunglasses!

Also there is also the power dissipation of the LED, 125mW. You must never exceed this limit.

Ioannis

[mekohler]

I see what you're saying but I am at a complete loss right now

he Dlay loop is just the time delay until I move on to my next pattern/letter on the WHOLE table..in my real code it is modified to read the value off a pot so I can control the speed of patterns.

the i loop is to scan all 5 columns

the n loop is the delay between scans I believe...if I increase the n value then you can notice a flicker in the table as it scans...so If i program it to spell "Hi"...you can see the H flash on and off over and over, then it goes to I and flashes that on and off over and over...if n <259 there is no visible flashing/scanning...not even sure I need this loop!


That is all I have control over, and besides lowering/raising the n loop delay, I am not sure what I can do.

[Ioannis]

Well, I see that we both are not good at C, so why don't you drop it and use the PicBasic Pro that we all do here?

I am sorry but cannot help you more with the C program.

The tips at my last post I believe are enough to get your display bright enough at scan speed specified. But after that, the coding is another matter.

Ioannis

[T.Jackson]

i'm not a C programmer but it looks like the line that says 4ms delay is your delay between rows. you could try making 259 a smaller number. i think that would get rid of your flicker but may make it even dimmer.

The faster the better is what I concluded with all the research I did in this area. Forget about any sort of delay on top of pulse width control. Just scan the thing like a bat out of hell.