Author Topic: Ideal speed for LED Matrix  (Read 5385 times)

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Offline Electroalek

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Ideal speed for LED Matrix
« on: July 26, 2012, 10:06:57 pm »
I made one LED matrix with 4017. I started programming it myself. The only problem is the timing. I want to ask what is the preferred speed for the human eye to recognize as one image ?
P.S. This LED Matrix is controlled with PC via the parallel port and I program the LED Matrix with VB.Net. 
« Last Edit: July 26, 2012, 10:14:27 pm by Simon »
 

Offline Simon

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Re: Ideal speed for LED Matrix
« Reply #1 on: July 26, 2012, 10:16:17 pm »
why did you remove your last topic and then start again on the same subject ? You know the idea of a forum is that it is the collective knowledge of the users and in time to come others can come and read the discussion and gain from it. Why do you have an obsession with deleting your topics ?
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Offline Electroalek

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Re: Ideal speed for LED Matrix
« Reply #2 on: July 26, 2012, 10:26:52 pm »
I knew that you will say this. I removed the last topic because no one replayed. And can you please give me answer ?

« Last Edit: July 27, 2012, 06:11:48 am by Simon »
 

Offline KTP

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Re: Ideal speed for LED Matrix
« Reply #3 on: July 26, 2012, 10:41:08 pm »
In our matrix, we found that refreshing each LED at >60hz caused no flicker.  Because I was also concerned with fluorescent lights at 60hz, we increased the refresh rate to 90hz.

As low as 50hz looked *ok* but you got the impression after several seconds that something was not quite right with the image.  40hz or so was very noticable flicker.



 

Offline Electroalek

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Re: Ideal speed for LED Matrix
« Reply #4 on: July 26, 2012, 10:51:08 pm »
Thanks KTP,
90Hz yess, but how to convert it to seconds ?
 

Offline David_AVD

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Re: Ideal speed for LED Matrix
« Reply #5 on: July 26, 2012, 11:03:48 pm »
Thanks KTP,
90Hz yess, but how to convert it to seconds ?

You have to convert to Fathoms first.   ;D
 

Offline KTP

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Re: Ideal speed for LED Matrix
« Reply #6 on: July 26, 2012, 11:04:36 pm »
Thanks KTP,
90Hz yess, but how to convert it to seconds ?

Are you asking how to convert hertz to seconds?

Frequency is measured in hertz (abreviated hz)

Time in seconds is simply the inverse of frequency in hertz, ie 1/frequency

So 90hz = 1/90 seconds = about 11.1 milliseconds
 

Offline Psi

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Re: Ideal speed for LED Matrix
« Reply #7 on: July 26, 2012, 11:13:00 pm »
Yes, ~100hz will be fine from the eyes perspective.
Around 60hz it appears ok when looking straight at it but if you shift your vision and see it out of the corner of your eye you will see the flickering.

Most LEDs are pulse rated at 1khz, so if you want to drive the LED at its pulse rated current you need to use what the datasheet says.
If you're just driving it as normal current then it doesn't matter.
« Last Edit: July 26, 2012, 11:15:38 pm by Psi »
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Offline Electroalek

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Re: Ideal speed for LED Matrix
« Reply #8 on: July 27, 2012, 12:54:40 am »
Thanks ;D
 

Offline Simon

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Re: Ideal speed for LED Matrix
« Reply #9 on: July 27, 2012, 06:15:07 am »
I knew that you will say this. I removed the last topic because no one replayed. And can you please give me answer ?

And what was that going to achieve except for throwing away what little information you had gained ? continually asking the same question annoys people particularly if you delete a thread and then restart it, it is like creating identical topics all over the forum in different sections. The way you go about things does not exactly inspire people wanting to help.
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Offline Jon Chandler

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Re: Ideal speed for LED Matrix
« Reply #10 on: July 27, 2012, 06:19:13 am »
The way you go about things does not exactly inspire people wanting to help.

Well, at least his logo is slightly smaller than it was.  If he cuts in it half again it will almost be tolerable.
 

Offline Simon

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Re: Ideal speed for LED Matrix
« Reply #11 on: July 27, 2012, 06:50:57 am »
The way you go about things does not exactly inspire people wanting to help.

Well, at least his logo is slightly smaller than it was.  If he cuts in it half again it will almost be tolerable.

Yea I might end up doing it myself. As it is I have to keep removing the annoying scrolling text he puts on most posts for his silly blog.

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Offline OndraSter

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Re: Ideal speed for LED Matrix
« Reply #12 on: July 27, 2012, 09:26:17 am »
Pff 90Hz :D

I have got 32x48 dualcolor (red + green) LED matrix built from those 8x8 modules (24 in total) and I am always showing two lines at once. (I got a lot of Allegro A6275 drivers for free.)

In order to be able to get different "shades of colour" I had to go much, much higher. Each line I am now refreshing at over 400 times per second. The ATmega is pumping over 1.2Mbps on SPI!

Also the whole firmware is written in pure ASM :D
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Offline KTP

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Re: Ideal speed for LED Matrix
« Reply #13 on: July 27, 2012, 11:39:07 am »
The 90hz was for the refresh rate

We are also doing color (15 bit color, so 32768 colors) but doing the color using PWM of each element (5 bit per element).

The serial line from the Xmega to the shift registers runs at 16Mbit  ;D

Edit:  Not really one line...actually 6 lines, each shift register gets its own data line...clock and latch are the other two bits in a byte that the Xmega DMAs out.  So overall it might not be 16Mbit...I haven't added it up since my wife switched to assembly.  I know she was able to use virtual ports to get single cycle toggle for the clock data and the Xmega is running at 32mhz.
« Last Edit: July 27, 2012, 11:45:46 am by KTP »
 

Offline Electroalek

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Re: Ideal speed for LED Matrix
« Reply #14 on: July 27, 2012, 07:17:17 pm »
Can i get 100Hz from 555 timer chip(for the 4017)?




P.S. To Simon: What ever man. Aren't those ads annoying all over the place on almost any website that you are visiting every day? Or, you are removing their ads as well ?
And for that scrolling text, I will remove it. But don't remove my logo. And BTW my blog isn't silly, let me see your blog  >:( >:( >:( >:(
 

Online SeanB

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Re: Ideal speed for LED Matrix
« Reply #15 on: July 27, 2012, 07:28:36 pm »
555 will do 100Hz no problem, it will work from less than a pulse per minute ( with terrible accuracy as you will be using an electrolytic for timing or a room sizes polycarbonate unit) to over 1MHz with no problems, just using R and C as appropriate, and a 15v supply.

scrolling text is annoying, and advertising without taste is the same as well. I hate using IE at all, it is so annoying to have an unfiltered internet, with all the screaming adverts. I ignore them, and am much more likely to use a text ad instead in a search result.
 

Offline Simon

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Re: Ideal speed for LED Matrix
« Reply #16 on: July 27, 2012, 10:09:08 pm »
P.S. To Simon: What ever man. Aren't those ads annoying all over the place on almost any website that you are visiting every day? Or, you are removing their ads as well ?
And for that scrolling text, I will remove it. But don't remove my logo. And BTW my blog isn't silly, let me see your blog  >:( >:( >:( >:(

What adds ? on what websites ? Every time you fill out a box that is designated for entering content about the discussion you include an annoying scrolling advert text too. Put it in you signature instead of the logo you already have the logo as your avatar.

My opinion is my opinion and I'm not silly enough to start a blog that's why I don't have one (about electronics at least) if you have not spotted my web presence then your not looking very hard.
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Offline Electroalek

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Re: Ideal speed for LED Matrix
« Reply #17 on: July 29, 2012, 08:42:46 pm »
I've came up with this table:
__________________
|    R1  |     R2   |  C1    |         
|_________________ |
|5.1K? | 4.7K? | 47nF  |
|6.1K? | 150K?| 1 µF   |
|_________________ |
Both of them are 100Hz(from different 555 calculators) , but I'am not sure about them.

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Offline hlavac

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Re: Ideal speed for LED Matrix
« Reply #18 on: July 30, 2012, 01:52:55 am »
Controlling LED matrix from PC at this level is not a good idea. It will be slow and jerky.
You would be better off controlling the matrix using some micro-controller and using the PC link just to send the data you want displayed.
Good enough is the enemy of the best.
 

Offline Electroalek

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Re: Ideal speed for LED Matrix
« Reply #19 on: July 30, 2012, 03:11:46 pm »
Yes, yes, yes but i made it like this. It is not slow, it is not jerky it is good. I'm just asking can i use 555 timer chip to drive the 4017 chip.
 


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