Hi my dear friends;
I have long been workin on some LED matrix MMD circuits, but only in Proteus.
In relation to the implementation always arises the required peak current issue:- how much average current should be to get a good LED brightness, in case of the
In my case 16 rows are multiplexed, all with 96 columns (LEDs), so the duty factor
is equal to 1/16 (6.25%).
Details are in my prev. thread:http://www.sonsivri.com/forum/index.php?topic=33957.msg107490#msg107490
Does it possible significantly reduce
the power consumption?
The worst case peak current can be 3-5 A, and not the theoretic (horrible) 15 A ?
Really bothered me this so I'm looking for a very long time on the net for a solution...
I've read several times this statement:"The human eye functions as both a peak detector and an integrator;
therefore, the eye perceives a pulsed LEDís brightness somewhere (?)
between the peak and the average brightness"
Finally found a site where practical experience and test results released:http://www.dr-iguana.com/prj_LEDactus/LEDactus_pwm_intensity.html
Using the published curve, the 1/16-os multiplexing (6.25% duty-factor) causes
only approx. 70% brightness-decreasing, instead of the expected (theoretic) 93.75%.
This means that it is sufficient to increase the LED's current (the nominal 10 mA)
only three to fourfold (not 16x).
Also a much smaller secondary power supply is needed ...
However, this would be good to try with the used LEDs too.And now (after a long description of the above), my request is as follows:
Do you build the simple circuit below to try out this?
I can not do this anymore (because of my bad eyes), I'm too old (66)
unfortunately,is no longer going to soldering.
A pulse generator (for example a simple two-transistor astable multivibrator
or a 555) produces a 120-140 Hz signal with a 6-7% duty factor. This drives
one of the two identical LED, through a variable resistor. The second LED gets
10 (max 20) mA DC what you need to get the correct brightness.
Best would be two LEDS of a cheap 5x7 or 8x8 LED matrix are used.
Then the same subjective brightness is set with the variable resistor to find
out how much peak current need to use.
And ...does anybody have concrete practical experiences in this matter?
This would be a great help for the construction of the system.
Please help me!