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Sammich LEDs


Amanita

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As there are only 8 LED dropping resistors on the control pcb, are the LEDs multiplexed at high frequency? Can't fit ohms law into it otherwise... I want to use my own LEDs and understand that I will need to trial a few resistances to get the intensity right so I intended to just set up a 5vdc psu and breadboard until happy - then fit. But only 8 resistors and 48 LEDs which come on in different quantities.....enlighten me please....:)

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I am very sure that you are right, 8 resistors for all the LEDs on SammichSID!

MB6582 has over 100 LEDs (64x LEDs for modulation matrix, 48x other CS LEDs on control surface, 1x LED for power on) and it has only 16 Resistors for all of them.

Thank Wilba for the lovely LED-matrix voodoo which makes this possible :)

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The LEDs on sammichSID are multiplexed... they are in an 8x6 LED matrix, but driven by the PIC using the default MIDIbox SID 8x8 LED matrix code, so in reality they are really in a 1/8th duty cycle.

In my experience, if you are testing what resistor will work, testing one LED with constant 5V will be about the same brightness as when it is in the matrix, it won't be much less bright when put in the matrix. It depends on the LED type, though. But as a rule, it's OK to pick a resistor using constant 5V as a test.

Alternately, solder the LEDs before soldering the resistors, run the sammichSID CS test app (I really should put this somewhere better):

and then touch resistors in the pads to see actual brightness. You could in theory put all 8 resistors in the pads (without soldering) and trim/bend the leads to make good contact.

As a general rule, ultrabright LEDs (especially white or blue) will need at least 1K resistors... perhaps even as much as 3K.

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