You can wire them in parallel (with one series resistor) but there a couple of issues... The current is limited by the resistor and is split between the two LED. But because of that non-linearity and manufacturing variations the current may not split evenly and one LED may be brighter than the other. You can often get-away with it, but it's "bad practice".I now understand that it's not worth the trouble, and I might as well just solder a resistor to the end of each LED, cover it with heat shrink and be done with it... Thanks,Mark
Is 300ohms a good value for the resistors
Or maybe a better question is, what is a good value for the individual resistors to achieve those two goals?
It would help if you got your terms right.Voltage is across, current is through. Power is the product ( like in multiplying voltage and current ) is nether across nor through.
Bought a Mega later as I need a lot more I/O and memory than the UNO provides..
it will involve several relays and several LED's...
That's kinda what I thought might be the case.. But I really don't understand how LEDs are measured resistance wise.
I guess I kinda saw them as diodes (switches), but I know that can't be right, otherwise wiring them directly across a voltage source would create a short circuit,
meaning they must have 'some' resistance, but it sounds like their resistance changes according to the power passing through them?
Even if the LEDs all had constant resistance, adding more branches of the parallel circuit would change the dynamics of the overall series circuit, moving the dividing point of the voltage dividing network...2 LEDs @ 100 ohms each in parallel = 50 ohms seen by the single resistor meaning that across a 100 ohm feeder resistor, the LEDs would be dropping a third of the total voltage...4 LEDs at 100 ohms each in parallel = 25 ohms seen by the feeder resistor, meaning that the LEDs would now be drawing only a fifth of the total voltage..So each time another LED is added, they all get dimmer...Thanks, it's clear as mud in my bean now!
So to control the brightness of an LED do I just take it's max rated current draw,
and then use that to calculate how much current flowing through a resistor provides that much current (ignoring the internal resistance of the LED)?
The fact that the LEDs change resistance according to the power supplied to them is confusing from a design standpoint... Obviously, thinking of them as regular ole light bulbs doesn't cut it... How is all that calculated?
I was planning to post all this over in the feasibility forum, but you asked.. lolI guess I can copy and paste all of this over there after this...
Your photos are pretty useless as - common blunder - they are taken in darkness. The best way to do this unless your workshop is lit by multiple floodlamps, is to take it outside in full daylight but not direct sun and use a digital camera (that is, not to be confused with a telephone) at least a metre away from directly above (or very slightly offset to ensure all the connections are able to be distinguished) using the (actual - "optical") zoom to just include all parts of the assembly.
My big question at this point is "Can the Mega handle something like this?" If so, great, I'll plug ahead..
You can see that I'm gonna need a lot of I/O, and as much memory as possible.
Your title should mention MIDI