i have two that i made recently. one is 4ct full spectrum epistars from ebay for 9$ so what the heck. ill change them later or just make another light. these lights are really cheap to make.
the other is a spectrum range of blue and a spectrum range of red. they are powered separately on one panel like your basic commercial monos.
i did not use the 2-3$ monos, they are pretty nice IMO 14-45$ chips.
To find the voltage here you need to kind of play around with the characteristic curve of the I and V chart for the particular LED but in basic if you have a 30-35v @ 3-3.5a LED then you should do ohms law to find the resistance at one of the minimum or maximum given. so i go with minimum 30/3=10 Ohms characteristic of one LED while it is on. It'd be something toward infinity when it is off. This is clarified by how semiconductors transition from 0 to infinity ohms at the rate of epsilon (verify).
ok so i now have 10 ohms but only 30v. i want to have 120v capable so i get 4 in series which would be 30volts*4=120v @3 amps. the resistance will add up in series but inversely if you are adding in parallel. so there will be 40 Ohm load desired.
well if i plug up a rectified wall outlet to four LEDs they'll see a peak voltage of 170v ever 60th of a second and burn out fairly quick. theyll try to push about 8 amps through them actually
so whats going to happen here is the AC is 60hz and if i place an 250vAC (or greater for safety) capacitor in series with the rest of my desired circuit, the AC going across the capacitor will make it appear as a resistor by the formula X=1/(2*(pi)*(frequency)*(capacitance in whole Farads)). X is capacitive reactance in Ohms. so by kirchoff's loop law i know that if i had 120VRMS and placed a low value resistance in series with my load then the load must be SOMEWHERE lower than 120 volts. But this is in AC still so i rectify it and get some voltage lower than 120v.
lets say i have a 300 microfarad capacitor available. that is .0003 Farards.
if i plug into my formula above i get out 8.84 ohms.
this looks like it is in series with my 40 ohm resistive load. i add 8.84 to 40 and get 48.8ohm total circuit impedance. 120*(40/48.
=98.4 volts across the LEDs. well that'd make sense if my LEDs were still a 40ohm load but the voltage just dropped on them to around 100v between 4 LEDs. ok theyre now only powered to 25v each. but that wouldnt be a guaranteed true number either. so all i leave with is confidence that i am in a safe range of power at a nominal amount of light. i just measure the voltage across it and current through it to determine what i am actually at and the math is always pretty easy.
the capacitors are really cheap and so is the fuse and rectifier. i spend about 10-15$ on a ballast
i used 120v chines capacitors to bump up my capacitance and get more power and they suck. they kinda boiled internally. the 250vac work like a champ and stay completely cool. so i ordered some 450vac capacitors to simplify each circuit to only one capacitor.
ill use the others i take off for either some ebay money or some science stuff.
