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If a 2W 110 Ohm resistor has 1V across it that does not mean the current is 2A! Use Ohm's Law and tell us what the current really is, Ritesh.1v across 110ohm collector resistance of 2watt. p=V x i 2=1xi i=~2Amp
p=i2rIf a 2W 110 Ohm resistor has 1V across it that does not mean the current is 2A! Use Ohm's Law and tell us what the current
Why did you take it as 5-4? What is 4V. Forward Voltage across diodes wont be 3v ot 2v always. You need to take the resistance of the diode in this case, and not the Vf.Hi again,
Today i have taken Vf for Led for white it is 3V and for Red is ~2V. and it is working well in 4mA to more than 80mA.
so, my question is if i connect 2 Led in series and with 110Ohm V cc of 5V.
so, 5-4=1v across 110ohm collector resistance of 2watt. p=V x i 2=1xi
i=~2Amp so, if i make series of 2 Led so, how many parallel combination should be there??
so, for increasing current i have to increase voltage drop across it..?No.
I=V/R = 1/110 = 9mA.
P = I^2*R = V^2/R = I*V = 0.009*1 = 0.009W = 9mW.
OR!!!! Drop the resistance... See my early pots....so, for increasing current i have to increase voltage drop across it..?
OR!!!! Drop the resistance... See my early pots....
this....?15 * .02A = 300mA ...
You will need about 2 watt (with heat sink) 15Ω resistor..... You'll need to generate about 371mA to run 15 LED's at about 20mA each..... You'll need a heat sink on the BC337 aswell..
OR!!!! Drop the resistance...
OK, i was just checking and testing the whole experiment after taht i have some result it was good to study..
i have used series combination of two red led which has Vf of 2V and combined several parallel led with them near about 15+15=30 it was working fine as i increases the led the currents increasing very slowly in very few mA near 2mA. and the voltage across 110ohm was 1V, after that i have added total 12 parallel 110ohm one by one the voltage become across R was 0.78V and current also increases and there was not so much power diss across R which was achievement then earlier....
so, my red led project is over and i am thinking about white LED which has Vf of ~3V so, how to combine with 5V 2V across resistance so, should i use 9V for it making 3 or 2 in series??/
sorry not getting you i have tested red not white.Have you considered having two White LED's each with its own resistor, using a 5V supply, connected in parallel from Vdd to the Collector.?
It is not battery project it is professional market board.. with SMPS.Everyone has said to use @ 4mA per LED.. ( Even thats too much for a battery project...)
that 3.2V across collector resistance will diss power and become to hot!5v - 1.8v = 3.2v... Right!!!
what is problem wit 9V SMPS??professional market board.. with SMPS.