FreeTrack Forum

Hey again guys

Got a simple question. I made a track clip for my dad. Here is specs

Power supply = 6v, 300ma
LED = 1.6v, 20ma
Resistor = 150ohm, 20ma, 6th watt

I used the calculator for the resistor. Well this setup was just to take place till the SFH485P showed up. He ordered 70 of them and they were backordered so it took a little while for them to come in. Well the showed up yesterday. So I placed the 485P on and forgot about changing the resistor. But the points are really weak looking on the cam.

The calculator with this setup is like this.

Power supply = 6.v, 300ma
LED = 1.5v, 70ma
Resistor = 47Ohm, 70ma, .23watts

Now my question is, is a 150ohm putting out MORE resistence than a 47ohm???? Is this what is causing the dim leds? Reason I am asking is because if so and I need to change out the resistors with the 47Ohms then I am going to run to the electrial store and put him one on tonight to see if that corrects the problem.

Thanks guys
Hotshot

Well, the 150 Ohms resistor gives alittle more than threefold resistance a 47 Ohms resistor would give. If we consult the Ohms law (I=U/R), then this means you get proportianally lower electric current in the diodes then you would be getting with a 47 Ohms resistor. The emitting power of the diodes depends on the available eelctric current, so no wonder your diodes seem weak with three times more resistance than needed. Shortly put, slap in apropriate resistors and you're set to go

Leopoldk @ 13/03/2008 - 20h30 a dit:

Well, the 150 Ohms resistor gives alittle more than threefold resistance a 47 Ohms resistor would give. If we consult the Ohms law (I=U/R), then this means you get proportianally lower electric current in the diodes then you would be getting with a 47 Ohms resistor. The emitting power of the diodes depends on the available eelctric current, so no wonder your diodes seem weak with three times more resistance than needed. Shortly put, slap in apropriate resistors and you're set to go

Thanks Leop just the answer I was looking for ol buddy  

later guys, running to store  
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