# thampiverghese

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I am a retired physician. I still spend a large block of my time learning about new components, circuits and refreshing knowledge about laws of electronics. I do all these mostly using parts from old devices. My 1st big project was making a superheterodyne radio while I was in medical school using thermionic valves! I have a diploma in electronics and one in computer science through online courses.

• thampiverghese commented on geekrex's instructable The Ultimate 1 \$ Emergency Light2 years ago

Thanks Wobbler for the correction. You are right. I messed up the calculation.

Thanks, mikeanton. You are right. I multiplied E with C instead of dividing. I should have used the resistor calculator. Things get rusty with age.

Thanks mikes ton for the correction. I am sorry I messed up the calculation.

• thampiverghese commented on geekrex's instructable The Ultimate 1 \$ Emergency Light2 years ago

Led looks like SMD 5025. The voltage is 2.0 and max current is 50 ma. To be safe it needs a voltage drop of 1.7(3.7-2.0) So it will need a .085 ohm resistance. Ideally LEDs should have individual resisters because the characteristics of LEDs vary Even if 10 are used it needs .85 ohm. (1 Ohm 1 W)Probably the wires + the internal resistance of the battery may account more than that. That is why LEDs didn't burn out. If dry cells are used there should be no problem because they have much larger internal resistance compared to Lithium battery. Is the battery going to be recharged in a cell phone?A solar battery from China is very cheap. That will make it a forever light especially in tropics. These days nobody has to buy Lithium batteries with so many discarded cell phones. If cost is not a...

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Led looks like SMD 5025. The voltage is 2.0 and max current is 50 ma. To be safe it needs a voltage drop of 1.7(3.7-2.0) So it will need a .085 ohm resistance. Ideally LEDs should have individual resisters because the characteristics of LEDs vary Even if 10 are used it needs .85 ohm. (1 Ohm 1 W)Probably the wires + the internal resistance of the battery may account more than that. That is why LEDs didn't burn out. If dry cells are used there should be no problem because they have much larger internal resistance compared to Lithium battery. Is the battery going to be recharged in a cell phone?A solar battery from China is very cheap. That will make it a forever light especially in tropics. These days nobody has to buy Lithium batteries with so many discarded cell phones. If cost is not a factor using super capacitors and solar instead of lithium battery will make it a forever light.