In addition to the power dissipation formula, to calculate the required resistance: (Vin-Vdrop)/I So if you’re using 220v input, an amber led with 2v drop, and you want to pass 20mA, then you’d need (220v-2v)/20mA = 10.9kohm resistor. So round it to 10k or use two 22k in parallel to get a closer result.
Thank you for the helpful explanation. You are right, If the voltage drop and the required current of the LED are available, the required resistance can be calculated by the formula you mentioned.
While the calculations and blabbering about Ohm's law in the description are vaguely correct (some nitpicking: it's not 220V across 100k, it's 220V -3V across the LED, so it's 217V across the resistor, mind Kirchoff Voltage Law), I highly doubt an LED can withstand 311V peak of reverse voltage when the sine wave is in the negative cycle. Therefore I'm very skeptical about this video. I might be wrong, maybe there are some LEDs with a breakdown voltage higher than 300V
Although you are right that I didn't consider some parameters for the sake of simplicity, but the result of the calculation is nearly close to the experimetal values. I have been using this circuit in my room without any problem for many years. Try it yourself, trust in science.
In addition to the power dissipation formula, to calculate the required resistance:
(Vin-Vdrop)/I
So if you’re using 220v input, an amber led with 2v drop, and you want to pass 20mA, then you’d need
(220v-2v)/20mA = 10.9kohm resistor. So round it to 10k or use two 22k in parallel to get a closer result.
Thank you for the helpful explanation.
You are right, If the voltage drop and the required current of the LED are available, the required resistance can be calculated by the formula you mentioned.
Very useful, I did it, it works, Thanks
Happy to hear that 🙏
❤️🔥 da 🏠
While the calculations and blabbering about Ohm's law in the description are vaguely correct (some nitpicking: it's not 220V across 100k, it's 220V -3V across the LED, so it's 217V across the resistor, mind Kirchoff Voltage Law), I highly doubt an LED can withstand 311V peak of reverse voltage when the sine wave is in the negative cycle. Therefore I'm very skeptical about this video. I might be wrong, maybe there are some LEDs with a breakdown voltage higher than 300V
Although you are right that I didn't consider some parameters for the sake of simplicity, but the result of the calculation is nearly close to the experimetal values.
I have been using this circuit in my room without any problem for many years.
Try it yourself, trust in science.
50k is ok for 110V?
When the voltage is halved, the resistance should be halved, too. You should use a 25k resistor, please read the description.