I admit that I’m a hacker. I have strengths (coding and creative approaches) and weaknesses. I have a set of skills that I’ve built over time, but it’s an effort for me when I try to extend myself. I admit that I must frustrate the real engineers on here. But I try.
So here I am, stuck. I can calculate the component values necessary to drive an LED or an inductive/ resistance load. But here’s the rub...
I have an LED string. It’s recommended to use a 6V battery to light it. That’s way too bright! At 6V, the string draws 150ma. But,
it also works acceptably at 3V.
Based on 150ma current draw @ 6V, I’ve calculated that the average current draw when used per my design is 22.5ma. The string will only be on 15% of the time. I forgot to measure the current draw at 3V.
I am using an ATTINY85 to control this string. The ATTINY85 operates between 2.7 & 5.5V. So we’re coming up to my question.
Powering with a 235mAH button cell battery, I have very little headroom for the uP. But using two batteries, the LED string is too bright and the battery life is only 10 hours. And the uP current draw needs to be taken into consuderation as well. I think that an iterative approach may work. Where I ignore the uP current and then recalculate once I’ve resolved the LED string problem.
What I want to do is three-fold. 1) maximize battery life, 2) reduce the LED brightness and current draw and 3) I’m at Disney World drinking a beer and forgot what 3 is...
I had thought of adding a series resistor to the LED string but don’t see enough information to calculate the value of said resistor.
As a final nite, there will be multiple strings, but only one will be active at a time.
Any comments?
So here I am, stuck. I can calculate the component values necessary to drive an LED or an inductive/ resistance load. But here’s the rub...
I have an LED string. It’s recommended to use a 6V battery to light it. That’s way too bright! At 6V, the string draws 150ma. But,
it also works acceptably at 3V.
Based on 150ma current draw @ 6V, I’ve calculated that the average current draw when used per my design is 22.5ma. The string will only be on 15% of the time. I forgot to measure the current draw at 3V.
I am using an ATTINY85 to control this string. The ATTINY85 operates between 2.7 & 5.5V. So we’re coming up to my question.
Powering with a 235mAH button cell battery, I have very little headroom for the uP. But using two batteries, the LED string is too bright and the battery life is only 10 hours. And the uP current draw needs to be taken into consuderation as well. I think that an iterative approach may work. Where I ignore the uP current and then recalculate once I’ve resolved the LED string problem.
What I want to do is three-fold. 1) maximize battery life, 2) reduce the LED brightness and current draw and 3) I’m at Disney World drinking a beer and forgot what 3 is...
I had thought of adding a series resistor to the LED string but don’t see enough information to calculate the value of said resistor.
As a final nite, there will be multiple strings, but only one will be active at a time.
Any comments?