I'm kind of new here. I've been roaming around the forum for a while trying to figure out how to finish up this circuit I'm building and really need some help.
I'm trying to build a blinking LED circuit using 39 5mm yellow 2Vf 20mA LEDs, pn2222A transistors, and a 9V battery. I have the LEDs wired in 2 parallel strings(one string containing 12 LEDs and one containing 27 LEDs). From what I've learned so far, It would've been best for me to wire them in strings of 3-4 with each string having its own resistor, but I have them wired, soldered, and held in place already so I prefer not to dismantle everything and start over.
This is what I have so far:
simulate this circuit – Schematic created using CircuitLab
Sorry, part of the post is missing for some reason. Allow me to start over.
I'm working on an art piece that contains a spinning object which represents planet Earth. I'd like to add lights to the spinning earth and making the lights battery powered is best. I can't use a slip-ring to run power to everything because a slip-ring won't fit. The spinning Earth as a 8" diameter. I should be able to install all the components (battery, lights, transistors, capacitors, resistors, etc.) to the spinning object, as long as the overall circuitry is light-weight and simple.
I have resistors ranging from 10-10k ohms, pn2222A transistors, 10 and 100uF capacitors, and AAA & 9V batteries. So is there a better way to make 39 lights blink in a light-weight, remote, and efficient fashion?
Did I mention I'm way out of my comfort zone but really really really need this to work?
Best Answer
You need to understand the power capacity of various battery technology in Ah, Wh and how this degrades due to ESR self-heating and when you exceed rated current.
Using a 9V battery rated for 550mAh in 20 hours when drops well below 8V.
Ideally under low current, a 9V battery can provide 550mAh * 9V <5Wh or 27.5mA for 20 h.
You have 39x 2V LEDs @ 20mA = 1.56 Amps or more than 50x times ~~ its 20h rated capacity. Then by dropping 7V in resistors you are wasting 7/9= 77% of the battery power.
Rules to remember
So your battery choice is N.G.
More Rules to Remember
simulate this circuit – Schematic created using CircuitLab