I need some help in two categories- First and most important is the basic wiring and soldering of LED lights. This should be a pretty straight forward deal, but imagine you are teaching a 10 year old. A not very bright 10 year old… a not very bright 10 year old who can buy a six pack of beer for your trouble… I can meet you at the space when you have a few minutes to let me show what I am doing and you can walk me through it. Thanks. You can also DM me.
3 Likes
It’s not too hard. What you tradeoff in LED’s is brightness versus lifetime. The higher the bias current the brighter the LED abut at a cost of thermal degradation. I would start with the datasheet for your LED. See for a given bias current what the footage drop across each LED. Then calculate what resistor you need and make sure the sum of the voltage drops from the LED’s does not exceed your supply voltage (battery, bench, etc). Can you post the part number you are using?
I recently helped a member get unstuck on a large (~300) led project as well. Looks like you have help already above but willing to help also.
More to the point is the mission of these LEDS. Do you intend to just turn them on? Turn them on at a certain brightness? Have them controlled by a processor? Have the color and brightness controlled?.. Have them flash? (Flash a Morse code message?) Which begs the question of… what KIND of LEDS are you using… (There was a time that “on” and “Off” were the only game in town… those days are sadly gone forever. So much to know…)
Soldering is a skill you have to acquire yourself unless you get someone to do it for you.
As for the circuitry to drive an LED, it is fairly simple. You want a ballast resistor in series with the LED between your supply voltage and ground to control the amount of current.
The voltage drop across the LED ranges from about 1.8 volts to about 3.2 volts, depending upon the part, namely color. You can look it up in the datasheet. If you do not know, just use 1.8 volts; the LED may not be as bright as if you used the correct value, but you will not risk damaging the LED with too much current.
The voltage drop across the ballast resistor is the supply voltage minus the voltage drop across the LED.
Use a current limiting power supply in the Electronics Lab to determine the current needed to get the brightness you want. Again, consult the datasheet for the absolute limit on the current.
Ohm’s Law says the resistor value is the voltage drop across the ballast resistor divided by the needed current.
One more thing. Current only flows through an LED in one direction. If you have the LED installed backward, you will not damage anything, but the LED stays dark.
1 Like
Not fully true. You can actually destroy an LED if you manage to get it into the reverse avalanche breakdown region with sufficient V times I since it is a diode after all. But if you’re feeding off a voltage source with a low current clamp or a battery it should be okay. 