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Step 4First Phase: Component Construction
The following images should all be properly captioned, but before getting there, I should tell that all my white LED's are 3.5 V, 20mA. Thus, I solder them in series of three with an 82 ohms resistor for a twelve volts power source (the car's battery). I don't do LED circuits without resistors because:
A) By getting the LED's over nominal voltage you make them change colour.
B) By getting the LED's over nominal current you make them overheat and rob them their extraordinarily long lives. A 20mA LED working at 50mA will be giving out slightly below double its normal light emission (the overheating makes it far less efficient), but it will only live between 100 and 500 hours (4 to 20 days), contrary to its theoretical mean life of 50,000 hours (5.7years).
C) You have to be out of your mind to try and get a no-resistance circuit connected to a no-resistance, very high current power source, such as a lead-acid battery. Let's put it this way: if I ran our of matches and my lighter ran out of gas, I would be able to turn on my gas stove using an LED, jumper cables and a motorcycle battery.
Something else not to forget: I didn't do all the component construction before opening up the hood for the next step: preparing the area. Before that, I had only made the 2 arrays of 24 5mm LED's.
A) By getting the LED's over nominal voltage you make them change colour.
B) By getting the LED's over nominal current you make them overheat and rob them their extraordinarily long lives. A 20mA LED working at 50mA will be giving out slightly below double its normal light emission (the overheating makes it far less efficient), but it will only live between 100 and 500 hours (4 to 20 days), contrary to its theoretical mean life of 50,000 hours (5.7years).
C) You have to be out of your mind to try and get a no-resistance circuit connected to a no-resistance, very high current power source, such as a lead-acid battery. Let's put it this way: if I ran our of matches and my lighter ran out of gas, I would be able to turn on my gas stove using an LED, jumper cables and a motorcycle battery.
Something else not to forget: I didn't do all the component construction before opening up the hood for the next step: preparing the area. Before that, I had only made the 2 arrays of 24 5mm LED's.
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If each LED is 3.5V, then the voltage drop of having 3 of them is:
12V (source) minus (3.5V times 3LED's)= 1.5V at the resistor.
I'm using the resistor to limit current. 1.5V/20mA=75ohms, but I use 82ohm (the next higher value) resistors to mitigate the slightly higher voltages that any car pumps when it accelerates.