A good place for resistors... i generally get most of my staff from futurlec.com. They have some good prices there. Also, you may find some very good mushrooms on ebay. But take extra care when selecting seller.
180 ohms resistor is not to be considered as good or bad. An 180ohm resistor would be good if for example lighting an LED at 9volts. In general, you need more than one type of resistors to be safe.
I have a set of resistors about 30 of them.
For your project now, you need to tell us specifications of the 5 mm LEDs to calculate them. In general, 5mm LEDS would draw about 40mA current and would operate at 3.1 volts
but this is something to confirm. Now, according to
this LED theory here that i strongly recommend you to read, i would choose to have sets of 3 leds in a row. Considering that the car voltage is 12 volts, the resistor needed would be 67.5 ohms. Now, this is not actually a resistor value that exists, so i use
this standard value resistor calculator, i go for 5% resistors (E24), paste this 67.5 and the best match would be 68 Ohms. That is what you need. Series of 3 LEDs connected in series with a resistor 68Ohms. But again, you need to make sure that the voltage and current of the LEDs and the voltage of the car are correct.
A simple schematic drawing for your application would be as the attachment.
As for the number of LEDs, each series would draw 40x3 = 120mA. So, keep in mind that you need to have about 33 lines of 3 leds, and that would result 33x120 = 3960 mA. This is about 4 amperes. Have the right cable used and not the good old handy color ribbon cable as it could be toasted.
Home
Forum
Projects
Experiments
Circuits
Theory
BLOG
PIC Tutorials
Time for Science
