id like to know how to make a police light bar for 12v?

id like to make a light bar with an arduino or an ic chip i have a few of the chip but idk what all i have but id like to be able to change the flash modes with a push button and id like to run it on a 12v power with 100 or a 1000 leds. but idk  what ic chip i could use or what resistor size i should use and idk what the leds are rated for they are parts. any thing would help.

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rjkorn3 years ago

i do this all the time for RC models. on a vehicle its a felony here.....

I use mosfets because theyre easier to saturate and have really low on resistance so there is little loss.

the example blink program can be easily changed to make an alternating blink/strobe pattern. that will get you started.

There is a great example on the arduino site called crossfade that will do nice effects out of the box.

also shows how to mix colors and switch patterns. that would be a good
start to merge a keypad demo with to get what you want.

i use a bare 328P chip with the nano bootloader. the headphone jack is a serial port for programming/control.

the port pins connect to n channel mosfets with 1k resistors. sometimes I even drop the resistors to a low value to help with faster strobe patterns. I haven't seen the need to use a dedicated fet driver chip yet but Im playing with 100W chips now and am finally seeing some heat in the fets but that's at 36V and over 3 amps on an 5 amp fet....

see movie clips

IMG_2324.MOV(516x290) 24 KB
IMG_2323.MOV(516x290) 21 KB
IMG_2325.MOV(516x290) 20 KB
iceng4 years ago
Make your lights Orange & Black :¬]
or Green and Orange if you have a hard time finding power UV..

blkhawk4 years ago
Make sure that it is not illegal to install police lights on civilian vehicles in your state/country.
iceng4 years ago
This is a perfect application for a servo which swings rows of  LEDs in that
characteristic police cartop light display viewable by drivers and pedestrians alike
no matter where they are in relation to the police car.

Using an arduino connected to 12 through it's onboard regulator is doable. You can run the LEDs directly off the 12V. You will just need to use a transistor switch or relay to take the signal from the arduino and turn the lights on and off as needed. There are all sorts of LED calcs online to help you figure out how to wire up your array of LEDs to the power source you want and it will tell you what resistors values you will need.