Control module for car roof rack light bar

Thread Starter

Kosmis

Joined Nov 19, 2017
6
Hello everyone. So im new to circuits, studying automation engineering but only first year. I want to build control module for light bar.
Simple description:
One button turns on the light bar, one potentiometer regulates the brightness of the leds. Other button turns on flashing and other potentiometer should regulate flashing intensity. Also it should be nice if there would be led indicator of light bar.
Circuit should be powered by car battery (12V) and light bar is 180W. I need just the circuit and components information so I could solder it.
Waiting for you ideas:)
 

Thread Starter

Kosmis

Joined Nov 19, 2017
6
It's not homework project, just trying to learn some new things.
About difference between those things you have mentioned - sorry, I can't understand what is the question :/ English is not my native language.
 

Picbuster

Joined Dec 2, 2013
997
Use a Pic16f690 pot's, switches and fet 's to control the PWM to your led bar.
And a simple pwr supply to feed the pic.
As you study automation you must be able to write a program for the Pic.
Building the hardware could be a problem but demo kits with pot's and power are available at low price ( see Farnell or Microchip direct)
The only thing you have to add are the Fets.
Compiler is free and easy to use.

Picbuster
 

DC_Kid

Joined Feb 25, 2008
796
although that pic can work, something a tad more user friendly is Adafruit Trinket Pro (atmega). Arduino IDE and USB is all that's needed to program it. output control stages will be slightly different from the pic.
 

crutschow

Joined Mar 14, 2008
24,914
sorry, I can't understand what is the question
What is the difference between "flashing intensity" and "brightness " in your design? :confused:
You said you needed a potentiometer adjustment for each, but they would appear to be the same adjustment.
Do you mean "flashing frequency"?
 

DC_Kid

Joined Feb 25, 2008
796
What is the difference between "flashing intensity" and "brightness " in your design? :confused:
You said you needed a potentiometer adjustment for each, but they would appear to be the same adjustment.
Do you mean "flashing frequency"?
i dunno what OP meant, but i do sometimes see folks distinguish between how hard led's are on (amps) vs their on time via PWM. but i think you are right, the "intensity" seems to be PWM freq & %.

so, you could have a high intensity short burst which looks more like a flash bulb, or a lower intensity longer burst. i find the 1st is better for attention getting when the human eye is involved, like for highway safety vehicles and you see the flash from miles out. on the flip side, the local town water authority is out in the street with their big truck and the yellow caution lights are on, i think the latter is visually better.
 

D6equj5

Joined Nov 4, 2017
5
I recently made something similar for my car.
I used an Arduino, something to take care of the power - cars are typically 13.8vdc but can climb to around 15vdc so that needed to be held at 12vdc. I then used and arduino mosfet board to handle the on's and off's.

NB check local laws for having flashing lights on your car.
Good luck.
D6
 

Thread Starter

Kosmis

Joined Nov 19, 2017
6
I have tried to do it with arduino and mosfet, but something went wrong, it doesnt work like it should. And I prefer not to use microcontroller :) its more interesting to solder components(and cheaper also). So, the idea with pin pots looks fine to me, but I do not realy understand everything, could you please simplify it? :)
 

crutschow

Joined Mar 14, 2008
24,914
So conceptually you could use one 555 astable timer with pot adjustment to control the flashing frequency, and one astable 555 timer at a higher frequency with PWM adjustment to control to brightness.

You could also use one dual D-flipflop chip (CD4013), with one FF to select the on/off, and the other FF to select the flashing/not-flashing, each triggered by a push-button.

A few appropriate logic gates can tie them all together.

A google search should turn up circuits to do all those functions.
 
Last edited:

DC_Kid

Joined Feb 25, 2008
796
So conceptually you could use one 555 astable timer with pot adjustment to control the flashing frequency, and one astable 555 timer at a higher frequency with PWM adjustment to control to brightness.
i did this exact thing ~2yrs ago using 555/556, i needed PWM with adjustable freq & %.

but, there's an existing library for just this for Arduino, although i have it for a Adafruit Trinket Pro, you can use analog input (pots) one for % and one for freq.
 
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