i would like to build a electronics project that look similar to the flashing of the blue n red lights that is found on police car.

the blue light should be flashing twice before the red light that will be flashing twice. and this whole process continue.

how do i start ?

 

Probably the best place to start I would say is here: http://forum.allaboutcircuits.com/blog.php?bt=682, it is a section of Bill_Marsden Blog. His whole blog is packed with useful information.

 

Try a 556 timer. It will allow you to adjust the speed of the blue and red separately.

 

I'm finishing up a design on this thread that will fit your needs.

http://forum.allaboutcircuits.com/showthread.php?t=37409

 

I'm finishing up a design on this thread that will fit your needs.

http://forum.allaboutcircuits.com/showthread.php?t=37409

i have read it. it's great !!
i have found another circuit but not sure whether it will do the same thing.

link:
http://electroschematics.com/5598/police-car-lights-with-leds/

 

The lettering on Electro Schematics on my screen is verry fuzzy. By guesswork Blue flashes 50 ms, then again .4 s later,long pause, .8 s, R flashes twice, followed by only .15 s for B again. Unless I mis read the numbers, I would connect R to Q5 & Q7 to make a more uniform display.

 

You can see the flash pattern on YouTube links I put on that area, I also added a pot to control the number of flashes. The design is verified, and will handle the number of LEDs specified.

The other design will work. I don't thinkt has very little control over flash timing other than the duration, but for your application it may not matter.

Check this article out, it might have some other ideas on how to do it.

LEDs, 555s, Flashers, and Light Chasers

 

for the variable resistor, can i replace is with the one in the link ?

http://singapore.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=5222261

I'm finishing up a design on this thread that will fit your needs.

http://forum.allaboutcircuits.com/showthread.php?t=37409

 

I think it needs to be 100K. RS seem to have plenty.

 

how do i go about chosing the types of LEDs (view angle, Luminous Intensity) to use for this circuit ?

what types of LEDs do you use ?

I'm finishing up a design on this thread that will fit your needs.

http://forum.allaboutcircuits.com/showthread.php?t=37409

 

Hello,

Did you read you other thread?
http://forum.allaboutcircuits.com/showthread.php?t=39661

Bertus

 

I would like to know is it TTL or CMOS type better for the 556 timer?

I have also found some of the 556 timer in RS.
Which one is better ?

http://singapore.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=1125368
http://singapore.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6623993

 

The 555 will drive LEDs directly, the CMOS 555 is iffy.

I also have some other schemes that might suite your needs.

LEDs, 555s, Flashers, and Light Chasers

 

Actually the CMOS 555 specs say output current is 10mA sink, or 50mA source. If that 50mA isn't enough for your LED, you have one hell of an LED! But yes, the regular 555 would provide even more.

 

Many LED blinking circuits use a CD4060 oscillator/counter and a few diodes at the outputs to select the flashing.

 

Actually the CMOS 555 specs say output current is 10mA sink, or 50mA source. If that 50mA isn't enough for your LED, you have one hell of an LED! But yes, the regular 555 would provide even more.

Depends on the voltage feeding the CMOS 555, at 12 to 15 volts you might get that, but at 3 V you are lucky to get 10ma, the norm is 2ma.

Take a look at those specs again with an eye for supply voltage.

 

For the experiment I use run of the mill high intensity LEDs. You might try modifying the LEDs you can get.

 

For the experiment I use run of the mill high intensity LEDs. You might try modifying the LEDs you can get.

what is the range of mdc n view angle for the LEDs that you used ?
what is the range of mdc n view angle for bright white n colour LEDs ?

 

Truth to tell I have not a clue. I buy my LEDs from many sources (but mostly off the shelf), nowdays they are high intensity (the kind you can't look directly into) but narrow beam. There are tricks you can use if you want to defuse them, such as fogging up the clear lense or adding translucent paper or plastic. At the HAM Con they had a bunch of different colors (6 to a bag) for $1 each.

 

Actually the regular LM555 isn't specified for a power supply below 5V, whereas the LMC555 (CMOS) will work down to 1.5V. The spec sheet doesn't seem to say how much current it can source/sink at that level, but if the device has to run on batteries for a long period, CMOS is definitely the best bet. As happens so often, choice of parts depends on what's most important.