LED flasher help needed

Wendy

Joined Mar 24, 2008
22,177
OK, I'll draw something tonight. My current thought is 2 flash patterns, the double flash per side, and a straight alternate per side using this layout.



Any other patterns occur?
 

Wendy

Joined Mar 24, 2008
22,177
elwilliams said:
Sent 1/3/2008 11:23PM

oh ok its fine here though, so do you think i will be able to do that and make it double flash a group of 5 LEDs then double flash another group of 5 LEDs...
Please don't use private mail, these types of posts should be in the public forum. That's how it works here.

5 LEDs per side, heh? This won't be very visible, more like something an RC car would use I would think. If this is the case I would have done this anyhow, you could have saved me some time doing the physical layout of the board. You could have given me the board layout too.

Here is the schematic according to your revised specs...



If this is really going into a car let me know, I'll do a touchup on the LED circuits. Cars do not have a very regulated power supply. There was a reason I was trying to do do the LEDs in groups of three.
 

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Wendy

Joined Mar 24, 2008
22,177
The easy fix is to add 2 LEDs, otherwise we need to add 2 more transistors, 2 resistors, and 8 more diodes. Here is the easy method...



FYI: The 1N4454 is a general purpose signal diode. Almost any reasonable rectifier will work here.
 

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Wendy

Joined Mar 24, 2008
22,177
Sorry, missed the post. Yep. PM is OK to point out posts, we just transact business here.
 
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Wendy

Joined Mar 24, 2008
22,177
A doubt.. Would a 4017 and a 555 make an easier circuit than 4 timers??
Depends, you can have a 14 pin chippie where every pin is used with diodes everywhere, or you can have 4 555's. Parts count is a lot lower with 555's, along with complexity. Troubleshooting is a lot simplier too. I've build a lot of these circuits, I went with my best opinion for what was wanted. The 4 555's will look a lot different, better flash pattern.

Don't police cars use very bright lights, not just dim little LEDs?
I've had the same thought. I'm willing to help the OP with whatever though, but I just keep missing his posts.

PM's are usefull if you only come back every so often.
 

Wendy

Joined Mar 24, 2008
22,177
Another thread showed an alternate way, so I'm posting it here too. No more than 3 LEDs per chain (2 max for blue, and you can have fewer LEDs with no other changes), no more than 10ma. This design is cleared for automotive use, since the current regulator will compensate for a cars voltage fluctuations. I've used a design extemely similar to this for over 20 years with no problems, though it is a terrible idea to use a CMOS chip to drive 10ma.

What is it about police lights that bring em in?

 
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Wendy

Joined Mar 24, 2008
22,177
yes it is for a police car for a mini light bar, im sry i was getting confused there is going to be 15 LED's on one side and 15 LED's on the other, i know its not going to be very bright but i dont want it bright, and i need them to flash twice on 15 and switch sides and flash another set of 15, like that picture of the car i showed you but with LED's, so if you can make a schematic for that, and it will be ran by 12v
OK, the good news is the design has jelled and simplified somewhat. Soon as I get one done I'll post a revised schematic up here.

Another guy, Soren, has finalized an extremely similar design, complete with printed circuit board. You can find a link here...

http://forum.allaboutcircuits.com/showpost.php?p=112404&postcount=12

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I don't like this version, I finished it to have a reference, but I'm going back to the drawing board and do it another way.

 

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Wendy

Joined Mar 24, 2008
22,177
OK, I think this would be a good design. I didn't show them yet, but I'm thinking fuses would be a good idea on the collectors of Q1 and Q2.

 

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jj_alukkas

Joined Jan 8, 2009
753
Thats what I was talking of using a 555 and a 4017... It looks cleaner as long as you run the lights in a symmetrical fashion.. otherwise your other circuit..
 

Wendy

Joined Mar 24, 2008
22,177
One of the problems you fight is the power for cars isn't really regulated. If Blue and White LEDs were just a little less voltage it sure would make life easier.

The other thing to remember is parts count is not that far off. One of the 555's was an inverter, and you didn't need the diodes. Personally I would put them about even in complexity, with the added benefit that 555's are a bit more rugged than CMOS. This is important when inexperienced people build electronics.
 
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