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Emergency flasher help...?

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Scratch

New Member
Hi all, I'm lookin' for some help designing a circuit. I'm a volunteer EMT and I need a flashing light for my vehicle. I went with high intensity LED's and I have a normally open switch that turns each light on. The entire lights are already made, I need to make them flash.
I have one red light and one white light. I want the red to flash either 2 or 3 times, about a 1/4 second apart, then I want the white to do the same.
Is this possible without programming an IC as I don't know how to do that.
 

john1

Active Member
Hi Scratch,

You could probably do this using relays.
The plug in types, made for motor cars.
And maybe a car flasher unit to operate
the change from red to white.
That would be a sort of 'electrical'
approach, rather than electronic.

Or you could make electronic circuit
boards up using transistors or SCRs
with their attendant control circuitry.
That would involve some understanding
of electronics, and assembling discrete
components.

Or you could put together a system of
ICs and chips to control an output for
the lights, that shouldnt need any
programming, it would just be free
running when you switch it on.

Whatever your preference, im sure that
the folk here would be happy to
produce a diagram for you.

Regards, John
 

bogdanfirst

New Member
here is how i think os a simple circuit, it does this: red-pause-red-pause-white-pause-white-pause+=>to the baginneing.
is it good?
use a 4017 counter a 555 for the pulse generator 2 transistors and 2 relays plus discrete components, diodes resitors?
is it good?
do you want me to draw the schematic to you?
 

Scratch

New Member
Yep, that's what I was thinking for a pattern. A schematic would be greatly appreciated!
Thanks!
 

pkshima

Member
just one modification to bogdanfirst's idea.

maybe u can use a single ULN2003 in place of two transistors, diodes and a few resistors. it will also clean up the layout of the whole circuit.

bye,
Shima
 

john1

Active Member
Hi pkshima,

bogdanfirst hasn't posted a diagram,
but i guess the two transistors he mentions
are to operate two relays for the lights.

Unless one relay is for the lights using
a n/o and a n/c set of contacts.

so whats the other for ?

come on bogdanfirst, lets have a diagram

john
 

bogdanfirst

New Member
o, i forgot to mention, the two transistors only support 100mA, but if your relays draw more, put something else, like bc639, wich handles 1 amp, but i never needed highter power transistors.
and the circuit can run from 5 to 15 volts, but it depends on the relays you use.
and (not shown on the diagram) pin 16 goes to +12V, and pin 8 goes to GND, (from ic 2, the counter).
if you need more details, ask!!
 

kinjalgp

Active Member
In what mode have you wired the 555? It doesn't seem like it is in astable mode.
 

bogdanfirst

New Member
OOPPPPPPSSSSSSS!!!, i used the circuit with the so called astable fro another schematic, it is an astable but not in this schematic....
ill redraw.
 

kinjalgp

Active Member
One more thing don't forget to place junctions points at required places. It is difficult to find out if the wire is connecting to the crossing wire or not.
 

kinjalgp

Active Member
OK, a big design mistake that most of us make. The 1k resistor (R1) shown in the circuit should be always greater than 5k. This is because of all the internal reference setting resistors in 555 are of 5k and if you use R1 less than 5k, it will allow more current to flow through the chip thereby destroying it and it will also alter the operting points of internal comparators.
 

Scratch

New Member
Boy, lotsa help!
Gotta love it.
So is the one that bogdanfirst posted about 5 posts up the re-drawn one?
 

Sebi

Active Member
Why You need relays?It sucks more current as load.Connect the LED-s direct to collectors. (The circuit accu-powered)
 

bogdanfirst

New Member
first the scematic is the one above( half a meter or so.. :lol: ).
i thought or relays for using high power lamps, but if you only use leds its ok to connect them dicetly between the collector and +12v
 

pkshima

Member
please guys keep my heart :p

use ULN2003A IC. it has seven darlington pairs inside. each can give bout 0.5 AMP. whats more the outputs can be paralleled to furnish more current.

bye,
Shima.
 

bogdanfirst

New Member
well you could use that too, but there is no need.
if the lights are needed for a vehicle, i dont think that current consumption is a big problem, so the realys can be used.
 
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