i try to make a police light using this schematic and it works perfectly


but, when i'm change the source to 12v DC and change the led to 4 high powered led 1watt each transistor, it doesn't work.
i try change the transistor to TIP31 and diode to 1N4007 but doesn't help.

what should i do to make it work with 4 hpl 1watt ??? please help me, thanks..
(i am newbie here. sorry for the bad language and disorderly post)

 

Changing the diodes is unnecessary. Be specific about which LEDs you're using. A link to the datasheet is best.

 

Can you be more specific?
What doesn't work?

 

The current-limiting resistors R3-R6 will need to be changed to lower values, to allow more current to the high power LEDs.

 

Hello,

How much current does the led take?
(post the datasheet of the leds please).
With a TIP31 it is unlikely you can drive 2 power leds.
You should have a look at some mosfet to drive the leds.
The 4017 can only put out about 7 mA.

Bertus

 

the 500mW.abs.max a white LED datasheet
NB! the appropriate red LED would have likely a lower voltage drop (say 2.5V) on it
and with 12V DC supply you likely can connect 2x of such in series
thus 5V 100mA = half the max rated power
NB.no.2 ! all of the above except the datasheet is speculative guessing - you have to know your device´s actual operating parameters to set them (the LED-s) up correct in your circuit !!!

 

Replace the transistors with a single ULN2004 and drive each LED with a seperate output

 

I would replace Q1,2 with mosfets IRF540, better current pulsing.

 

Changing the diodes is unnecessary. Be specific about which LEDs you're using. A link to the datasheet is best. You probably will need to separate the four LEDs into two parallel strings.

i am going to use this blue led View attachment 1W High Power LED.pdf

Can you be more specific?
What doesn't work?

i mean it blink randomly and sometime bright sometime dull.

Hello,

How much current does the led take?
(post the datasheet of the leds please).
With a TIP31 it is unlikely you can drive 2 power leds.
You should have a look at some mosfet to drive the leds.
The 4017 can only put out about 7 mA.

Bertus

this is the datasheet View attachment 1W High Power LED.pdf
i am use the blue led

Replace the transistors with a single ULN2004 and drive each LED with a seperate output

i will try your circuit

 

You need to use a current regulator. That LED wants 350mA while the forward voltage varies between 3.0V and 3.6V. It's possible to rely on a resistor for this regulation but by the time you factor in the LED Vf variation and the supply variation, you have significant heat loss in the resistor.

 

I would replace Q1,2 with mosfets IRF540, better current pulsing.

Strongly agree with dave.
Change Q1 and Q2 to n-channel power MOSFETs.
Delete R7 and R9
Increase R8 and R10 to 22 K each.

That fixes the circuit in terms of its output drive. Separate from that is doing whatever your LEDs require for current limiting.

ak

 

One more in agreement with using MOSFETs. Comment in #4 still stands.

 

Hi

The ULN2004 can't handle that much continuous current (approx. 700mA for two WAYJUNG LED's)
Your better off using a PWM/Mosfet LED driver.

Also-
What type of power supply are you using?

 

Here is circuit with driver changes recommended per Doggydave and AK

 

I think he wants one pair of LEDs to be much dimmer than the other. Looks good though.

 

I think he wants one pair of LEDs to be much dimmer than the other. Looks good though.

Hmmm...I would've thought he wanted one pair a different color? oh well...

 

Hmmm...I would've thought he wanted one pair a different color? oh well...

I assumed the high values of R3 and R4 were to produce just a slight glow. I'm not sure what a high power LED needs to accomplish that.

 

Looks good. To be clear, I suggested 22 K gate resistors only because that value was used somewhere else in the circuit. Now that the timer and reset have 10 K resistors, that value is fine for Rgs.

ak

 

I assumed the high values of R3 and R4 were to produce just a slight glow. I'm not sure what a high power LED needs to accomplish that.

Hmm...I didn't notice that....interesting.

 

Hmm...I didn't notice that....interesting.

That's what forums are for.