Need some electronic help, Simultaneous flashing LEDs Options

[Abarth Mike]

I wish to add two simultaneous flashing roof lights. I have a Scalextric Roof light PCB but it is 26mm x 17mm. I don't have enough room for that inside the car and the underside of the roof is curved so flat circuit won't fit. So I thought a scratch built circuit using a collection of components bundled rather than on a PCB and tuck it away in the 21x9x15 space I have. Judicious use of heat shrink tubing etc..

I found this Circuit But it is for alternating flashing.

One transistor looks to be triggered from the other LED. Can I simply halve the circuit, triggering the transistor off the negative side of the capacitor for the same LED?

Is there a better way? Physically I know what a 780X voltage regulator is but I really need to use the minimum of components.

Secondary thought: Below the 21x9x15 is a space underneath that is 11x8x 18 so i could if necessary split the circuit into two "clumps"

[Mr Modifier]

You could just buy a prewired flashing LED - they come in a variety if colours or a colour changing version. If you want both LEDs to flash at the same time get one flashing LED and one ordinary one and wire them in series with a suitable resistor. No transistors or fancy electronics required.

[Abarth Mike]

OK I'll see what my neighborhood electronics shop has. Although I suspect flashing ones will not be in stock. I hope to be pleasantly surprised. I have some red/blue flashing ones but need yellow or orange.

Hmm. Maybe I could hide a red/blue flashing one and use it to trigger two yellow ones?

[Abarth Mike]

BRILLIANT Thanks Mr. M.

Sometimes the simplest solution is not obviously apparent.

Proof of concept. I now have a red/blue and two orange lights flashing in unison. At 6.5v the orange ones flash but never completely go out because I suspect of the red/blue changeover. But at 8 volts the red/blue still flashes but the orange ones stay on.

More experimentation required or a single colour flashing LED.

[rick1776]

Refering to the circuit you posted. Just connect two LEDs in series and reduce the resistor value from 470 to say 330. Remove the LED from the "other" side and replace with say a 120 resistor. You want it to flash faster then reduce the R2 and R3 values from 39k to say 33k etc. Want it to flash slower then increase to 47K. Want it to have different on/off times than change only R2 and keep R3 the same.

cheers
rick1776

[Abarth Mike]

You could just buy a prewired flashing LED - they come in a variety if colours or a colour changing version. If you want both LEDs to flash at the same time get one flashing LED and one ordinary one and wire them in series with a suitable resistor. No transistors or fancy electronics required.

BUMP.

I'm back to this project

I need some resistor advice.

I have one flashing blue LED and two "normal" orange LED in series with the blue. I have a 410 Ohms resistor in the circuit followed by the blue and then the two orange and then my diode.

If the voltage is too high above 11.5-ish the blue still flashes but the orange ones stay on and do not flash. Threshold seems to be about 7 volts to start flashing.

Most LED voltage calculators do not allow for multiple colours in one circuit or should I treat them as two?

[rick1776]

Youre making hard work of this Mike. A flashing LED is really an oscillator circuit with a LED attached. That is it has a circuit just like the one you tried to build already included in the LED. Its just very small and you cant see it. Youre then trying to add more standard LEDs in series??? Cant see how this is going to work reliably. Why not get a flashing blue and a flashing red and be done with it. Or build the simple circuit you posted and incorporate my simple mods. Just put a blue and red in series and they will flash on/off at the same time. Or put them on opposite arms of the circuit and they will flash on/off, that is as red goes on blue goes off.

You do not need a resistor in series if you have just the flashing LED. You do need the resistor in series if you want to include the other LEDs otherwise you will fry them. But really I cant see how its going to work reliably.

cheers
rick1776

[Abarth Mike]

Thing is is I don't have a lot of room so that is why I thought the flashing one driving the other two might work. I was hoping for the KISS principle. I can drill a hole and poke the flashing one out the bottom of the car and put the other two in the roof.

[rick1776]

What you are proposing wont work. Its that simple. The flashing blue LED will not "drive" the other standard LEDs. Just buy blue and red flashing type LEDs, job done. If you want one on with the other off and then swapping over then you are left with no alternative but to include the cct you posted. You can not reinvent the laws of physics.

cheers
rick1776

[lordjw]

I respect the KISS principle..... but.

Few years ago I modified FLY Corvette pacecar to have six leds flashing at quite complicated repeated sequence.

I was able to do this with PIC12C508 micro. Unfortunately this is not a simple solution if you do not know electronics.

Cheers!

Julius

[scuderia_turini]

Hello Mike,
I have several times put one flashing LED in series with a non-flasher, along with a resistor (around 500 ohms). The result is that they both flash in sync, although they never go completey "off". Putting two non-flashers seems too much, so you should get a flashing orange LED to pair up with the non-flasher. In a separate chain, put the blue flasher in series with a resistor. This will mean that the two oranges flash together anf the blue flashes at a different rate. Will that not do the job ?

Leo

Head lights on this are done the way described - across the car as it were...