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Flashing LED circuit

Dear All,

Please can you advise on the wiring of a flashing LED circuit.

I want to connect 5 off 10mm red flashing HE LEDs (RS no.262-2977 Kingbright no.L-816BID) to a 9v DC supply.

It says on their spec sheet:

VF 9-12v IF 22mA IF max 38-56mA Power dissipation 310mW VR max 0.5v

Should I wire them in parallel?

I believe I cannot wire them in series as the voltage drop across each LED will be too much for the supply won't it?

It says in the catalogue that series resistors are not required and cannot be used to drop a higher voltage.

Any advice will be gratefully received!

Reply to
nick
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Yes.
Reply to
John Fields

It seems that your LEDs have built-in current-control. So wiring them in parallel should do.

HTH, Mark Van Borm

Reply to
Mark VB

Thanks for your advice guys!

I was asking these questions because having constructed a few of these circuits in parallel arrangements for use at work, some of them have packed up completely. Presumably one LED blew and caused the others to blow.

Is there any way I can prevent this from happening again? Adding a resistor to each LED? If so what size would you recommend? Thanks in advance for your help!

Reply to
nick

Generally, each LED should have a resistor in series to limit the current through the LED. You will have to look at the spec. sheet for your particular LED, but most are looking for 2-3V and 20 mA operating current. The size of the resistor depends on supply voltage, and will have to be calculated accordingly. Paralleling LED's is not a good idea without a series restor on each LED.

Nels

Reply to
Nelson Johnsrud

Probably, the polarity was reversed when they blew, so adding a resistor won't help much.

Mark VB

Reply to
Mark VB

This is probably not the mechanism. The LEDs in your original post DO NOT need a series dropping resistor. I'm guessing that you used ordinary LEDs in parallel, with only one dropping resistor. This will NOT work, because they have different forward voltage drops and one will hog all of the current until it blows, and then you get a cascade effect as the rest of the LEDs are overdriven by the lower-value resistor.

THESE LEDS:

do NOT need any resistor - in fact, you said yourself that the spec sheet specifically says not to use one.

Any other "standard" LED DOES need a series resistor, because when the forward voltage reaches 1.2V (or whatever the Vf), there is no mechanism to limit the LED's current other than the series resistor. This might be helpful:

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Have Fun! Rich

Reply to
Rich Grise

those flashing leds detailed above are designed to operate off 9v DC. as long as they are connected correclty. Hook them up backwards and they'll die pretty quickly. if you're operating them off batteires I'd put a diode (eg 1N4001) in series with the group of flashing leds to protect against that.

not for those LEDS.

Bye. Jasen

Reply to
Jasen Betts

Thanks for your helpful advice everyone!

Nick

Reply to
nick

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