Flashing leds

[Robmatthews]

You have indeed wired em wrong and with the forward voltage of the diode being 4 volts will need wiring in twos, in series, with a 220 ohm resistor

option b In three's, in series with a 1ohm resistor and only have 15 leds.

wiring in pairs will draw the least current too at 120ma as opposed to 160ma for option b

Hope that helps Rob

[POPEYE]

Work this one out then!! when i wired a load of leds up to light the model car display they worked fine from a 12v battery but when i connected a domestic light fitting (the ones with 12v spots, GU thingy's) they went crazy, they'd go dim then bright and do it again, then flash like mad, then back to dim and bright, all led's were wired with a ristor each, (no series or paralell)
gave up in the end and now i have "SMD" tapes (light strips) much easier, just hook em to a suitable tranny,

if you have a small "gell cell" battery handy just test each led before fitting, ya never know thye might have accidentally dropped a flasher in there,
i've had flashers, duff ones in some packs, especially from the peoples republic of tiddley winks sorry that was a bit "politicly incorrect" of me

[shokenore]

You have indeed wired em wrong and with the forward voltage of the diode being 4 volts will need wiring in twos, in series, with a 220 ohm resistor

option b In three's, in series with a 1ohm resistor and only have 15 leds.

wiring in pairs will draw the least current too at 120ma as opposed to 160ma for option b

Hope that helps Rob

Me no understand


Have cut out the last two runs so am only using 8 leds (two lots of 4)

And they are lit

Why do I need resistors?


In simples please I am but a simpleton

[Robmatthews]

from the little diagram you done it appears that you,ve linked them negative to positive in a chain which is in series rather than paralell.led,s are very current sensitive rather than voltage sensitive and require the same current to each(within a few milliamps).link all the positives together and all the negatives then you will have a paralell circuit providing constant current to each.with domestic led,s you would normally have a led driver to regulate the current,not sure about ones used in cars.

They'll all pop without resistors...

In the house you need a dc driver for led stuff not to be confused with a 12 transformer. On a vehicle the batterys are dc so obviously dont need a regulator/driver or resistors if you buy 12 volt leds which is not always possible anyway.

[Robmatthews]

In simple terms you'll shorten the life of them, by how much, im unsure, could be hours could be weeks all depends on the quality of the led.

If you wired them in rows of 4 you should be ok, but they wont be at full brightness, if you want to experiment try doing a row of three and see the difference although they will be on the limit without the resistor there and may pop.

[slobodan]

And the answer is.................























Get Apache to do them for you.

[POPEYE]

You can run them in series without a resistor but as said any flxuation (?) in the supply can over load and shorten their life (or blow them alltogether if it's a big fluxuation (i'll get it right eventually) ya need to add up the forward voltage on each one till it comes out at 12v, they'll work ok but who knows how long for, i always add a resistor, as you know the alternator on a car can push out 13v or slightly more at times, so it aint a constant supply, resistor's just a safegard,

[Robmatthews]

Work this one out then!! when i wired a load of leds up to light the model car display they worked fine from a 12v battery but when i connected a domestic light fitting (the ones with 12v spots, GU thingy's) they went crazy, they'd go dim then bright and do it again, then flash like mad, then back to dim and bright, all led's were wired with a ristor each, (no series or paralell)
gave up in the end and now i have "SMD" tapes (light strips) much easier, just hook em to a suitable tranny,

if you have a small "gell cell" battery handy just test each led before fitting, ya never know thye might have accidentally dropped a flasher in there,
i've had flashers, duff ones in some packs, especially from the peoples republic of tiddley winks sorry that was a bit "politicly incorrect" of me

Indeed they can be mixed up sometimes.

Thanks for the laff, (im an electrician) A 12 volt transformer as found on lv(12v) downlights in a house is only stepping down the voltage the current is still ac-alternating current.-which works at 50hz meaning the current is 'switching' on and off 50 times a second.Im suprised the leds worked at all!

led's work on dc-direct current, If using them on a mains supply in a house you need a 12 volt driver.

A driver and transformer are two different things

[Albannach]

Get Apache to do them for you.

That's what I did, mine don't flash

[shokenore]

More than likely my first attempt failed due to crappy soldering and poor earth.

Just finished mk2

16 leds

4 lots of 4 wired + - common + and common -

tested on my spare battery and all shiny shiny not twinkly twinkly.

[POPEYE]

Indeed they can be mixed up sometimes.

Thanks for the laff, (im an electrician) A 12 volt transformer as found on lv(12v) downlights in a house is only stepping down the voltage the current is still ac-alternating current.-which works at 50hz meaning the current is 'switching' on and off 50 times a second.Im suprised the leds worked at all!

led's work on dc-direct current, If using them on a mains supply in a house you need a 12 volt driver.

A driver and transformer are two different things

Yes as you guessed i'm no electrictian, the gu10 thing was just a try, i thought (foolishly) that if it powered three spots it'd do for the led's
anyway it didn't explode in my face so no damage done,
this is the new case and "SMD" strips i got the transformer/driver from the same supplyer, they do verious units that can drive strips from 3mt to about 30, (theres about 15 mt's of smd's in there,

[Ambobeer]

If the flashing LEDs were in series with normally working LEDs then that is strange. The current that passes through will be the same in a series circuit so if some are working and some flashing in the same 'string' I'd say faulty LEDs.

As previously mentioned, best to have some form of resistor too. This is there to limit the current.

Resistor can be calculated (I think) from {(Vs-Vled)*1000}/Iled=R
Where Vs is supply voltage (12v on a car) Vled is forward voltage required to drive LED - from manufactures data and Iled is current in LED again from manufactures data. This will no doubt be in milliamps which is why you multiply the top row by 1000. R is resistance in ohms. Resistors tend to be manufactured to standard values so you'd need to go up to the next nearest value.

That's what my memory says, it's not what it was so I might have got some of that wrong.

[wald]

led s

seen these n just ordered seems easier
http://www.ebay.co.uk/itm/2905910790...84.m1423.l2649

[Apache]

Thanks for the pointers, but Apache is retired from the LED business. My 'real' job is so busy these days that I don't have a great deal of time, get home tired, and as what I do is 'electronics' based, I don't really want to do it when I get home too.

Current (no pun intended) orders will be satisfied ASAP, but no more will be accepted. That goes for stickers too I'm afraid, probably at least til next summer.

[slobodan]

Thanks for the pointers, but Apache is retired from the LED business. My 'real' job is so busy these days that I don't have a great deal of time, get home tired, and as what I do is 'electronics' based, I don't really want to do it when I get home too.

Sanatogen may help.