Topic: all LED lighting with flasher relay not working.

[Loki]

im using the specs that the calc shows. it says 3.3 v for white light and 20 mA. but is that not for one led?...the array has 24... that would mean 470 ohm resistor multiplied by 24. resistance is additive in series...so i would need a 11.28 Mohms...seams high...really high.

[Duke McDukiedook]

Read my post, you don't need resistors for your flashers if you run regular bulbs on the rear flashers. They will only run when you turn the flasher on and won't sap power from your electrical system. They will give enough load to get your flashers to work.

[Loki]

this isnt for the signaks, i have those working. this is for the tach/speedo back light. i changed it to a 24 led array very much like this one :

http://cgi.ebay.ca/2-24-LED-white-Strip-Car-Flexible-Bulb-Light-Waterproof-/400181161295?pt=LH_DefaultDomain_0&hash=item5d2ca7ed4f

so even though it says 12v im assuming i still need a resistor and using that calc mystic showed me each individual led will need a 470 ohm resistor....24 in series means a 11.28 Mohm resistor.

[Bodi]

huh?
LEDs have a characteristic forward voltage drop, different for different types of LED but mostly in the 2v to 3.5v range. The packaging should tell you a few things - the LED color and maybe a light wavelength (the exact color), the forward voltage, operating current, and intensity. You want the current you feed the LED to be close to the specified operating current, a LED will burn out if you feed it too much current.
I don't understand the 24V LED, it must have a correct resistor to work at 24V.
Anyway, if you have a 14VDC power source (ie a motorcycle) and a 3V forward drop LED that runs at 30mA (0.03A), figuring the required resistor is pretty easy. First you subtract the forward voltage, 14-3=11V. Then you use Ohm's Law to calculate the resistor - R=E/I meaning resistance in ohms (R) = voltage in volts (V) divided by current in amps (I). R = 11 / 0.03 = 367 ohms.
You talk about 24 LEDs in series. The forward drop for a 3V led with 24 in series would be 72V: this is not going to work at all with a 14V power source. A 24 LED array for automotive use usually has several series sets connected together in parallel. You don't want to have the forward drop total very close to your power source voltage because that makes the current and brightness very dependent on voltage, and your voltage will swing a fair bit between 11 and 14+ volts. You need a few volts dropped in the resistor to stabilize the current over that much swing. Car arrays I've seen have 3 LEDs in series, so a 24 LED array would have 8 strings of 3 LEDs plus a resistor each, all paralleled. You can't use one current control resistor to run paralleled LEDs or strings of LEDs, the minute forward voltage drop differences between "identical" LEDs will mean the LEDs or strings of LEDs will be different brightness and the one with the lowest forward voltage drop will draw more current than expected and probably burn out. Each LED or series string needs its own dropping resistor.
What this means is that your 24 LED cluster has to have built-in resistors I think. So it's probably all set to work at 12V, 24V is a fairly unusual voltage for automotive lamps (but they are available).
And... as the LED forward drop voltage gets higher because you have several in series, your resistor gets a lower ohms value. Lets look at 3 3V LEDs in series: 3 * 3V = 9V. 14-9=5V. R=5/0.03 (still looking for 30mA current) = 33 ohms.
Think about your calculations: a 11.2 MOhm resistor with a 3V LED will give you a current of 0.7 microamps, you might see the LED light if you sit in total darkness for an hour and then hold it right up to your eye with that tiny amount of current.
There are also some very simple circuits that use a cheap IC and a resistor or three to give a constant current to the LED regardless of supply voltage like this http://www.ae5d.com/led-1.html

[mystic_1]

What this means is that your 24 LED cluster has to have built-in resistors I think.

Yes, I agree that those light strips probably have their own current-limiting resistors already.

As I've said, products sold for "12V automotive applications" will already be set up properly.  You only add resistors if you're using bare LED's, and if your product needs them, there will be specs for Forward Voltage drop and max Forward Current.

Have you tested those light strips by hooking them straight to the battery?

mystic_1

[Loki]

thanks alot! this is definitely helping a bunch. the package the leds came in did not have any info on it. as for connecting it to the battery, i did this the other day and it worked for a moment and then just stopped working. the back lights are connected and when i switch the key from off to on you see them bleep on for a moment.

[mystic_1]

thanks alot! this is definitely helping a bunch. the package the leds came in did not have any info on it. as for connecting it to the battery, i did this the other day and it worked for a moment and then just stopped working.

I'm assuming that the above refers to the indicator lights on your triple tree.  Unfortunately, this does not sound good.  What you describe is what LEDs do when they burn out, they come on for a second, then go dark forever.  Got any good ones left?  If so, wire one up in series with a 390 ohm, 1w resistor, directly to the battery.  It should light up and stay on.

the back lights are connected and when i switch the key from off to on you see them bleep on for a moment.

I'm assuming that you mean the instrument backlights.  Does this happen every time you turn on the key?  If so then they may not be burned out, but I'm not sure why they'd be doing that unless there's some other problem.  I would definitely try these connected direct to the battery and see if they stay lit.  If so, then the problem is elsewhere.

mystic_1

[Loki]

sorry i should be more specific. i was referring entirely to the instrument backlights. i had one of them connected to the battery and it was on for a while then just stopped. the other two that i do have installed as the back lights flick on then off when ever i turn the key off to on. so to clarify, im talking about the 24 LED 12v array that i bought off the ebay...one seems to have burn out by connecting it to the battery and the other two just flicker when the bike is turned on and off with the key. does this mean that it is likely that they will need a resistor? when i use the calc you gave me, it has a 120 ohm resistor for every 3 leds....how do i figure out the total size of the resistor i need for the whole array?

[mystic_1]

It's hard to say about those LED strips without more detailed information.  With setups like that you don't typically need to add anything to make them work.  Have you tried contacting the seller?

mystic_1

[Loki]

no i havent contacted the seller. i assumed by it being a 12v setup for vehicles it should just be plug and play. ill go down to the eletronic store and talk to those guys. ill do a voltage test on all the lines befor hand and report back. thanks for the help guys!

cheers

[mystic_1]

ill go down to the eletronic store and talk to those guys. ill do a voltage test on all the lines befor hand and report back.

Good plan on both points.  Good luck, and keep us posted.

mystic_1

[Loki]

ok gents, well i decided to look over the bike and do a voltage test to make sure that there is in fact voltage at the right points and well there was. so pissed off that i had possibly bought wrong leds i decided to try one more thing...... switch the leads and see what happens.

well turns out when i was soldering the wires on i soldered everyone on the opposite sides...
that being said, all leds work perfect after doing the switch.ppphhhhewwwww!!!

heres a pic of the tach/speedo ( not the best quality, but gets the point across)

thanks alot guys, thats a huge load off!!

[Gaither]

All's well that ends well! (And some of us got to watch and learn.)

'Glad you got 'em figured out

OH, HOW I HATE WIRING!!!!

[moumintroll]

Glad you got everything working!  How did you solve your blinker problem?

[Loki]

unfortunately, i havent. iv installed three separate led blinkers, but the lights are just staying on.

[phil71]

you need a different type of flasher. Bi-metal (thermal) flashers need a load to heat up and disconnect, so without a bunch of extra loads hidden in your flasher circuit, you can just buy a solid state flasher unit and be done with it. Any automotive shop will have it.

[moumintroll]

You do need a non-thermal flasher.  I tried this unit (CF12ANL-01) from Autolumination, but after replacing all my stock blinkers with LEDs, I had the same problem...every time I hit the turn signal switch, all 4 blinkers would light up and not blink! 

However, if I wired in one of the old stock filament blinkers (replacing one of the LEDs), everything worked as planned.  Because of this, I'm assuming there still wasn't enough load in the circuit to trigger the solid state blinker (which is odd).   My solution is to go with after market dual filament turn signals in the front so I can use them as running lights as well as turn signals, and LED turn signals in the rear. 

You can also try wiring in some resistors parallel with your LEDs to increase the load slightly.