Buell Forum: Modify your stock flasher relay for LEDs

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Buell Forum » Knowledge Vault (tech, parts, apparel, & accessories topics) » Electrical - Battery, Charg Sys, Lights, Switches, Sensors & Guages » Archive through October 14, 2011 » Modify your stock flasher relay for LEDs

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Terrys1980

Posted on Monday, August 01, 2011 - 10:51 pm:

I found this mod on another forum so I thought I would post it up here. Very simple to do and saves you $20.

Just pull the cover and remove the 2nd pin on the ic chip.

Froggy

Posted on Monday, August 01, 2011 - 11:37 pm:

Good find!

Reepicheep

Posted on Tuesday, August 02, 2011 - 08:16 am:

For the record, that would technically be the 7th pin, but we know what you mean. : )

Cool! From:
http://pdf1.alldatasheet.com/datasheet-pdf/view/56 280/ATMEL/U643B.html

quote:
Pin 7, Lamp outage detection
The lamp current is monitored via an external shunt
resistor R3 and an internal comparator K1 with its
reference voltage of typ. 81 mV (VS = 12 V). The outage
of one lamp out of two lamps is detected according to the
following calculation:
Nominal current of 1 lamp: 21 W / (VS = 12 V):
Ilamp = 1.75 A
Nominal current of 2 lamps: 2 x 21 W / (VS = 12 V):
Ilamp = 3.5 A.
The detection threshold is recommended to be set in the
middle of the current range: Ioutage 2.7 A
Thus the shunt resistor is calculated as:
R3 = VT (K1) / Ioutage
R3 = 81 mV/2.7 A = 30 m.
Comparator K1�s reference voltage is matched to the
characteristics of filament lamps (see �control signal
threshold� in the data part).
The combination of shunt resistor and resistance of wire
harness prevents Pin 7 from a too high voltage in the case
of shorted lamps.

So you loose your dead lamp indicator, but the flash rate is correct.

And I wonder why on earth that chip is socketed on that part? That's an expensive way to build a commodity part...

Terrys1980

Posted on Tuesday, August 02, 2011 - 09:01 am:

I'm an ET by trade and one thing I've learned when explaining electronics is that you gotta keep it simple for the simple minded!

Doncasto

Posted on Thursday, August 04, 2011 - 10:35 am:

Mr. Simple Minded asks . . ."So Terry, . . .if I take apart my flasher, disconnect the part shown, put it back on the bike . . .can I than use LED bulbs rather than stock?"

Thanks in advance . . .(and remember to keep it simple)

Terrys1980

Posted on Thursday, August 04, 2011 - 11:11 am:

Yes but you can use LED bulbs without the mod they will just flash faster. I rather the faster flash.

Greg_e

Posted on Monday, October 10, 2011 - 02:02 am:

So if we really want to get anal, we could adjust the resistor so that if we lose an LED fixture we will once again get the rapid flash, right?

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