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 Resistors for LED indicators

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Tanabuso
Tanabuso


Posts : 60
Join date : 2014-11-29
Age : 42

PostSubject: Resistors for LED indicators   Wed Oct 28, 2015 1:49 am

Has anyone ever tried to determine which is the maximum resistance you can add with LED indicators for not getting an error on the dashboard?
The idea behind my question is as follows.
A LED indicator has too much resistance to be detected as a "good" indicator. To avoid a constant error on the dash we need to add a resistor in parallel. Now, I'm looking for the point that the resistor at its own just has too much resistance for being detected as "good" but together with the resistance of the LED it should be just enough to be detected as a working indicator.
When the LED indicator should be broken, the dash could detect it and give an error.

Anyone tried this yet?
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Oz1200Guzzi
Don Abbondio
Don Abbondio


Posts : 1783
Join date : 2014-03-13
Age : 62

PostSubject: Re: Resistors for LED indicators   Wed Oct 28, 2015 3:31 am

Assuming a 12W light to be replaced by a LED, then:

P = V x I then I = P / V = 12 / 12 = 1 Amp

Assume LED current is 23 mA then I - 23 mA = 0.977 Amp

R = V x I = 12 x 0.977 = 11.724 Ohm

Try a 12 Ohm or 15 Ohm resistor for starters, maybe even an 18 Ohm; a 12 Ohm resistor needs to be V x I Watts = 12 x 0.977 = 11.72 Watt say 12 watt - that way the dash will be happy that there is a "bulb" in circuit that is not blown. Increasing resistance will equal a smaller wattage resistor.

That's for starters...
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ghezzi
Fra Cristoforo
Fra Cristoforo


Posts : 1699
Join date : 2014-05-22
Age : 59

PostSubject: Re: Resistors for LED indicators   Wed Oct 28, 2015 5:21 pm

Don't over complicate it, quality LED's are long life and more reliable than a filament bulb.
Jam in a resistor, ride and be happy.

If you are concerned about electrical failures, do a pre and post ride check everyday.
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Guzzi Cat
Grignapoco
Grignapoco


Posts : 178
Join date : 2014-09-02

PostSubject: Re: Resistors for LED indicators   Thu Oct 29, 2015 3:42 pm

My Son's cbr 600 had LED indicators that were flashing too fast, so instead of fitting resistors I changed the flasher unit with one for use with LED's that I picked up on ebay for €15.

I'm not sure if you want to go that route or which unit will work with the GRiSO but it made for a quick fix.
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Oz1200Guzzi
Don Abbondio
Don Abbondio


Posts : 1783
Join date : 2014-03-13
Age : 62

PostSubject: Re: Resistors for LED indicators   Thu Oct 29, 2015 6:53 pm

MG's use the dash to control it - hence the resistor to fool the dash all is OK and it thinks there is a real bulb in the loop
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Ralf z
Tiradritto
Tiradritto


Posts : 315
Join date : 2014-01-02
Age : 49

PostSubject: Re: Resistors for LED indicators   Thu Oct 29, 2015 9:11 pm

I bought inline resistors from mcas,
They were very simple plug and play.
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ScottMellor
Carlotto
Carlotto


Posts : 43
Join date : 2014-05-02
Age : 59

PostSubject: Re: Resistors for LED indicators   Sat Oct 31, 2015 10:48 am

Oh! I remember this from 6th form physics:
Ohms LAw
V=IR
V = Voltage
I = Current
R = resistance
P = Power (Watts).
P = Vsquared/R

Rt = total resistance the dash wants to see:
So for your 12 watt bulb and a 12 volt battery
Rt = 12v x 12v/12watts
Rt = 12 Ohms.

Rled = led resistance
Rr = additional resistor.
1/Rt = 1/Rled + 1/Rr

Rr = (Rled x Rt)/(Rled-Rt)
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PostSubject: Re: Resistors for LED indicators   Today at 5:25 am

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Resistors for LED indicators
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