[Author Index] [Date Index] [Thread Index]
[Date Prev][Date Next][Thread Prev][Thread Next]

Re: [ST] Spastic turn signals



Historically, flasher units were an electro-thermal oscillator.  The
load current flowed though a heater that bent a bi-metal strip that
broke the circuit after a delay while it warmed-up.  When the circuit
broke, it all cooled and re-made.  Hence the current drawn affected the
speed of oscillation.  The fact that it flashed fast when a bulb blew
was seen as a usefull diagnostic feature.
With modern power semiconductors, it is possible to provide the same
functionality without the naff side-effects.
Chris Harwood
00 RS

>>> Neil.Lindsey@xxxxxxx 10/09/2005 00:27:00 >>>
I just HAD to jump in here.

For starters, the typical function of a relay is to allow the
controlling/low-current switch (in this case the turnsignal switch) to
avoid having to carry the higher current drawn by the LOAD (in this
case
the LEDs or lightbulbs) and this allows the controlling switch to the
be
mounted relatively far away from the relay and the load itself.  The
only thing that varies when you change from lightbulbs to LEDs is the
load current
(nothing changes on the controlling/input side).  So if the new load
is
LESS (as it will be for LEDs only), then the existing relay is, in
fact,
now MORE THAN ADEQUATE to handle the load and there is no need for a
change to the relay. Just as an aside, when you add additional
turnsignal bulbs to the circuit, as you would be doing, for example,
by
wiring in trailer turnsignals, you will be increasing the load
current.
Only then is it possible that you could conceivably exceed the
current-carrying capability of the output side of a relay.

However, as has been pointed out, the decrease in load current caused
by
replacing turnsignals with LEDs, can upset the flash rate.  That's why
you add more load (suitable resistors added in parallel to the LEDs to
increase the current back to what it was before the lightbulbs were
replaced.

I had a look at the schematic of the Sprint RS and here's what I
found:

There is no relay.  There is an Indicator Unit and no, this is not
just
a case of semantics. It is the OUTPUT of this flasher unit that is
directed (by way of the turn signal switch) to either the left- or
right-side indicators depending on which way you throw the switch.
Therefore the entire load current drawn by the signals IS passing
through the turnsignal switch.  Any decrease in this load current can
change the flash rate.  So you would need the additional 'load
equalizing' resistors to increase the total current drawn from the
flasher unit.

Neil

----- Original Message ----- 
From: "Paul English" <tallpaul@xxxxxxxxxxxxx>
To: <ST@xxxxxxxxxxxxxx>; <rgalea@xxxxxxxxx>
Cc: <brian@xxxxxxxxxx>
Sent: Friday, September 09, 2005 12:28 PM
Subject: Re: [ST] Spastic turn signals


>
>
> On Fri, 9 Sep 2005, Rupert Galea wrote:
>
> > On 9/9/05, Brian Nobles <thenobles@xxxxxxxxx> wrote:
> > > I bought some Lockhart Phillips Short Stalk III LED turn signals
(like
> > > these:
http://www.newportcycleparts.com/categories/electrical/turn_sigs-short.htm).
> > >
> > > They work great but... now my signals flash at about a rate of
3x's per second.
> > >
> > > Anybody know how I can get them to slow down?
> > >
> > > I assume it has something to do with resistance or ohms or watts
or
> > > volts or something else like that (I can barely spell
elektrickle
let
> > > alone speak intelligently about it).
> >
> > You need to add a resistor
> > http://www.customdynamics.com/led_motorcycle_lighting_faqs.htm 
>
> Bringing the resistance (and wattage) of your LED signals back up to
the
> same as your original bulbs in order for the original flasher relay
to
> work. Thus destroying any possible value of going to LEDs in the
first
> place (power savings) and then you get to live with the reduced
viewing angle that the LEDS have.
>
> What you *really* want to do is replace the turn signal relay with
one
> sized for the lower power draw of the LEDs. This is a pretty common
> problem on 4-wheeled vehicles when you ad a trailer and suddenly
you've
> got twice the power draw on your turn signals - the original relay
doesn't
> work any more.
>
> Unless of course it is just a matter of having a separate wire
controlling
> flash and the original relay *can* handle the power difference & the
> "flash" signal just isn't getting through. In that case the fix
referred
> to by others will work.
> _______________________________________________
> Triumph Sprint ST/RS mailing list
> Send list posts to ST@xxxxxxxxxxxxxx 
> Change your list options at www.Triumphnet.com 
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Anti-Virus.
> Version: 7.0.344 / Virus Database: 267.10.19/93 - Release Date:
9/08/05
>
>




-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.344 / Virus Database: 267.10.19/93 - Release Date:
9/08/05

_______________________________________________
Triumph Sprint ST/RS mailing list
Send list posts to ST@xxxxxxxxxxxxxx 
Change your list options at www.Triumphnet.com
_______________________________________________
Triumph Sprint ST/RS mailing list
Send list posts to ST@xxxxxxxxxxxxxx
Change your list options at www.Triumphnet.com