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'[EE] means of dimming auto tail light?'
2005\11\27@210014 by Danny Sauer

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Since I'm down to only a few hundred useful things that I need to get
done at home, I though it'd be entertaining to make the taillights on
my Caprice light sequentially.  But really, a simple R/C time delay
seems boring, whereas the ability to make the 3 bulbs flash in amusing
patterns is interesting.  Off-road, of course - I'm not sure if it's
legal or not to do anything like that on the road, but I don't want
some boob ramming the back of my car due to screwy brake lights either
way.

So presume that I'm capable of determining whether or not the light
is being activated by the brake or a turn signal, and whether or not
the car's in drive.  In fact, presume that I've got everything figured
out but how to actually control a few bulbs.  I guess that using a
PWM-like "turn them on and off real fast" thing will work fine for
making the lights appear to fade in and out.  The bright side of an
1157 should be on the order of 25-30 watts, which means I have to
switch about 2.5 amps at 12 volts.  I need individual bulb control,
and there are 6 or 8 bulbs, depending on how ambitiously I try to kill
my time.

A relay likely won't work very long, if at all, under that kind of
use.  So, I need a transistor of some sort, right?  Probably PNP,
since I can't really interrupt the negative side and therefore have to
switch the positive lead?  Basically, I don't know jack about how to
select an appropriate transistor for this application or what to look
for other than current rating.  Do I need a particular type, do I have
to set something up like a Darlington pair, does that even make sense,
etc?  I'm pretty sure that all I have is enough knowledge to make me
sound stupid to those who know in this area, so I'd appreciate both
general knowledge and specific part numbers. :)

Thanks!
--Danny

2005\11\27@211604 by Jinx

face picon face
> A relay likely won't work very long, if at all, under that kind of
> use.  So, I need a transistor of some sort, right?  Probably PNP,

> to set something up like a Darlington pair

Danny, this would be similar to one side of the high-side of an
H-bridge. The 5V control (from the PIC presumably) goes to
the base of an NPN, which in turn controls the base of the PNP
high-current switch in the +ve. The NPN not only isolates the
PIC from the 12V on the PNP base, but also amplifies the PIC's
pin current. The bulb hot goes to C and cold side to 0V

Like Fig1

instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s1999/bell/abel
l.cnazarian.ee476.finalproject.rccar.html

2005\11\27@213606 by David Van Horn

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> A relay likely won't work very long, if at all, under that kind of
> use.  So, I need a transistor of some sort, right?  Probably PNP,
> since I can't really interrupt the negative side and therefore have to
> switch the positive lead?  

PNP bipolar transistor, or P channel Mosfet.
Have a google on "inrush current" with lightbulbs though.
Read the resistance when cold, LOTS more current flows then, than when
they warm up.




2005\11\27@220352 by Jinx

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> PWM-like "turn them on and off real fast" thing will work fine
> for making the lights appear to fade in and out

A filament bulb isn't going to be *that* fast because of thermal
inertia. Moderately crude PWM would do. If you want fast and
fancy you'd have to use LEDs (no bad thing - another project for
you)

http://www.siliconchip.com.au/cms/A_30305/article.html

I have the print article (a very comprehensive 10 pages), showing
how to make the various "bulbs" etc, which I can scan

2005\11\27@220654 by David Van Horn

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> Danny, this would be similar to one side of the high-side of an
> H-bridge. The 5V control (from the PIC presumably) goes to
> the base of an NPN, which in turn controls the base of the PNP
> high-current switch in the +ve. The NPN not only isolates the
> PIC from the 12V on the PNP base, but also amplifies the PIC's
> pin current. The bulb hot goes to C and cold side to 0V



Szaiklai pair, right?



2005\11\27@222048 by Roy

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> -----Original Message-----
>
> www.siliconchip.com.au/cms/A_30305/article.html
>
> I have the print article (a very comprehensive 10 pages), showing
> how to make the various "bulbs" etc, which I can scan
>

Jinx - Hope you have permission for copy write from Silicon Chip :-(



--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.362 / Virus Database: 267.13.8/183 - Release Date:
25/11/2005


2005\11\27@225715 by Jinx

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> Jinx - Hope you have permission for copy write from Silicon
> Chip :-(

I think I might do actually, on a one-to-one basis. I asked them
a couple of years ago if it was OK to scan an article for a friend
in Romania and they said yes, they had no problem with that, on
the proviso that I wasn't to assume carte blanche to reproduce
swathes of the magazine to put in the public domain

2005\11\27@232508 by R. I. Nelson

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Sorry to play the devils advocate here but there is something to
consider here.

In some states and countries if you are not running stock from the
factory lights and you are in an accident where it may have been a
contributing factor.  You open your self up to a lawsuit or ticket.

Many years ago when I brought a motorcycle from Japan to the US  I was
stopped and forbidden from riding it on the roadways.  It seems in Japan
the rear signal lights have a yellow lens  but in the US at that time
all lights on the back of the vehicle had to be RED.  Except for the
reverse or back up lights.



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2005\11\28@005505 by Vitaliy

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Danny Sauer wrote:
> patterns is interesting.  Off-road, of course - I'm not sure if it's
> legal or not to do anything like that on the road, but I don't want
> some boob ramming the back of my car due to screwy brake lights either
> way.

Three years ago someone I know built a circuit based on the 12C509 to make
the headlights of a car oscillate in the same pattern as the headlights of
American police cars. He built about 20 of them, and I've heard first person
accounts of people using this device to make other motorists pull over
(often, on the freeway). It is interesting to note that the *only* thing
needed to make most people pull over are the flashing headlights.

Anyway, seeing that his invention was so popular, he called a lawyer to see
if he could commercialize it. The answer was, using any kind of oscillating
lights is illegal. However, they are not illegal to possess, and it is
perfectly legal to sell such devices.

Best regards,

Vitaliy

2005\11\28@012108 by Russell McMahon

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>> http://www.siliconchip.com.au/cms/A_30305/article.html

>> I have the print article (a very comprehensive 10 pages), showing
>> how to make the various "bulbs" etc, which I can scan
>>
>
> Jinx - Hope you have permission for copy write from Silicon Chip :-(

Very possibly comes under "reasonable use" aspect of copyright
depending on what country you are in. As long as he is sending it to
an individual and not posting it on the web it may be 100% kosher.


       RM

2005\11\28@030347 by Vasile Surducan

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On 11/28/05, Jinx <.....joecolquittKILLspamspam@spam@clear.net.nz> wrote:
> > PWM-like "turn them on and off real fast" thing will work fine
> > for making the lights appear to fade in and out
>
> A filament bulb isn't going to be *that* fast because of thermal
> inertia. Moderately crude PWM would do.

But what about the filament life time ? One of the biggest problem
of the halogen lamps appear in the cold-warm transient of the filament.
The PWM is keepig the same pulse current through the filament, even
the effect for the eyes it's a dimmer light.
I saw many lamps dying like this with a lot of electronics nearby.

cheers,
Vasile

If you want fast and
> fancy you'd have to use LEDs (no bad thing - another project for
> you)
>
> http://www.siliconchip.com.au/cms/A_30305/article.html
>
> I have the print article (a very comprehensive 10 pages), showing
> how to make the various "bulbs" etc, which I can scan
>
> -

2005\11\28@031324 by Jinx

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> Very possibly comes under "reasonable use" aspect of copyright
> depending on what country you are in. As long as he is sending it to
> an individual and not posting it on the web it may be 100% kosher.

Leo Simpson, the publisher of Silicon Chip, had a thing or two to
say about people copying his magazine in an editorial a little while
ago (6/05). His major gripe, and biggest worry from a revenue POV,
is institutionalised (schools, labs, offices etc) photocopying in regions
where the magazine is available in the print version. I think that, in
conjunction with the reply I received from them, shows that a
scanned article or two sent by email (more than likely to a place
where SC is not available) is a miniscule concern

If there's a library in Danny's area that has Silicon Chip, then by
all means he can scoot along and have a look. And probably
photocopy it ? (In b/w probably). I'd guess that Silicon Chip is
quite rare or even unknown in Illinois (?), so I'd be more than
happy to scan the article and email it to him, if he wants it that is

2005\11\28@031620 by Jinx

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>  But what about the filament life time ? One of the biggest
> problem of the halogen lamps appear in the cold-warm
> transient of the filament

I know halogens have their problems with dimmers Vasile, but
Danny was asking about tail lights. Are tail lights usually halogens ?

2005\11\28@032540 by Jinx

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> In some states and countries if you are not running stock from
> the factory lights and you are in an accident where it may have
> been a contributing factor.  You open yourself up to a lawsuit
> or ticket.

Perhaps if you keep the colour correct, changing the intensity
(withing reason) isn't so frowned on. In fact it's encouraged if
used practically

USA flasher

http://www.brakeflasher.com/cycle.htm

NZ flasher

http://www.databrake.co.nz/

2005\11\28@043034 by Enrico Schuerrer

picon face

----- Original Message -----
From: "Jinx" <joecolquittspamKILLspamclear.net.nz>
To: "Microcontroller discussion list - Public." <.....piclistKILLspamspam.....mit.edu>
Sent: Monday, November 28, 2005 9:16 AM
Subject: Re: [EE] means of dimming auto tail light?


>
> >  But what about the filament life time ? One of the biggest
> > problem of the halogen lamps appear in the cold-warm
> > transient of the filament
>
> I know halogens have their problems with dimmers Vasile, but
> Danny was asking about tail lights. Are tail lights usually halogens ?

In general car bulbs (normal ones and halogen bulbs) do have a big
difference between cold and hot resistance. For instance a 12V/5W bulb
(often used in European cars for taillight) has a "hot" filament resistance
of around 28 Ohms and a "cold" filament resistance of < 2 Ohms. One solution
of the car industry is to switch between around 3V and 12V, then the
difference will not kill the driving mosfet and the intensity of the 3V
"preheating" is nearly not visible.
The driving Mosfets are dimensioned for maximum peak sourcecurrent of up to
100A.

In the meantime many (new) cars have now LED tail- and braking lights which
are easier to dim between tail- and braking lights. There are up to 10mm
high intensity LEDs available I have used on my motorbike for tail- and
braking light together with a constant current regulator (LM317) switched
between 28mA for taillight and 200mA for braking lights. I used 16 diodes in
groups of 4 (4 LED in serial connection) and 4 of this groups in parallel
connection, driven by one LM317. The switch between taillight and braking
light is done by a small relay operated from the brake switch - this relay
switches between a 7.5 Ohm/1 W resistor for braking lights and 39 Ohms/ 0.5W
for taillights.

Regards
Enrico





2005\11\28@045218 by Russell McMahon

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> I though it'd be entertaining to make the taillights on
> my Caprice light sequentially.

> ... I guess that using a
> PWM-like "turn them on and off real fast" thing will work fine for
> making the lights appear to fade in and out.  The bright side of an
> 1157 should be on the order of 25-30 watts, which means I have to
> switch about 2.5 amps at 12 volts.  I need individual bulb control,
> and there are 6 or 8 bulbs, depending on how ambitiously I try to
> kill
> my time.

1.    A FET switch is liable to be MUCH easier to implement. Bipolar
takes significant drive for significant load. Even using Darlingtons
you tend to have to deal with this.

A FET with Rdson of say 100 milliohm (very poor spec) achieves an
equivalent bipolar Vsat of 0.25 volts at 2.5 A which is hard to
achieve with bipolar.

PIC etc will drive a logic FET gate directly.

Even if you use a P channel FET so as to be able to switch the high
side the drive circuit is still modest and simple.

An N Channel FET can be used as a high side driver if you are willing
to provide an "above top rail" gate drive supply. using a P Channel
FET is easier.

2.    Be aware that cold bulb filaments have inrush currents many many
times that of operating current - typically around 10 times operating
or around 25A in your case. As you'd probably be using a TO220 FET or
SMD equivalent anything you'd sensibly use should handle this OK.

Here's a simple but useful primer on driving incandescent bulbs

       http://www.allegromicro.com/techpub2/an/an295012.pdf

Adding either a "warming resistor" or a series limiting resistor will
increase lamp lifetime and give the driver an easier job. Both methods
have good and bad points.

__________

An Agilent lab lesson here with some impressive current/voltage/time
curves.

   www.educatorscorner.com/media/Exp17i.pdf
   From    http://www.educatorscorner.com/index.cgi?CONTENT_ID=2188


3.    For PWM above about 1 kHz you are not liable to annoy the bulb
too much as it's thermal time constants *should* be rather longer than
this. A photodetector and scope would prove this. Note that a bulb run
from AC experiences 100 or 120 Hz half sinusoid cycles constantly.
Anything substantially faster than that, even with a square wave form
should be OK.

I am currently PWMing halogen bulbs at 1 kHz plus at present for a
non-automotive application but don't have any lifetime data yet.







       Russell McMahon

2005\11\28@050913 by Jinx

face picon face
> of around 28 Ohms and a "cold" filament resistance of < 2 Ohms.
> One solution of the car industry is to switch between around 3V
> and 12V, then the difference will not kill the driving mosfet and
> the intensity of the 3V "preheating" is nearly not visible

Ah, I knew pre-heating is used in displays but was not aware of
it in vehicles. This would be for a very short time before the 12V
is applied - 3V not there all the time ?

2005\11\28@072304 by Enrico Schuerrer

picon face

----- Original Message -----
From: "Jinx" <EraseMEjoecolquittspam_OUTspamTakeThisOuTclear.net.nz>
To: "Microcontroller discussion list - Public." <piclistspamspam_OUTmit.edu>
Sent: Monday, November 28, 2005 11:09 AM
Subject: Re: [EE] means of dimming auto tail light?


> > of around 28 Ohms and a "cold" filament resistance of < 2 Ohms.
> > One solution of the car industry is to switch between around 3V
> > and 12V, then the difference will not kill the driving mosfet and
> > the intensity of the 3V "preheating" is nearly not visible
>
> Ah, I knew pre-heating is used in displays but was not aware of
> it in vehicles. This would be for a very short time before the 12V
> is applied - 3V not there all the time ?
>
As far as I know from some european upper class models, where no Xenon
lights or LEDs are used (f.i. last S-class models) but the lights are driven
with CAN-bus the electronic "preheats" the bulbs with around 3V. If it is
from start on or only a quasi soft-start is a fact I don't know (I read this
in a german car magazine a few years ago).

Kind regards

Enrico

2005\11\28@080541 by David Van Horn

picon face
>  But what about the filament life time ? One of the biggest problem
> of the halogen lamps appear in the cold-warm transient of the
filament.
> The PWM is keepig the same pulse current through the filament, even
> the effect for the eyes it's a dimmer light.
> I saw many lamps dying like this with a lot of electronics nearby.

You really don't want to dim a halogen unless you need to.  The heat is
required to drive the cycle that re-deposits the tungsten on the
filament.



2005\11\28@081842 by Danny Sauer

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Vitaliy wrote regarding 'Re: [EE] means of dimming auto tail light?' on Mon, Nov 28 at 00:01:
> Danny Sauer wrote:
> >patterns is interesting.  Off-road, of course - I'm not sure if it's
> >legal or not to do anything like that on the road, but I don't want
>
> Anyway, seeing that his invention was so popular, he called a lawyer to see
> if he could commercialize it. The answer was, using any kind of oscillating
> lights is illegal. However, they are not illegal to possess, and it is
> perfectly legal to sell such devices.

It's legal.  The car in question is a retired police car.  It's still
black and white, has a spotlight, etc.  I regularly attend car shows,
cruise-ins, etc, and it'd be fun to have the ability to make the tail
lights flash in different patterns at those events.  I'm planning to
make a headlight flasher, too, but relays will be fine for that
component.  Yeah, I could probably do illegal things like pulling
other people over, etc, but let's try to assume that I'm smarter than
that.  As a related example, I've got several firearms as well, but
they're for target shooting purposes, not killing people.

I've actually been hassled just for driving the cop car out-of-state.
Turns out that some moron had actually pulled someone over (by just
blinking his high beams on and off) a few weeks prior to my visit to
this small town, and the locals had apparently all called the cops
when I pulled in to town on the way to the bed and breakfast my wife
and I were staying at.  Never mind that I was driving a black and
white Caprice with IL plates and my wife in the car, while the person
doing the impersonation was driving a grey Crown Victoria with
Tennessee plates - I was probably out to kidnap some girl.  Sigh.  I
can't think of a better means of entertainment than getting my wife,
driving 4 hours, and kidnapping a stranger.  Especially by doing it in
the "population: 1000" town where the B&B we're staying at is located.

Anyway, the plan for standard operation is for the inner bulbs to
activate immediately, with the outer two fading in fairly quickly -
basically the same thing that the new Mustangs have done for several
years now.  I checked the vehicle code, and this behavior is perfectly
fine.  A few quick flashes is also fine on a motorcycle, in order to
increase visibility, and is not explicitly forbidden for a car.
Tailights flashing on and off otherwise is only for emergency flasher
use, etc.  In other areas (states / countries) the law may vary.

--Danny

2005\11\28@082031 by Howard Winter

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Jinx,

On Mon, 28 Nov 2005 21:25:45 +1300, Jinx wrote:

{Quote hidden}

The critical feature of both these systems is that they are *in addition* to the original brake lights - the
OP was talking about modifying his existing lights, and this is very likely to render them illegal in any
place where the functioning and brightness is laid down.

Cheers,


Howard Winter
St.Albans, England


2005\11\28@083558 by Danny Sauer

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face
Howard wrote regarding 'Re: [EE] means of dimming auto tail light?' on Mon, Nov 28 at 07:26:
> The critical feature of both these systems is that they are *in
> addition* to the original brake lights - the OP was talking about
> modifying his existing lights, and this is very likely to render
> them illegal in any place where the functioning and brightness is
> laid down.

No, I was talking about a system which would behave like stock (or
similar) on-road, with the capability of behaving differently
off-road for demonstration purposes.  On road, the plan is for the
bulbs to come on immediately when the brake pedal is depressed.  When
the turn signal comes on, which would normally cause three bulbs on
one side to blink, I'd like the bulbs to fade in sequentially from
just the inner bulb to all three.  Both actions are done on modern
cars from teh factory, and both are allowed by the state vehicle code.

Sorry I didn't make that more clear. :)

--Danny

2005\11\28@085041 by Howard Winter

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Russell,

On Mon, 28 Nov 2005 22:46:16 +1300, Russell McMahon wrote:

>...
> I am currently PWMing halogen bulbs at 1 kHz plus at present for a
> non-automotive application but don't have any lifetime data yet.

Dimming halogen lights it generally a Bad Thing, because they need the heat of their full-on state to cause
the tungsten that has evaporated to be re-deposited on the filament (the so-called Halogen cycle).  If you
lower the temperature, the tungsten deposits on the inside of the "glass" (actually some form of manufactured
quartz) and is lost from the filament.  Result is a dimming of output because of occlusion, and premature
failure of the filament.  Sometimes *very* premature!

There's a trend to fit extra-low-voltage halogen lights in houses here, and because they create a very intense
light some people want to dim them.  They then find out the drawbacks as above!

Of course in the OP's case, we're not talking about halogen lights anyway...

Cheers,



Howard Winter
St.Albans, England


2005\11\28@085535 by olin piclist

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part 1 1319 bytes content-type:text/plain; (decoded 7bit)

Danny Sauer wrote:
> I guess that using a
> PWM-like "turn them on and off real fast" thing will work fine for
> making the lights appear to fade in and out.  The bright side of an
> 1157 should be on the order of 25-30 watts, which means I have to
> switch about 2.5 amps at 12 volts.  I need individual bulb control,
> and there are 6 or 8 bulbs, depending on how ambitiously I try to kill
> my time.

Sounds like a great job for a 16F630.

> A relay likely won't work very long, if at all, under that kind of
> use.  So, I need a transistor of some sort, right?  Probably PNP,
> since I can't really interrupt the negative side and therefore have to
> switch the positive lead?

That depends on how the bulbs are wired.  Chances are one side ties to
chassis ground and the high side is switched.  In that case you need a high
side switch, which would be either a bipolar (PNP) or FET (P channel).  I
like the P channel FET better, because you'd probably dissipate a watt or
two in the base drive from the PNP.  That by itself isn't a big deal
considering its driving a 25-30 watt bulb, but now you need a power resistor
and some way of making sure it can get rid of the heat.

I've attached a simple circuit that I think will work fine.


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2005\11\28@085601 by Alan B. Pearce

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>When the turn signal comes on, which would normally cause
>three bulbs on one side to blink, I'd like the bulbs to
>fade in sequentially from just the inner bulb to all three.
>Both actions are done on modern cars from teh factory,
>and both are allowed by the state vehicle code.

Good grief, I seem to remember seeing this on a mid to late 60s (IIRC) Chevy
or Ford. Certainly wasn't done by electronics back then ;) Must have been
one of those two makes, as we didn't get very many US originated cars in NZ
back then.

2005\11\28@122026 by Danny Sauer

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Olin wrote regarding 'Re: [EE] means of dimming auto tail light?' on Mon, Nov 28 at 08:14:
> Sounds like a great job for a 16F630.

Coincidentally, I just received a pair of 16F630s with a Digikey order
a couple of days ago - picked up because "someone" helpful suggested
that I use them on my other project.  How'd you know? :)

> chassis ground and the high side is switched.  In that case you need a high
> side switch, which would be either a bipolar (PNP) or FET (P channel).  I
> like the P channel FET better, because you'd probably dissipate a watt or
> two in the base drive from the PNP.  That by itself isn't a big deal
> considering its driving a 25-30 watt bulb, but now you need a power resistor
> and some way of making sure it can get rid of the heat.

Thanks for the circuit suggestion - that helps out quite a bit.  I did
some reading on FETs in general this morning, and they do sound like
they'd be a good choice.  The suggestion to use an IRF7416 is
appreciated, as well - but I've never worked with surface-mount stuff.
Is it reasonable to use a regular soldering iron to attach those
things, or would I maybe be better off looking for a through-hole
equivilant, like something in a TO-220 package?  I'm using Eagle to
create the board and having a local shop make it, so it doesn't make
much difference from a layout perspective (as far as I can tell) - but
I'm a bit concerned about things like heating the chip up too much,
etc.  Or would this be like any other IC in that regard?  It looks
like the pinout won't exactly be super demanding with regards to
soldering adjacent pins together, which I guess is my main concern
with SMT.

Thanks.
--Danny

2005\11\28@130414 by Alex Harford

face picon face
On 11/28/05, Alan B. Pearce <@spam@A.B.PearceKILLspamspamrl.ac.uk> wrote:
> >When the turn signal comes on, which would normally cause
> >three bulbs on one side to blink, I'd like the bulbs to
> >fade in sequentially from just the inner bulb to all three.
> >Both actions are done on modern cars from teh factory,
> >and both are allowed by the state vehicle code.
>
> Good grief, I seem to remember seeing this on a mid to late 60s (IIRC) Chevy
> or Ford. Certainly wasn't done by electronics back then ;) Must have been
> one of those two makes, as we didn't get very many US originated cars in NZ
> back then.

It was the Mercury Cougar (although more than possible it was rebadged
as a Ford for export).

They used a DC motor to spin a shaft that made/broke contacts to light
the turn signals.

www.thuntek.net/cougars_unlimited/seqts.htm
http://mustangmonthly.com/howto/173_0404_ford_tail_light_install/

Alex
- who was born about 35 years too late for the muscle car era :(

2005\11\28@134715 by Danny Sauer

flavicon
face
Russell wrote regarding 'Re: [EE] means of dimming auto tail light?' on Mon, Nov 28 at 04:10:
[...]
> Here's a simple but useful primer on driving incandescent bulbs
>
>        www.allegromicro.com/techpub2/an/an295012.pdf
>
> Adding either a "warming resistor" or a series limiting resistor will
> increase lamp lifetime and give the driver an easier job. Both methods
> have good and bad points.
[...]

The warming resistor I think might be a bad idea, since the brake
light circuit is constant-power (so the brake lights work even if the
ignition circuit has some problem), and I'm not sure if it'd be worth
the complexity to add in an ignition-powered warming circuit (which
would require another wire running the length of the car).  If I power
the PIC and everything from the brake circuit, though, then there's
really no warming time and it's useless. :)  A series resistor might
be an alright idea, though it seems pretty inexpensive to come up with
a FET that'll handle the inrush by itself (as you said in a trimmed
part).  I hadn't thought about the low initial resistance, though, and
am glad that several people pointed it out.  Hooray for smart people!
:)

--Danny

2005\11\29@043052 by Alan B. Pearce

face picon face
>It was the Mercury Cougar (although more than
>possible it was rebadged as a Ford for export).

It would have been a saloon, and probably one that would have been supplied
to NZ as a CKD (completely knocked down) kit that would have been assembled
locally, due to import restriction regulations protecting local employment.

>They used a DC motor to spin a shaft that made/broke
>contacts to light the turn signals.

Sounds a suitable low tech way of doing it ;))

2005\11\29@043336 by Alan B. Pearce

face picon face
>The warming resistor I think might be a bad idea, since
>the brake light circuit is constant-power (so the brake
>lights work even if the ignition circuit has some problem),
>and I'm not sure if it'd be worth the complexity to add
>in an ignition-powered warming circuit (which would
>require another wire running the length of the car).
>If I power the PIC and everything from the brake circuit,
>though, then there's really no warming time and it's useless. :)

Now you know why they run CAN bus around - to tell the system when the
ignition is on to turn on the lamp warmer ... ;)

2005\11\30@011525 by Grinder Smith

picon face
subject:  [EE] means of dimming auto tail light?

.
.
.
>I regularly attend car shows, cruise-ins, etc, and
it'd be fun to have the ability to make the taillights
flash in different patterns at those events.
.
.
.

Ah, very nice.  At a recent show I was surprised to
see a Japanese fart pipe car with a full LED matrix
taillight/fill panel system.  Maybe 100 LEDs?  There
were several moving patterns displayed.  Any
microcontroller could do that.  I liked the idea.


               
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2005\11\30@022145 by Jinx

face picon face
> Ah, very nice.  At a recent show I was surprised to
> see a Japanese fart pipe car with a full LED matrix
> taillight/fill panel system.  Maybe 100 LEDs?  There
> were several moving patterns displayed.  Any
> microcontroller could do that.  I liked the idea.

When it gets to that stage though it's bordering on illegal. Cops
do not like anything on the road that is "distracting". I asked
about using a LED moving sign on a vehicle and got a definite
"no"

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