Come up with a brilliant solution .......

[Ken Taylor]

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Ken, since you say you have the inside knowledge here it would be helpful
if
you could let us know how it is done, so we could be more hopeful to the
OP

David

Here's what you wrote:
<<
I don't know 'this' - just guessing. And since the computer measures
current
draw, it seems unlikely it is an RF or Audio pulse, but rather a DC pulse.
And
to superimpose a DC pulse onto a 24v DC line, it seemed logical that it
would
have to be higher than 24v in order to be detected.
No offence, but you don't know what you're on about. If reading that back
again doesn't tell you that, then don't let it bother you.

The OP has plenty of good (and some mediocre) advice to go on, including the
non-trivial nature of what he wants to do.

Cheers.

Ken

 

[two bob]

Ken, since you say you have the inside knowledge here it would be helpful

Here's what you wrote:
<<
I don't know 'this' - just guessing. And since the computer measures
current
draw, it seems unlikely it is an RF or Audio pulse, but rather a DC pulse.
And
to superimpose a DC pulse onto a 24v DC line, it seemed logical that it
would
have to be higher than 24v in order to be detected.

No offence, but you don't know what you're on about. If reading that back
again doesn't tell you that, then don't let it bother you.

The OP has plenty of good (and some mediocre) advice to go on, including
the non-trivial nature of what he wants to do.

One of the best lessons I learnt at tech was KISS (Keep It Simple Stupid)
The answer to this problem has been answered already in this thread. Let the
computer do the fancy pulse stuff, the only thing it is looking for is a
load. Not return pulses, not higher than supply voltages, just a substitute
load. Give it a load which fools it into thinking it has a working globe and
it will be happy.

 

[swanny]

One of the best lessons I learnt at tech was KISS (Keep It Simple Stupid)
The answer to this problem has been answered already in this thread. Let the
computer do the fancy pulse stuff, the only thing it is looking for is a
load. Not return pulses, not higher than supply voltages, just a substitute
load. Give it a load which fools it into thinking it has a working globe and
it will be happy.

Except now you don't know when the LED lamp array has failed, so the
diagnostic is useless.

 

[Geoff C]

As far as we've been able to check this mess, yes, the current pulse
is sent when the ignition is switched on, and will keep on pulsing
until the load sense is satisfied. Vehicle diagnostics are performed
(obviously, the lights are only one of the tests) and any errors are
indicated on the dashboard. However - it would appear that the system
has a continuous checking routine to determine whether a lamp has
failed during the run. Sorry I sound so hazy over this, but trying to
get a truck to play with is not easy. Suppliers are not too
interested, and the operators are not keen on taking a truck out of
service for us to investigate further. Sometimes, I hate my job!!!!!

I think it would be best in the long run to solve this by the cheapest
way, and that is to lean on the computer suppliers for the manufacturer
to modify their code or hardware. Your business seems to be in the middle
of a new trailer lighting paradigm and it is obvious that the future lies
in solid state lighting. So what about more effort in debating with the
computer makers? They must be aware of the impending change, they may
even be planning engineering solutions now. If they are stone walling,
maybe point out the marketing advantage of an LED friendly system would
give them an advantage over competitors. After all, YOU are the customer
of these suppliers and they need to listen to YOU.

 

[The Real Andy]

I think it would be best in the long run to solve this by the cheapest
way, and that is to lean on the computer suppliers for the manufacturer
to modify their code or hardware. Your business seems to be in the middle
of a new trailer lighting paradigm and it is obvious that the future lies
in solid state lighting. So what about more effort in debating with the
computer makers? They must be aware of the impending change, they may
even be planning engineering solutions now. If they are stone walling,
maybe point out the marketing advantage of an LED friendly system would
give them an advantage over competitors. After all, YOU are the customer
of these suppliers and they need to listen to YOU.

Aside from the fact that most manufacturers are based in the US/Europe
and couldn't give a flying **** about the Aus market. From what I can
gather is that for some trucks you cant even get a program that
matches some certain australian engine-transmission combos. Why would
they care about a LED lamp on trailer?

 

[Ken Taylor]

Aside from the fact that most manufacturers are based in the US/Europe
and couldn't give a flying **** about the Aus market. From what I can
gather is that for some trucks you cant even get a program that
matches some certain australian engine-transmission combos. Why would
they care about a LED lamp on trailer?

OP is apparently in South Africa so there's even less chance....

Ken

 

[two bob]

Ken, since you say you have the inside knowledge here it would be

Except now you don't know when the LED lamp array has failed, so the
diagnostic is useless.

A simple comparitor cct using an op amp. Everyone wants to turn this into a
major project.

 

[Ken Taylor]

A simple comparitor cct using an op amp. Everyone wants to turn this into a
major project.

Per light? Sheesh, who's making it a major project?

Ken

 

[The Real Andy]

Per light? Sheesh, who's making it a major project?

Ken

I have it down to one comparitor and 1 transistor plus a few passives.
I reckon i can get it down to at least 3 transistors, perhaps 2 and no
comparitors. Mind you. thats in spice, not in the real world, and
thats with a few glasses of red wine too....Dang its been a while
since I used spice...

 

[MC]

A simple comparitor cct using an op amp. Everyone wants to turn this into a
major project.

It starts getting complicated because ;
- LEDs can fail short-circuit OR open-circuit.
- To get adequate luminance, the LED-lamp will probably consist
of several parallel 'series-strings', where each 'series-string'
would have several LEDs and a current-limiting resistor or
driver connected in series fashion.
- The environment is not electronic-friendly, what with noise,
spikes and wide operating temperature-range.

 

[Ken Taylor]

I have it down to one comparitor and 1 transistor plus a few passives.
I reckon i can get it down to at least 3 transistors, perhaps 2 and no
comparitors. Mind you. thats in spice, not in the real world, and
thats with a few glasses of red wine too....Dang its been a while
since I used spice...

Spice your wine...? Cool!

All that electronics so you can use LED's in a trailer light - I think this
project is in serious need of management oversight.

Cheers.

Ken

 

[quietguy]

So you were just bullshitting hey? You don't really know how that system
works?


David

 

[quietguy]

After thinking about the situation I am beginning to think the problem may be
more complex than it seems at first glance.

I presume the OP is talking about the sort of trailers that are attached to
'semi-trailer prime movers, and that the computer thingo is located in the
prime mover. If this is so, then somehow that computer must have some way of
telling how many tailights/sidelights/number plate lights/brake
lights?/clearance lights etc are located on the trailer. Do these vary from
trailer to trailer? And remembering that one practice is for (say on the
Sydney to Melb run) there to be a change over of trailers at Tarcutta, then the
computer must be able to know how the lighting setup of any trailer that might
be connected to the prime mover.

Is any of this relevent to the OPs situation?

David

 

[Ken Taylor]

<sigh> Is it that difficult to sense current in a circuit with a processor
attached? You referred to RF and audio in such a way as to reveal you know
zip on the subject in particular and probably electronics in general.
There's no need to send a 'higher than 24V' pulse down the line when the
lamps are lit, as they can then be detected easily by a sensor. When they
are not lit, the methodology gets cute but not at all tricky, sending a
pulse which can be sensed but doesn't actually light the lamps. The OP
suffers because the processor system isn't smart enough to see the LED
array's reaction to the pulse as anything other than a fault, and is trying
to produce a work-around, which is unfortunately bound to be futile in a
general system (but could be done in a one-off, albeit whether it's really
worth it is another point entirely). That's the meat - the rest is
'conceptually trivial', as they say.

Cheers.

Ken

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[Ken Taylor]

message

After thinking about the situation I am beginning to think the problem may
be
more complex than it seems at first glance.

I presume the OP is talking about the sort of trailers that are attached
to
'semi-trailer prime movers, and that the computer thingo is located in the
prime mover. If this is so, then somehow that computer must have some way
of
telling how many tailights/sidelights/number plate lights/brake
lights?/clearance lights etc are located on the trailer. Do these vary
from
trailer to trailer? And remembering that one practice is for (say on the
Sydney to Melb run) there to be a change over of trailers at Tarcutta,
then the
computer must be able to know how the lighting setup of any trailer that
might
be connected to the prime mover.

Is any of this relevent to the OPs situation?

David

Having just fired off a reply to your other post, this one deserves some
credit. That's a very valid point because either the controller in the rig
gets told how many lights on the trailer or it is assumed by the
manufacturer that there is a general response curve by a lamp, and that any
number (within some limit, no doubt) will behave in a certain fashion. The
LED's of course react differently. An intersting point is what happens if
only *some* of the lamps are replaced with LED's. At what point does the
system fail to detect the lights?

Ken

 

[The Real Andy]

Spice your wine...? Cool!

All that electronics so you can use LED's in a trailer light - I think this
project is in serious need of management oversight.

You could get even trickier, use 1 4bit uP and a transistor. Even
better if the uP has an ADC on board..

 

[Ken Taylor]

You could get even trickier, use 1 4bit uP and a transistor. Even
better if the uP has an ADC on board..

There are some neat networked chips that fit into an RJ45 socket - now if
they just had wireless......

Ken

 

[newinwa]

seems to me all it would take is a capacitor in parallel with the lamp and
possibly a resistor to limit the current a bit...

my guess is try 100-200 ufd and if it works add in a bit of resistance
until it quits working (use a 1k-10kpot) then back up till it works again
and measure the resistance...replace with a similar value fixed resistor and
your done.



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