I Want to make LED shut off when car is running

J

Joseph A Zupko

Guest
I would like to hook a LED on the dash board. How can I have it shut off
when the car starts and come back on when the car is off? For a 93 lumina
sedan
Thank you
 
Easiest way is to use a small 12vdc relay. Coil of relay goes to ground and
to a 12vdc source that works only when the ignition key is on. Wire the LED
through the normally open contacts. Now when you start the car, the relay
pulls and the circuit opens and LED goes off. Turning the ignition off, also
turns off the relay and it's contacts close and the led lights.

Jan

"Joseph A Zupko" <jaz2@sbcglobal.net> wrote in message
news:DMmnb.5560$P%1.4589341@newssvr28.news.prodigy.com...
I would like to hook a LED on the dash board. How can I have it shut off
when the car starts and come back on when the car is off? For a 93 lumina
sedan
Thank you
Click to expand...
 
On Tue, 28 Oct 2003 05:03:31 GMT, "Joseph A Zupko"
<jaz2@sbcglobal.net> put finger to keyboard and composed:

I would like to hook a LED on the dash board. How can I have it shut off
when the car starts and come back on when the car is off?
Click to expand...
The following circuit uses a flashing LED. I haven't tested it, but I
think it should work.

BAT +12V
0
|
|------|----------|
| _|__
/ Ign SW \ /
___________| _\/_ D2
| _|__ |
| D1 \ / | IGN voltage drop
| _\/_ _|__ compensation
| | load \ /
| | isolation _\/_ D3
| | diode |
| | |
| | /
| | |*
| |--------------| Q2 (PNP)
| | |\
| | \
| | |
Ignition |-| |-| R1 |-| R2
Loads | | | | | |
|-| |-| |-|
| | |
| | |-----------|
| | _|__ _|__/
| | <~~ \ / / /\
| | _\/_ /__\ 8V2
| | LED1 | | ZD1
| | | |
=== === === ===
= = = =

In the absence of ignition voltage, the transistor is biased on and
LED1 flashes at 2Hz. Diode D1 isolates the circuit from the various
ignition loads. Zener ZD1 protects LED1 from excessive voltage. Diodes
D2,D3 ensure that voltage drops in the ignition circuit do not prevent
the transistor being turned off when the ignition is switched on.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
 
On Tue, 28 Oct 2003 17:46:59 +1100, Franc Zabkar
<fzabkar@optussnet.com.au> wrote:

On Tue, 28 Oct 2003 05:03:31 GMT, "Joseph A Zupko"
jaz2@sbcglobal.net> put finger to keyboard and composed:

I would like to hook a LED on the dash board. How can I have it shut off
when the car starts and come back on when the car is off?

The following circuit uses a flashing LED. I haven't tested it, but I
think it should work.

BAT +12V
0
|
|------|----------|
| _|__
/ Ign SW \ /
___________| _\/_ D2
| _|__ |
| D1 \ / | IGN voltage drop
| _\/_ _|__ compensation
| | load \ /
| | isolation _\/_ D3
| | diode |
| | |
| | /
| | |*
| |--------------| Q2 (PNP)
| | |\
| | \
| | |
Ignition |-| |-| R1 |-| R2
Loads | | | | | |
|-| |-| |-|
| | |
| | |-----------|
| | _|__ _|__/
| | <~~ \ / / /\
| | _\/_ /__\ 8V2
| | LED1 | | ZD1
| | | |
=== === === ===
= = = =

In the absence of ignition voltage, the transistor is biased on and
LED1 flashes at 2Hz. Diode D1 isolates the circuit from the various
ignition loads. Zener ZD1 protects LED1 from excessive voltage. Diodes
D2,D3 ensure that voltage drops in the ignition circuit do not prevent
the transistor being turned off when the ignition is switched on.


- Franc Zabkar
Click to expand...

Why bother with a transistor at all? Take an LED and a 1k resistor
in series. Connect one side to +12v, and the other side to the hot
lead of something that only gets power when the ignition is on (eg
radio, dash lights). Power flows through LED when accessories isn't
powered, therby providing a path to ground. (This is essentially how
those el cheapo $3 headlight reminders work, a diode and buzzer
between +12v and the headlight fuse))

12v ---->|------/\/\/\/--- Acc+


Of course thisr would only indicate whether the ignition was on, not
necessarily whether the engine was running. Maybe something to look
at charging voltage would work for that.
 
On Wed, 29 Oct 2003 06:14:47 GMT, chris@nospam.com put finger to
keyboard and composed:

On Tue, 28 Oct 2003 17:46:59 +1100, Franc Zabkar
fzabkar@optussnet.com.au> wrote:

On Tue, 28 Oct 2003 05:03:31 GMT, "Joseph A Zupko"
jaz2@sbcglobal.net> put finger to keyboard and composed:

I would like to hook a LED on the dash board. How can I have it shut off
when the car starts and come back on when the car is off?

The following circuit uses a flashing LED. I haven't tested it, but I
think it should work.

BAT +12V
0
|
|------|----------|
| _|__
/ Ign SW \ /
___________| _\/_ D2
| _|__ |
| D1 \ / | IGN voltage drop
| _\/_ _|__ compensation
| | load \ /
| | isolation _\/_ D3
| | diode |
| | |
| | /
| | |*
| |--------------| Q2 (PNP)
| | |\
| | \
| | |
Ignition |-| |-| R1 |-| R2
Loads | | | | | |
|-| |-| |-|
| | |
| | |-----------|
| | _|__ _|__/
| | <~~ \ / / /\
| | _\/_ /__\ 8V2
| | LED1 | | ZD1
| | | |
=== === === ===
= = = =

In the absence of ignition voltage, the transistor is biased on and
LED1 flashes at 2Hz. Diode D1 isolates the circuit from the various
ignition loads. Zener ZD1 protects LED1 from excessive voltage. Diodes
D2,D3 ensure that voltage drops in the ignition circuit do not prevent
the transistor being turned off when the ignition is switched on.


- Franc Zabkar


Why bother with a transistor at all? Take an LED and a 1k resistor
in series. Connect one side to +12v, and the other side to the hot
lead of something that only gets power when the ignition is on (eg
radio, dash lights).
Click to expand...
I thought of this, but I didn't like the idea of current flowing to
ground through some unknown accessory. Seems very sloppy to me.

Power flows through LED when accessories isn't
powered, therby providing a path to ground. (This is essentially how
those el cheapo $3 headlight reminders work, a diode and buzzer
between +12v and the headlight fuse))
Click to expand...
Yes, I have one of these.

12v ---->|------/\/\/\/--- Acc+


Of course thisr would only indicate whether the ignition was on, not
necessarily whether the engine was running. Maybe something to look
at charging voltage would work for that.
Click to expand...

- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
 
I wonder if you're hitting the right nail here. The guy said he wanted it off
when the car is running, not when the key is on.

If that's the case the easiest way is to hook the LED anode to "BAT" and
through a resistor, to the "FIELD" terminal of the alternator. The internally
regulated alternators still require a "trickle" to this terminal to "start" the
alternator. The "BATT" light on the dash usually fulfills this requirement.
Even on a self starting alternator it should work. Of course in addition to the
engine not running, it will indicate an alternator or belt failure. :)

Another method could be devised using the MAP or TACH signals or the "bypass"
line from the computer to the ignition module.

If all you need is to know if the key is on, of course it is very simple, if
you need absolute reliability, the "bypass" line to the ignition is the surest
bet. It changes states when the engine hits about 200 RPM or something and
tells the module to obey the computer for ignition timing. When it is cranking
the timing is preset inside the ignition module.

If this is required I recommend an enhacement mode FET to drive the light
because I'm leery about loading any of those computer outputs, and it is an
output. The module does not tell the computer when to take over, the computer
tells the module that it is taking over.

Note that since this signal is only 5V you won't be able to saturate the FET,
so stick with an led. If you want to drive something else, buff it with a
bipolar.

JURB
 
<chris@nospam.com> wrote in message
news:88mupvgcf6u76rat32r52f8olr9lhjtupi@4ax.com...
On Tue, 28 Oct 2003 17:46:59 +1100, Franc Zabkar
fzabkar@optussnet.com.au> wrote:

On Tue, 28 Oct 2003 05:03:31 GMT, "Joseph A Zupko"
jaz2@sbcglobal.net> put finger to keyboard and composed:

I would like to hook a LED on the dash board. How can I have it shut
off
when the car starts and come back on when the car is off?

The following circuit uses a flashing LED. I haven't tested it, but I
think it should work.

BAT +12V
0
|
|------|----------|
| _|__
/ Ign SW \ /
___________| _\/_ D2
| _|__ |
| D1 \ / | IGN voltage drop
| _\/_ _|__ compensation
| | load \ /
| | isolation _\/_ D3
| | diode |
| | |
| | /
| | |*
| |--------------| Q2 (PNP)
| | |\
| | \
| | |
Ignition |-| |-| R1 |-| R2
Loads | | | | | |
|-| |-| |-|
| | |
| | |-----------|
| | _|__ _|__/
| | <~~ \ / / /\
| | _\/_ /__\ 8V2
| | LED1 | | ZD1
| | | |
=== === === ===
= = = =

In the absence of ignition voltage, the transistor is biased on and
LED1 flashes at 2Hz. Diode D1 isolates the circuit from the various
ignition loads. Zener ZD1 protects LED1 from excessive voltage. Diodes
D2,D3 ensure that voltage drops in the ignition circuit do not prevent
the transistor being turned off when the ignition is switched on.


- Franc Zabkar


Why bother with a transistor at all? Take an LED and a 1k resistor
in series. Connect one side to +12v, and the other side to the hot
lead of something that only gets power when the ignition is on (eg
radio, dash lights). Power flows through LED when accessories isn't
powered, therby providing a path to ground. (This is essentially how
those el cheapo $3 headlight reminders work, a diode and buzzer
between +12v and the headlight fuse))

12v ---->|------/\/\/\/--- Acc+


Of course thisr would only indicate whether the ignition was on, not
necessarily whether the engine was running. Maybe something to look
at charging voltage would work for that.
Click to expand...

You might want to look at a 555 in missing pulse configuration. Configure
the timer to detect pulses at a rate that is lower than the rate of ignition
at idle. Wrap a few turns of wire around one of the spark plug wires to
sense the ignition pulses. Condition it with RC and limit with a zener.
Feed the resulting pulse into the 555 missing pulse circuit. Result is as
long as the ignition pulses are coming in, the 555 says the engine is
running. When the ignition pulses stop, the 555 changes state and says the
engine is stopped.
Cheers!!!
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!
 
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