news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

You can't add resistance to the circuit and make an led light up from a
spark. The led needs a certain amount of current at around 1 volt.
There is not that much current in the spark. The coil trades currrent
for voltage when it steps the voltage up to that many volts. You would
need to build a trigger circuit tha detects the spark and the powers
the led.

basskisser wrote:
news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

"basskisser" wrote in message
ups.com...

news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

How much resistance would you need? Series, parallel?

Why in the world go to all this trouble when neon bulb spark detectors
are under a buck apiece?

Terry K

"D.Duck" wrote in message
...

"basskisser" wrote in message
ups.com...

news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

How much resistance would you need? Series, parallel?


Last time I checked (which may be very outdated info) an LED's forward bias
"on" was around 3.6 volts DC or something like that. You'd need a voltage
divider network to supply that to each LED or enough LED's in series that
the voltage drop across each was in that ballpark.

The series resistor is to limit current ... it depends on the rating of the
LED. It's been a long time since I played with them, so take it for what
it's worth .... which is nothing.

"RCE" wrote in message
...

"D.Duck" wrote in message
...

"basskisser" wrote in message
ups.com...

news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

How much resistance would you need? Series, parallel?


Last time I checked (which may be very outdated info) an LED's forward
bias "on" was around 3.6 volts DC or something like that. You'd need a
voltage divider network to supply that to each LED or enough LED's in
series that the voltage drop across each was in that ballpark.

The series resistor is to limit current ... it depends on the rating of
the LED. It's been a long time since I played with them, so take it for
what it's worth .... which is nothing.




Enough resistance to allow the LED to light and be usable again, would stop
the spark at the plug.

In the case of the neon lights the bulb and resistor is in parallel with the
spark plug.

There is not enough current to light an led in an ignition spark.

"Calif Bill" wrote in message
nk.net...

"RCE" wrote in message
...

"D.Duck" wrote in message
...

"basskisser" wrote in message
ups.com...

news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

How much resistance would you need? Series, parallel?


Last time I checked (which may be very outdated info) an LED's forward
bias "on" was around 3.6 volts DC or something like that. You'd need a
voltage divider network to supply that to each LED or enough LED's in
series that the voltage drop across each was in that ballpark.

The series resistor is to limit current ... it depends on the rating of
the LED. It's been a long time since I played with them, so take it for
what it's worth .... which is nothing.




Enough resistance to allow the LED to light and be usable again, would
stop the spark at the plug.

"James" wrote in message
nk.net...
In the case of the neon lights the bulb and resistor is in parallel with
the spark plug.

There is not enough current to light an led in an ignition spark.

"Calif Bill" wrote in message
nk.net...

"RCE" wrote in message
...

"D.Duck" wrote in message
...

"basskisser" wrote in message
ups.com...

news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

How much resistance would you need? Series, parallel?


Last time I checked (which may be very outdated info) an LED's forward
bias "on" was around 3.6 volts DC or something like that. You'd need a
voltage divider network to supply that to each LED or enough LED's in
series that the voltage drop across each was in that ballpark.

The series resistor is to limit current ... it depends on the rating of
the LED. It's been a long time since I played with them, so take it for
what it's worth .... which is nothing.




Enough resistance to allow the LED to light and be usable again, would
stop the spark at the plug.



A simpler method might be to wind a few coils of wire around each plug wire
and connect them to the base of a triac and ground. Use a conventional 12
volt LED circuit, running off the car battery with an LED and triac for each
plug wire (cylinder). When the plug fires, the coil will briefly turn on
the triac and associated LED.

"James" wrote in message
nk.net...
In the case of the neon lights the bulb and resistor is in parallel with
the spark plug.

There is not enough current to light an led in an ignition spark.

"Calif Bill" wrote in message
nk.net...

"RCE" wrote in message
...

"D.Duck" wrote in message
...

"basskisser" wrote in message
ups.com...

news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....

How much resistance would you need? Series, parallel?


Last time I checked (which may be very outdated info) an LED's forward
bias "on" was around 3.6 volts DC or something like that. You'd need a
voltage divider network to supply that to each LED or enough LED's in
series that the voltage drop across each was in that ballpark.

The series resistor is to limit current ... it depends on the rating of
the LED. It's been a long time since I played with them, so take it for
what it's worth .... which is nothing.




Enough resistance to allow the LED to light and be usable again, would
stop the spark at the plug.




There is enough current to light a LED. the ignition, even point and coil
take a fairly good flow of current to run. And a LED requires less than 10
milliamps to light.

edolo wrote:
Have a couple of manual testers, but would like to build an LED
in-line unit to test spark on two, four, and six cylinder outboard
motors. Anyone have a design or know where such a unit can be obtain?
tks, alp


Wouldn't a neon glow lamp be a better choice than an LED?