IGN outputs for led

TimH
JT Innovations
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Re: IGN outputs for led

Post by TimH »

stevieturbo wrote: Sat Apr 18, 2020 11:10 am
TimH wrote: Sat Apr 18, 2020 10:48 am
Not sure about protection - I would hope there is, as that would be good design practice.
I busted a fuel output on an S6...so no protection there.
The age of the S6 design may mean the injector driver devices are not self-protecting and a short to 12V might kill them. More modern omnifet injector drivers have inherent current limiting and thermal protection - but guess you can still kill them somehow!
Trickster
Posts: 63
Joined: Mon Nov 28, 2016 6:09 pm

Re: IGN outputs for led

Post by Trickster »

That would make sense, TTL signal can be anything below 1v is off and anything above 3v is on, so there is a tolerance.

I'm about to do some work on my car anyway and I have the ignition wires accessible for testing, I'll throw some leds on and see how they fair up, maybe without resistors they will be fine if the voltage is low enough

Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6
TimH
JT Innovations
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Re: IGN outputs for led

Post by TimH »

I would use a resistor. Let's say the Vf of your diode is 3V and the ignition drive is 3.5V - without a resistor the driver may fail as too much current is drawn. A 22ohm resistor would limit the current to 20mA and keep it all safe.
Trickster
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Joined: Mon Nov 28, 2016 6:09 pm

Re: IGN outputs for led

Post by Trickster »

I don't have any resistors that low, I'll play around but use what I have and see what we get to start with 👍

Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6
Trickster
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Re: IGN outputs for led

Post by Trickster »

Pretty pleased actually

I hooked up a white led with a 470ohm resistor and it worked fine and was much brighter than I expected considering the resistor size.

My ecu is in the boot so I used a long length of wire to simulate any voltage drop too

Image
Image
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6
TimH
JT Innovations
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Re: IGN outputs for led

Post by TimH »

Excellent!
Trickster
Posts: 63
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Re: IGN outputs for led

Post by Trickster »

I would of thought 3 or 4 of these would be OK on one output with 470 resistors?

Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6
TimH
JT Innovations
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Re: IGN outputs for led

Post by TimH »

If the TTL output is 3.5V and the Vf of the diode 3V, say, then you are only drawing 1mA - which is nice and low so must be a super-duper nice-n-bright LED :idea: 8-)

So, yes, 4 would be AOK
Trickster
Posts: 63
Joined: Mon Nov 28, 2016 6:09 pm

Re: IGN outputs for led

Post by Trickster »

Thanks Tim 8-)

They were about 4 pound for 50 off ebay haha, it said ultra bright, I guess it didn't lie!

Graeme
MR2 Turbo 5sgte 750hp 527ft/lb Syvecs S6
stevieturbo
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Re: IGN outputs for led

Post by stevieturbo »

Other option would be buy a full shift light lol
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