Using JS0 and JS2 as outputs - Clarification

[Danbob]

Hello again,

Using MS3 on V3 board with MS3X

I've read JS0-JS1 and JS2-JS3 are complimentary and can be used as 2 programmable outputs - But need to clarify a few points;

1. Will these outputs go to ground? Or give an output voltage?
2. Are these only logic level 5V outputs or 12V outputs?
3. Could somebody clarify; JS0 is normally ??? When activated it ???
4. What kind of current can I run through these outputs? At the moment I am only thinking of running a 12v Check Engine lamp on one output and haven't assigned the other one yet

Thanks, sorry if this seems obvious, but this is my first electrical project in this sort of detail!

Thanks
Dan


My Jumper proposal:
JS0 -> IAC1A - 1st Programmable output
JS2 -> IAC2A - 2nd Programmable Output
IAC1B - Used for Knock line in
IAC2B - Spare Pin

[elutionsdesign]

My understanding is the raw outputs are all 0-5V transitions, things like the fuel pump and FIDLE run to a transistor and the transistor inverts the signal to ground.

[Danbob]

My understanding is the raw outputs are all 0-5V transitions, things like the fuel pump and FIDLE run to a transistor and the transistor inverts the signal to ground.

OK, so in that case if I want to use those two outputs I'd have to build a circuit for them on the proto area?

Maybe I'll use F-Idle for my check engine lamp then, it just seemed a bit overkill to waste the F-Idle for a little bulb so was exploring any other options available..

[Danbob]

Found some more info....

According to the IAC testing info here... http://www.diyautotune.com/tech_article ... r_iac.html
The IAC outputs (JS0 JS2) should output 12V,

And in the MS3 pin table in the manual here..... http://www.msextra.com/doc/ms3/hardware.html#pins
It says they can handle 0.5A current

So i think in that case I think I should be able to use JS0 for a check engine light?

Please let me know if this sounds correct and if you can see any problems?


Thanks
Dan

[dontz125]

JS0-3 are special, as those signals are run through the stepper driver chip on the daughter card before they reach the pins. These pins are actually connected to an H-bridge, so when JS0 (JS2) is high at +12v (not 5!), JS1 (JS3) is a ground path, and vice versa.

As to the actual condition of the pin, that is selected by the programmable output conditions.

[Danbob]

OK thanks that makes sense with what I've now found.

Is it possible to set JS0 to be normally open circuit and then switch to ground my 12V check engine lamp when activated by software?

[Danbob]

I can see in Tuner Studio that I can set IAC1 (JS0/1) as the "light output" for Check engine light - but I can't see how to specify what IAC1 should do when check engine light parameter is activated?

I'm hoping to have IAC1/JS0 ground the OEM check engine lamp - But I would prefer to not have IAC1 outputing +12V at all over times if this is possible?

[dontz125]

If your CEL is activated by grounding JS0 (IAC1A low), then when IAC1A is flipped high it IS going to output +12v. This shouldn't be an issue, since you also have +12v from the battery upstream of the CEL. 12v on both sides of a device = no current flow.

[Danbob]

Hi, OK I understand that should work in theory.

Are there any potential problems with doing it that way - having the off condition as 12V output against Battery 12V rather than open circuit?
I am speaking from no experience whatsoever, but I feel like it might have the potential to cause more problems than a switch that goes to open circuit?

For example is there a possibility for there to be a voltage difference between the 12V from MS3 and 12V battery due different resistances? Could that cause a potential problem?
I suppose the risk of a short circuit damaging the MS3 card would also be increased as the wire to the meter/clocks would be live most of the time?


Is it better to just use the F-idle output for my CEL and leave these outputs for now? They seem like they are more suited to a specialist application?

If I use F-Idle will it be open circuit and then switch to ground when CEL is activated by software?


Thanks again
Dan