Shiftlight-Upgrade: Problems with wiring

Dominik · Post by **Dominik** » Tue Jan 04, 2011 5:43 pm

Hello everybody,

today I upgraded my Megajolt with five shiftlight LEDs. They include series resistors and could be connected to 12V directly.

As an anti-theft protection (open Super Seven kit car), the power supply for the MJ goes over a hidden switch. So normally the power LED only glows, if both ignition switch and the hidden switch are on. As described in the manual, I connected the user out pins 1-4 and the shift light pin to the negative terminals of the LEDs. The positive terminals go to ignition switched +12V.

Now I have the following phenomena: The power LED always glows, when ignition is on. Even if there is no 12V at the regular power supply pin (checked). So the MJ seems to get voltage from another pin?! If I enable my hidden switch, ALL shiftlight LEDs are glowing! I didn't try to start the engine...

Do you have a hint to solve this problem? Thanks a lot in advance!

Regards from Germany,
Dominik.

NITROPIXIE · Post by **NITROPIXIE** » Tue Jan 04, 2011 7:53 pm

It sounds like you are getting a power supply through the ULN2003 chip as these drive the LED's by sinking the voltage. These chips have internal pull up resistors incorporated inside (hence the power coming through the pull up resistors - IIRC).

Now the best way to connect power to the leds is at the same point as the MJLJ unit itself, so in your case your secret switch. This should solve what you are seeing.

Once rewired you can check the operation of each LED without starting the engine by connecting up your computer and changing the state of each of the outputs (where you set value and whether it's rpm,map or aux). You should then be able to turn each LED's on and off in turn.

If you have any further problems then get back in touch.

Ryan

van · Post by **van** » Tue Jan 04, 2011 9:54 pm

Hi Dominik ,
I think it's better to use hidden switch for coil + , or ground via switch one wire from CP sensor .
Ignition can work on EDIS without MJL

NITROPIXIE · Post by **NITROPIXIE** » Tue Jan 04, 2011 10:00 pm

van wrote:Hi Dominik ,
I think it's better to use hidden switch for coil + , or ground via switch one wire from CP sensor .
Ignition can work on EDIS without MJL

I tend to agree with Van actually, this does make more sense.

Dominik · Post by **Dominik** » Wed Jan 05, 2011 10:53 am

Hi Ryan and Van,

first of all: Thanks a lot for your help!

In my understanding - as a total electronic noob *g* - it doesn't make a difference from where the power comes. 12V are 12V. So, did I understand you correctly, that it is a "temporal" problem? The MJ is not designed to get power over your mentioned ULN2003 chip BEFORE there is current at the main power supply of the MJ. Hence my hidden switch leeds to some kind of shunt circuit? Is this right?

By the way: It's a long time ago since I installed my MJ. But the engine definitely doesn't start, when the hidden switch is off. So I think I wired both the MJ control unit and the coil with 12V over the switch. I have to check it again...

Do you think that I could have destroyed something in the MJ with my wiring?

Regards,
Dominik.

NITROPIXIE · Post by **NITROPIXIE** » Wed Jan 05, 2011 11:42 am

In my understanding - as a total electronic noob *g* - it doesn't make a difference from where the power comes. 12V are 12V. So, did I understand you correctly, that it is a "temporal" problem? The MJ is not designed to get power over your mentioned ULN2003 chip BEFORE there is current at the main power supply of the MJ. Hence my hidden switch leeds to some kind of shunt circuit? Is this right?

Sounds about right.

Do you think that I could have destroyed something in the MJ with my wiring?

No I don't believe it would have, it should be fine. If the ULN2003 has been damaged they cost less than £1 to replace. Your circuit board should be fine, a visual inspection should confirm this.

van · Post by **van** » Wed Jan 05, 2011 5:51 pm

I was talking about anti-theft protection. Connect coil + to secret switch , not MJL . Car can be stolen , even if you take out MJL . Ignition can operate on edis , and egine would run , so it could be stolen .

Dominik · Post by **Dominik** » Sat Jan 08, 2011 9:47 am

Hi Ryan,

what should I say? IT WORKS!!!!

I wired the LEDs directely to the power supply of the MJ and everything was perfect. Thanks a lot for your help!

Regards,
Dominik.

NITROPIXIE · Post by **NITROPIXIE** » Sat Jan 08, 2011 12:50 pm

That's great Dominik, so the MJLJ is working properly as it should?? No defects??

Ryan

Dominik · Post by **Dominik** » Mon Jan 10, 2011 6:05 am

Yes, it does! I didn't start the engine since the carbs aren't installed. But everything else works. I can drive the shift light LEDs and even my ignition configuration switch works great.

Regards,
Dominik.