Shift cut input wiring ?

[mk123gti]

Hello. I have a question about the wiring of the shift cut input trigger.

The only way I can get it to activate is to apply +12V to the input wire then touch it to ground. Then It will activate the shift cut. SO I have it wired to a relay so when shift cut is not in use the input wire is connected to +12v. When I hit the paddle shifter It switches the relay and the Input wire sees ground and It activates as long as I hold in the paddle switch. It seems to be working fine. But I would think the input wire would only need to be grounded to activate. Not apply +12v then switch to ground

The relay is wired
85    +12V
86      to paddle shifter to ground
87a    +12V
87       ground
30       shift cut input to ecu

Any thoughts on this? Is it Ok. I would think the ecu would just want a ground input

Thanks

[VEMS]

Hello mk123gti,

Do not apply 12v to the ADC inputs, they are 0-5v capable only, it will break your ecu! The paper that came with your ecu had very clear instructions on that, for reference check: http://vems.hu/download/v3/doc/RescueKit.pdf.

The correct way to activate shift cut is using a channel with internal pullup (also indicated on the paper that came with your ecu which channels have them) and switching the input to GND to activate.

Best regards, Dave

[mk123gti]

Dave thanks for the reply. Sorry I was wrong in the above post. I was applying +5V to the shift cut input then touching it to ground so 87a on the relay is +5v.  Now that I went back and looked at the settings in the log. It looks like I need to switch the input to "Inverted CH1" To ground activate. I had it on channel 1. Correct? Im heading to the shop now and Ill give it a try..

I got a pre setup ecu and pigtail harness from Lugtronic. I think I just missed the inverted part..

[VEMS]

Hello Mk123gti,

I am not sure how Lugtronic wired it up internally, but using his pinout below, i would recommend connecting a 4k7 pullup resistor between ec18-pin16 and ec36-pin28 this takes care of the "NEEDS Pull-Up"part. Secondly connect your relay (or clutch switch) switching to GND only between ec18-pin16 and GND. There is no need for 5v on the relay 87a actually this is counter recommended.

Your shift cut channel will indeed be ch1, but in non-inverted mode.

Best regards, Dave

[jrussell]

Dave is right on. Here's a diagram of it.



If your shifter switch is just simply a switch with no power normally connected to it, you can simplify things by removing the relay, as shown here.


The value of 4.7k on the resistor is fairly arbitrary. Anything in the 1k-10k range will work, but 4.7k is the best choice if available.

[mk123gti]

I get it now. I didnt know what pull up meant. I thought it meant pull up in vems software and assign the correct channel. He just said needs "pull up" in the wiring diagram. I wish he said "Needs 4.7K  resistor" 
I never heard of a resistor being called pull up before..
Thanks so much for your help. Ill give it a try next week

[jrussell]

The resistor isn't necessarily a pull-up. Just that it is part of the pull-up "circuit". Circuit is in quotes because it's so simple it's hard to think of it as a circuit. :)

With the input floating (no pull-up or pull-down) there's no way to be sure what voltage is on the ECU input. With a pull-up, we're ensured that it's 5V if the switch is open. When the switch closes, it goes to 0V. This is also called a low-side switch since it switches GND.

In a pull down scenario, the resistor would be between the ECU input and gnd. Then the switch would switch 5v. This is also called a high side switch since it switches a positive voltage.

For what it's worth, some of the analog inputs have internal pull-ups in the ECU. Not all sensors are compatible with pull-ups though, so we leave a couple without pull-ups. Whether it has a pull-up or not (internally) is specified on the RescueKit.pdf (Dave linked to a template of it) sheet that should come with your ECU.

BTW, Lugnuts should be providing you with this kind of stuff, but we're happy to help.

Jason

[mk123gti]

Thanks for the help guys. Works awesome now..

1 more question if you dont mind.
My build is a twinn engine vr6 drag car. I am using the same paddle shifter to shift both motors and turn on the launch controlls.

Can I wire the 2 ecu input wires together?
Should I use a dpdt relay to isolate the ecus?
Or can I use a diode to isolate the circuit?

I am using a latching relay for the left evo paddle to turn on and off launch control and the right for upshift air shifter selonoid and shift cut..

Thanks
Bruce

Last page has some videos of the shifter and setup to clarify..
http://forums.vwvortex.com/showthread.php?6061512-Twin-VRT-Drag-Car-Build/page16


Lugrtonic is awesome but sometimes hard to get ahold of. 

[VEMS]

Hello Mk123gti,

Wow thats an awesome setup you've got going there!

Yes the two launch and shift cut inputs (assuming you mean 1 shift cut/launch input from each 2 Vems ecu's) can be wired together without any need for diode or dpdt relay, and switched to GND by a common switch (like in Jasons example diagrom above, just two times ec18-16 connected to the same spot).

Best regards, Dave

[fphil]

Wow thats an awesome setup you've got going there!

+1