Anything not specifically related to the Speeduino hardware. Eg sensors, bluetooth, displays etc
Digging in to making a speeduino work on my 1NZ, I found that my clutch switch switches to 12V when the clutch is disengaged. Looking at the circuits on the retail speeduino pcbs, it appears that they only accept a ground switch, or a 5v switch. To make my clutch input work, do I just need to adjust the resistor value on the input to drop the voltage to an acceptable 5v range? Or is there more to it than that? Still a noob when it comes to hardware design so I appreciate any help :D
Activation may be from either a high or low input, with the high or low offset (pullup/down) in one of three ways;
  • Input held high by external resisted 5V pullup (for grounding switches)
  • Input held high by internal uC pullup (for grounding switches)
  • Input held low by resisted grounding (for high switches)
Check the Launch Control page in the Wiki, and the options in TunerStudio for concept of the action. Also review the schematics for your specific board for options that may guide your choices.

In your case with a 12V signal, and input to the uC limited to 5V, a voltage reduction to the LC input would be required. The board would ground the floating input through a resistor to hold ground until switch activation. The switch would provide a 5V signal to the input to raise input voltage above 3V to a maximum of 5V to activate the function.

An example that includes these options is the UA4C Launch input, which options all three modes above. In this example, the jumper to Ground would be used (solder-jumping pads 2&3), and the positive voltage input from your switch would pull it up for activation going high. In this example the pulldown is through a 2k7 resistor, so a 6800 input resistor would pull the input voltage at the uC pin to about 3.8V (@13.5V) to 4.3V (@15V) as a voltage divider circuit. There are other options. Hope that helps.

UA4C_Launch_in.jpg (13.66 KiB) Viewed 1632 times
edited to add pulldown voltage divider example
Thank you so much! You answered my question better than I could have imagined :mrgreen: It looks like I just need to make some minor changes to my circuity and I should be good to go then. I am still learning all this hardware stuff.. I am just a automotive technician with no formal electrical training so I really appreciate you guys sharing your wisdom :ugeek:
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