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Mode Switching with C12x Aux Out

PostPosted: Wed Mar 18, 2020 8:56 am
by RR213
I have used a driver rotary switch wired to a C12x to set the diff map of a CAN based MDC2 and Gems diff controllers before.

I'm having an issue with a new install where AUX2 (pin 30) is hard wired to MDC pin 47 yet the MDC mode switch is not registering when AUX2 switches high.

I've traced this to inadequate voltage (2.4v vs 11.6v battry voltage) on the AUX2 output when connected to MDC pin 47. Presumably this is due to a low resistance (relative to the C12x 10k pull-up) pull-down resistor within the MDC.

I've identified two possible work around options and would welcome others thoughts or suggestions.

- Option A -
add an external 1k pull-up (to battery voltage) resistor to the wire between C12x AUX2 (output) and MDC Mode Switch (input).

- Option B -
Wire AUX2 to low side switch a relay coil with the relay output used to connect MDC Mode Switch to battery voltage when the coil is energized.

I would ether use a 5 pin relay to connect to ground when the coil is not energized, or a 4 pin relay with a weak pull-down resistor to ensure the Mode Switch input is pulled down to 0v.

Re: Mode Switching with C12x Aux Out

PostPosted: Wed Mar 18, 2020 10:08 am
by adrian
Option A is the way to go. Just make sure you wire the 1k resistor to the same switched battery source the Dash is powered from, you don't want the output to have power when the Dash is turned off.