Hi all,

I’ve been tasked with building a “shifter box” for a race car. The purpose is to manually place the transmission into neutral after a crash, since the car sometimes remains stuck in gear. To achieve this, I need to send a 14.5 V signal to the electronic shifter box, while maintaining a 3 V idle state under normal conditions.

I designed a comparator-based circuit to mimic the paddle shifter: when the button is pressed, the output switches from 3 V (idle) to 14.5 V. The problem is that when I tie the outputs together, they form a voltage divider, which throws off Vout.

I came across the idea of using Ideal Diode Controllers on each output line to isolate them, and then tying the outputs together. Would this approach work, or is there a better way to achieve this?

Thanks!

 

Pretty sure there's a better way.
Isn't there just one output line at 3 volts nominal then switching to 14.5 volts when needed?

 

Pretty sure there's a better way.
Isn't there just one output line at 3 volts nominal then switching to 14.5 volts when needed?

Could you elaborate more on this? I agree there is a simpler way, I just can't quite figure out the logic for the 'simpler' way yet.

EDIT: Would something like a 2-position switch work? I think this would be much simpler lol

 

Pretty sure there's a better way.
Isn't there just one output line at 3 volts nominal then switching to 14.5 volts when needed?

...... XD

 

View attachment 354422...... XD

Possibly using a single supply of 14.5 volts and a 3 volt regulator.

 

Welcome to AAC.

Given this is a safety device on a vehicle, it seems most prudent to use an automotive relay to do the switching.

The automotive environment is noisy and inhospitable, standard automotive relays are purpose built for it.

A you need is an SPDT (Single Pole Double Throw) with the input to the transmission on the common, 3V on the NC (Normally Closed) contact and 14.5V on the NO (Normally Open) contact. The crash condition would just have to energize the relay coil.

 

Welcome to AAC.

Given this is a safety device on a vehicle, it seems most prudent to use an automotive relay to do the switching.

The automotive environment is noisy and inhospitable, standard automotive relays are purpose built for it.

A you need is an SPDT (Single Pole Double Throw) with the input to the transmission on the common, 3V on the NC (Normally Closed) contact and 14.5V on the NO (Normally Open) contact. The crash condition would just have to energize the relay coil.

Would it not be safer to wire it in a fail-safe way where 14.5V is on the NC and 3V on the NO? Then in a crash mode, if the power to the relay coil is damaged, it will remain in crash mode.

 

Welcome to AAC.

Given this is a safety device on a vehicle, it seems most prudent to use an automotive relay to do the switching.

The automotive environment is noisy and inhospitable, standard automotive relays are purpose built for it.

A you need is an SPDT (Single Pole Double Throw) with the input to the transmission on the common, 3V on the NC (Normally Closed) contact and 14.5V on the NO (Normally Open) contact. The crash condition would just have to energize the relay coil.

Got it, thank you!