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Driving backwards wireless …

Similar to most sequential gearboxes, the activation of the reverse gear is done in a mechanical way. This is also the case with our Sadev gearbox.

Despite our goal is to drive as much as possible forward, it can be very nimble to drive backwards from time to time.

We didn’t like the original cable system too much. We agree it’s by far the most simple solution but since the cable is twisted every time a gear is changed, we want to find a better solution.

Since we are electronic engineers, it’s obvious we had to change the cable by a pair of copper wires. But still somebody had to pull the plunger in the gearbox. It was an easy choice to move this task away from the co-driver and use a solenoid instead. Some quick measurements instructed us that a 30N solenoid could do the job.

We found a reasonable sized 12V cylindrical solenoid. To make sure we have enough force in all circumstances we boost the 12V to 48V to energize the coil. This is no issue at all since the duty cycle is very low.

Still we were not happy. Now the wire had to move with every gear change so still no ideal solution.
What about wireless?? Everything today is wireless, so why not activating reverse gear by RF?
You must admit, it’s a cool idea.

So we started building a prototype. We use a ultra low power 433Mhz transmitter with a switch on the gear stick. If we activate the switch, an encrypted message is send to the receiver who decodes the message and triggers the booster to energizes the coil.

The 48V shot makes sure the solenoid pulls strongly the cable and the plunger in the gearbox releases so the reverse can be enabled.

A lot of complexity but we are happy with the solution. Even more since we finally could have a custom part 3D printed. The housing of the RF transmitter is our first printed part 🙂

The battery life for the transmitter is about 10 years.

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