Hi Chris and Sam here, we have been asked to write a bit about how we put together ‘Scream if you want to go Faster’.
So… it started with a Razor E300 Scooter. In theory, we were going to replace the speed controller with a variable speed controller then use an Arduino and a digital potentiometer to control it.
The Arduino would take the sound from the
icrophone and map the volume level to the digital pot over SPI. The digital pot connected to the speed control the speed controller.
Originally, we were concerned about whether volume alone would be sufficient to control the scooter, or whether the frequency of scream would need to be taken in to account. It turned out volume was enough, so that was one job that was easier than expected. 😊
All hooked up it was good to go. The first test runs were fun. But then there was a failure, a closed failure, the engine would not stop!!! NOT GOOD. So we knew that it worked in theory but we needed to build in some safeguards. This was achieved through the addition of relays to ensure that should the speed controller fail the release of the throttle would kill the power to the motor.
There were several points that needed calibration,
- The maximum volume needed to be set to calibrate the volume that will result in the maximum speed.
- The gain added to the microphone signal as it was sent to the Arduino was changed using a variable resistor. This was set to find the sweet spot to pick up a voice, but not be over sensitive. When it was too sensitive the sounds of the motor would set off the sensor which resulted in a feedback loop.
- The minimum speed is set via a potentiometer in the base.
After these things were calibrated it was a few more test runs then off to ludic rooms for delivery.
The Arduino code will be made available shortly.
A big thank you to Ludic rooms for giving us the opportunity to work on such an amazing project.
Chris and Sam