Bryan Cockfield of Hackaday writes:
Sometimes you use a Raspberry Pi when you really could have gotten by with an Arudino. Sometimes you use an Arduino when maybe an ATtiny45 would have been better. And sometimes, like [Bill]’s motorcycle tail light project, you use exactly the right tool for the job: a 555 timer.
More details on William F. Dudley’s project page:
The 555 is a clever chip; not only will it supply the oscillator for the flashing effect, it has a reset pin that can be used to force the output to a known state (low) when (other circuitry tells it that) it’s time to stop flashing. Thus the brake light will be steady “on” after a few flashes every time the brake is applied.
The 555 is happy to run directly off the nominal 12 volt vehicle electrical system, so no voltage regulator is needed. The 555 is almost immune to electrical system noise, so no worries about your Arduino code going off into the weeds if there’s a spike from the electrical system.
[Written by OSH Park engineer Jenner Hanni on Wickerbox Electronics]
This was a collaboration with Tom Hogue (tz89 from the Venture Rider forum) to translate his prototyped design onto a printed circuit board. He’s done all of the software; my contributions were entirely in hardware.
The Carb Sync Shield monitors the up to six carburetors and displays the vacuum pressure in realtime on an LCD display so the user can make adjustments to the air/fuel mix in each cylinder.
There’s an additional RPM feature that will be useful to set and monitor the idle speed on bikes that don’t have a tachometer.
The kit can be assembled by a novice using a basic soldering iron. The pressure sensors have extra-large surface mount pads and all other components are through-hole.
The shield is compatible with both the Arduino Uno v3 and the Bluetooth-capable RedBear Blend v1. It displays the RPM calculated from each of up to six simultaneous 3.3V or 5V pressure sensors on an LCD display which can be mounted directly or connected with the rainbow jumpers as shown above.
The board draws power from the carrier Uno or Blend board, which in turn can run off a 9V battery or a USB plug. The blue trim potentiometer controls the brightness of the LCD so it’s visible indoors or outdoors. The large switch sets the analog pressure sensor reference voltage to 3.3V or 5V. In the final version of the board, the switch is replaced with a 3-pin header and jumper cap.
Three digital I/O lines are broken out along with dedicated 5V or 3.3V pins to support extra sensors. It’s up to the user to match the sensor voltage on the digital line to the expected operating voltage of the Uno or Blend.
We had the boards fabricated through OSH Park, a local batch PCB service based in Oregon, and did a successful test in early November on Tom’s bike.