RayL posted:Just curious -- what is the chip you show in the video?
It is just a buffer chip to drive the LED. It's meant to represent a "generic" digital input as you'd have on the Arduino. That is, it requires low input-current which is how the capacitor works to easily extend the pulse detection time. The "schematic" if you can even call it that is:
A 100K resistors pulls the input of the digital gate "high" until the reed switch closure drives it low. The 100K value is a typical value used on digital inputs with some microcontroller chips even having this type of "pullup" built-in to the chip enabled/disabled by software. Adding a capacitor of about 10uF makes the time-constant about 1 second (R x C = 100K x 10uF = 1 sec) which seemed like a reasonable starting point.
In this application, 3 sensors decode 3-bits in parallel, 1 bit per sensor.
SPST switches are of course 2-pin devices. So 4 wires run from Arduino or equivalent to the "reader" board in the trackbed. Ground would be common to all 3 switches, then 1 wire for each switch output.
Hall sensors are typically 3-pin devices. So 5 wires run from Arduino to "reader" board. +5V and Ground would be common to all Hall chips, then 1 wire for each Hall sensor output.
If you get beyond the experimental phase and reach implementation, there are details wrt noise, spike, glitch protection that might be worth discussion. I think you mentioned a 3V Arduino so there may be some 5V vs. 3V level translation issues and what not.
