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Question Seeking help to re-set Audino timing system with RC


I've rebuilt my old wood routed track into a small spare room, which necessitates redoing the timing system.
I know the Audino Uno connection to the PC is ok and working, but am unsure about wiring up the sensors. Can anybody help with what should be a simple question?

I have replaced separate IR LEDs and sensors with an intrack combined unit (Jaycar ZD1901 photo interrupters).
I need help identifying which connections to attach the old wires to as it has both LED and sensors in the one unit. Connections are: 
Cathode (K); Anode (A) on one side, and Collector © and Emmitter (E) on the other. I also need advice as to which of these should have the resistor added.

The Audino sketch and connection is already set up, so should be ok if I wire the hardware the right way.
Previous setup used twin IR LEDs on a gantry, and single sensors in track. I've gone for this combined solution now due to a lack of space above the track (a gantry will hinder marshalling and means the timing is in the wrong (less useful) sector of the track.

Track is a now a 12m 3 lane 3 level twister, fitted into a 2.4 * 1.8m space.

many thanks
[+] 2 members Like Difinity's post

That's definitely a neat solution - although guide blades need to be black. The white NSR blades don't break the beam sufficiently to trigger the switch. Red or blue blades can be problematic, depending on the specifications of the components.

I found the ZD1901 on the Jaycar website - unfortunately they don't include a circuit diagram on the listing. However, I did find this via a Google search...


The diagram gives you a set-up and resistor values for the module being powered from the 5v output of the Arduino board.

In that circuit diagram, the cathode and anode of the diode are like this...


And the power supply symbol means this...


That should sort you out with wiring the diode - anode to +ve (5V) and cathode to -ve (GND) and a 100 ohm resistor between +ve and anode.

The 'bulb' at the top is the Arduino input pin (which are defined in the Race Coordinator instructions). As I understand it, Emitter should be connected to the GND pin on the Arduino and the Collector to the specified pin for that lane. A 1k ohm resistor going in to the lane pin on the arduino would be sensible.

Test that works on one lane first (using a car with a black guide blade!) - if it doesn't work, reverse the Emitter and Collector (keeping the resistor on the lane pin). It will depend if the Arduino sketch programs the board to expecting a signal when the car passes (as per the diagram above) or a constant signal that is broken when the car passes (the opposite). With my deadstrip / Arduino / RC set-up is the former - a pulse when the car passes.

I hope that helps. It'll be great to see pictures of your track Thumbup
[+] 1 member Likes woodcote's post

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