Hall-sensor
Hello Leon,
Hall sensors (unipolar) may be used. However ...
The Hall sensor which I used for testing is of the unipolar type, however the polarity is wrong compared to the magnet of the steering slider and magnetic strip on my test track. Of course I can turn the magnet and the strip, but I still try find the proper sensor, that will match with the existing polarity. Or may bipolar sensors be used.
Test's I've done myself showed that Hall sensors (the one you mention) are less sensitive than an average reed contact. It may be a difference if you use them in or on top of a magnetic strip.
My intention is to cut the strips approx. every 15 cm and put the sensor in between the ends. The top of the sensor will be at the same level as the top of the strip.
As Hans pointed out, Hall sensors need power supply. Consumption is about 3,5mA each, so if you have 100 sensors, you draw 350mA, Nothing to worry about, but you cannot simply "steal" it from the signal wires. It requires additional wiring, although it may run through the same flatcable as the signals.
Why not use an external power source to drive the Hall sensors and connect it to the SWDEC.
You need to do something in terms of multiplexing, otherwise you need quite some cable between the road and the electronics. This can be done, but it requires additional electronics. Could fit on a PCB like the SWdec, but it needs te be developed, which costs time an money.
We may not need additional circuitry to multiplex the signals. I've discussed this matter with my son and he thinks that even an better option may be to include the optocouplers, a voltage clamp and some resistors in a redesigned version of the SWDEC. He is planning to test this on a breadboard.
Best regards,
Jaap Knol
