Hi! everyone, i am making an intelligent traffic signal system that changes the lights according to the traffic. i am using 4, 1.5 inch force sensitive resistors. The cars i am using will be hotwheel cars. Now there are 2 problems, a) the cars are not that heavy hence, these FSR tend to give no or little readings at low weight objects. which resistors should I put in the circuits of the FSR to make them more sensitive at lower weights. simply adding greater resistance resistors (even a 82k Ohm) made made it much more sensitive but not optimum, but since the FSR itself has a maximum resistance of 100k Ohm should i go above it? or is there any other method to make it detect lower weight objects more easily. the second problem is that the cars wheel bases are longer than the sensor, so i trying to make a square frustum to make a platform (that will come under the tracks) to measure, is this adviseable?
What is the weight of the cars ?
I think a FSR is not the right sensor for this. A micro-switch with a lever needs less force. Or something with IR light: IR Break Beam Sensor with Premium Wire Header Ends - 5mm LEDs : ID 2168 : $5.95 : Adafruit Industries, Unique & fun DIY electronics and kits.
A light beam sensor or inductive proximity sensor perhaps?
What is the rating of your FSR? It has to be very sensitive to reliably detect a 30-40g car rolling over it.
I agree, a light gate of sorts is probably the best solution. Even a microswitch needs significant force to move, a good fraction of the car's weight, and the lever has to be physically moved some distance by the car as it moves by. That will affect the movement big time.
A lever could be used to increase the force applied to the FSR. But, based on the scanty information given so far, a light-based gate does sound like a better solution for this application (aka light beam sensor, beam break sensor, electric eye.......)
Or magnets on the cars and a hall effect sensor.
Come to think of it... aren't hotwheels cars made of metal? In that case an inductive sensor should work as well. No need to add magnets to the car.
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