hi,
I am looking to built a project to detect the weight chosen in any of the fitnes equipment. A am looking for a sensor which will detect the presence of the pin (metal) when inserted into the slot for the right weight chosen. What kind of sensor would work for this. How do i built a circuit to get different inputs (numbers) based on the selection of the weight?
Here is a link with the weights stack and the pin which selects the weight.
Just a wild idea, but maybe you could just measure the resistance between the weight pin and an analog input of your Arduino which would be connected to the bottom of the stack. No sensors or messy wiring required! Of course, if the weights are all connected to a metal rod at all times it won't work, but judging by the picture it looks like there's a plastic bushing isolating the weight from the rod. It all depends on how the machine is constructed. A quick way to tell would be to use a multi meter to read the resistance between any weight and the weight on the bottom. If you get different values for each, you're golden.
What I'm thinking is just connect 5v to the weight pin with a resistor in between (in case it goes to ground. Also, the cable holding the pin could even be the wire) and connect the bottom of the stack to an analog input that's pulled up with a resistor. See this topic for more details: http://forum.arduino.cc/index.php/topic,21614.0.html
Each weight in between the 5v and the input should increase the resistance by a certain amount. If you write down the reading you get for each weight, you should be able to use those values to determine which weight is selected. If the weights are too good of a conductor, you could potentially add little foam pads between each with a 100 ohm resistor bridging the two sides of them or something.
Of course, there's a lot of reasons why this may not work, but hey, it could be awesome if it did.
gauravguptak:
I am looking to built a project to detect the weight chosen in any of the fitnes equipment. A am looking for a sensor which will detect the presence of the pin (metal) when inserted into the slot for the right weight chosen. What kind of sensor would work for this. How do i built a circuit to get different inputs (numbers) based on the selection of the weight?
Thinking a bit out of the box, if it's possible to attach a flat plastic plate to the pin, you could mount a ping sensor (ultrasonic) at the bottom of the stack, facing up, and when the stack is at rest, the echo from the plate will tell you how high the plate (and pin) is from the sensor, allowing you to calculate which weight the pin is in.
Some good ideas here. They let us for it to be generic across equipment. Think plug and play and retrofit clip on to any weight stack irrespective of the stack material. I am going to try couple of these methods and see what comes out of it. The best could be a metal contact detection won each of the holes of the weight stack which would give me a definite number. Let me know if you have any other suggestion.
generic across equipment means you will be dealing with some all metal plates and some solid metal shafts.
means you need to add something to the pin like a handle that contains something.
maybe an rfid that will report distance ?
dave-in-nj:
generic across equipment means you will be dealing with some all metal plates and some solid metal shafts.
means you need to add something to the pin like a handle that contains something.maybe an rfid that will report distance ?
How does RFID report distance?