Hey everyone,
so I got this project a month ago and I've been working on it but I just can't seem to figure this out. Now very important thing is that this is not a "real" project and I won't build it, it's just to teach us how to use op-amps and comparators. The project says:
"The pressure that the foot exerts on the surface is measured using 8 sensors that are arranged in the insole of the shoe
so that they measure the pressure that the foot exerts on the front, back, left and right part of the shoe and the intermediate positions.
There is also a button that is activated when the patient leans on the leg on which the measurements are performed.
When the button in the shoe is activated (when the patient leans on the foot on which the schedule is measured
loads), the pressure on all eight sensors should be measured. The sensors are resistant, linear and identical,
resistance 18 kΩ when unloaded and with a positive slope of 2 kΩ / kg load. Based
pressure differences should turn on one LED of eight, which shows the approximate position of the foot,
that is, which sensor burdened the patient the most. If the load on the two sensors is equal (in
limits +/- 10%), two LEDs should be switched on. Make a signal to turn on the LEDs
using differential amplifiers and comparators that compare the difference of two voltages with zero, and if
the difference is less than zero, turns on one, and if it is greater than zero, turns on the other LED."
Now for the linear reading of the force exerted on the sensor I used 2 PNP transistors to create a constant current flowing through the sensor and giving me a linear voltage.
Next I thought about finding the highest value of voltage coming from the sensors and comparing it to the voltage of the sensors and based on that I would either turn on LED or do nothing. This is pretty bad as far as I can see it and I think there is an easier way to do it.
Biggest problem I have is coming up with the logic to turn on the LED based on the difference of 2 voltages. I thought about using window comparator but I'm not sure if I can set the negative voltage as the lower bound and it seems it would take a lot of work to turn positive voltage to negative. Other thought I had is to use hysteresis comparator but I have no idea how to set that up.
This is one idea I had about logic for LED but I still need that 10% window.
This is the second idea and professor said that op-amps don't like to be in saturation and that I should use comparators instead.
Note: I don't have any prior experience building any kind of circuit, I just solved circuit problems in my 1st year.
Any help would be amazing even if it's to say how bad something here is. Thanks
so I got this project a month ago and I've been working on it but I just can't seem to figure this out. Now very important thing is that this is not a "real" project and I won't build it, it's just to teach us how to use op-amps and comparators. The project says:
"The pressure that the foot exerts on the surface is measured using 8 sensors that are arranged in the insole of the shoe
so that they measure the pressure that the foot exerts on the front, back, left and right part of the shoe and the intermediate positions.
There is also a button that is activated when the patient leans on the leg on which the measurements are performed.
When the button in the shoe is activated (when the patient leans on the foot on which the schedule is measured
loads), the pressure on all eight sensors should be measured. The sensors are resistant, linear and identical,
resistance 18 kΩ when unloaded and with a positive slope of 2 kΩ / kg load. Based
pressure differences should turn on one LED of eight, which shows the approximate position of the foot,
that is, which sensor burdened the patient the most. If the load on the two sensors is equal (in
limits +/- 10%), two LEDs should be switched on. Make a signal to turn on the LEDs
using differential amplifiers and comparators that compare the difference of two voltages with zero, and if
the difference is less than zero, turns on one, and if it is greater than zero, turns on the other LED."
Now for the linear reading of the force exerted on the sensor I used 2 PNP transistors to create a constant current flowing through the sensor and giving me a linear voltage.
Next I thought about finding the highest value of voltage coming from the sensors and comparing it to the voltage of the sensors and based on that I would either turn on LED or do nothing. This is pretty bad as far as I can see it and I think there is an easier way to do it.
Biggest problem I have is coming up with the logic to turn on the LED based on the difference of 2 voltages. I thought about using window comparator but I'm not sure if I can set the negative voltage as the lower bound and it seems it would take a lot of work to turn positive voltage to negative. Other thought I had is to use hysteresis comparator but I have no idea how to set that up.
This is one idea I had about logic for LED but I still need that 10% window.
This is the second idea and professor said that op-amps don't like to be in saturation and that I should use comparators instead.
Note: I don't have any prior experience building any kind of circuit, I just solved circuit problems in my 1st year.
Any help would be amazing even if it's to say how bad something here is. Thanks