Okay this is the problem:
I am using a joystick (just a variable resistor) to control the speed of a stepper motor. The variable resistor ranges from 0 to 100kΩ - the motor does not move when the variable resistor is at 50kΩ. Currently I'm using a potential divider and op-amp to detect whether the joystick is moved left or right, which then makes the motor turn clockwise or anti-clockwise. But I need to be able to control the speed of the motor depending on the resistance of the variable resistor.
The speed of the stepper motor is determined by clock pulses created by a 555. The way i thought it could work would be by taking the voltage across the variable resistor and putting into Pin5 of the 555 to vary the time between pulses. The problem is that the potential difference across the variable resistor only ranges from 0 to 0.6V. How can I "amplify" this voltage?
Ie. if the voltage across variable resistor = 0.4V, voltage to 555 = (0.4/0.6)*supply voltage.
Also, this doesn't take into account that the resistance gets less when I move the joystick left, and greater when I move it right... perhaps there is a better way to do this?
Thanks
I am using a joystick (just a variable resistor) to control the speed of a stepper motor. The variable resistor ranges from 0 to 100kΩ - the motor does not move when the variable resistor is at 50kΩ. Currently I'm using a potential divider and op-amp to detect whether the joystick is moved left or right, which then makes the motor turn clockwise or anti-clockwise. But I need to be able to control the speed of the motor depending on the resistance of the variable resistor.
The speed of the stepper motor is determined by clock pulses created by a 555. The way i thought it could work would be by taking the voltage across the variable resistor and putting into Pin5 of the 555 to vary the time between pulses. The problem is that the potential difference across the variable resistor only ranges from 0 to 0.6V. How can I "amplify" this voltage?
Ie. if the voltage across variable resistor = 0.4V, voltage to 555 = (0.4/0.6)*supply voltage.
Also, this doesn't take into account that the resistance gets less when I move the joystick left, and greater when I move it right... perhaps there is a better way to do this?
Thanks