J
Hi! my name is John I am a recent graduate from ITT Technical Institute who is in dire need for a solution to what I would guess is a not so complex problem for someone with a degree higher than that of my own which is an associates.
First I must note that this is not a work related problem. I am accually a self employed cabinet maker who never worked profesionally in electronics but have been tinkering ever since I can remember. I am currently designing a robotic arm which operates much like a backhoe but with a gripper at the end of the boom instead of a bucket. It is made of wood and metal and its motion is accomplished by 12 volt DC linear actuators. I have two dual axis analog joysticks which I plan to use for speed and direction control of the various linear actuators. I purchased them from a company I found online that sells replacement parts for arcade games. The joysticks each have two 5K pots. I also bought a PWM DC motor speed controller circuit kit at an electronic store. It basically consists of a 556 Dual timer IC that uses a 10K pot to control the modulation of its output which in turn controls the switching speed of a power mosfet transister that is connected to the linear actuator. I planned on building one of these control circuits for each joystick function which would be a total of four thus controlling four linear actuators.
Sounds easy enough, rite? well I thought so until I got my elbows into it and discovered the problem I now have and have had for months now. The control circuit I bought used the 10K pot it came with to vary the voltage at the control input of the IC between VCC and ground. This varied the modulation of the IC's output thus controlling the speed of the linear actuator. The pot was connected between VCC and ground. The wiper of the pot was connected to the control input of the IC. The closer the voltage of the pot's wiper came to VCC the faster the motor turned and the closer it came to ground the slower the motor turned. So my Question to anyone willing to help me is "HOW DO I USE THE JOYSTICK POT IN PLACE OF THE 10k POT THAT CAME WITH THE CIRCUIT"?
There is also something you should know about the pots in the joysticks. First of all they are only 5K pots and when the joystick is pushed all the way in either direction there is still between 600 and 700 ohms measured between the wiper of the pot and the other terminals of the pot. Also when the joystick is at its resting position (in the center of the pots overall travel) there is about 2.5K ohms not zero ohms. If I try to hook up the pot as is to the circuit the motor is turning even before I touch the joystick because of the voltage at that central point of the pot not equalling zero. Also if I push the Joystick all the way forward the motor does not turn at maximum speed because of the fact that the pot's wiper never actually reaches VCC, there is still that 600 to 700 ohm of resistance between the wiper and VCC. I also need the motor to turn in the opposite direction when the joystick is pulled back past that center (or resting) position. I have tried many different ways to make this work including the purchase of an analog to digital converter IC to somehow connect the two but sadly had no success. Maybe I am overthinking the whole thing and overlooking something obvious but all I know is I paid $125.00 per joystick and I would hate to not be able to somehow make them work. If someone has a solution to my problem that may or may not involve the use of these joysticks that would be greatly appreciated.
First I must note that this is not a work related problem. I am accually a self employed cabinet maker who never worked profesionally in electronics but have been tinkering ever since I can remember. I am currently designing a robotic arm which operates much like a backhoe but with a gripper at the end of the boom instead of a bucket. It is made of wood and metal and its motion is accomplished by 12 volt DC linear actuators. I have two dual axis analog joysticks which I plan to use for speed and direction control of the various linear actuators. I purchased them from a company I found online that sells replacement parts for arcade games. The joysticks each have two 5K pots. I also bought a PWM DC motor speed controller circuit kit at an electronic store. It basically consists of a 556 Dual timer IC that uses a 10K pot to control the modulation of its output which in turn controls the switching speed of a power mosfet transister that is connected to the linear actuator. I planned on building one of these control circuits for each joystick function which would be a total of four thus controlling four linear actuators.
Sounds easy enough, rite? well I thought so until I got my elbows into it and discovered the problem I now have and have had for months now. The control circuit I bought used the 10K pot it came with to vary the voltage at the control input of the IC between VCC and ground. This varied the modulation of the IC's output thus controlling the speed of the linear actuator. The pot was connected between VCC and ground. The wiper of the pot was connected to the control input of the IC. The closer the voltage of the pot's wiper came to VCC the faster the motor turned and the closer it came to ground the slower the motor turned. So my Question to anyone willing to help me is "HOW DO I USE THE JOYSTICK POT IN PLACE OF THE 10k POT THAT CAME WITH THE CIRCUIT"?
There is also something you should know about the pots in the joysticks. First of all they are only 5K pots and when the joystick is pushed all the way in either direction there is still between 600 and 700 ohms measured between the wiper of the pot and the other terminals of the pot. Also when the joystick is at its resting position (in the center of the pots overall travel) there is about 2.5K ohms not zero ohms. If I try to hook up the pot as is to the circuit the motor is turning even before I touch the joystick because of the voltage at that central point of the pot not equalling zero. Also if I push the Joystick all the way forward the motor does not turn at maximum speed because of the fact that the pot's wiper never actually reaches VCC, there is still that 600 to 700 ohm of resistance between the wiper and VCC. I also need the motor to turn in the opposite direction when the joystick is pulled back past that center (or resting) position. I have tried many different ways to make this work including the purchase of an analog to digital converter IC to somehow connect the two but sadly had no success. Maybe I am overthinking the whole thing and overlooking something obvious but all I know is I paid $125.00 per joystick and I would hate to not be able to somehow make them work. If someone has a solution to my problem that may or may not involve the use of these joysticks that would be greatly appreciated.