I ran into a problem on my last robotics project. I wanted to hook
up a lynxmotion dual h-bridge motor driver to the OOPIC. The motor driver
requires 4 PWM (Pulse Width Modulation) lines to operate it correctly. The OOPIC only supplies 2 PWM
lines. I needed a way to guide the PWM to the right motor driver inputs. the
solution is very easy and only requires a NOR gate (chip # 74LS28). this chip
includes 4 NOR gates on it. what we want to do is set up a small circuit that
will allow you to use 2 PWM lines to control a 4 PWM input driver. lets
look at just one motor. we have 4 inputs (2 on each NOR gate). One of the OOPICs
PWM line should be tied to one input on each NOR gate. So you have 2 NOR gates,
with one input on each gate tied to the same PWM line. the 2 extra inputs on the NOR
gates are the control lines. when control line 1 goes low, the PWM signal will be on
the output of gate 1. When control line 2 goes low, the PWM signal will be on
the output of gate 2. this is done for each motor on the robot. your 4 NOR gate outputs go to the 4 inputs of the motor driver. once this is done,
you will have complete control of the motor driver. this little circuit is a great
way to split PWM signals. you can also cascade the nor gates as many times as you
want, creating as many PWM signals from the original as you need for you application.
sorry for the poor schematic drawing, i hope you get the idea.
Jeff Clayton
I ran into a problem on my last robotics project. I wanted to hook
up a lynxmotion dual h-bridge motor driver to the OOPIC. The motor driver
requires 4 PWM (Pulse Width Modulation) lines to operate it correctly. The OOPIC only supplies 2 PWM
lines. I needed a way to guide the PWM to the right motor driver inputs. the
solution is very easy and only requires a NOR gate (chip # 74LS28). this chip
includes 4 NOR gates on it. what we want to do is set up a small circuit that
will allow you to use 2 PWM lines to control a 4 PWM input driver. lets
look at just one motor. we have 4 inputs (2 on each NOR gate). One of the OOPICs
PWM line should be tied to one input on each NOR gate. So you have 2 NOR gates,
with one input on each gate tied to the same PWM line. the 2 extra inputs on the NOR
gates are the control lines. when control line 1 goes low, the PWM signal will be on
the output of gate 1. When control line 2 goes low, the PWM signal will be on
the output of gate 2. this is done for each motor on the robot. your 4 NOR gate outputs go to the 4 inputs of the motor driver. once this is done,
you will have complete control of the motor driver. this little circuit is a great
way to split PWM signals. you can also cascade the nor gates as many times as you
want, creating as many PWM signals from the original as you need for you application.
sorry for the poor schematic drawing, i hope you get the idea.
Jeff Clayton