JohnP
Well-Known Member
Before trying driving the coils with a higher voltage I have decided to try something else.
The drive circuit is currently configured to maintain a constant voltage to the coils, reversing the voltage polarity as the pendulum passes BDC so as the pendulum passes BDC the magnetic field attracts the pendulum as it continues its swing to its maximum, but as the pendulum reverses and swings back down to BDC the magnetic field is still trying to attract it thus actually retarding its motion till it reaches BDC where the field reverses and it is attracted in the other direction. To prevent this retarding force I have modified the drive electronics to pulse the drive voltage to the coils and to turn it off just before the pendulum reaches its maximum swing thus allowing it to swing back unimpeded till it reaches BDC where the drive voltage reverses attracting the pendulum in the other direction.
It now swings through the full arc, triggering the over swing circuit on every 3 or 4 swings. This is with 5 volts supplied to the L298 drive module resulting in ~3.4 volts being applied to the coils.
It has been running like this for the last 24 or so hours. I plan on letting it run for a week or so before committing the circuit to a PC board just to confirm no other problems arise.
In the video again the green LEDs indicate the drive to the coils, you can see that they are only on for a short time, not continuously, the yellow LEDs are the one second pulses to the clock stepper, and the lower right red LED is the trigger as the pendulum passes BDC controlling the duration of the pulse to the coils, and one in the middle is the limit sensor. You can see it come on for every 3-4 swings of the pendulum for about 2 seconds as it inhibits the coil drive to reduce the swing of the pendulum.
It will be interesting to see how its time keeping compares with the old version, should be less variation with temperature changes in my shop.
John
The drive circuit is currently configured to maintain a constant voltage to the coils, reversing the voltage polarity as the pendulum passes BDC so as the pendulum passes BDC the magnetic field attracts the pendulum as it continues its swing to its maximum, but as the pendulum reverses and swings back down to BDC the magnetic field is still trying to attract it thus actually retarding its motion till it reaches BDC where the field reverses and it is attracted in the other direction. To prevent this retarding force I have modified the drive electronics to pulse the drive voltage to the coils and to turn it off just before the pendulum reaches its maximum swing thus allowing it to swing back unimpeded till it reaches BDC where the drive voltage reverses attracting the pendulum in the other direction.
It now swings through the full arc, triggering the over swing circuit on every 3 or 4 swings. This is with 5 volts supplied to the L298 drive module resulting in ~3.4 volts being applied to the coils.
It has been running like this for the last 24 or so hours. I plan on letting it run for a week or so before committing the circuit to a PC board just to confirm no other problems arise.
In the video again the green LEDs indicate the drive to the coils, you can see that they are only on for a short time, not continuously, the yellow LEDs are the one second pulses to the clock stepper, and the lower right red LED is the trigger as the pendulum passes BDC controlling the duration of the pulse to the coils, and one in the middle is the limit sensor. You can see it come on for every 3-4 swings of the pendulum for about 2 seconds as it inhibits the coil drive to reduce the swing of the pendulum.
It will be interesting to see how its time keeping compares with the old version, should be less variation with temperature changes in my shop.
John