- Redesigned the Veroboard to make the connections more logical; eg power terminals on the left adjacent to the DC/DC Converter Module and Actuator Motor connectors in the middle, closer to the Motor Drive Board.
- For consistency, the Veroboard is the same width as the one used for the B-Model Interfacing. However, it is only 11 holes deep instead of 16, because there are no ICs to carry and we need the space for the Motor Drive Board.
- Minor circuit changes - again for consistency with the B-Model Interfacing.
- Adjusted the wire lengths to suit the new layout.
- Removed the 10 k protection resistors from the three GPIO pins because they aren't really needed and they add labour to assembly.
Gate Valve Drive Electronics
Re: Gate Valve Drive Electronics
Attached to this post is the latest version of the Gate Valve Circuit and Assembly Drawing. Changes that I have made since the last prototype:
- Attachments
-
- Actuator_Motor_Drive_Circuit_(LM298D_Board)_V05.odg
- (2.34 MiB) Downloaded 81 times
Terry
Re: Gate Valve Drive Electronics
The recent problems with over-current in the Actuator Motor, related in the Status topic viewtopic.php?f=13&t=31 has triggered a discussion about the need for over-current protection. A number of options have been proposed, which are summarised here:
More thought and discussion is needed.
- Over-current protection implemented wholly in hardware, eg limit the current drawn from the +12V into the motor drive circuit in hardware. No detailed design for this has yet been proposed.
- Measure the current drawn by the motor via a sense resistor and feed that back to the RPi for action:
- Add a sense resistor to the Veroboard and include a comparator to generate a logic signal that the Pi would monitor.
- Hack the Motor Drive Board to add the sense resistor in the return of the current for each motor as described in the L298N Data Sheet. This would generate a voltage that could be measured by a channel of the A/D Converter to shut the motor down by removing the drive voltages of the enable (which is currently unused.
More thought and discussion is needed.
Terry