Engine Simulator - Page 2
This project is about making a rig that simulates the most important sensors of an engine, it also reads injection and ignition outputs to confirm things are functioning correctly.
Follow this link to see the previous page - Page 1
Since the servo drive will be running at a high frequency it may put some interference in the supply, likewise other appliances may also put some interference in the line supply. The most damaging parts may be high voltage transients which can cause components to fail, to combat this a filter is used. Filters are a very common aspect in any kind of supply whether it be a power supply or the drive for a motor. I designed a mount to be 3D printed for the filter to screw into.
The next step was to finish off the servo drive board, this required some connectors to be ordered along with some screws to mount the MOSFET's to the heat sinks. I worked out the values of the resistors for the feedback loop. The feedback loop reads the emf across the windings to determine whether it needs to increase switching frequency or decrease it to stay synchronised. The bus voltage will be approximately 170Vdc and the control voltage 5V. The divider reduces this voltage down to a maximum of 5V. The voltage across the windings will also be dependant of the pulse width modulation duty, the amount of time the MOSFET's are on and off. If the duty is to be on for example 50% then we can expect to see around 85V across the windings, this will also correlate to 50% of the motor speed. The drive will work as a closed-loop system in order to maintain speed via duty cycle and also synchronicity via emf.
A wise tip is to remove all of the flux from the board and layer it in a conformal coating. The reason is that flux is an acidic compound, it is not the corrosive properties we have to worry about but it's ability to conduct in humid conditions. Old circuit boards were prone to failure because dust would retain moisture and the flux would allow it to conduct, something I have experienced with one of my own boards. I thoroughly wash all of my boards in solvent and detergent to remove all flux residue, I then seal it with an acrylic conformal coating. The lacquer also keeps all the traces looking bright and the board clean.
The board installed on the rig, the supply wires attached and the motor phases terminated. If flying leads have to be used like in the line wires or those for the filter capacitor then one end should always use a crimp terminal for disassembly. Soldered wires are often a weak point since the solder wicks the cores making them rigid. This is a stationary board but in something like a car the vibrations would lead to failure over time.
I decided I would go with a socket and lead for the supply since I don't like trailing wires if I have to transport the rig. I made sure to design the housing long enough so that the terminals would not be exposed, I do not like electrocuting myself. The reason I put the servo drive at the back was to avoid accidental electric shock, I may however go a step further and encase it in acrylic. I would probably have to install a cooling fan to stop overheating, although unlikely.
I designed a housing for the power switch, again I made it long enough as to not expose any terminals.
Please check back later for updates, this is my current project.
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