I knocked up this quick & dirty solution just before leaving my cat for a weekend away. Ashly (cat) is quite happy with us going away for a few days AFAIK but is now geriatric and on thyroid medication so I decided to address this. I needed a wooden box with a lid I could hinge so I used an old drawer I was throwing out. I sawed a couple of cuts in the back, drilled holes and used cut-off nails for hinge pins. I pulled out a 12V solenoid from my parts box and bent up a bracket to mount this on. I just used my bench power supply for a 12V supply. The flap is vertical so needed a spring to ensure it opened. Only trampoline springs in my spring box!! Ball point pen spring considered, finally remembered a couple of neodymium magnets I have so I mounted these with cable straps so they repelled each other and this works a treat! Finally, the brains; a Sonoff S20 WiFi wall socket with a timer setting on E-Welink on my phone to turn on the power supply at feed time and another a minute later to turn it off. Tested it through a cycle then loaded it with food and medication and shot off for a weekend family reunion. It was weighed down with a pot plant (anti-cat tamper) on an outside table in a covered veranda along side his bed and water. Ashly would be very aware of it because it had no baseboard and the wet food smell would be emanating.