A coin operated timer power supply.
A few of the property managers tried putting them on household laundry units. The customer puts money in and the timer runs for however long you program it. Me being me, I helped a 'friend' rewire the washer to plug directly into an outlet ;-)
If I might add my two cents to this, if it were me, I'd find a restaurant supply or local auction or something and pick up a low temp commercial warewasher. The control box could be re-wired to where a coin-op/bill acceptor would be the trigger after the door is closed. It wouldn't be hard to wire into one of the safety lines.
You could install the unit, have the chemical dispenser set up, have all the workings out of users reach, behind cages etc, they load the rack, slide the rack into the warewasher, close the door and place their money in the vending unit. When there are sufficient funds, the relay clicks and starts the washer. Since its low temp, the chemicals dispense as needed, the cycle runs, completes and user pulls dishes out the other side.
If you were to set something like that up, ecolab gives you the dispensing equipment as long as you buy the chemical from them.
Someone would just need to pop in throughout the day and check the filters etc make sure there isn't stuff stuck in the sump etc.
*edit: Ugh, I didn't realize ... the age of this thread... there needs to be a way to keep people from reviving posts older than two years.... .......*
