Hardware Hacker Reverse Engineers Both the Electronics and Soap of a Bob Dishwasher Cassette
This one simple hack can save you 98%.
Bob from Daan Tech is a mini-dishwasher designed to fit on a kitchen counter. Users tend to like its performance but not the price of the consumable soap cartridge, or "cassette." Feeling the inkjet-trap vibe, a determined hardware hacker, dekuNukem, reverse engineered both the cassette's electronics and soap to make the Bob Cassette Rewinder!
If you are not familiar with the Bob Dishwasher, Matt of Techmoan did a thorough video review of it. There are three takeaways:
- Bob works well.
- Bob does not require plumbing.
- Bob has an all-in-one soap and rinse-aid cartridge called a "Bob Cassette."
One advantage of the Bob Cassette is that you do not need to mess with detergent. Bob uses the amount it needs automatically. The downside is that after a certain amount of washes, you need to replace the cassette. Of course, there is only one source of them and they are not cheap!
Immediately after inspecting a brand new Bob Cassette, dekuNukem noticed a small edge connector. Using a sophisticated technique known as "melting the plastic with a soldering iron," the PCB became free from its plastic prison. Upon inspection of the lone 8-pin SOIC, dekuNukem discovered it was a 24C02 EEPROM. This chip only holds 256 bytes of data. But, it must contain the wash count.
dekuNukem built a prototype circuit to read and modify the EEPROM's contents. It took a couple of washes to determine that a single byte stored the remaining wash count. A little bit more testing revealed the magic value of 0x4E "rewinds" the cassette back to its initial 30 washes.
From there, the Bob Rewinder became a thing. The small board plugs into the Cassette's edge connector. A single button on the rewinder resets the cassette's wash count. But, what good is resetting the wash count if you do not refill the cartridge with soap?
Bob Cassettes do not use the same detergent as household dishwashers. Instead, it is a commercial detergent. For information on what to buy and how to refill the cassettes, dekuNukem has detailed steps in the Bob Cassette Rewinder's manual.
For additional information and design files, check out the Bob Cassette Rewinder GitHub repo. If you would like to purchase a pre-made board, they are available for 29.99 USD from dekuNukem's Tindie store.