DOdocdeek·May 22, 2026Submission
Bob Cassette Rewinder: Hacking Detergent DRM for 98% Cost Saving
2 points · Open discussiondekuNukem
bob_cassette_rewinder
C2021–2026
dekuNukem / bob_cassette_rewinder
bob_cassette_rewinder
Renew and Refill Bob Cassettes for 98% Cost Saving!
13Distinct people
13Mentions
0Explicit recommenders
1.5KGitHub stars
What to know before exploring
What it is
Renew and Refill Bob Cassettes for 98% Cost Saving!
GitHub
Where it is used
No documented product use was verified in the last source check.
What people are saying
No recommendation phrase was found in the indexed comments.
No classified warning is attached to this page. Read the discussions before treating silence as approval.
Also in these discussions
No other repository is repeatedly linked in the same discussions.
This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 5:04:57 PM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year13 dated mentions
Observed mentions: 2021-05-02 10:18:33 UTC to 2026-05-22 19:43:55 UTC.
* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 3 | 1 | 2 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 5 | 1 | 4 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 2 | 1 | 1 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 2 | 1 | 1 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2026 (partial) | 2026-01-01 00:00:00 UTC | 2027-01-01 00:00:00 UTC | 1 | 1 | 0 |
What Hacker News says
13 sourceshttps://daan.tech/discover-bob-cassette/
Scroll down to FAQ, and expand the first question: Is the use of a Bob cassette mandatory?
LE: It's also mentioned in the rewind project's README.
> Credit where credit's due, Daan Tech didn't completely lock down the machine with Bob cassettes. Once empty, you can leave it there and add detergents manually.
https://github.com/dekuNukem/bob_cassette_rewinder?tab=readm...
In Bob_cassette_rewinderRenew and Refill Bob Cassettes for 98% Cost Saving
2 points · Open discussionThere's an interesting project about refilling their proprietary detergent cartridges here:
https://github.com/dekuNukem/bob_cassette_rewinder
In Nobody needs a faster dishwasher – solve real user needsI (being not a hardware person but able to blink a LED) would start with the diagrams of talking with the device on page 7 and refer to them while reading the text descriptions of same on pages 5–6, maybe refresh my memory on how I2C works[1,2] as well. At the same time, almost any controller you can get is happy[3] to talk I2C for you, so it’s unlikely the details matter beyond “controller writes device address and RW bit then (either!) reads from or writes to the peripheral accordingly until end of transaction” (whence the “dummy write” the datasheet says is needed to set the read address). Many even come with libraries that will talk to I2C EEPROMs specifically (because they are everywhere), so the diagrams might not be so important either.
The rest of the datasheet is (as commonly happens with simple digital components) concerned with
Read the rest
“how do I wire this up”, “how good of a digital signal can I expect to get out”, “how bad of a digital signal can I get away with putting in”, a refresher on I2C, and miscellanea like power consumption, operating temperature, and sizes of little plastic boxes it comes in. Necessary if you want to design a board properly, not so much if you’re just going to wire it up for a quick hack (the device seems to have a supply voltage and logic levels of “whatever”).
The only thing you maybe do need these for is to look at the board photo and figure out how they wired it. Dot indentation marks pin 1. Pins 1–4 shorted, picture on page 1 says 4 is ground and 1–3 are address, so per page 4 it ends up with[4] address 1010 000. Power (called Vcc for reasons that are not important here) is on pin 5, wired up to top pin of connector on the close-up photo; the next one down goes to data (SDA as I2C calls it) on pin 8; following one goes under the chip but is almost certainly the bus clock (SCL) on pin 6 because that needs to go somewhere; and the bottom is at first glance only connected to an isolated island of copper but the small holes (“vias”) to the other side of the board probably connect it to the other islands so it has to be ground. That leaves write protect on pin 7, unconnected to anything but Vcc (through a dummy “pull-up” resistor to limit how much power the chip will waste examining it), which, to do a sanity check, page 3 says means writes are permitted (so the name of the pin is a bit unfortunately).
There. Done. You still need to find or make something for the other side of the I2C conversation, but either an off-the-shelf programmer or a tutorial for a cheap board with a controller should be sufficient for that. (Won’t be completely trivial the first time around, but it’s a one-time thing like any other development environment.)
[1] https://learn.sparkfun.com/tutorials/i2c/all
[2] https://learn.adafruit.com/i2c-addresses/overview
[3] https://github.com/dekuNukem/bob_cassette_rewinder/blob/6227...
[4] https://github.com/dekuNukem/bob_cassette_rewinder/blob/6227...
Oh, and there's a continuous feed mod too: https://github.com/dekuNukem/bob_cassette_rewinder/blob/mast...
In Bob Cassette Rewinder: Hacking Detergent DRMI didn’t read their other guide, but yea, they did that. You do have to keep track of your reservoir manually.
https://github.com/dekuNukem/bob_cassette_rewinder/blob/mast...
> The easiest way is to melt the solder on the WP pin, and gently lift it up off the pads so it is no longer making contact
(And then bridge it to vcc).
FYI for anyone that breaks the pin, you can usually scrape into the chip a bit and solder onto the rest of the leg past the point of fracture.
In Bob Cassette Rewinder: Hacking Detergent DRMYep, exactly that is also described on the tutorial page.
https://github.com/dekuNukem/bob_cassette_rewinder/blob/mast...
(Hmm, the images are loading in way after my browser has scrolled to the anchor, pushing it far offscreen--first time I've had that in a while, actually)
In Bob Cassette Rewinder: Hacking Detergent DRMBob Cassette Rewinder: Hacking Detergent DRM
653 points · Open discussionI don't understand how refilling for $0.86 per wash is better than the $0.67 per wash if you use their cartridges? Or how that becomes "75 times cheaper".
https://github.com/dekuNukem/bob_cassette_rewinder#cost-show...
How does this math make any sense?
With that, the total cost per wash is:
0.62p + 0.018p = 0.638p, or 0.87 US cent!
We know from earlier that Bob Cassettes costs 48p (67c) per wash.
Therefore, refilling it yourself is more than 75 times cheaper, resulting in a massive 98.7% cost saving compared to buying new!
Huh?
In Bob Cassette Rewinder: Hacking Detergent DRMIt looks like the connector just happens to fit so it's only being used to make the electrical connection. The 4 pins are actually power, ground and I2C data and clock.
Edit: Here https://github.com/dekuNukem/bob_cassette_rewinder/blob/mast... you can see the white and red wires coming from the USB connector labelled as SDA and SCL.
In Bob Cassette Rewinder: Hacking Detergent DRMBob Cassette Rewinder: Hacking Detergent DRM
1,260 points · Open discussion