Electronic toilet flushing. The cheap mechanism they use here does not allow for water control. With this I could control the water inlet and the flushing to limit water usage.
This is Arduino based but no reason this can’t be done with NETMF and a Cobra 2 board I have lying around. I can also use the WiFi to record the flushing and upload somewhere. 
@ Dave McLaughlin - so you will use MF to upload download data?
How about you just have a toilet with 2 different flush systems? One for half tank, and one for whole tank. Why do people have to make such complicated solutions!!! not everything is a nail Mr. Hammer.
After replacing all my flush mechanisms in four toilets to flushers that have two flush systems and then replacing them all back a year later, I can tell you… Anything that makes it harder or more expensive to replace the basics flush mechanisms (seals) that go out regularly is not worth the time or expense to install. An electronic flusher that has easy to replace seals would be a very welcome thing in my house. The systems currently available at the big box hardware stores are not going to save you money in the long run. Especially if you have “hard” water.
Ha, you’re no fun Mister JS.
As Ian points out, there are solutions but it would mean I have to replace the complete system. This is a rented apartment so a system I can install to save water and then remove later would suit me perfectly. Anyway, it would be a fun thing to build.
Water saving device for toilet flushing: brick in the cistern.
You should add a camera for collecting Research data 8)
NOT SAFE FOR WORK
There used to be a website called www.ratemypoo.com that you used an app on your phone to upload you know what but it’s blocked here in Indonesia
Just for fun, I am going to go overboard on this with a G120 I have with an LCD that is gathering dust.
The display will show water level in the tank and you select your flush size before you do your business. At the end, just click on the BIG FLUSH button and you can watch the water level drop on the LCD.
Overkill I know but hey, that’s why we do these things.
I dunno. That’s a lot of pressure having to make that kind of decision before-hand. I used to have a bathroom with a timer instead of a light switch and I found the pressure of that much advance planning to be a burden there too. Bonus points if you can make the water decision after the fact, and not as a required part of pre-flight planning.
That would be easy. Normal fill is for minimum flush and if they choose the full flush it will pre-fill the tank before doing the flush. Just a wee short delay before the big one.
How about this:
Use a sensor to determine how long the “user” was present infront of the toilet. If present for more than 2 minutes then use a big flush, otherwise use a small flush. While the user is standing/sitting there the tank could be filling.
Good idea. I could use a sensor I have for short range detection of the user being seated, a bit like those you see in airport toilets (you know, the ones where you lean forward and get your butt splashed with water as it thinks you stood up and flushed the toilet)
how will we get water when that virus hits and the Walking dead are among us with all the drinking water supplies gone :whistle:
as you know the fastest way to get that drinking water is usually the toilet tank 
given the above situation it looks like you are going to create a problem more than actually solving one :think:
i’m feeling thirsty all of the sudden 
[quote=“Dave McLaughlin”]Good idea. I could use a sensor I have for short range detection of the user being seated, a bit like those you see in airport toilets (you know, the ones where you lean forward and get your butt splashed with water as it thinks you stood up and flushed the toilet)
[/quote]
I’m not sure that’s going to work for the females. 
I had a thought, though, on how to improve the toilet and add two-stage. Because I believe its essential to keep the stock flapper components in place for ease of annual replacement, what if you were to just replace the chain with a rod that’s attached to a servo. Then you could activate a flush and force the end of the flush at anytime rather than the traditional method of waiting for a float to sink.
A gas/smell sensor can be used to detect what sort of flush is needed
Nah, using smell isn’t reliable enough because urine can smell like various things, like when we drink coffee or when we are ill.
Actually, I was thinking you would detect methane. It’s very easily detected. I’m currently helping to evaluate/test this product that a local company has created. It is very good at creating smell profiles and detecting complex smells. Calibrating it for this use case would be interesting, though…
[quote=“Dave McLaughlin”] Just a wee short delay before the big one.
[/quote]
I just ordered up a $10 sensor from one of the local companies to try your idea out
I’ve started the project now but will be a few weeks before I get around to installing it as up to my eyes with work. G120 based for the display and control unit with 5" cap touch LCD. Cerbuino Bee for the cistern unit with the PWM for the servos and I2C for the gas sensor. Might use Zigbee for the link to save on wiring to the cistern and then I can put the controller away from the toilet.
Power is the only issue I need to consider. Indonesia toilets have power sockets (they don’t go in for safety too highly here) so I can run a supply in a sealed box under the sink. I will use a DC-DC supply so that there is complete isolation from the AC side.
[quote=“Dave McLaughlin”]
I just ordered up a $10 sensor from one of the local companies to try your idea out [/quote]
Awesome. I’d say I can’t wait to see it in action but I’m not really sure I want to “see” that… 
If you don’t have luck with just the cheap methane sensor then I’d suggest picking up one of the ArduiNose modules I linked to above. A local university professor developed it. The Arduino shield is the only one he has for sale to the public but he also has several other formats that are smaller and one even has BTLE built in. If you tell him what you’re up to and agree to document the project he might send you one to test. PM me if you want contact info/reference.