Core Electronics Forum

Silent Alert to help Incontinent dementia patient

Thank you for helping with the problem of a dementia sufferer being unable to complete all the steps to use the toilet. They go to the toilet, but either do not flush, do not clean themselves, or may not take off their underwear. As a carer, I must make sure any missing steps are rectified by flushing or cleaning up.

The current system is to check regularly and/or use my nose. The longer the delay, the more mess can appear and the greater risk of disease. A possible electronic solution is to detect any use of the toilet, and trigger a silent alert.

There are plenty of sensors that can detect the use of the toilet. It would need to be out of the way, because we don’t want it dirty, wet or played with. In our bathrooms, there is a cabinet on the side where wiring can be completely out of sight. I was thinking an interrupt beam. Bryce thinks an ultrasonic sensor would be better. Wiring would be through the walls and roof. I’d use a transformer to power the two toilets.

The alert would b e a set of lamps in the hallway, two for each toilet. The first lamp would switch on when the beam was interrupted. The second lamp would switch on after detection and stay on until reset. Alternatively it could be a single lamp, with two colours. Red for toilet in use. Yellow for needs cleaning.

The reset would be a button next to the lights. I’d see one or both lamps go on. I’d know to wait for the patient to finish using the toilet. When the toilet was free, I would then go over to clean the toilet indicated by the lamp. After finishing everything, I’d reset the lamp.

I don’t want to have a software or complex solution, but otherwise have I overlooked anything, and how do I wire up such a circuit?


Hey David,

This sounds like an excellent project. More than happy to help code up some stuff.

Off the top of my head I don’t think there will be an off the shelf solution unfortunately.

I think both the sensors you and Bryce mentioned were really good, a few backups would be handy as well such as a button when the toilet is flushed and maybe even a door switch to also keep track of if its occupied/open/closed.

I can think of a couple ways you could set the colours of the lamps, the use of binary gates(might be a bit tough to make up and be compliant with all of the sensors) or a simple program on an Arduino Uno.
PS: an SR latch would be the binary solution and a state machine would be used with the Arduino.

The light could be made quite easily with an RGB LED such as this one: Light Disc with 7 SMD RGB LED Australia


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Hey David,

Thanks for putting the post up on the forum, as I said in our chat earlier today, my personal solution to the problem would be to have an Arduino running a very simple continuously repeating loop that would check each of the sensors (or just whether or not a single ultrasonic sensor such as a HC-SR04 has been triggered) and then also confirm whether the button has been pressed, this can easily be stored in two variables that could then let you determine whether the bathroom is occupied, clean, or requires cleaning based on the number of times it’s been triggered. You should be able to easily turn on or off the red/yellow lights or write a very simple function to either have it on, off, or flashing to show the state the bathroom is currently in. We’re happy to help you write some simple code to throw this together if you’d like :smile: should be very simple to hookup each of these components back to a board such as an Arduino Uno. All the best with your project!

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So it’s a programable microprocessor? I’ve never worked with these before, but you’re right. That’s probably the best way to do it. If I found that the exact procedure needed adapting, then I could reprogram it without pulling apart the house.

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Hey David,

Yeah! There are tons of great resources online if you want to try it yourself. As I said before I’m happy to personally help out if you like/give some suggestions!


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Hey David,

Hope you had a great Easter, you’re exactly right, it’s completely open-source, and as Liam said there are loads of resources online. To learn the basics, I’d suggest checking out our tutorial on the site, the workshop should take you through everything that you need to know to setup something like this (we’re also happy to help with your code for this, should be a fairly simple state machine)

Hi. I’m still waiting for opinion about how the device should work in practice. If there’s no objections or further advice from the various people involved in my mother’s care, I’ll come up with a full parts order sometime next week.

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Hi David,

Certainly, if they have any concerns or questions feel free to let me know!

I had a quick think about how you could handle all of the control and sensors for the system.

Let me know if you would like a quick rundown and I can send you a private message.


Well, I have some opinions. Next stage is to create the parts list.
There’s two toilets and I have enough wire. So I guess the parts list would be

a) 1 Arduino Uno Board
b) 2 Ultrasonic sensors
c) 2 Red LED 10mm
d) 2 Yellow LED 10mm
e) 4 Black LED holders 10mm

Because it is my first project using a microprocessor, I think it’s easier to separate the function of “Occupied” and “Needs Cleaning” into two LEDS. The Occupied LED will help me make sure the sensor function is working. Once the basic functionality works, have flexibility to make improvements using the code. I want to use the ultrasonic sensor to also act as a reset - waving at the sensor says the cleanup is done.

Hey David,

That’s looking like a good parts list so far, but if you are going to be wiring it into another room it might be worth investing in a way to make sure the signal carries far enough while negating a voltage drop. Also, just to confirm, the output of the Arduino GPIO (what you’d turn the LED’s on and off with) is 5V, so you will need some 5V LED’s or a way to drop the output voltage to something more suitable.

Why would a signal fail to carry 10 or even 20 metres? I used a voltage drop calculator and it says there’d be less than 0.1% drop.

I see that I will also need
f) 4 x 150 ohm resisters