Hi all,

I recently had an operation which has left me with an Ostomy appliance. At the moment I'm struggling with it a lot and am not really having a good time of things. I have no electrical engineering skills and have limited knowledge of electronics, but I have a six month recovery ahead of me and a passion to learn. Thought I might as well start with a project that'll help me in the long run.

I'm looking to create a sensor that'll alert me when the Ostomy bag is too full.
There is currently one device on the market, but it's £75 and currently not available on the NHS. If I can make something cheaper, that'd be awesome.
The device is called an Ostom-I Alert and from what I can tell uses a flex-resistor to determine the capacity of the bag and connects via bluetooth to a smart phone. I'm not looking for anything as complex, a simple LED colour change would be sufficient enough for me.

Obviously open to other sensors and whatnot. Was thinking of a weight based sensor at one point...

Is anyone able to help me create this? Point me in the direction of components to buy and whatnot...

My thanks in advance!

 

My condolences.
What is the bag material?
Is it opaque or transparent?

 

There are hundreds of different bags available, so anything from completely clear plastic, to opaque - most have multiple layers and materials to ensure it's air and water tight and not likely to break.
The current one I'm using is opaque.

 

So he decided to build his own, first making prototypes with parts he picked up on eBay, before finding that a strip in a Nintendo Wii handset could accurately measure pouch fullness by sensing the arc of the bag’s external curvature.

https://www.sparkfun.com/products/8606

 

What about a flexible resistor chain, wrap it around the bag, when the bag gets filled it changes resistance, use that to feed a comparator to set off an alarm, buzzer ,led etc...

https://www.pololu.com/product/1697


http://m.instructables.com/id/How-to-Make-Bi-Directional-Flex-Sensors/?ALLSTEPS

 

Thanks for the replies.
If I were to get one of those flex sensors, what else would I need to get in order to make this work?

 

An op amp as a comparator,

http://people.ece.cornell.edu/land/..._fl229_old/sign_language_files/comparator.png

 

what else would I need to get in order to make this work?

What do you want to do with the data?.. or how would you like the data displayed...

The Ostomy-I has bluetooth/app,etc...

 

If you wanted to light more than one LED to give an indication of how full it is you could use an LM3914.
It has built-in comparators to display 10 steps with 10 LEDs, but you don't have to use all of the LEDs, just as many as you want.
You could also use an LED bar graph display for the LM3914 such as one of these.

 

Hi all,

Thanks for the replies.

I'm fine with the data being translated to LED's. No need to overcomplicate things at this stage.
Something like:
White LED - Permanently active to indicate everything is on.
Red LED - Bag 50% full
Red LED flashing - Bag too full

Is a flashing LED overcomplicating things?

 

................
Is a flashing LED overcomplicating things?

Not at all. You can buy a flashing LED that has a built-in flasher circuit.

 

Not at all. You can buy s flashing LED that has a built-in flasher circuit.

Ah awesome.
Gosh, this is really exciting.
So looking forward to attempting this project.

 

You could also use an LED bar graph display for the LM3914 such as one of these.

That LED bar graph is awesome! Definitely, definitely going to use one of those!

 

If you're going to use the Lm3914, use a circuit like a battery monitor on the datasheet,where R1 and vr1 would be your flex strip,

http://www.electronicecircuits.com/electronic-circuits/lm3914-12v-battery-monitor-circuit

 

Hmm. Does this have to use a 12v power supply? That's going to be pretty chunky, no?
Would be swell if I could run this off a 9v battery - perhaps I might have to cut down on the LED's? It needs to be bright enough to illuminate through I t-shirt.

Also, what's the basic shopping list?
- LM3914
- LED's of some kind (single or bar graph)
- Flex Strip

 

6 - 12v , so a 9 v battery is fine, the leds will draw all the current, so use as little as needed, i would use a couple of leds, one Green and one Yellow,one Red like traffic lights, and a buzzer on the red led.

 

Note that the life of a 9V battery will be rather limited if you continuously operate several LEDs at a time. The typical capacity of a 9V alkaline is about 500mA-Hr. You divide that by the circuit current to get the battery operating life.
You can help that by using high brightness type LEDs and operate that at as low a current as possible. Some of them will give a good indication at a mA or less.

 

Note that the life of a 9V battery will be rather limited if you continuously operate several LEDs at a time. The typical capacity of a 9V alkaline is about 500mA-Hr. You divide that by the circuit current to get the battery operating life.
You can help that by using high brightness type LEDs and operate that at as low a current as possible. Some of them will give a good indication at a mA or less.

Thanks for this. Like I said, my knowledge of electronics is rather limited, such a valuable learning experience.
Would it be better to use another power source? AA, AAA?

Going to order some items soon and have a play about.

 

....................
Would it be better to use another power source? AA, AAA?
.................

It's a trade-off between how long you want the battery to last and the weight of the batteries.
AAA's have two or three times the capacity of a 9V and AA's at least 5 times.
Note that since an AA or AAA is only 1.5V you will need several to achieve the needed operating voltage (which likely could be less than 9V, such as 6V which would require 4 batteries).

You might want to consider rechargeable NiMh batteries.

 

It's a trade-off between how long you want the battery to last and the weight of the batteries.
AAA's have two or three times the capacity of a 9V and AA's at least 5 times.
Note that since an AA or AAA is only 1.5V you will need several to achieve the needed operating voltage (which likely could be less than 9V, such as 6V which would require 4 batteries).

You might want to consider rechargeable NiMh batteries.

Ahh, I see. Thanks! Very interesting. I'll look into NiMh batteries now.

On another note, I was suggested to look into Arduino as a way to go about achieving this project. Thoughts?