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Help with a design idea

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Richard Sugden

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Hi,
I need help in the design of a micro circuit to do the following:

Turn on a LED and make it flash when temp reach certain temperature.
LED to flash when battery is getting low.
How long would it stay in a dormant state when not used?
Just how small could this be manufactured?

As you can appreciate this is not my field of work so any help with this would be appreciated (answers in layman's terms please)

Regards
 
You need to be more specific. Temperature going which way, triggering at what temperature? With what kind of battery?
 
Hi
Yes i did rush the question.
This is a design for a not for profit safety object to try and save the thousands of children and adults that get scalded in hot water each year.
The object will float and detect the temp of the water in the bath.
If it above a certain range it will flash a red LED light.
As the object will be factory sealed the battery needs to last as long as poss.
But when the battery is running down again we need a visual sign to say that the item needs to be thrown away and replaced.
I hope this helps answer some of your questions as i said its a safety item that needs to be produced to try and cut down on these horrific burns, so any input would be appreciated.

Regards

Richard
 
I like it. First guess: Let the water be the "on" switch for a button cell battery powering a CMOS amplifier. As soon as it gets wet, a green light comes on. The amplifier feels the water with a thermistor and switches to red if it's too hot. The time to detect will be fairly predictable, so the instructions will say something like, "If it isn't red in 30 seconds, the water is below "X" degrees.
 
At the risk of being labeled a callous un-caring old sod, I cant help but think that this is a mis-directed effort.

The object will float and detect the temp of the water in the bath.
Why not just quickly dip your hand in the bath to test the temperature, that is what most people do, I think.
There has to be a definite action to put the "device" into the bath, if that action is missed, the device will not be effective.

But when the battery is running down again we need a visual sign to say that the item needs to be thrown away and replaced.
Not exactly eco-friendly is it?
What happens when the battery is completely dead or the electronics have just plain died.
There will be no flashing LED to tell you it does not work, will there.

Why not go for a completely passive solution, something like an LCD thermometer?
No batteries to run down, no problems of limited shelf life, very little to go wrong.

JimB
 
Hi Jim,
As i said i am not expert in this field and all input would be welcome.
37000 children under sixteen are admitted into causality each year (RoSPA).
On the adults side its mainly the elderly and disable that end up in water that burns.
Children and adults do die because of these burns.
My idea is a toy type object for the kids and a same for the old folk.
The object will remain in the empty bath and float when the bath is run.
Regards
Richard
 
How about this:



seems a good solution to the problem.

Or, if you want toys, how about the DIGI DUCK:



JimB
 
JimB: About my idea, what happens when the battery is completely dead is that the green light doesn't come on when you put it in the water and the red light doesn't come on, either.

However, I think you have demonstrated that the product already exists. No need to design something that is already available.
 
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