powering from 1.5v...

Hello,

Just wandering if anyone ever did a project that require powering from a single 1.5v battery like the one used in watches or wall clock.
Just wandering how they manage to get the device working from 1.5v or do they use a boost converter to 5v. If so how is the boost converter made. I looked into my wrist watch and could not see any coil or obvious boost up converter of any kind..

K

MAX1674, MAX1675, MAX1676 ; High-Efficiency, Low-Supply-Current, Compact, Step-Up DC-DC Converters

http://www.maxim-ic.com/datasheet/index.mvp/id/1878


http://circuitschematic.blogspot.com/2010/07/15v-to-5v-converter-circuit.html

Why use an extra chip when you already have a pic?! Here's a rather ingenious way to run a controller off a single cell!

http://spritesmods.com/?art=ucboost&page=2

Hope it helps.

Regards,

Anand Dhuru

Quote:

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Originally Posted by lerameur

Hello,

Just wandering if anyone ever did a project that require powering from a single 1.5v battery like the one used in watches or wall clock.
Just wandering how they manage to get the device working from 1.5v or do they use a boost converter to 5v. If so how is the boost converter made. I looked into my wrist watch and could not see any coil or obvious boost up converter of any kind..

K

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Do you want to use a coin cell battery? Why don't you use a 3.0 volts lithium coin cell battery?

Robert

I want to keep the price as low as possible. Lithium batteries are very expensive compared to round alkaline battery. but even at 3v, it does not leave much space for its lifespan , no ? when it falls just .5v then its game over.. i guess, I could be wrong.

I have heard that Lithium batteries have a flat discharge. A coin cell may last longer a 3 volts than several alkaline at 1.5. The alkaline will start showing a voltage drop as soon as it is used.

Quote:

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Originally Posted by lerameur

I want to keep the price as low as possible. Lithium batteries are very expensive compared to round alkaline battery. but even at 3v, it does not leave much space for its lifespan , no ? when it falls just .5v then its game over.. i guess, I could be wrong.

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Many chips minimum operating voltage is at 1.8V, so I don't see any problem. Check out this application note about the coin cell lifetime.

http://www.maxim-ic.com/app-notes/index.mvp/id/505

Robert

Quote:

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Originally Posted by lerameur

Lithium batteries are very expensive compared to round alkaline battery. .

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Really? Here in my city a CR2032 costs about 20 cents US, and thats retail. The cheapest alkaline would be at least twice as much.

Forget coin and costs. Here is the final solution:

http://www.microchip.com/wwwproducts...cName=en548192

http://www.microchip.com/wwwproducts...cName=en548193

These chips will drain every mV from your battery untill is very very dead!

Ioannis

Quote:

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Originally Posted by mackrackit

I have heard that Lithium batteries have a flat discharge.

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Dave,

Thanks. That is good to know for future design reference. According to the app note that I mentioned above the discharge rate of these Lithium batteries is pretty flat.

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