Tiny power source

[Panrock]

Can anybody suggest a very cheap photodiode for the following application?

I'm thinking to use a string of them in photovoltaic mode to keep a small battery charged, rather like in a calculator.

Or have you any other ideas to produce an 'eternal' (self re-charging) power supply? Maybe there is exist pre-built 'calculator' power modules ?

The load is as yet unknown but won't be more than half a milliamp or so at three or four volts...

Just wondering...

Thanks,

Steve O

[Lawnboy]

wouldnt a small solar cell seem easier to use than a string of photodiodes? or maybe i am missing the point...

[Panrock]

Thanks for your suggestion Lawnboy.

Yes it would, but as far as I can tell so far, the cost of solar cells is much greater. This device I'm developing has to be ultra-cheap to produce.

[Steve Anderson]

...as far as I can tell so far, the cost of solar cells is much greater. This device I'm developing has to be ultra-cheap to produce.

I would have suggested the same, if small ones are cheap enough to put in a two quid calculator they surely can't be that expensive? Don't bother with RS, Farnell or Maplin, go direct to the distributor of Chinese made solar cells.

You're unlikely to get anything even approaching 500uA from a photodiode, perhaps 5uA if you're lucky!...and you'll need several of them.

Steve A.

[Panrock]

Or... because I'll be likely making dozens rather than thousands of these things, simply buy the two-quid calculators and strip them...

Steve_O

[Steve Anderson]

Or....simply buy the two-quid calculators and strip them...Steve_O

If that fits the budget including the time to do so then go for it! Assuming they meet your requirements.

What I have found is that you tell the distributor that you wish to do a 'pilot run' of say 25 for assessment and later say that the project was canceled or a change of design was implemented. This is quite normal. You can then do another 'pilot run' using the same devices but with a 'revamped' design. There's always more than one way to skin a cat.

A lot of my 'real work' is in prototypical devices where I only need a few but my client might wish to order thousands, this is true and the way forward in a design. Whatever you are pulling together maybe a hot seller, they just don't know. And presumably at this stage neither do you.

One of my clients has ordered 4.5 million serial EEPROMs as a consequence of one of my designs over the past two years or so. Made in China, and the market? China.

Steve A.