Electro-ramblings

For some foolish reason I automatically assume that precision was invented recently.

I am not quite sure exactly what year I think people started quantifying in parts-per-million.

But I am sure that I am wrong.

For example, I was wandering around the York National Railway Museum a year or so ago when I came across an unexpected treat....

There are an awful lot of Li-ion charging chips out there, and you would have thought there was one for every eventuality.

But it turns out there isn't.

For example, there is a sort of no-designer's-land between 6.5V where linear Li-ion chargers top out - although Linear's LTC1734 works up to 8V - and around 12V where switching chargers start. 

And even without an input voltage restriction, what if you don't want to charge the thing at less than 4.2V?

I want to drive power led from a Li-ion cell.

I have a few specific requirements.

One is that the driver must tolerate a second current source feeding the led, and only supply current when the other source is under 250mA.

It should also not be blown up by this second feed.

And it should shut down to a few µA when switched off.

There do seem to be a few chips that can do this lot, but I thought I would try a home brew version.

 

Eventually the whole thing will be linked up by a microcontroller, but as I have yet to finish testing a surprisingly large amount of code - I finally rewrote the whole thing using a state-machine rather than the rat's nest of flags that graced the MkII.

So I need a nice simple hardware controller to road test the analogue bits now.

The criteria for input and output of the mystery box are:

As LED technology advances so the range of possible applications increases. This is most clearly seen with the move into lighting. With increasing brightness capability, LEDs have moved into applications that were previously the domain of filtered incandescent light, for example.

Whether it be general home lighting or automotive applications, such as, car rear light clusters, this guide brings together all Electronincs Weekly content related to LEDs and lighting.

They were spotted on many houses on the Canary Island of La Palma, all pointing east - possibly towards the larger island of Tenerife - and mostly pointing slightly upwards.

'Alice'

Respond below, or to alice@electronicsweekly.com

If the designer of the first watch had had access to digital technology, I am fairly sure he or she would have gone straight to digits.

And those with too much money buy mechanical watches.

It impresses me that firms still design mechanical watches - and it pleases me that those that buy them support a thriving and innovative niche engineering industry.

So if you have lots of money, please buy an expensive mechanical watch.  

So when an engineer friend of mine was mulling over options for a five minute delay circuit, I chipped in that I thought the 4060 14-stage ripple counter and oscillator should be able to do it.