I want to fit a battery backup to a small audio device. Something that
will charge a 7.2 volt Ni-Cad pack without damage no matter how long left
on and run the device at the same time - and switch over automatically if
power fails. Maximum consumption of the device is about 250 mA.

There appear to be 'millions' of supervisory chips out there and I was
hoping someone could recommend one.

--
*If your feet smell and your nose runs, you're built upside down.

Dave Plowman London SW
To e-mail, change noise into sound.

I want to fit a battery backup to a small audio device. Something that
will charge a 7.2 volt Ni-Cad pack without damage no matter how long left
on and run the device at the same time - and switch over automatically if
power fails. Maximum consumption of the device is about 250 mA.
There appear to be 'millions' of supervisory chips out there and I was
hoping someone could recommend one.

It sounds like a maintained emergency light would do what you want

Colin Wilson wrote:
I want to fit a battery backup to a small audio device.
Something that will charge a 7.2 volt Ni-Cad pack without damage
no matter how long left on and run the device at the same time -
and switch over automatically if power fails. Maximum
consumption of the device is about 250 mA.
There appear to be 'millions' of supervisory chips out there and
I was hoping someone could recommend one.

It sounds like a maintained emergency light would do what you want

Many cheap alarm clocks run on mains but with 9v PP3 backup...?

"Steve Walker" wrote in
:


I want to fit a battery backup to a small audio device.
Something that will charge a 7.2 volt Ni-Cad pack without damage
no matter how long left on and run the device at the same time -
and switch over automatically if power fails. Maximum
consumption of the device is about 250 mA.

Many cheap alarm clocks run on mains but with 9v PP3 backup...?

My extremely expensive radio alarm, wot loses it's brains if there's a
power cut, and we have lots here just outside the M25, runs off a UPS
consisting of a Maplin 6V 1.3 ah gel battery and a fully automatic charger,
about 14 quid the pair.

It runs a lot cooler that the origial wallwart, so if 6V would do, it's an
easy solution

mike

Dave Plowman (News) wrote:

I want to fit a battery backup to a small audio device. Something that
will charge a 7.2 volt Ni-Cad pack without damage no matter how long left
on and run the device at the same time - and switch over automatically if
power fails. Maximum consumption of the device is about 250 mA.

There appear to be 'millions' of supervisory chips out there and I was
hoping someone could recommend one.

You dont need a chip to do that, just a trickle charger.

When it comes to recommending ICs, I'd definitely recommend
sci.electronics,.design.


NT

In message , "Dave Plowman (News)"
writes
I want to fit a battery backup to a small audio device. Something that
will charge a 7.2 volt Ni-Cad pack without damage no matter how long left
on and run the device at the same time - and switch over automatically if
power fails. Maximum consumption of the device is about 250 mA.

There appear to be 'millions' of supervisory chips out there and I was
hoping someone could recommend one.


You could try looking here

http://www.maxim-ic.com/PowerSupplies.cfm


--
geoff

In article ,
raden wrote:
You could try looking here

http://www.maxim-ic.com/PowerSupplies.cfm

Thanks Geoff - I'd got there, but they have a rather bewildering range.

--
*Constipated People Don't Give A Crap*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Steve Walker wrote:
I want to fit a battery backup to a small audio device.
Something that will charge a 7.2 volt Ni-Cad pack without damage
no matter how long left on and run the device at the same time -
and switch over automatically if power fails. Maximum
consumption of the device is about 250 mA.
There appear to be 'millions' of supervisory chips out there and
I was hoping someone could recommend one.

It sounds like a maintained emergency light would do what you want

Many cheap alarm clocks run on mains but with 9v PP3 backup...?

A PP3 wouldn't last long enough - but I want a re-chargeable anyway.

--
*Ah, I see the f**k-up fairy has visited us again

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
mike wrote:
My extremely expensive radio alarm, wot loses it's brains if there's a
power cut, and we have lots here just outside the M25, runs off a UPS
consisting of a Maplin 6V 1.3 ah gel battery and a fully automatic
charger, about 14 quid the pair.

Just a bit too big for what I want.

--
*A dog's not just for Christmas, it's alright on a Friday night too*

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
I want to fit a battery backup to a small audio device. Something that
will charge a 7.2 volt Ni-Cad pack without damage no matter how long left
on and run the device at the same time - and switch over automatically if
power fails. Maximum consumption of the device is about 250 mA.

There appear to be 'millions' of supervisory chips out there and I was
hoping someone could recommend one.

The SAB module from a burglar alarm bell will do the job, usually costs
under a tenner.

Rgds

Andy R