OT: help with low voltage regulation

[gvasale]

I have two old impulse driven clocks for which the battey is either no longer available, or stupidly priced. What I'd like to do is to place either a couple of C or AA batteries in parallel and regulate the voltage down to say, 1.2 or so volts.

Any suggestions on how to do this?

Thanks.

[DFMiller]

A quick search of Digikey shows options at that voltage range.
Need more details but have a look at this one.
http://www.digikey.ca/product-detail...7-1-ND/2339543

Dave

[gvasale]

That one shows voltage adjustable to .9 volts. A little short on the voltage...

[3jaw]

Here's one:

http://www.mouser.com/ProductDetail/...W0fIekSjDZk%3d

You will have to bump up your input voltage to 4.2 volts and it has an max output current of 100mA.

Here is the data sheet for it: http://www.ti.com/lit/ds/symlink/lm317l.pdf/

[lwalker]

Why does the voltage need to be regulated? You could use a NiCd cell to get 1.2V, parallel a few if you need more current.

[edit: grammar]

[Ernie]

Voltage regulators all drop some voltage in the process. To get 1.2 volts, you will need more than the 1.5 V that "C" cells provide. Putting 2 in series would give 3 V and may be enough to regulate down. Since rechargable batteries are already at 1.2 V nominal. Wouldn't that be easier?
Ernie
Looks like I was too slow in typing a reply.

[CountZero]

http://www.digikey.com/product-detai...ASCT-ND/969504

Might be an option. Include LDO in the search terms to get a low drop out regulator, the one above states 0,3v typical dropout@ 2A.

[gvasale]

I'm trying to do this with a small package. It used to have a battery pack about the size of 4 AA batterys. The object is to have something with as constant curve as possible.

I used to use ni-cads years ago but not for this purpose. They self discharge and I've always found it difficult to find high quality batterys.

AAs are cheap, and always available and make it un necessary to switch out batterys like if a rechargable is used.

It is also time consuming to have to try and constantly re regulate the clock for the change in voltage when the battery us new and after some length of service.

This not a quartz movement.

[MotorradMike]

That one shows voltage adjustable to .9 volts. A little short on the voltage...

Dave found you a viable option.
It's Low Drop Out and will regulate down to .9V.
That is a minimum, it will regulate fine at 1.2 as you specified with a 1.5V input.

However, I suspect you'll find this is non-trivial and this solution will eat batteries although it will work.

[gvasale]

Motor... Is there a better solution which doesn't "eat" batteries?