# small voltage regulator?

R

#### Rick J.

Jan 1, 1970
0
I want to power a small 3V LED blinky device for a week or so. Normally
it runs off watch batteries, so I tried building a little
flashlight-like container to hold it and a couple of AAA batteries.
Maybe not too surprisingly, it starts to fade significantly in a day or
so. After a couple months it's still blinking, but I'd much rather it
have a shorter, brighter life.

How can I use say, 3 AAA batteries to guarantee that the thing will run
at full brightness as long as possible? The blinky light is very close
to the diameter of the batteries, so of course I'd like something that
could fit into the same tube. For that matter it would be OK to have it
pulse at full brightness with 2 batteries as long as it doesn't take too
long to charge up.

Thanks,
Rick

E

#### ehsjr

Jan 1, 1970
0
Rick said:
I want to power a small 3V LED blinky device for a week or so. Normally
it runs off watch batteries, so I tried building a little
flashlight-like container to hold it and a couple of AAA batteries.
Maybe not too surprisingly, it starts to fade significantly in a day or
so. After a couple months it's still blinking, but I'd much rather it
have a shorter, brighter life.

How can I use say, 3 AAA batteries to guarantee that the thing will run
at full brightness as long as possible? The blinky light is very close
to the diameter of the batteries, so of course I'd like something that
could fit into the same tube. For that matter it would be OK to have it
pulse at full brightness with 2 batteries as long as it doesn't take too
long to charge up.

Thanks,
Rick

Use a circuit based on a TL499 or similar.
As the battery voltage decreases, the output voltage remains
unchanged, down to 1.1 volts on the battery. With 2 AAA's in
series, 1.1 volts total is long after the batteries would
normally be called dead. Whether you'll get a week with
the circuit is anybody's guess, but you will get a solid 3V
output right up almost to the end, and you'll get more total
energy out of the batteries by using them after they would
normally be called dead. *However*, if you use rechargeables,
running them that way is not good for them.

Ed

R

#### Rick J.

Jan 1, 1970
0
ehsjr said:
Use a circuit based on a TL499 or similar.
As the battery voltage decreases, the output voltage remains
unchanged, down to 1.1 volts on the battery. With 2 AAA's in
series, 1.1 volts total is long after the batteries would
normally be called dead. Whether you'll get a week with
the circuit is anybody's guess, but you will get a solid 3V
output right up almost to the end, and you'll get more total
energy out of the batteries by using them after they would
normally be called dead. *However*, if you use rechargeables,
running them that way is not good for them.

Ed
That looks like the way to go! Thanks, I'll try it.

Cheers,
Rick

B
Replies
9
Views
1K
J
A
Replies
3
Views
3K
Alex Silver
A
Replies
12
Views
1K
Replies
2
Views
826
Replies
6
Views
954