small voltage regulator?

Question

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

ehsjr · Accepted Answer

Use a circuit based on a TL499 or similar.

formatting link

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

Rick J. · Answer

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

small voltage regulator?

Join the Discussion

Didn't find your answer?