12vdc to 6vdc regulator

[kami]

Hi,
I have been searching for a voltage regulator that I can use to reduce the 12v on a lead-acid battery to about 6.7v with a bit over 1a draw. The original 6v batteries voltage drops too much after about 5 hrs and the sensitivity of the device suffers. I've heard that some are using a regulated 12v system with good results. I was able to find an article about an LM317T "Three terminal adjustable regulator" but it said that it was inefficient but appeared to be within my abilities to build. I'm wondering how inefficient that regulator is if I am using a 12v 12ah battery. I also saw that there are an assortment of 3 terminal regulators to choose from with current ratings of 1.5a (TO220), 3a (TP220 or TO3) and 5a (TO3). With my current requirements, should I select a regulator rated close to what I need or would it hurt to select a higher current rated regulator.

I also found mention of a "simple switcher" which was said to be much more efficient but read that it was "noisy" and a filter circuit would be required. Is a switcher another name for a shunt regulator?

I hope to use it on a detector so having a clean and stable power supply will be critical to avoid interference. Any help or advice will be appreicated. Thanks...

 

[Nigel Goodwin]

Hi,
I have been searching for a voltage regulator that I can use to reduce the 12v on a lead-acid battery to about 6.7v with a bit over 1a draw. The original 6v batteries voltage drops too much after about 5 hrs and the sensitivity of the device suffers. I've heard that some are using a regulated 12v system with good results. I was able to find an article about an LM317T "Three terminal adjustable regulator" but it said that it was inefficient but appeared to be within my abilities to build. I'm wondering how inefficient that regulator is if I am using a 12v 12ah battery. I also saw that there are an assortment of 3 terminal regulators to choose from with current ratings of 1.5a (TO220), 3a (TP220 or TO3) and 5a (TO3). With my current requirements, should I select a regulator rated close to what I need or would it hurt to select a higher current rated regulator.

Using a higher power regulator is fine, and it's what I'd do. You'll be dissipating about 6W of heat, so I'd go for the 5A TO3 regulator and a reasonable size heatsink.

I also found mention of a "simple switcher" which was said to be much more efficient but read that it was "noisy" and a filter circuit would be required. Is a switcher another name for a shunt regulator?

Switching regulators are far more efficient, but also more complicated, with a switcher you would only require a small heatsink, or even none at all.

 

[Optikon]

Hi,
I have been searching for a voltage regulator that I can use to reduce the 12v on a lead-acid battery to about 6.7v with a bit over 1a draw. The original 6v batteries voltage drops too much after about 5 hrs and the sensitivity of the device suffers. I've heard that some are using a regulated 12v system with good results. I was able to find an article about an LM317T "Three terminal adjustable regulator" but it said that it was inefficient but appeared to be within my abilities to build. I'm wondering how inefficient that regulator is if I am using a 12v 12ah battery. I also saw that there are an assortment of 3 terminal regulators to choose from with current ratings of 1.5a (TO220), 3a (TP220 or TO3) and 5a (TO3). With my current requirements, should I select a regulator rated close to what I need or would it hurt to select a higher current rated regulator.

I also found mention of a "simple switcher" which was said to be much more efficient but read that it was "noisy" and a filter circuit would be required. Is a switcher another name for a shunt regulator?

I hope to use it on a detector so having a clean and stable power supply will be critical to avoid interference. Any help or advice will be appreicated. Thanks...

Nigels suggestion is good. To add to that, consider using one 317 and one power transistor and create a "boosted output" design around the 317. There are many references on the web for this and it requires only a few parts. In essence, this will allow most of the power dissipation to be taken up by the transistor(for which you can get a suitably rated one) and much less dissipated in the 317. Put both on a suitably sized heatsink.

try searching for things like "Regulator boosted output" etc...

Also, a switcher is NOT another name for a shunt regulator. The 317 is a series type regulator. Shunt types are similar to how a zener diode works.