3 or 4 D / C batteries to power the PIC

Nick · Guest

is it better to have 4.5 volts or 6 volts without a voltage regulator? I plan on running 3 or 4 long life D batteries, but I would really like to get away without using a voltage regulator.

Could I put some diodes on the battery lines to keep the tech from hurting the sustem from putting the batteries in backwards?

Nick

valemike · Guest

At my place, we use 2 1.5V AAA batteries in series. Looking at the schematic, we don't have a diode to prevent damage from reversed batteries.

I run it without the brownout reset off, since the 16LF627A will not work below 4.x volts if it's on.

The PICDEM-2 Plus has a reference circuit for using a voltage regulator and a 9V battery, perhaps even some diodes. I run it all the time with a 9V battery, but by the end of the day, it is drained.

Wouldn't a voltage regulator end up wasting more current?

Guest · Posted: Thu Aug 12, 2004 9:59 am

Nick · Guest

a google search said that 6 volts could be to much for my clock, so I think I will stick with 4.5volts @ 18,000mah.

Nick

valemike · Guest

have you considered going to the nanowatt 16LF (or 18) series? You won't need such big batteries if you do that. Unless of course, you're other peripherals need the 4.5V.

Nick · Guest

I'm going to use the low power pic Pic16f373, its just the extra crap thats going to run up the current.

Personally I'd rather just run this setup off the AC line, but the head engineer says there is to much noise on the line and it would be easier/safer to do it with batteries. The last design they had is failing on the site, but they wont let me see the design or let know the details of the failure.

Nick

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Guest · Posted: Fri Aug 13, 2004 5:20 am

If I need a stable 5V (e.g. when I want to use A/D) then I use a LP2950CZ-5.0. It works from 5.2V input and the standby op. current is as low as 75uA.

Jeff King · Posted: Fri Aug 13, 2004 5:27 pm

Ti makes a very low quescent current linear regulator. I believe DigiKey stocks it.

D cells typically start out at around 1.55 or 1.6Volts, and end of life at around 0.9V, depending on how the battery maker wants to spec it.

So make sure you consider this. You also can use 6.0V if you put a diode in series with it, and that also gives you the reverse polarity protection. Would work from 5.5V to 3.1V over the life of the batteries.

D alkaline cells are great, cheap and a heck of alot of energy. Also make your product "feel" expensive since they weigh so much! Just be careful shipping a product with them installed as they are powerful missles at the hands of UPS!