Generating 5v from 4 batteries

[mackrackit]

A part was mentioned here that might do it.
http://www.picbasic.co.uk/forum/show...88&postcount=9

[Ioannis]

Hmm, 1724 will not do the job as it has absolute max vin at 6V.

What you need here is a Step-up/Step-Down converter at the sam time since input is within 4.4 to 6 volts while output at 5.

Maybe MAX856-859 is better for the case.

Can you afford to loose one battery cell? You will find more chips available.

Ioannis

[Melanie]

One rubbish Silicon Diode in the Supply line will do the job... 0.6-0.7v drop and you're in business. OK, OK I know, don't lecture me, but I dare you to find a cheaper solution than about 0.5 of a cent!

So you want to be pedantic and lose a whole volt... then a Silicon followed by a Germanium Diode...

[Melanie]

So, you don't like the simplicity of that idea....

One Transistor (BC639 as an example), one 5.6v Zener and a 22K Resistor... ten cents...

[BobP]

Thanks for the replies. Unfortunately the simple diode solution is no use! The Tx and Rx modules need a solid 5v. Any less and their range falls dramatically.

It seems the easiest solution is to power it from 3 cells use a step up regulator and take a hit on the slightly reduced battery life.

But thanks again for everyone’s help.
Bob