Generating 5v from 4 batteries

[BobP]

Hello All,

Building a small RF code transmitter and receiver units and need help finding a suitable 5v regulator. There seems to be a confusing amount of IC's to choose from. None seemingly ideal.

My problem is the unit will be battery powered from 4 cells. Voltage will range from 6v to 4.4v with current peaking around 40mA.

Can anyone recommend a simple IC (or discrete) circuit to use?

Thanks,
Bob
PS. I need to use 5v as the TX and Rx modules loose coverage at lower voltages (3.3v).

[mackrackit]

A part was mentioned here that might do it.
http://www.picbasic.co.uk/forum/showpost.php?p=76088&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

[jonewoo]

Hi guys,
Supporting multiple battery chemistries, LTC4110 combines 4 operating modes - battery backup, battery charge, no-loss battery calibration, shutdown - in 5 x 7 x 0.75 mm QFN package. IC can provide supply voltage to system load from main supply or battery and can also charge battery, providing uninterruptible power source for system. Ability to supply voltages above or below input supply rail lets designer optimize battery configuration independent of input supply considerations.

[dhouston]

Look at two BR2032 coin cells (or more in a series-parallel scheme). They will start at 5.4V and will remain above 5V for nearly the entire life of the batteries. They have a very flat discharge curve.http://www.panasonic.com/industrial/battery/oem/chem/lith/coin1.htm

40mA sounds awfully high. In most jurisdictions, maximum transmitting power can be achieved at much lower current. And, most jurisdictions restrict the total amount of transmission time per hour (depending on application). An efficient antenna design plus a wideband preamp on the receiving end can greatly enhance range.

[rsocor01]

I have a design where I use 4 regular C batteries and the voltage regulator shown in the link below and it all works nicely. But the output voltage is 3V not 5V.

For your particular design, I would use 2 regular 9V batteries with a 5V regulator. Or even better if physical space allows it, I would use 6 AA batteries. The theoretical average capacity energy for two 9V batteries is about 41000 Joules, and for six AA batteries is about 92340 Joules. So, six AA will last you longer.


http://www.mouser.com/Search/ProductDetail.aspx?R=TC1185-3.0VCT713virtualkey57940000virtualkey579-TC1185-3.0VCT713

Robert

[TinkersALot]

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

This sounds rather interesting. I know this is an older thread and the component arrangement being suggested here is likely super simple, but I'm wondering if Melanie can provide a sketch of this for the more analog circuit challenged (me and maybe others) here?

Thanks in advance.

[DanPBP]

I lost my touch with basic analog electronics, too much digital circuits nowadays, but I guess Melanie is talking about this...

http://www.circuitstoday.com/zener-controlled-transistor-voltage-regulators

:rolleyes: