I don't know how to get the voltages +5V and -5V from a 24V battery.
A DC converter is needed for the minus rail, isn't it?
I'm a newbie, Please help! what can be put instead of the '???' block?

 

Hello,

Take a look at this PDF:
http://www.maxim-ic.com/cookbook/powersupply/pdfs/CB15.pdf

It was found on the Power-supply Cookbook:
http://www.maxim-ic.com/cookbook/powersupply/

A page that I posted a long time a go in the useful websites thread:
http://forum.allaboutcircuits.com/showthread.php?t=9538

Greetings,
Bertus

 

Thank you for fast response,

But I'm looking for a simple circuit using ordinary components. Any circuit ?

 

Hello,

With the 78L05 (or 7805) you will loose almost 80 % power, that is transferred into heat.
With the circuit I pointed at you will loose 10-15 %.

Greetings,
Bertus

 

Hello Bertus, my needed current is less than 20mA. so a 78L05 will be ok. I connected one to 24V battery, it heated up soon!

Another problem is that I'm planning on using an ICL7660 to get the -5V supply. but its maximum input voltage is 10V. How do I connect it to the battery?

Regards!
Stryker

 

Hello,

For your heat problem you can take a LM7805 in a TO220 housing.
That has a metal plate to spread the heat.
( you can enlarge the plate for better heat spreading by mounting it to the a copper or aluminium plate).
For the ICL7660 : take the LM7805 output as input for the ICL7660 (this is the 5 Volts).

Greetings,
Bertus

 

OK, Thank you very much!