24V to 5V Voltage regulator circuit?

Question

I'm looking for the circuit diagram for diy 24V input to 5V output voltage regulator. I've found those with inputs of 18V and 28V but not one with 24V input.

Answer 1

Take the one for 28 volts and put in your 24 volts and it should work fine for you, as long as it will supply your current needs. 8-)

Answer 2

5v Voltage Regulator Circuit

Answer 3

A much better way to go from 24V to 5V would be a switching voltage regulator. You can get complete modules for little money these days. Look at Mouser or Digikey for DC/DC converter modules. There are thousands of choices. If you need to be linear because of switching noise issues, a good way of dealing with the voltage drop of (24V-5V)=19V is to use a pre-regulator. If you know your load current, a resistor will do fine. Just make it large enough that it drops 10-15V at the desired current. Diodes in series before the regular or a power zener diode (rare and expensive) will also do the job and take "most of the heat". You can also use two regulators in series, which also has the advantage that input noise is suppressed much better than with a single regulator. In your case, a 12V or 15V regulator followed by the 5V regulator is a good idea. No matter what you do with pre-regulators/cascaded regulators, you have to get rid of the heat. If your load current is 100mA, the total power dissipation on these parts is 1.9W. In a good design you will never stress the parts with that much without a heat sink that can bring the package temperature to below 50 degrees Celsius (that is the highest temperature on a metal surface you can touch for more than a short time before it feels very uncomfortable). You have to keep in mind that the silicon (junction) temperature is always MUCH higher than the case temperature. How much higher can be calculated from the junction-to-case thermal resistance and the total dissipated power. Whenever you design a power supply or any electronics that can get hot, YOU ABSOLUTELY HAVE TO DO THIS CALCULATION. Never get the junction beyond 125 degrees C. Most silicon will work as high as 175 degrees, but it will degrade much, much faster once you get close, especially if you also have high voltage across the parts or are running high currents through them. Keeping the temperature low is your best bet to build well working, reliable electronics. And then, please do not forget to put decoupling caps directly on input and output. 78xx parts are generally unforgiving if you don't and will oscillate. You might not notice or you may be marginally lucky but in a good design both caps are ALWAYS included. If you have two regulators, you will need three caps, of course, one on the input of the 12V regulator, the next one inbetween and the third one at the output of the 5V regulator. Good Luck!

Answer 4

using a 7805 chip, the input should be just fine at 24 volts.

in general, the minimum drop across a regulator is just a few volts. the input voltage specification is usually a maximum, not a target voltage.

Answer 5

If you are not using too much current a single linear regulator would work nicely. For example a LM7805 See

http://www.fairchildsemi.com/ds/LM/LM7805.pdf#search='lm7805'

Otherwise a nice step-down converter like

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/4777

may work for you.