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Power Supply Question set 2.0

Hello Pipol,

I would be very grateful if you could check on the 5v regulator circuit I am planning to add to my power supply.

I would like to know if its right and if I would be able to charge usb devices with it. Let me mention it outputs current at about 150ma

A very important detail, I would like to know if this runs at 24v, because when I want to output I voltage that high for my project and at the same time use the ports I dont want things blowing up.

To make it clear:

I have a separate power supply that outputs 1-24v. This one doesnt have any more space inside the box.

I want to make another one that connects to this one and is able to output 5v using the circuit I made from the 24v input from power supply one.

Another detail which I dont have questions about, is I´m adding another 1-24v regulator as I want to keep the voltage from supply one the same all the time so that when I want to use voltages lower than 8v I can still use the usb ports to charge a device.

The second one would also have a volt meter.

Thanks you in advance as always.


5v_regulator.sch3.34 KB
Voltageregulator5v.JPG43.17 KB

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I think the circuit is mostly OK. I"m concerned about the LED. Can it handle the current through it when your 'feeding' supply is at 24V? With a 470 ohm resistor, and assuming your LED drops about 2.1 V, you are pumping over 46 mA through the LED. If you are mostly going to run the 1-24V supply at the upper end, size the resistor to limit the current through the LED to a more reasonable value.

Regarding the capabilities of the 5V supply, you can support up to 1A at 5V if you use a proper heat sink. So 150mA is no problem. The Absolute Maximum input voltage of the 7805 is 35V, so 24V should be comfortable.

Keep in mind that since you are dropping from 24V to 5V, all that excess will be dissapated as heat. Use heat sink compound and a good heat sink.


Sorry, I don't have EAGLE or whatever you used to create that schematic. Can you post it as a .jpg?

Also, can you clarify something? Do you want a power supply that puts out 5V and also puts out 24V, or a variable power supply capable of putting out 0-24V? Or something else that I just don't understand.

Clear questions lead to clear answers.  Well, sometimes...   ; j