Splitting a power supply

[dimoune]

Hello,

I want to split my 30vdc power supply to make it as if it is two different PS. One output will power a digital ammeter/voltmeter and the other a usb. Just splitting the wires is not good enough especially that I am using the usb port to connect a usb tester. The usb tester gives incorrect reading. Thanks.

 

[Colin]

I want to convert my home into a submarine.
Please send me full details.

 

[dimoune]

lol. Is it possible or not?

 

[schmitt trigger]

It is possible, but you have to explain the required volts/amps for each output.
Also if the common (ground) return must be isolated from each other or not.

What I would do, is keep the 30 volt output as is. You can add a voltmeter and ammeter, there are plenty of offerings in Ebay, both analog and digital.
Then, with a switchmode power supply, I would convert the 30 volt to 5 volt for the USB. By the nature of your question I would not advocate that you design and build it yourself. Again, I would look at what Ebay has to offer. You will be able to buy fully assembled functional switchmode supplies for far less than the cost of the individual components.

 

[dimoune]

I need small current. My digital ammeter/voltmeter works with 3.5v to 30v. The current consumpion is less than 10ma.
The usb also consumes small current.

I agree to the fact of using the power supply as it is for the ammeter/voltmeter and regarding the switchmode powersupply to downgrade to 5v I checked quiickly on ebay but I find them to be quite bulky and expensive!

 

[schmitt trigger]

USB can source up to 0.5 amps.
If you are planing to regulate from 30 to 5 volt @ 0.5 amps, it would have to dissipate 12.5 watts.

The heatsink will be larger, heavier and more expensive that a SMPS, specially those sold on Ebay. This one is US$4.95, and is the very first one I checked.
**broken link removed**

Not only that, it is the size of a common 78xx type regulator.

 

[bountyhunter]

A radio-electronics magazine once ran a contest to give a prize for the person who came up with the cleverest way to create a dual supply from a single voltage. They got all the usual circuits but the winner was:

a guy who took a 9V battery apart and soldered a wire to the center connection of the six cells inside the battery.

 

[bountyhunter]

I need small current. //////
The usb also consumes small current.

I agree to the fact of using the power supply as it is for the ammeter/voltmeter and regarding the switchmode powersupply to downgrade to 5v I checked quiickly on ebay but I find them to be quite bulky and expensive!

You need to spec exactly what voltages and currents you need. If you need a 5V rail at low current, just run a 7805 off the 30V line. I don't know what your negative requirement is, but if it's low current you can make a cheap charge pump inverter using a 555 timer and a couple of caps.

 

[MikeMl]

How many new threads are you going to start about this same project?