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What is the safest method to split 12v DC input into 4 outputs (2x12v 2x5v)? Answered

Hope you can help out with this! I’m looking to build an automated system and am trying to figure out how to split and specifically what components I can use to spilt a 12vdc line into 4 lines. Specifically these 4 lines will power 2 12v peristaltic pumps on relay switch’s. A 5v raspberry pi and a 5v usb hub. Any input would be greatly appreciated!

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Jack A Lopez
Jack A Lopez

6 weeks ago

I think the way to do this, is by using a single DC-to-DC buck converter, one that is capable of using 12 VDC as its input, and producing 5 VDC, as its output.

Also note, the usual way this is done, the 5 volt supply and the 12 volt supply share the same ground (ie. 0V). That is to say, after connecting the little 12V to 5V converter, there will be three power rails, with voltage {0V, +5V, +12V}, where before there were only two {0V, +12V}.

Then you connect all the 12V loads between the 0V and +12V rails,

and you connect all the 5V loads between the 0V and +5V rails.

The only tricky part is choosing a converter with a maximum output current (in amperes), greater than whatever your 5 volt loads will draw. I am guessing your Raspberry Pi will not want more than about 2 A.

Actually I can point to an example of an author here, wiring up a converter of this kind... in Step 5 of Samuel_Alexander's "Samytronix Pi: DIY Raspberry Pi Desktop Computer", here:

https://www.instructables.com/id/DIY-Raspberry-Pi-Desktop-Computer-with-Accessible-/

He uses a 5V output, buck converter, that he calls "UBEC 5V 3A". (Guessing the "3A" is the max current rating for this converter.) I am thinking he probably should have left that little ferrite donut on the output wires, because it was probably there to help keep switching noise out of the 5V output.

Anyway, the reason he is doing this, is because his display wants 12 VDC, and the Pi wants 5 VDC, and you know, this is kind of the easy way to do this.

By the way, these 5V output buck converters are common. In fact you might have seen one before, in a package that converts 12VDC from a cigarette lighter socket input, to 5VDC output, through a micro USB plug, you know, for charging your phone from car's cigarette lighter socket.

In fact, I have seen versions of that sold at DollarTree, for 1 USD each.

The trouble with the super-cheap versions of this buck converter, are they might burn up at modest output current (guessing 1 or 2 A), or have problems with switching noise on the output.

Although switching noise can maybe be improved by putting some big electrolytic capacitors on the input and output, and maybe one of those ferrite donut things on the output, like the one seen in Step 5 of Sam's 'ible I linked to previously.

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Josehf Murchison
Josehf Murchison

6 weeks ago

Using 2 x 5 volt regulators connect all 4 in parallel just watch the amperage.

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Rav_Abot
Rav_Abot

6 weeks ago

It is not so hard, and you do not have to split the input voltage into 4 lines.
Just provide 12V to your two 12V relays or pump directly, and use voltage regulator IC "LM7805"(which is 5 volt regulator) to power your Hub and R-Pi.
But one thing you need to keep in mind, the input power(voltage multiplied by Current) should be sufficient enough to run all the mentioned components in your question.