Reply With QuoteCan get complicated, not recommended, even if viable, any expansion may cause overloading of other elements.
You simply can't run a regulated and variable power supplies to the same load.
Running two DC power supplies together - same ground?
Hi all....
I've had some issues running multiple items on a telescope together, using different power supplies ?ground loops ?floating grounds??
Anyway, the going advice seems to be to run everything from one power supply, with the one ground, seems to keep a lot of problems at bay, including smoking $$$ worth of gear....
I've so far got 3 items running from one 12v DC supply (a 3A 0-30V DC variable PSU from Jaycar), and need to run another piece of attached equipment preferably at 15V. So.... this power supply has a ground post (currently unused), as well as pos/neg, so far I've just wired it to pos/neg.
Can I set up a second one of these variable supplies, and connect the grounds together?
I believe I can put a jumper across neg-gnd on the PSU I'm using, can I set up the other next to it the same way, and connect the two grounds??
Thanks for any advice....
Lee
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Can get complicated, not recommended, even if viable, any expansion may cause overloading of other elements.
You simply can't run a regulated and variable power supplies to the same load.
astrodog73 (25-07-13)
What I would do is buy a regulator called a L7812 + a couple of 10uf capacitors and a heatsink to mount the L7812 regulator on. This L7812 will be used to supply 12 volts to the 12 volt items.
Then you can set the Jaycar powersupply to 15 volts to run the 15 volt item.
Then all circuits will have a common gnd and no need for the second power supply.
EDIT The L7812 can handle maximum current of about 1.5 amps. So you'll need to make sure that the three 12 volt items use less than that.
Last edited by mickstv; 25-07-13 at 08:30 PM.
astrodog73 (25-07-13)
Thanks for the quick replies....
At the moment I use a Kemo 3-15V adjustable DC-DC converter to power a USB hub from the 12V supply....
I could probably use another one of them from the PSU set to 15V to supply the 12V?
With the PSU: how is the GND post used generally??
If needed, you can amplify the current using a circuit like one from
They are commonly connected to a ground stake or other earthing system, separate from the main electrical earth.Originally Posted by astrodog73
Grounded power supplies are particularly useful when powering radio equipment to reduce noise, etc..
Almost all variable bench power supplies provide a floating (not connected to mains earth) output.
The Earth terminal is to allow either polarity to be connected to mains earth if required.
If you want to use two of the supplies together, just join the negative terminals together.
If you want plus and minus supplies just join the positive terminal to the negative of the other supply.
The junction of the two becomes circuit ground an then you have a plus and minus supply.
astrodog73 (26-07-13)
In long past times, the Railways (NSW) used batteries to operate certain signaling equipment and one set of instructions was the direction if the Instruments had a problem was to ensure the 'Ground Stake' was 'watered' as there was no wire 'Earth' used.
Over a long period of time they did install wire earths as the 'Ground Return' could be unreliable.
From what I remember both the Linesman and Signal Electrician said this 'Wire Earth' was a common earth for everything.
This was mostly DC with batteries ranging from a single cell up to multiples and this operated relays, motor and solenoid driven signals, lighting was mostly kerosene except in those with no mechanical arms.
In later times AC was used in certain track circuiting as well charging the batteries at locations but I have no idea how that was arranged.
I do know AC was used in powering the Colour Light type signals as there was a transformer for each globe in the 'Head'.
I stand unequivicably behind everything I say, I just dont ever remember saying it !!
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