Adding GND to dual power supply.

Thread Starter

AdrianKludge

Joined Jan 16, 2019
4
Hello, I am trying to get a 12V power supply hooked up to a homemade synth which thus far has operated off of two 9V batteries. I bought a power supply (in the attachments)
Though the outputs of both 5V and 12V contain the + and -, there is no ground. In certain schematics for power supplies it appears that ground is created via capacitors or resistors coming from the + and - and meeting in the middle.
Question is, can I wire up a GND or am I doomed, hopelessly doomed. (AKA need to invest in something else)
Any assistance, advice is much appreciated. Thanks!

Product page: https://www.amazon.ca/DROK-Switching-Transformer-Converter-Wide-range/dp/B01LENMPUO/ref=sr_1_9?keywords=dual+power+supply+drok&qid=1550595728&s=gateway&sr=8-9
 

Attachments

MrChips

Joined Oct 2, 2009
21,326
A power supply with 5V and 12V outputs is not quite what you need.
However, you can turn the 12VDC output to +6V and -6V with a common GND.
As you said, something like this might work depending on how much current the synth requires.
Replace the 9V in the schematic with 12V.

 

AlbertHall

Joined Jun 4, 2014
10,022
Were the two 9V batteries connected in series making 18V total?
If so then you a 'centre-tapped' 18V supply or two 9V supplies which you can connect in series.
Given an 18V supply it would be possible to make a circuit which could split it into two 9V in series.
 

Thread Starter

AdrianKludge

Joined Jan 16, 2019
4
A power supply with 5V and 12V outputs is not quite what you need.
However, you can turn the 12VDC output to +6V and -6V with a common GND.
As you said, something like this might work depending on how much current the synth requires.
Replace the 9V in the schematic with 12V.

Thank Mister Chips. I'll figure out the voltage, though offhand I think it requires a minimum of 9V. Thanks for the quick reply and good info!
 
Last edited:

Thread Starter

AdrianKludge

Joined Jan 16, 2019
4
Were the two 9V batteries connected in series making 18V total?
If so then you a 'centre-tapped' 18V supply or two 9V supplies which you can connect in series.
Given an 18V supply it would be possible to make a circuit which could split it into two 9V in series.
Yes, the +/- were joined and sent to ground. I think I'll just be on the lookout for something else. Thanks for the reply.
 

MrChips

Joined Oct 2, 2009
21,326
How much current does the synth require?

According to the info on the 5V & 12V switching supply, the two outputs are isolated. If that is the case you can combine the two in series to create a 17VDC supply.

Then you can use the split supply circuit to get +8.5V an -8.5V.
 

LesJones

Joined Jan 8, 2017
2,665
I suggest first checking first that the negative of the +5 volts is NOT connected to the negative of the +12 with a resistance test before connecting them in series. (This is confirming that they are isolated from each other.)

Les.
 

Thread Starter

AdrianKludge

Joined Jan 16, 2019
4
The project is the Music From Outer Space Sound Lab Mini Synth.
The schematics give the default option of running two 9V batteries in parallel to create a dual power supply: 18V. However, if connected to a line powered dual power supply (+/-9V to +/-15V) must be provided.
I think my solution is to get something else. Alright though as I now understand the scenario.
Thanks for the input, all.
 

Audioguru

Joined Dec 20, 2007
11,249
Two 9V batteries in parallel DO NOT make 18V. They schematics of the Mini-Synth show that they are in series to make 18V, and they make plus and minus 9V. Where they join is ground.

The 100k resistors shown previously will not produce enough current.
 
Top