DPDT switch - two 12v power sources in, one 12v power source out

Thread Starter

greentree

Joined Feb 20, 2018
17
I'm just wondering if this is possible;
  • I have 2 different 12v input sources, I would like both of them to go through a DPDT switch (or other if neccessary).
  • I would like the switch to function as On/Off (On regardless of which power source is being fed, sometimes both)
  • I would like the switch to output 12v when in 'On' position
Is this possible? I don't want to just sum the 12v power sources and blow something up!

Thanks in advance,
Rob
 

djsfantasi

Joined Apr 11, 2010
5,685
Are you selecting one power source from either of two? Or are you powering separate devices from two different sources, each device with one dedicated source?

It’s not clear from your post. Both are possible. Likely, especially if in the latter scenario ground can be tied together.

In the former scenario, search for a “DPDT On-Off-On” switch.
 

Dodgydave

Joined Jun 22, 2012
8,467
A DPST switch will work, this will give each12V signals at each pole,. If you want to join tge 12V sources together, then use Shotkley Diodes on the switch contacts.
 

djsfantasi

Joined Apr 11, 2010
5,685
As DodgeDave stated, you may only need a DPST switch. I’d still look for the On-Off-On type to give you the off functionality.
 

Thread Starter

greentree

Joined Feb 20, 2018
17
Are you selecting one power source from either of two? Or are you powering separate devices from two different sources, each device with one dedicated source?

It’s not clear from your post. Both are possible. Likely, especially if in the latter scenario ground can be tied together.

In the former scenario, search for a “DPDT On-Off-On” switch.
Apologies I wanted to simplify as much as possible.

I have one device, but with 2 options to power it. One option is a 12v input from an XLR, the other is a mains IEC plug (this goes to a transformer which turns 230v AC into 12v DC). There may be a scenario where someone plugs in both the XLR and IEC, and I want a safety net so the device does not get 2 feeds of 12v at the same time.
 

Thread Starter

greentree

Joined Feb 20, 2018
17
A DPST switch will work, this will give each12V signals at each pole,. If you want to join tge 12V sources together, then use Shotkley Diodes on the switch contacts.
I do want to join them together in theory. Will placing a Schottky Diode in line on the positive bring the voltage back down to 12v? Or what would the circuit look like?

I've not come across Schottky Diodes before so am not familiar with them. What is the difference between using this and a much more expensive regulator? Current rating will be varying from 0.46A up to 2A
 

mvas

Joined Jun 19, 2017
538
Use an Ideal Diode in each positive power supply wire to feed the load.

Schottky diodes typically have a lower forward voltage than Regular Diodes
Ideal Diodes typically have a lower forward voltage than Schottky Diodes
 
Last edited:

djsfantasi

Joined Apr 11, 2010
5,685
I do want to join them together in theory. Will placing a Schottky Diode in line on the positive bring the voltage back down to 12v? Or what would the circuit look like?

I've not come across Schottky Diodes before so am not familiar with them. What is the difference between using this and a much more expensive regulator? Current rating will be varying from 0.46A up to 2A
Forget the diodes.

I’m assuming by “join”, you want to supply one or the other to your switch and everything is joined at the switch.

IMHO, if you don’t need to switch supplied automatically (I.e., you power it from one or the other, with off in between), all you need is the DPDT On-Off-On switch in my original post. Check that the switch you get had it’s common terminals in the center. At one end, connect the two terminals to one supply. The same for the other supply at the other end. The center terminals go to your device. Make sure the ground terminals are on the same side of the switch; +12V likewise are connected on the same side.
 
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