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Common connection of two power supplies.

qwertyqwq

Member
Hello.

The power supplies are transformerless basic power supplies. Because of the transformerless situation , i desided to post this thread here on high voltage section.

As i have said before the power supplies are transformerless. First one's output is 36Vdc and the second one's is 12Vdc. There is also ( one of them )scheme down below of thread (the other one has also same wiring diagram except fuse, which i added on high voltage section).
The goal was control 36Vdc with FET by 12Vdc gate voltage . Just a few minutes ago i tried to connect two power supplies 0V 's. And then ZZZZZZtttttt ,,, BOoooooomm...
The connection between 0V made by crocodile. After the "Boooooomm" the crocodile's wire burnt somewhere in it.
Im confusied cause, both circuit's has own glass fuse and they didnt blow up.. 12Vdc 's has 1Amps glass fuse and the other one has 8 Amps glass fuse.

Can someone tell why this situation may happen ?
 

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Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
You've shorted across the mains, you can't connect transformerless supplies together, things WILL go BOOM!.

Basically you shouldn't use things, they aren't safe - OK for their original purpose, and if constructed correctly and safely - but NOT as any kind of general purpose supply.
 

qwertyqwq

Member
You've shorted across the mains, you can't connect transformerless supplies together, things WILL go BOOM!.

Basically you shouldn't use things, they aren't safe - OK for their original purpose, and if constructed correctly and safely - but NOT as any kind of general purpose supply.
Holly...YES.. Arrrhhh:arghh:. What a silly i am. I'm ashamed that I didn't notice of it......:banghead::banghead::banghead::banghead:
 

ronsimpson

Well-Known Member
Most Helpful Member
First one's output is 36Vdc and the second one's is 12Vdc.
More information.
You want 36 and 12 and 0 I assume. (or is it 36 on top of 12 more like 48, 12, 0)
Are your loads from 36 to 0 and from 12 to 0 with no load from 36 to 12?
OR
Is it more like +24 to 0 to -12? Where the load can be across any direction.
What is the load(s)? current?
 

unclejed613

Well-Known Member
Most Helpful Member
please keep in mind the 0V terminal is NOT GROUND...
 

v1.5

New Member
Hello.

The power supplies are transformerless basic power supplies. Because of the transformerless situation , i desided to post this thread here on high voltage section.

As i have said before the power supplies are transformerless. First one's output is 36Vdc and the second one's is 12Vdc. There is also ( one of them )scheme down below of thread (the other one has also same wiring diagram except fuse, which i added on high voltage section).
The goal was control 36Vdc with FET by 12Vdc gate voltage . Just a few minutes ago i tried to connect two power supplies 0V 's. And then ZZZZZZtttttt ,,, BOoooooomm...
The connection between 0V made by crocodile. After the "Boooooomm" the crocodile's wire burnt somewhere in it.
Im confusied cause, both circuit's has own glass fuse and they didnt blow up.. 12Vdc 's has 1Amps glass fuse and the other one has 8 Amps glass fuse.

Can someone tell why this situation may happen ?
Same here ?
 

qwertyqwq

Member
More information.
You want 36 and 12 and 0 I assume. (or is it 36 on top of 12 more like 48, 12, 0)
Are your loads from 36 to 0 and from 12 to 0 with no load from 36 to 12?
OR
Is it more like +24 to 0 to -12? Where the load can be across any direction.
What is the load(s)? current?
The 36vdc is Vds of the fet. And the 12V is gate volt.
it cant handle current i think. current will be high like 5amps.
 

ronsimpson

Well-Known Member
Most Helpful Member
Transformerless power supplies will not do 5 amps. More like 0.05 amps.
-----edited-----
If you need +12V or +5V to run some circuity, use a cell phone charger. (small and low cost) (isolated!)
 
Last edited:

Pommie

Well-Known Member
Most Helpful Member
It would be much safer (and convenient) to produce the 12V from the 36V supply. If only a little current is needed (mAs) then a simple zener & resistor may be sufficient.

Mike.
 

Pommie

Well-Known Member
Most Helpful Member
If you tell us what you are trying to do we may be able to help more. I.E. how will you switch the 12V to the gate? If you're using an Arduino then other problems need to be overcome.

Mike.
 

ronsimpson

Well-Known Member
Most Helpful Member
1572012828171.pngNo ground.
Even if the 0V was connected to ground it can be connect to the 0V of a 32V 5A power supply. (no bang)
 

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