Common connection of two power supplies.

[qwertyqwq]

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 ?

 

[Nigel Goodwin]

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]

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. What a silly i am. I'm ashamed that I didn't notice of it......

 

[ronsimpson]

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?

 

[ronsimpson]

 

[unclejed613]

please keep in mind the 0V terminal is NOT GROUND...

 

[v1.5]

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]

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.

View attachment 121289

it cant handle current i think. current will be high like 5amps.

 

[ronsimpson]

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!)

 

[Pommie]

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.

 

[qwertyqwq]

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!)

Can i combine 36V's 0V to the charger 0V's bus ?

 

[Pommie]

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]

Can i combine 36V's 0V to the charger 0V's bus ?

Yes.

 

[Nigel Goodwin]

Yes.

Only with a lot of qualifictions - it MUST be entirely floating, if the charger 0V is grounded there will be another big bang!.

 

[ronsimpson]

No ground.
Even if the 0V was connected to ground it can be connect to the 0V of a 32V 5A power supply. (no bang)

 

[Nigel Goodwin]

View attachment 121314No ground.
Even if the 0V was connected to ground it can be connect to the 0V of a 32V 5A power supply. (no bang)

Except this thread is about a few mA from a transformerless supply - there's been no mention of a proper PSU at all. I presume his questions refers to the circuit in post #5?.

 

[ronsimpson]

Except this thread is about a few mA from a transformerless supply - there's been no mention of a proper PSU at all. I presume his questions refers to the circuit in post #5?.

I thought #5 was going to work but #8 "5A"