Softstart delay

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Hello everyone!

I realized what softstart that works perfectly but I think the relatively short time (~ 1s), the tests were done without any transformer connected.
I do not know if we can extend it a little time and which components must be changed.

Thank you!
 

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David_Web

Member
2008-09-27 1:17 pm
I serviced an amp that had resistors pulling up a relay. Resistors where before the rectifier connected directly to mains(230V), and the cap after it gave it a short delay before clicking.
The four 5W resistors dissipated 15-20W of power and the circuit board was burned to a crisp.
I though something was wrong before I realized it was meant to work that way.

Long story short, DON'T do it that way.

Using the soft start after the transformer would be way better (and safer).
 
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wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
Mains = Directly connected to the electricity outlet, with NO transformer. That is if your electricity supply is 240V, the rectifier bridge is rectifying that 240V directly, with no step down, or isolation transformer present..

Discussion of such circuits is not allowed under the diyAudio rules.

Tony.
 
Thank you wintermute for this precision!

Actually my original post was about a change in value of components to extend the contact time of the relay only, I never mention how to connect.

Regards!

PS: I'll be more careful now to avoid any misunderstanding!
 
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David_Web

Member
2008-09-27 1:17 pm
I just simulated it in LTSPICE and it appears to be a 230V circuit. Is this correct?

Increasing C1 does increase turn on time as far as I can see.

If it where me I would adapt it to go after the transformer. Unless the transformer was really big. Then I would buy a real time relay.
 
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Hmmm...I have a soft start circuit from a company called NewClassD that is rated for 20A and designed to go between the mains and the power transformer, right on the 120V line. Input is clearly labeled "Mains". It gives ~1 sec delay. I can't possibly put it after the B+ transformer, as that is at 2500VAC.

Are you folks saying this is unsafe?

It's similar to this one:

http://www.newclassd.com/index.php?page=80
 
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