Soft as a Feather Pillow (SFP) SSR Soft Start Circuit GB

[xrk971]

I use a dorm room style hot plate and an aluminum frypan. Not exact one but similar. The lower medium-low setting is about right. Use an IR thermometer to check temps. The low temp paste works real well and I set the pan for 160C. A variac is a great idea. Heat from the bottom and local hot air at 340C from the pencil on top.

https://a.co/d/7b0d9eL

 

[Vunce]

I am missing what the variac is used for during the SMD soldering adventures?

 

[bloqhed]

For me it's to control temp of the hot plate I use, it's just a 300w max heating element that plugs directly into an AC source. I found that setting it around maybe 95VAC output gets me just the right temp for Chip Quik SMD291AX10T5

 

[Vunce]

Ahhh…..
My hotplate is too fancy then, it has temp control 🤩😂

 

[JWCoffman]

The cheap hot plate/variac idea is fantastic. I've been meaning to pick up a variac and this seals the deal.

 

[namghiwook]

I've built FH9HVX amp with this soft starter.
When I power it up, it sounds immediately without any delay (default 2sec delay).
What is the problem?
Any suggestion I have to try?

 

[xrk971]

Your photo shows a jumper installed on J9. Remove it for the full 2 second delay.

 

[namghiwook]

Sorry. The photo was taken before. I am using it without jumper now.
I will check it again.

 

[xrk971]

If D2 is flipped it will have no delay.

 

[namghiwook]

I am using it without jumper and the D2 direction seems correct.
Today I power it up and it sounds immediately without any 0.5sec delay.
I don't know why.
Will I have to reflow all solderings?

 

[xrk971]

A closeup top photo would be very helpful.

 

[Algar_emi]

Hi, is it still available, would like one pcb please. sB

 

[namghiwook]

@Algar_emi
If you want a pcb. you could buy this one. https://www.etsy.com/listing/769363...solid-state?ref=hp_active-mission-recs-rv-1-1

 

[namghiwook]

The led lights after 2sec delay but the output power is detected immediately.

 

[jhofland]

That sounds consistent with the design. On power up connection is made via the triac and the NTC devices. The initial current surge is moderated by the NTC's. After about 2 seconds the MOSFETs engage and short out across the NTC and triac.

 

[xrk971]

Yes, I was going to say what Jhofland said. Unless there is a load that draws a lot of current, the voltage will measure high when the triac turns on - immediately. Looks like your SFP is working as expected.

 

[namghiwook]

@jhofland @xrk971
You say that immediate playing sound after powering up is not a mal functioning, it's normal and SFP is working like this. right?
I am happy to know that my SFP is working normally.
I've been using soft starter first time . then I misunderstood 'soft starter'
Thank you so much!

 

[xrk971]

Yes it immediately plays but the current in rush is limited by the three NTCs in series. This prevents the mechanical and thermal stresses of a high current pulse hitting the trafo windings and other components. It’s different than an anti-pop turn on “mute” function. That requires an SSR at the speaker output with a delay - and you get that if you use my speaker protect SSR.

There is another type of PSU that has a soft start and that’s a capacitance multiplier with a topology similar to the one in this thread:

https://www.diyaudio.com/community/threads/jumas-easy-peasy-capacitance-multiplier.297921/

it has a slow 45 second long ramp up. At first there won’t be any sound until the voltage reaches a critical level where the amp plays music.

 

[voxxonline]

Good evening.
I am slowly progressing with my amp built.
Time to check if I have soldered soft start correctly.
Can anyone please confirm all is good so I can power it up ?
Thanks

 

[xrk971]

Looks good. Note that without a load, there will be a few volts after the triac when in the off state. But that’s normal.