Remote trigger, momentary switch, soft start PCB (for First Watt or other projects)

[Alarudin]

pardon my ignorance, if i was to connect a standard on/off switch instead of a momentary push button. is there a need to bypass the ne555 timer circuit?

 

[ghiglie]

Hi there! I'm quite sure this thread is not the adequate one for support, but... I don't where I should.
So, I have two boards working regularly on tho projects I'm revising. I'm now using a smart socket to turn off the powerstrip , and I noticed that the boards start in ON state, so preamp and amp are starting "together", vanishing the master/slave effect (at start, at least).
Any way to have them to start in OFF state, so I can power the chain from master?

Thanks in advance!

Marco

 

[xrk971]

You might want to use large NTCs like 8D-20 or CL60’s instead of those 5W power resistors on the soft start. If the relay ever fails to connect to bypass the resistors they will get so hot under Class A that they melt burn up and desolder themselves. I learned this the hard way on my design. The NTCs can tolerate indefinite on because resistance drops as they get hot.

 

[ghiglie]

You might want to use large NTCs like 8D-20 or CL60’s instead of those 5W power resistors on the soft start. If the relay ever fails to connect to bypass the resistors they will get so hot under Class A that they melt burn up and desolder themselves. I learned this the hard way on my design. The NTCs can tolerate indefinite on because resistance drops as they get hot.

I saw some NTC implementation here on the forums - but I admit, I'm very limited on circuit design and I couldn't review MFly's one.

My main concerns are, for now , the ON status on power on, and my personal investigation is definitely slow...

 

[ghiglie]

Oh, darn... both pushbuttons has somehow failed, both starting as Normal closed... :|

 

[Mfly]

Oh, darn... both pushbuttons has somehow failed, both starting as Normal closed... :|

Do you mean that this was the cause of your issue?

Otherwise: I do think that the starting in the 'on' state is due to transients caused by the power up of your smart sockets. I never accounted for this in the design because it was meant as a 'standby' always power on design. This is a known issue with this type op implementation of the 555 timer. After some researching I found the following possible solution:

To solve this problem, you could tie the reset line (pin 4) to another resistor/capacitor combination with the capacitor at ground and the resistor at the +V point. This will cause pin 4 to be held near ground for a short period which will reset the output when power is applied. As for values.... maybe somebody else can advice on this.

 

[ghiglie]

Do you mean that this was the cause of your issue?

Otherwise: I do think that the starting in the 'on' state is due to transients caused by the power up of your smart sockets. I never accounted for this in the design because it was meant as a 'standby' always power on design. This is a known issue with this type op implementation of the 555 timer. After some researching I found the following possible solution:

To solve this problem, you could tie the reset line (pin 4) to another resistor/capacitor combination with the capacitor at ground and the resistor at the +V point. This will cause pin 4 to be held near ground for a short period which will reset the output when power is applied. As for values.... maybe somebody else can advice on this.

Hi Maarten!
Yes, I solved changing the pushbutton, it looks like the inner contacts stood in NC position. I just added a small cap between pin 1 (GND) and pin 2 (TRI).
Now it starts in OFF state.

I felt so lame complaining about the circuit ...