Yet another softstart PCB

[harryeng]

Hi Group,

This is my own softstart PCB design. Yes, I know, there are lots of others in the forum. But I am particularly proud of this one, because it’s mine. I presented it inside another thread, and got a lot of questions about it, so I decided to give it it’s own thread.

The softstart is designed specifically for Pass amps. You can use it to start up the amp with both an external signal, and with a switch.
I wanted to minimize both loose parts, and 230 cabling inside my amp. So I integrated the fuse on the board. The incoming power cable is connected directly to the board, and the on-off switch is integrated in the control circuit. I also integrated the bi-metal protections into the control circuit, which results in a minimum number of switches (and cables) in the 230 VAC circuit.

It’s small: 5.5cm x 10 cm. I use it inside my Aleph 5, but it can switch up to 12 amps. Start-up is done with four resistors in series, and after the chosen start-up time a second relays short-circuits these resistors leaving just one relay contact in the power path.

The development took a long time, as this was my first PCB and I had to bone up on a lot of knowledge. The first designs had way too many options, so I “Passed” it, and threw everything out that did not really attributed to the start-up function. The only option I left, were three connection points that can be used for powering a DC protection circuit. The selected transformer can supply power for four relays

I know a question that is coming, but I do not have enough PCB’s left. As this was a sort of try-out for me, I only ordered a small set with 10 boards. Those left are spoken for, by Berry and Leeuwarden.

Greetings, Harry

[harryeng]

This is the schematic belonging with the PCB.

All the parts (without the PCB) are only 20 Euro's

[harryeng]

This is the PCB


Harry

[harryeng]

And here is the BOM, and the original Eagle files


Have fun!
Harry

[promitheus]

that looks cool.
How do you use that DC control.

[Berry]

There is no dc protection in the circuit, you can use a dc protection with this board. The External DC in is an output from a pre-amp that turns the amp on.