Soft Start / Missing Cycle Detector / On-Off Mute Controller

[FdW]

All,

Soft Start / Missing Cycle Detector / On-Off Mute Controller

In the past few weeks I have developed a soft-start circuit with mute-control. The circuit is shown here. My question is, is there anybody interested in this project and if so what would you like to see (added/changed). Also I did select a mains transformer and the relays to be used (by me). What transformer/relay footprint would you like to see on a future board.

Have a look at the scheme and let me know what you think about it.

Frans.

Transformer: http://www.block.eu/en_US/products/720897.htm ECO 2003 Primair: 230 V Secundair: 12 V 125 mA 1.5 VA ECO2003-1,5S12
Relay's: JVN1A-12V-F Panasonic Electric Works | 255-2362-ND | DigiKey
NTC's: Amphenol 527-CL40 Inschakelstroombegrenzers | Mouser

Update:
Thanks to gmphadte, improved version @ http://www.diyaudio.com/forums/soli...detector-off-mute-controller.html#post4181085 (Post #10)

Update:
Less components @ http://www.diyaudio.com/forums/soli...tector-off-mute-controller-2.html#post4182601 (Post #11)

Update:
Two diodes less @ http://www.diyaudio.com/forums/soli...tector-off-mute-controller-2.html#post4197576 (Post #14)

Update:
Enhanced muting timing @ http://www.diyaudio.com/forums/soli...tector-off-mute-controller-2.html#post4197595 (Post #15)

Update:
Final version, using comparators @ http://www.diyaudio.com/forums/soli...tector-off-mute-controller-2.html#post4226233 (Post #20)

Update:
Gerbers (and more) @ http://www.diyaudio.com/forums/soli...tector-off-mute-controller-3.html#post4284209 (Post #25)

 

[FdW]

No one, please give me some sign of life 🙂

 

[Ketje]

Something like shooting a mosquito with an elefant gun ?
Mona

 

[FdW]

Something like shooting a mosquito with an elefant gun ?
Mona

Why not 🙂 But it's all very cheap, a hand full of carbon resistors and about the cheapest transistors will do. Only the relay and transformer cost a bit. The three things that I absolutely need are the safety of the missing cycle detector, the control for muting and the soft-start for my amplifier (it has a 2KW linear PSU).

Total construction cost will be low(ish) so I thought maybe someone else wants a few or is interested in a thing like this.

 

[Ketje]

Shure for a diy-er a resistor more or less...
It was't ment that negative, more as a first cheap to get things going 🙂
Mona

 

[gmphadte]

The missing cycle detector...

you can make one with a 555.

Gajanan Phadte

 

[FdW]

The missing cycle detector...

you can make one with a 555.

Gajanan Phadte

The missing cycle detector here is made with one transistor.

 

[gmphadte]

D8 anode and D4 cathode reaches the same point.

You can connect D8 after the bridge followed by C2. Take missing pulse sense at anode of D8.

Gajanan Phadte

 

[FdW]

D8 anode and D4 cathode reaches the same point.

You can connect D8 after the bridge followed by C2. Take missing pulse sense at anode of D8.

Gajanan Phadte

Yep you can, but the bridge will be a 3n256 (or alike) and then the 'extra' 1n4148 is o.k.

Edit: On second thought the answer should have been 'Yes' 🙂

P.s. I have to check the timing for that, in the current scheme there is a 20mS gap and after that mod it is a 10mS gap (but full wave detect). So I will check that, thanks.

 

[FdW]

D8 anode and D4 cathode reaches the same point.

You can connect D8 after the bridge followed by C2. Take missing pulse sense at anode of D8.

Gajanan Phadte

Attached is an updated schema, with updated timing to detect half-cycle-dropouts.

 

[FdW]

This version uses 2 transistors, 2 diodes and 4 resistors less 🙂 it was found that the 'extra' transistors that provide some hysteresis to the relay drivers is not needed. The rise-time (of the voltage across the relay) is still 8.5ms.

Changing the on/off-switch to a mosfet-model brought an other problem to light, for this purpose the on/off-switch-detector has been corrected. Also the total input impedance of this circuit was lowered to prevent problems picked up on the cabling.

And, the standby-power-consumption has been brought down to below 1mA (that is less then 20mW total).

 

[FdW]

Something like shooting a mosquito with an elefant gun ?
Mona

The current version uses less components (8 in total 🙂) is this better?, the standby power has been brought down to below 20mW. Anny comments are welcome. See post #11.

 

[RCruz]

Following 🙂

 

[FdW]

This is the final one for this series, it has 2 diodes less 🙂 (than the previous one). This is not what I am going to build (more to come).

 

[FdW]

For completeness, I was experimenting with muting the amplifier just before switching it off. This again adds to the cost, and complexity of the circuit. One other problem is depending on Vbe's as switching threshold's makes it all very imprecise and needs larger capacitors for timing. For these reasons I am going to try something different, stay tuned 🙂

Attached the version with 'enhanced muting switch'.

 

[RCruz]

This is a very advanced project for me to grab properly so please excuse my naïf questions: What is the purpose of the missing cycle detector ?

 

[FdW]

This is a very advanced project for me to grab properly so please excuse my naïf questions: What is the purpose of the missing cycle detector ?

Hi Ricardo,

The missing cycle detector detects missing cycles 🙂 When the mains is about to fail most of the time it will drop a few/some cycles, this may produce lots of dangerous artifact's (high voltage pulses, capacitor over charging, and other) (these cycles are not cut at zero crossing, and they are not distributed evenly, even short term high voltage DC may exist on the mains). The missing cycle detector shuts the connected electronics down and restarts a safe startup sequence.

 

[RCruz]

Thank you Frans 🙂

 

[FdW]

Still working on this (but not the only thing), first Hamburg, HiFi-Tage | Norddeutsche HiFi-Tage, Messeveranstaltung, then I will finish this here 🙂 See me at the 'Suesskind Audio' room.

 

[FdW]

Now is the time, the show in Hamburg was a good success, and de flu (that seems to have been a result of this show) is almost past. Here is my final design for the soft-start with muting-control and fail-safe operation. The system has also been tested by building an working version 🙂 Later I will lost some pictures of the build including the gerbers. If there are questions about the circuit I will attempt to answer them. When there is a 'huge' need for PCB's I may order (and sell) some 🙂