Relay for amp power switch (240V non-polarized mains)
I have an F5 build that until recently only had a back panel switch. This week I did some manual Dremel machining and put a nice NKK flat toggle switch on the front. It's 3A rated at 250V, and may work well for some time, but I'm considering using it with a relay to make it more reliable/longer lasting.
There are some nice soft start/switch relay boards out there, but I already have the DiyAudio soft start board built and installed. And I'd rather not have to add a third transformer (the second is the one for the DiyAudio speaker protection).
A simple solution I've come across is to use a relay with a coil voltage matching the mains voltage. A SPST relay would be fine, for example, in North America where plugs are polarized. But I am in Spain where the Schuko plugs don't enforce polarity, and a SPST relay could end up having the transformer connected when switched off... So it would seem like DPST is the way to go.
I am considering this relay to do the job: TE Connectivity / P&B T92S7A22-240
The front panel power switch would be connected in series with the coil. Then both L and N from the IEC inlet would be switched by the relay, and connect to the soft start (then transformers).
Would the part linked to above be suitable, and does the implementation seem valid? I found other threads mentioning relays for this purpose, but mostly going in to detail on 120VAC mains voltages with polarized plugs. I want to make sure I do it the right way for this situation (no mains polarity assumption, different voltage).
I have an F5 build that until recently only had a back panel switch. This week I did some manual Dremel machining and put a nice NKK flat toggle switch on the front. It's 3A rated at 250V, and may work well for some time, but I'm considering using it with a relay to make it more reliable/longer lasting.
There are some nice soft start/switch relay boards out there, but I already have the DiyAudio soft start board built and installed. And I'd rather not have to add a third transformer (the second is the one for the DiyAudio speaker protection).
A simple solution I've come across is to use a relay with a coil voltage matching the mains voltage. A SPST relay would be fine, for example, in North America where plugs are polarized. But I am in Spain where the Schuko plugs don't enforce polarity, and a SPST relay could end up having the transformer connected when switched off... So it would seem like DPST is the way to go.
I am considering this relay to do the job: TE Connectivity / P&B T92S7A22-240
The front panel power switch would be connected in series with the coil. Then both L and N from the IEC inlet would be switched by the relay, and connect to the soft start (then transformers).
Would the part linked to above be suitable, and does the implementation seem valid? I found other threads mentioning relays for this purpose, but mostly going in to detail on 120VAC mains voltages with polarized plugs. I want to make sure I do it the right way for this situation (no mains polarity assumption, different voltage).
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Here is a quick drawing of what I tried to describe in the first post. Note that in my case L and N have a 50/50 chance of being swapped due to the unpolarized plugs common in Europe. The small box in the upper right corner is the power switch.
An externally hosted image should be here but it was not working when we last tested it.
While the relay you pointed to would do the job for you your electricity mains would certainly not be approved in the UK nor I notice in Australia .
Long ago way back in the 30,s or earlier tenement buildings had two round pin sockets but that changed to three pin later on for obvious reasons .
You do have a point though several online US giants of commerce allow selling of European two pin plugs connected to electrical appliances to UK citizens --this is illegal but it hasn't stopped them and I had to answer very many complaints on another website--answer- return the goods.
And before you ask the said giant got out of its legal obligations by operating a "marketplace " where the small print says they take no responsibility--yes I have read their headquarters policy on this matter --funny they don't try that in the USA as several US government authorities I know would impose heavy fines/take them to court.
Long ago way back in the 30,s or earlier tenement buildings had two round pin sockets but that changed to three pin later on for obvious reasons .
You do have a point though several online US giants of commerce allow selling of European two pin plugs connected to electrical appliances to UK citizens --this is illegal but it hasn't stopped them and I had to answer very many complaints on another website--answer- return the goods.
And before you ask the said giant got out of its legal obligations by operating a "marketplace " where the small print says they take no responsibility--yes I have read their headquarters policy on this matter --funny they don't try that in the USA as several US government authorities I know would impose heavy fines/take them to court.
I'm aware that the US (my old home) and UK both use polarized plugs/sockets.
However, I live in Spain, which uses Schuko plugs, along with most European countries. All but a handful of those use Type F plugs which allow insertion of plugs in either orientation.
Almost every electronic audio device I've opened has a DPST (or DPDT) power switch. This isn't necessary with UK/USA/... polarized outlets. But for everyone using non-polarized outlets, it certainly is!
So long story short, this isn't an issue with commerce giants (as far as I'm aware). Power switches on out DIY devices should be DP (in case the item ends up in a non-polarized location). And if I am replacing a switch with a relay then the relay needs to be DP for the same reasons.
However, I live in Spain, which uses Schuko plugs, along with most European countries. All but a handful of those use Type F plugs which allow insertion of plugs in either orientation.
Almost every electronic audio device I've opened has a DPST (or DPDT) power switch. This isn't necessary with UK/USA/... polarized outlets. But for everyone using non-polarized outlets, it certainly is!
So long story short, this isn't an issue with commerce giants (as far as I'm aware). Power switches on out DIY devices should be DP (in case the item ends up in a non-polarized location). And if I am replacing a switch with a relay then the relay needs to be DP for the same reasons.
Normal modern power supply cables in the UK are now molded and cannot be reversed or opened up this cuts down people being killed by electrocution .
As you know the very reason the USA has a regulation =115 V RMS/120V RMS voltage is to cut down the electrical pressure if the current traveled across your chest (heart ) it does entail heavier cables for the higher current though.
As you know the very reason the USA has a regulation =115 V RMS/120V RMS voltage is to cut down the electrical pressure if the current traveled across your chest (heart ) it does entail heavier cables for the higher current though.
Still, most of the used gear I've bought from UK (e.g. 2000's Sony, 90's Naim & Quad) have serviceable plugs. A Hakko soldering station I bought new from amazon.co.uk had a serviceable plug that I converted to Schuko.
Even if plugs are typically sealed, that's not to stop inept home DIY'ers from wiring sockets backwards.
So are you saying SP power switches are common in the UK? What happens when you relocate to another country and swap out the IEC cable? DP switches cover the bases and don't rely on any assumptions.
BTW, your first reply said the relay wouldn't be allowed in the US or Australia. What makes you say that? Did you see something in the spec?
Even if plugs are typically sealed, that's not to stop inept home DIY'ers from wiring sockets backwards.
So are you saying SP power switches are common in the UK? What happens when you relocate to another country and swap out the IEC cable? DP switches cover the bases and don't rely on any assumptions.
BTW, your first reply said the relay wouldn't be allowed in the US or Australia. What makes you say that? Did you see something in the spec?
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I said-quote -"your electric mains wouldn't be approved in the UK/Australia " nothing to do with the relays -re-read it.
I am saying in the last 10 years or more molded plugs and cable are legislated by the UK Standards Institute as being the type that should be sold to the UK public --nothing to do with power switches -re-read my post .
Of course you bought gear from the 90,s with separate plugs but UK electrical standards have changed .
Amazon UK is the very company I am complaining about its not complying with UK electrical regulations - FYI- Amazon (UK ) gets its orders from Amazon USA and that includes the USA law system not the UK one this is a major issue with the UK online buying public.
The UK is no longer classed as a major world consumer the EU is , its divided the world into zones to rationalise electrical distribution as its cheaper to production line EU electrical goods than a minority of UK legislated electrical standards so the UK gets sent EU plug types .
I am saying in the last 10 years or more molded plugs and cable are legislated by the UK Standards Institute as being the type that should be sold to the UK public --nothing to do with power switches -re-read my post .
Of course you bought gear from the 90,s with separate plugs but UK electrical standards have changed .
Amazon UK is the very company I am complaining about its not complying with UK electrical regulations - FYI- Amazon (UK ) gets its orders from Amazon USA and that includes the USA law system not the UK one this is a major issue with the UK online buying public.
The UK is no longer classed as a major world consumer the EU is , its divided the world into zones to rationalise electrical distribution as its cheaper to production line EU electrical goods than a minority of UK legislated electrical standards so the UK gets sent EU plug types .
> SPST relay could end up having the transformer connected when switched off...
So? You don't trust insulation? Will somebody die if the amplifier comes on unexpectedly?
> your electricity mains would certainly not be approved in the UK nor I notice in Australia .
So are you demanding that booja30 move to a country you can approve of?
So? You don't trust insulation? Will somebody die if the amplifier comes on unexpectedly?
> your electricity mains would certainly not be approved in the UK nor I notice in Australia .
So are you demanding that booja30 move to a country you can approve of?
Oh come on PRR stop being so childish and nitpicking you are putting words into my mouth that a politician would be proud of.
While consumer electronics are usually sold with moulded plug in the UK, this is to suit mass production. It is not a requirement.
There are plenty of products still sold in the UK with rewirable plugs - including all extension cables & reels, surely the most polarity sensitive of all electrical goods.
Whether rewirable or moulded, it is a step forward from when appliances were sold without a plug and you had to buy (or pinch from another appliance) and wire the plug yourself before using your new purchase. I well remember stripping cables with a kitchen knife trying not to break too many strands, usually using the tip of the same knife to do the cord grip screws if I didn't have a suitable screwdriver to hand.
There are plenty of products still sold in the UK with rewirable plugs - including all extension cables & reels, surely the most polarity sensitive of all electrical goods.
Whether rewirable or moulded, it is a step forward from when appliances were sold without a plug and you had to buy (or pinch from another appliance) and wire the plug yourself before using your new purchase. I well remember stripping cables with a kitchen knife trying not to break too many strands, usually using the tip of the same knife to do the cord grip screws if I didn't have a suitable screwdriver to hand.
Back to OP.
With a soft start is there any benefit to using the relay or a complication too far?
With a soft start is there any benefit to using the relay or a complication too far?
Good question!
Soft start is excellent for limiting inrush current, and will definitely help keep it under the switch rating.
But arcing is the main problem that the relay would solve. The worst arcing for a device with an inductive load (big transformer, PSU) is when you switch it off. The contacts pull apart but an arc forms, and the extreme heat it generates helps sustain the arc. This causes pitting and degrades the contacts...
The big relay might be heavy handed but it seems easier than more compact than a power switching PCB and extra transformer to power it.
But X1 caps across the switch poles might be good enough, as well as keeping a couple extra spares of the switch since I really like it.
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But this is in series with K1 contacts. Break the switch, the soft start relay also drops out breaking the arc.
That's an interesting idea. I'm imagining the soft start relays don't open instantaneously. They must open sometime after the power switch opens, but who knows how long after. I wonder if the arc on the main switch provides enough current to keep the soft start relays closed until it extinguishes.
I'm not trying to be argumentative here. This is definitely more interesting to think about and discuss than comparing electrical standards among countries. 🙂
Ah yes, C3 will keep relay closed until it discharges.
How about a DPST panel switch, one contact for mains, one in series with relay coil.
Power on, C3 charges & activates relay.
Power off, relay coil is instantly disconnected, both power switch & relay contact break.
You might be as well asking in the DiyAudio soft start board thread.
How about a DPST panel switch, one contact for mains, one in series with relay coil.
Power on, C3 charges & activates relay.
Power off, relay coil is instantly disconnected, both power switch & relay contact break.
You might be as well asking in the DiyAudio soft start board thread.
These types are supposed to be heavy duty and are used on heaters and disco smoke machines.
12 VDC 20A SPDT Appliance Relay Songle SLA-12VDC-SL-C | MPJA.COM
All my grounded audio stuff only breaks one wire. I don't call it the live wire since it depends on the Schuko plug orientation, but usually it is the brown wire.
Some transformer wires have the same color.
I'm not concerned about one of the wires be connected all the time, nor are the manufacturers.
12 VDC 20A SPDT Appliance Relay Songle SLA-12VDC-SL-C | MPJA.COM
All my grounded audio stuff only breaks one wire. I don't call it the live wire since it depends on the Schuko plug orientation, but usually it is the brown wire.
Some transformer wires have the same color.
I'm not concerned about one of the wires be connected all the time, nor are the manufacturers.
Most amps I have worked on that were built in the last 30 years have had DPST switches (Sony TA-F3000ES, Rega Brio-R, Naim NAP140/HiCap, Quad 34/306). The DiyAudio/Modushop deluxe chassis uses DPST on the IEC inlet, with both L and N fused...
Anyway, I am planning on using the NKK 3A/250V toggle switches I bought (along with a couple of spares) with snubbers across the switch poles. If it sounds like it's making arcing sounds on switch-off I will wire in the DPST 240V coil relay I linked to from above. It's pretty compact and designed to power motors.
Anyway, I am planning on using the NKK 3A/250V toggle switches I bought (along with a couple of spares) with snubbers across the switch poles. If it sounds like it's making arcing sounds on switch-off I will wire in the DPST 240V coil relay I linked to from above. It's pretty compact and designed to power motors.
I've assembled for a power amp
Soft as a Feather Pillow (SFP) SSR Soft Start Circuit GB
works very well , power mosfets and is faster than a relay ,20mohm resistance . Instead of 3 , 5 NTC needed for 230v and 60mohm cold resistance .
Soft as a Feather Pillow (SFP) SSR Soft Start Circuit GB
works very well , power mosfets and is faster than a relay ,20mohm resistance . Instead of 3 , 5 NTC needed for 230v and 60mohm cold resistance .