I just thought I would post up to help anyone else that would benefit from this or was looking to do similar. This would include wanting to control the power to anything based on the power of something else. i.e. Electronic device X turns on/off, so turn device Y and Z on/off too, or do something else.
*Free =
1: I used some smart plugs I already owned (you can buy a pair for about £15)
2: Setup and ran homeassistant on my home server. This is free and easy to do. It is "Open source home automation that puts local control and privacy first. Powered by a worldwide community of tinkerers and DIY enthusiasts." You could run this on your PC or on a cheap Raspberry Pi using very little energy. There may be ways to achieve this without even needing home assistant though.
We started talking about it in this post where it became apparent that it was cost prohibitive to send off BK Subs to add the backplate which includes the auto on/off feature. This is because it would need a new transformer, amplifier board and filter board. This is pretty much everything except the subwoofer driver/cone assembly itself so would cost too much in parts and labour.
So why would you even want auto on/off feature?
A lot of subwoofers don't come with auto sensing signal inputs that can trigger the thing to turn on and off. A lot also don't come with a remote to turn them on. In these high cost energy times, it's good to do what little you can to save electricity and hence money. Besides, many people don't want to crawl around the back of the sofa and reach down and flick the rocker switch of a sub every time they want to use it and then turn it off again. It can become tiresome.
So what options are there?
There are a few options available to achieve this, but they are typically either for where the subwoofer is close to the amp already, or where an additional wire can be ran to it easily, or they simply cost too much for such a simple task, and/or a combination of all of these problems. If you want auto on/off and you do have the sub in a place where you can run it close enough to the amp or tv you can:
1. Buy a master/slave smart mains extension lead which are about £20. This works by triggering things in mains sockets 2, 3 and 4 for example, when things in socket 1 gets turned on. Simple. Cheap.
or
2: Utilize the 12v trigger on the back of your amp/avr which sends a signal to an external device to turn it on. You can use this with a smart mains socket strip as well or other products.
or
3: There are some products out there which use 12v trigger which then wirelessly send a signal to another trigger accross a room, to remotely turn something on. I could only find products in the US that did this and they cost a lot.
But...
What if your sub is the other side of the room? You can't run a chunky 240v kettle lead to it under the carpet. Running a 12v lead could add noise next to your signal cable and be a pain to run in terms of route if you've already done the conduit or signal run etc.
Using smart plugs to control power intelligently
In recent years, smart plugs have risen to popularity where you have a mains plug socket in the wall, added to your home network so you can control it with Alexa/Google Home etc.
You could use a simple smart plug on a timer and just set the schedule to only turn the sub on in the daytime, or when you tend to use it. Crude, but it would help a bit saving money.
There is a better way if you want to go down this road. These smart plugs now have energy monitoring sensors built into some of them where you can get real time output of the current power being used. Perhaps you can see where this is going...
We want to turn our sub on, whenever the amp is on. Or, you could turn it on whenever the TV gets turned on if you want to. Your TV would need to show up in homeassistant and be able to report it's current state as on/off.
We will focus on the former.
You basically plug your AV Receiver or Amp into Smart plug A, and your sub into smart plug B the other side of the room, or wherever it is next to a socket.
Smart plug A will always stay on, but will report it's current draw and/or power usage in real time to home assistant. The amp/avr allowed to go in and out of standby.
Smart plug B is configured in home assistant to turn on when the current draw on smart plug A is detected as more than 0.1 amps. (These amounts can obviously be tweaked to suit your situation. My AVR idles in standby at 0.0XXX amps and 2watts. When on, it goes to about 0.28 amps and 25watts.) The subwoofer physical rocker switch is always left in the on position so smart plug controls power.
This is achieved via automation routines in home assistant. Routine 1 is the turn on routine. Routine 2 is the turn off routine basically in reverse. You can set conditions and customize it to suit. i.e. Don't bother running routine 1 if Smart Plug B state is ON. Wait for 2 minutes of detected amp idle current draw before switching off sub etc.
I don't know of a way of doing these routines using only a combo of Alexa/Googlehome/Smart Life/IFTTT
Do you? Let us know if you do know a way.
But if you run a home server on your network (I know a lot of guys on these forums do) then you can install and run homeassistant with MQTT broker, and get up and running with some smart plugs to achieve the above.
I don't want to go into too much detail in the OP as it will get too long and become out of scope for initial discussion, but if anyone wants to discuss it in more detail we can in this thread. I run Homeassistant and MQTT inside docker containers on an unraid server. The smart plugs I used were cheap ones I had lying around since 2020 with brand name Gosund. They were very cheap. Please note that some modern day smart plugs with energy monitoring built in are not compatible with home assistant. You need to check first. A lot of smart plugs can be firmware flashed OTA (over the air) (i.e. without jtag cable and just wirelessly using a laptop) to tasmota firmware which allows them to play ball with home assistant much better, rather than rely on cloud limited firmware. If you need to flash the smart plugs it does require some technical competence but essentially it's all on youtube really to guide you through all of this. The more recent Gosund ones now can't be flashed apparently. The TAPO ones look good, and work with home assistant and a plugin someone has put on github.
TLDR
My sub automatically turns on and off with my amp using old smart plugs and a server I was already running. Works seamlessly. In fact I just turn the TV on and off as the amp comes on/off via CEC which in turn does the sub.
*Free =
1: I used some smart plugs I already owned (you can buy a pair for about £15)
2: Setup and ran homeassistant on my home server. This is free and easy to do. It is "Open source home automation that puts local control and privacy first. Powered by a worldwide community of tinkerers and DIY enthusiasts." You could run this on your PC or on a cheap Raspberry Pi using very little energy. There may be ways to achieve this without even needing home assistant though.
We started talking about it in this post where it became apparent that it was cost prohibitive to send off BK Subs to add the backplate which includes the auto on/off feature. This is because it would need a new transformer, amplifier board and filter board. This is pretty much everything except the subwoofer driver/cone assembly itself so would cost too much in parts and labour.
So why would you even want auto on/off feature?
A lot of subwoofers don't come with auto sensing signal inputs that can trigger the thing to turn on and off. A lot also don't come with a remote to turn them on. In these high cost energy times, it's good to do what little you can to save electricity and hence money. Besides, many people don't want to crawl around the back of the sofa and reach down and flick the rocker switch of a sub every time they want to use it and then turn it off again. It can become tiresome.
So what options are there?
There are a few options available to achieve this, but they are typically either for where the subwoofer is close to the amp already, or where an additional wire can be ran to it easily, or they simply cost too much for such a simple task, and/or a combination of all of these problems. If you want auto on/off and you do have the sub in a place where you can run it close enough to the amp or tv you can:
1. Buy a master/slave smart mains extension lead which are about £20. This works by triggering things in mains sockets 2, 3 and 4 for example, when things in socket 1 gets turned on. Simple. Cheap.
or
2: Utilize the 12v trigger on the back of your amp/avr which sends a signal to an external device to turn it on. You can use this with a smart mains socket strip as well or other products.
or
3: There are some products out there which use 12v trigger which then wirelessly send a signal to another trigger accross a room, to remotely turn something on. I could only find products in the US that did this and they cost a lot.
But...
What if your sub is the other side of the room? You can't run a chunky 240v kettle lead to it under the carpet. Running a 12v lead could add noise next to your signal cable and be a pain to run in terms of route if you've already done the conduit or signal run etc.
Using smart plugs to control power intelligently
In recent years, smart plugs have risen to popularity where you have a mains plug socket in the wall, added to your home network so you can control it with Alexa/Google Home etc.
You could use a simple smart plug on a timer and just set the schedule to only turn the sub on in the daytime, or when you tend to use it. Crude, but it would help a bit saving money.
There is a better way if you want to go down this road. These smart plugs now have energy monitoring sensors built into some of them where you can get real time output of the current power being used. Perhaps you can see where this is going...
We want to turn our sub on, whenever the amp is on. Or, you could turn it on whenever the TV gets turned on if you want to. Your TV would need to show up in homeassistant and be able to report it's current state as on/off.
We will focus on the former.
You basically plug your AV Receiver or Amp into Smart plug A, and your sub into smart plug B the other side of the room, or wherever it is next to a socket.
Smart plug A will always stay on, but will report it's current draw and/or power usage in real time to home assistant. The amp/avr allowed to go in and out of standby.
Smart plug B is configured in home assistant to turn on when the current draw on smart plug A is detected as more than 0.1 amps. (These amounts can obviously be tweaked to suit your situation. My AVR idles in standby at 0.0XXX amps and 2watts. When on, it goes to about 0.28 amps and 25watts.) The subwoofer physical rocker switch is always left in the on position so smart plug controls power.
This is achieved via automation routines in home assistant. Routine 1 is the turn on routine. Routine 2 is the turn off routine basically in reverse. You can set conditions and customize it to suit. i.e. Don't bother running routine 1 if Smart Plug B state is ON. Wait for 2 minutes of detected amp idle current draw before switching off sub etc.
I don't know of a way of doing these routines using only a combo of Alexa/Googlehome/Smart Life/IFTTT
Do you? Let us know if you do know a way.
But if you run a home server on your network (I know a lot of guys on these forums do) then you can install and run homeassistant with MQTT broker, and get up and running with some smart plugs to achieve the above.
I don't want to go into too much detail in the OP as it will get too long and become out of scope for initial discussion, but if anyone wants to discuss it in more detail we can in this thread. I run Homeassistant and MQTT inside docker containers on an unraid server. The smart plugs I used were cheap ones I had lying around since 2020 with brand name Gosund. They were very cheap. Please note that some modern day smart plugs with energy monitoring built in are not compatible with home assistant. You need to check first. A lot of smart plugs can be firmware flashed OTA (over the air) (i.e. without jtag cable and just wirelessly using a laptop) to tasmota firmware which allows them to play ball with home assistant much better, rather than rely on cloud limited firmware. If you need to flash the smart plugs it does require some technical competence but essentially it's all on youtube really to guide you through all of this. The more recent Gosund ones now can't be flashed apparently. The TAPO ones look good, and work with home assistant and a plugin someone has put on github.
TLDR
My sub automatically turns on and off with my amp using old smart plugs and a server I was already running. Works seamlessly. In fact I just turn the TV on and off as the amp comes on/off via CEC which in turn does the sub.
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