UM20 - Studio Power Switcher

This is a project that I've had in the background for several years. The basic function is to automatically control the power of several parts of my music studio with the idea of saving power.

So there are three 240vac power circuits that are controlled within this unit. They are connected to the Computer circuit, the Speakers circuit and the Audio Circuit.

A small controller box contains the wonderful Arduino Nano microprocessor which controls the solid state relays which in turn power off and on the 240vac circuits. It also monitors the state of the audio sensor input and the firewire voltage coming from the PC.

The two automatic controls within this project are:
  1. When there has been no audio fed to the Speakers for a pre determined period of time then they will be automatically powered down. They will power up again once audio is detected.
  2. Once the IBM-PC powers down, all the 240vac outputs will also be turned off and after a preset period of time.
The Arduino gets a feed from the PC which is the power from the Firewire connection. On this particular computer motherboard it turns off the 12vdc feed along the firewire when the computer is shutdown. So the Arduino monitors this 12vdc state via one of it's digital inputs.

To sensor the presence of an audio signal I made up a small audio buffer circuit which I installed within my UM1-UK mixer which sums the left and right channels and outputs a voltage just below 5v which can be read in via the Arduino's analog inputs.

So the main purpose of this unit is to save power. My daily backup starts at about 4pm which is often about an hour before I finish using it. But what is unpredictable is how long this backup will take as its time will be based on how data needs copying to the backup hard drive. On several occasions I have forgotten to return to the studio to turn off the power especially to the Speakers which use a good 200W when idle. I also will forget to turn off my synthesizer which are growing in number and also power consumption.

So once the unit is fully installed I can stop worrying about whether I've turned the system off or not as this UM20 unit will take care of operation for me.

Both parts of the UM20 Studio Power Switcher

Closeup of the 240vac relay box

Closeup of the Computer Control box

As you can see on this controller box there are several leds which simply light to show the state of the labelled relays or incoming signals. The S (speaker) led will flash when there is no signal monitored on the audio sensor input. If you hold either the A (Audio) or S (Speakers) button down for 2 seconds then they will turn off.

I've written the code to take into a few unwelcome situations. For example you don't want to be able to turn off the computer circuit from this box when there is a power signal being read on the firewire cable. Note that it does say USB on the front panel as originally I had planned to use the USB port as a computer state signal but alas I forgot to change the panel artwork when I realised the USB still had power once the computer was powered down.

The unit has always got power from a small plugpack (wallwart) that supplies the 5vdc to power the Arduino and leds.

If anyone would like circuit diagrams then I'm quite happy to put this on the pages.