Programmable Sequential Switch

[Folderol]

But you'll be using a finger as well, Folderol.

And yours has lights!

Yes, Yes! And sound, as the relays click over

[Folderol]

The switcher is now installed with everything now working correctly, although I hadn't realised just how long it takes the computer to fully initialise and start all the software. This is nearly a minute, and I'd only allowed for 30 seconds on the switcher's timers. Fortunately this is just long enough to ensure nothing conflicts. I'll probably change it later though to allow for any future additions.
Anyway, here is the promised view of the insides.



Top left, just below the mains input socket is the DC power supply. It's fuse is immediately below it - if this should ever blow, there's a serious problem, so it's not a 'user serviceable' part! Below this is the startup PCB, and to the right of this are the AC control relays. The first one being for the PSU itself.

Top right, you can see a resistor stuck in one of the DC output sockets I was using for testing, then there's the Arduino. The leads coming out on the right hand side have diodes hidden under the sleeving - part of the Wonks Mod. Alongside this is the Wonks Mod switch Half hidden is the DC/DC converter for channel 9, then there are the two DC control relays, and below that the Ch. 10 DC/DC converter, on top of which is the board with both current sense circuits. By shear chance, it works out that the sense threshold for both AC and DC output is with about a 1W load.

Below this are three 9V regulators. The two outside ones are for the 9V outputs, and have large heatsinks - only really needed if the output is shorted. The central one feeds the Arduino.

Along the bottom attached the the front panel, you can see the rest of the Wonks Mod. The grey wire supported by three 10M resistors has diodes going to each channel enable line so they can all be turned on. The only function those resistors serve is to act as convenient supports!

All of this is fairly benign stuff. The scary bit is the three tagstrips in the middle of the chassis. Ideally this would all be on a nice fibreglass PCB, but I don't have the facilities to produce such a thing with mains rated track distances and isolation slots under the optocouplers. Therefore I've fallen back to old-fashioned point-to-point wiring on tagstrips. Only the two outer ones have mains voltages on them and you'll notice I've spaced the channels out leaving a missing tag between them. The voltage across and rectifier assembly is never more than about 2.5V but the voltage between the channels can be full mains, depending on which ones are active.

It's not possible to get wire-ended optocouplers, so I've had to cheat and straighten the legs out, soldering them directly to tags on the low voltage centre tagstrip, and adding one short leg extension and a resistor directly on the mains side.

You'll notice I've dressed all the wiring away from the rectifiers (the couple going over the top of two are actually well above them). At maximum possible output, each individual rectifier assembly can dissipate just over 7 watts of heat. However, as the mains input is rated at 13A, the total for all 8 is about 30W. That's still quite lot of heat to get rid of. The way I'll be dealing with this will be to mount an earthed thin metal plate over the central area, supported by the two studs sticking up from the ends of the middle tagstrip. This won't quite reach the the rectifiers (the darker shaded area in the picture). Then I'll drill a pattern of holes in the top cover, just above this plate(the lighter inner area). The airflow will then be in through front bottom, up over the rectifiers then back over the plate to the top vent holes. This resolves both heat and safety issues.

[Martin Walker]

VERY neat wiring Will - I'm most impressed!

[Drew Stephenson]

That is very tidy.
And I almost understood what you were talking about as well!

[The Elf]

[Eddy Deegan]

That's art and science!

[Folderol]

Thanks Guys.
I must admit this was rather a rushed job - it only took about three years from start to finish

[Wonks]

Have you worked out the total cost of making the switch yet?

[Folderol]

Currently standing at a sniff under £250, but I need go through and sort out what I bought against what I actually used, and the value of what I already had.
Slave labour, so no costs there

[MarkOne]

I'm really interested in getting into Arduino projects.

I'm interested in what development environment people are using, loading the code in to the device etc?

[James Perrett]

I'm interested in what development environment people are using, loading the code in to the device etc?

There's Arduino/Genuino which is a complete development tool that you can download. You program it in C/C++ and each program has two sections - setup() where you set all the pin functions and initialise everything, and loop() where you run your actual program. To me, it seems extremely simple.

I don't see any more advanced stuff like interrupt handling so it is strictly for simple, non time critical programs.

Our lad also has a copy of UnoArduinoSim which allows him to test his programs on a simulator before loading them onto the real hardware.

[BJG145]

At the press of a button my entire music setup will be started in the correct sequence, and with the best timing for a clean start.

I use one of these.

I'm really interested in getting into Teensy projects.

FTFY

[Folderol]

Interesting. I didn't know these were sequential

[Drew Stephenson]

Interesting. I didn't know these were sequential

I don't know about you but I can't plug six plugs in at the same time!

[Wonks]

But for £250 you could pay one of your children (or a neighbours child) £1 a time to either plug them in in sequence or unplug them in sequence. That's 125 power-up and power-downs covered.

[Mike Stranks]

A lovely piece of work Will.

My late father-in-law - meticulous in doing the hidden things as neatly as possible - would have whole-heartedly approved.

I know it's not a direct comparison between your one-off and off-the shelf units, but yours bears cost comparison with commercially available units that aren't nearly as sophisticated.

[Folderol]

I'm interested in what development environment people are using, loading the code in to the device etc?

There's Arduino/Genuino which is a complete development tool that you can download. You program it in C/C++ and each program has two sections - setup() where you set all the pin functions and initialise everything, and loop() where you run your actual program. To me, it seems extremely simple.

I don't see any more advanced stuff like interrupt handling so it is strictly for simple, non time critical programs.

Our lad also has a copy of UnoArduinoSim which allows him to test his programs on a simulator before loading them onto the real hardware.

There are in fact two hardware interrupts available on the UNO (I don't know about any others in the series). I've used them in the past for exactly the purpose of precision timing. The Arduino's crystal is pretty accurate and stable (the smaller resonator ones less so).

[Folderol]

A lovely piece of work Will.

My late father-in-law - meticulous in doing the hidden things as neatly as possible - would have whole-heartedly approved.

I know it's not a direct comparison between your one-off and off-the shelf units, but yours bears cost comparison with commercially available units that aren't nearly as sophisticated.

Thanks Mike. It's in service now and I'm very happy with it - no more messing about with a bunch of switches, and zero power use when off.

[James Perrett]

There are in fact two hardware interrupts available on the UNO (I don't know about any others in the series). I've used them in the past for exactly the purpose of precision timing. The Arduino's crystal is pretty accurate and stable (the smaller resonator ones less so).

Thanks Will - I had missed that in all the Arduino code that I had looked at. I'm more used to programming PIC's where just about all inputs are handled using interrupts.