Automation Project: Shed

Starting shed automation. I know, it seems to be ass-backward to not be finished with physical moving-in stuff and already planning the improvements, but I have to plan, and also it was a bad bones day so hard physical exertion was out. 

A propos of drawing circuits, I need a Windows app that I can use to easily draw up circuit diagrams to post in here, does anyone know of something that's free, able to have components added without needing a degree in CAD / CAM / Ballyhoo BS? 

I'd just like to be able to quickly draw a box, add a few terminals to it and label the box and terminals, then use that in multiple drawings along with common components. (Or tell me one that isn't free and then help me out with a donation?) 

Anyhow. The thing I want to turn into a black box is this AC current sensor thingie. You can find them on AliExpress for a few bucks and a five-week wait, and they're a bit super-easy, just power them from the same 5V as the board you're using to monitor (in the case of that link, an Arduino Uno but I have a few others in mind) and measure the Out voltage on an analog pin. If I was a smart-ass I'd add voltage sensing, then work out the total power draw of the workshop but I'm a dumb-ass and all I want is to trigger an action if more than an amp or two is drawn on the monitored line.

Why Automation? 

This is the little gizmo in question, the ZMCT103C which will sense 5A, which I think is reasonable given the 700W - 1600W range of mains-powered tools I have. I'm not sure what the gizmo does with more current but I'm hoping it just silently maxes out and doesn't get blown up by a larger input voltage. We'll see. If desperate, I can actually wind myself a transformer and just make a circuit to switch at some predefined current.

If you want a ZMCT103C of your very own, a quic search of AliExpress will get you around a dozen hits, FSM knows how many more if you just type it into DuckDuckGo. (Or Google, not my recommended option though.)

But that doesn't get you to the "why" of the whole thing does it? Basically, it's simple. If a large enough device draws current and there's no voltage on the dust extraction, I want it to shut down until someone presses Reset. Dust extraction is paramount for me, wood dust from power sawing and routing is fine enough to go through a normal dust mask and play hell-high havoc with my respiratory issues. And when I turn on any such machine and the control board realises that there's power on the air/light circuit, then it should turn the dust extractor on. I'll try and arrange it so that all the dirtiest power tools have a suction hose on them, and a blast-gate that I can open to allow dust to be whooshed away and filtered so that I can get away with a relatively simple respirator.

Most workshops have these auto-on systems but they're built into the superduper shop vacs they buy, you have to plug the power tools into the shop vac and then it switches on when the tool is powered up. That's great for many smaller shops and hobby setups like mine, but as I said, my needs dictate something a bit better. Shop vacs produce a huge plume of 2u dust and that's just a limitation they have. They run high speed air, and that puts a lot of pressure on filters. 

I want a lower-speed, high volume setup and I'm building it. Also, those shop vacs are inside the workshop so that means that whole dust plume is going right back into the air I'd be breathing. You can (sometimes...) run a vent hose outside from the shop vac but it costs because it reduces the overall efficiency and so you get less dust extraction. 

Some of the low-speed high-volume dust extractor systems people use, also vent back inside the shop. Some have huge cylindrical folded-paper filters atop them but those filters only catch some of the dust in that dangerous size range, and even then, those filters cost a bomb, need cleaning (which need regular cleaning, generally with an air hose nozzle, and then there you are, shifting the dust out of the filter and into the air around you. Ya just can't win.)

The only thing you can do is take the best tips from it all and put the extractor outside - with all the filtering you can get - and be prepared for a few efficiency losses along the way. Because of course even the scenario where the machine is outside has drawbacks. For a start, it creates a vacuum inside the shop, and if the wind's in the right direction you can cop the dust right back. On cold days, the extractor system will cause that vacuum and then cold air will creep in through every gap. 

And THAT is why I want automation. To be able to make the shop as clean as possible for my lungs' sake. 

So some of the programming has just been sorted out:

If power tool on and no power to light / air circuit, emergency stop power to the tools.
If power tool on and power exists to light / air then activate dust extraction.
If dust extraction is on as per above, and pwer tool turns off, countdown 30 seconds and turn extraction off. (You want time for the dust in the lines to get to the cyclone, also sometimes you're just moving a length of wood along to make the next cut, so turning the extraction system on then off then on again is wasteful.)

The other thing is that I want to run the dust extraction off solar and an inverter, because even though it seems a negligible current, with the mitre saw turning on and the extraction system turning on, that could trip the circuit breaker for the garage. There's only a single 16A circuit into the place, meaning that in practice it's limited to 10A per outlet which means that two motors kicking in at the same time could easily exceed the 16A rating. 

For the moment I'll have to chance it - or power the extraction system from the laundry which is on a different circuit and circuit breaker. A new battery for the solar panel and a chunky 4000W inverter are outside the budget for now. But I want to allow for it in future. 

Anyway - just a progress report. As always, please share the link to this page, consider making a donation, and come back soon for the next article!

As always, be awesome, stay awesome!