I’ve been working on the automated dust collection and I thought I’d give an update.
The Blast Gate
I’ve completed my first prototype for the blast gate itself.
I’m quite happy with the design but there are a few improvements that are going to made to the second revision. Thanks to Ale and Josh for feedback on the design.
- A shorter piston that doesn’t poke out
- Strengthening of the mechanical linkages
- Adding bearings and bushings where they’re needed
- Adding a handle to the sliding portion to make it easy to open manually.
- Tweaks to the part that clamps the pipe for ease of assembly
- Decreasing the radius of the cutout on the sliding part to prevent dust build up.
The User Interface
I’ve changed my plans on the original design somewhat which necessitated a rethinking of the user interface. Originally I was not planning on detecting if a machine was running so I couldn’t automatically open and close blast gates but have since decided that the complexity added by automatic detection is totally worth it.
This is what I propose the user interface be like:
Most of the time the selector switch would be left in AUTOMATIC mode and the blast gate will open and close automatically as the machine is turned on and off. If, for whatever reason, you want to manually open or close the blast gate then you can set the selector switch to MANUAL mode and then use the second switch to select open or closed.
I’ll go into this in more detail later but selecting MANUAL completely bypasses the micro-controller/code so you can always be sure that the system will work.
Designing for Reliability
As some of you rightly pointed out, automatic systems that don’t work are a pain in the ass and there has to be a a way to override the when they fail. Excluding instances where something actually breaks (e.g. the blast gate explodes) I’ve broken down what the system relies on and what will happen if that thing fails:
Compressed air. The system uses compressed air to drive the piston that moves the blast gate. If the compressed air cuts out then blast gates will have to be moved by hand (like what happens now).
24V power supply. The system uses electrical power for everything, including pneumatic valves. If the power supply cuts out, a pneumatic relief valve will automatically bleed all the air in the system which will allow blast gates to be moved by hand.
WiFi. The system will use WiFi (in automatic mode only) to turn on or off the dust collector when a machine is being used. If the the WiFi cuts out then the dust collector will have to be turned on manually (like what happens now).
The code/ micro-controller. Obviously the code on the micro-controller needs to be functioning correctly for the automatic mode to work. If this fails, the blast gate can be set to manual mode and operated using the switch.
Here’s my sketch of the electrical and pneumatic systems. I’ve left out the current sensing circuit since it’s a little more involved. I might look into doing a JLC PCB order for the current sensing circuit but I don’t really know anything about making PCBs so we’ll see.