Here are some updates to Coasty – The Coaster Toaster, the tiny laser cutter specifically designed to cut drink coasters.
New Traction Roller
I made the traction roller diameter a lot smaller and moved it behind the beam. A smaller roller has a lot of advantages. It allows the beam to be closer to the contact points of the rubber orings. This improves the usable work area, because you can get closer to the edge of the coaster. With a smaller diameter the coaster travels less per revolution. This increases the torque and resolution.
Smaller Chassis
The chassis is now about 16mm smaller in depth due to the smaller roller and new location. The depth of the machine is quite a bit smaller than the coaster.
Fan Guard and Carbon Filter
I added a fan cover on the back. This acts as a finger guard and also allows a few layers of carbon filter cloth to be used. Bulk carbon filter cloth for use in air purifiers can be purchased on Amazon very cheaply. It removes a good portion of the odor of the smoke.
Carbon Filter Cloth
Door Interlock Switch
There is now a switch that cuts all power to the laser when the door is opened. You can still run the machine to test the motors, homing etc, the the beam cannot turn on with the door open.
IR Coaster Detector
I was not happy with the coaster homing switch used on the first version. While it never failed, it did not appear to be very robust and it caused some drag on the coaster. I changed to a IR LED and photo diode. When the light from the LED hits the photo diode, it conducts to the +5V. When the coaster blocks the light, it is pulled down to ground. I used a pot on the pull down because it did not know what he exact value would be. It turns out the value needs to be about 40k. The only catch was the microcontroller input pin pull up resistor on the Nano could not not used because it is less than the 40k. This required a slight hack to Grbl because Grbl is all or nothing on the pull ups for the limit switches.
I was not sure if ambient light changes might be a problem, like bright sunlight. The photo diode looks down and that appears to be good enough to avoid overhead light. I also have a mounting screw there in case I need to add a little shade/cover.
IR LED / Photo Diode Circuit
Bluetooth
I have been using Bluetooth on some other machines and really like it. Skipping USB cords and using a phone instead of a computer is great. I have found it to be very reliable. The real world bandwidth appears to be a little lower than 115200 USB. It has not been a problem, but I don’t do much gray scale engraving on this machine which needs higher bandwidth. Regardless, USB is still an option.
A standard HC-05 or HC-06 module plugs into a right angle connector.
Video
Here is a video of this version.
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