I’m not aware of any way of directly turning on the router from the TFT. All solutions have your BTT Octopus turning the router on and off. Some g-code command is sent to the Octopus board, which then turns on the router. Your TFT communicates with your control board using g-code, so it is possible to turn on the router using the TFT. Personally, I have my CAM postprocessor insert the g-code to turn my router on and off, so the router turns on at the start of the job and turns off at the end. No display required.
The first step is to find a relay to do the electrical switching. Here are four choices:
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Use an IOT relay strip. The tend to go in and out of stock. When they are in stock, multiple places will have them for $30 to $40 USD. This is the solution I use.
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Use a SSR. I’ve only seen one post where this was used, but for the cost, it seemed like a great choice. For indictive loads (like the router), they are only rated at 20% of the advertised current, so for your router, you need a 40A or above model. If you are going to be powering something else as well as the router,you will need to up the amperage rating of the SSR you select.
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Use a 30A relay module. I’m just a hobbyist with electrical stuff, but to me the higher amp rating plus the relay being optocoupled makes it a safer choice than a standard relay module.
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Use a simple relay module. This is my least favorite choice, but there are multiple topics on the forum where this relay has been used.
For choices 2, 3, and 4 you will have to work out some sort of housing and plug.
For choices 3 and 4, you will have to purchase a module that matches the voltage of the pin you use on your Octopus board. Your board will have 3.3V pins, 5V pins, and either 12 or 24 volt pins depending on the voltage you use for your stepper motors. Usually, modules designed for 5V will work with 3.3V. Choices 1 and 2 above will take a range of input voltages.
Next you need to decide what g-code you want to use to control your router. Three choices:
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You can use fan g-codes M106 and M107. This is what I do
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You can toggle pins directly with M42.
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You probably can use M3 and M5.
Using the fan ports and fan commands to control the router is the easiest solution. The ports are labeled and available. Using M3/M5 is the only choice where you might find a menu item or button already on your TFT to control the router. For example the laser is turned on and off using M3/M5. The other two solutions would require either typing the g-code into the terminal, or you editing the TFT firmware to add a button or menu. Choices 2 and 3 will require you to identify free digital pins. Naming and a pinout diagram can be found here.
There are some details that I left out. If you make your choices above, I can expand to include a bit more information.