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Turning on a machine automatically when another machine is turned on - using ad hoc ESP8266 network

donnybahama

I’m very new to microcontrollers and programming. I probably know just enough to be dangerous. I’m trying to devise a reasonably simple system for turning on the dust collector in my wood shop and positioning the sliding carriage (output side) of a blast gate manifold over the appropriate inlet for the tool that was just turned on. (The first 10 seconds of this video will clarify how the manifold works.)

The way I think I want to do this is using an ad hoc network of ESP8266 modules - 6 “sender” modules which send "Power ON” and [Machine ID] to the “receiver” module (mounted near the dust collector and blast gate manifold) when current is detected for the dust producing machine’s motor. The receiver module then triggers a relay which turns on a motor which turns a threaded rod which moves the manifold’s sliding carriage to position it over the inlet for the tool that was just turned on. Six reed switches - one each attached to the blast gate inlets - are connected to GPIO pins on the receiver module. A magnet mounted to the sliding carriage closes each reed switch as it travels. When the ESP8266 sees that the reed switch for the desired GPIO pin has been closed, it 1) deactivates the relay that’s supplying power (or ground) to the positioner motor, 2) activates a relay that turns on the dust collector, and 3) Turns on a green indicator that can be seen throughout the shop, indicating that the dust collector is on and the proper blast gate is open.

If that’s not the right way to do things, please let me know what the right way is.

Things I need guidance on:

  1. Because I have zero experience with microcontrollers and GPIO pins, I’m not exactly sure what the microcontroller expects to see on a GPIO pin in order to know that some trigger just occurred and some action must be taken. Does it want to see voltage? Ground? A particular frequency?
  2. The “sender modules send “Power ON” ad the machine ID to the receiver module when current is sensed. What’s the simplest/cheapest way to detect the current from a motor turning on and use that to trigger the GPIO pin?
  3. Again, because I have no experience programming a microcontroller, how do I tell the microcontroller to ignore the (momentarily) closed reed switches from the other manifold inlets as the carriage/magnet travels by reed switches 1, 2, and 3 to get to the desired (#4) position?
  4. Anything else I’m overlooking?

Thank you for your time and consideration.

Parents

  • Hello 

    That is a relatively complex project for someone new to microcontrollers but doable with effort.  The best advice I can give is to break it into pieces and prototype each step before proceeding to a final build.  There are others on e14 that are more knowledgeable than me on this topic but here are some thoughts:

    • As usual, there are lots of ways to approach this and do it - what I've listed below are ideas and not necessarily the best recommendations for your project.
    • I'm going to assume you will use an Arduino compatible board as there are lots of libraries and references on the internet to do the sort of things you have outlined
    • Regarding your question1):  Most microcontrollers including at least some versions of the ESP8266 have one or more ADC pins (a means to convert an Analog signal to Digital).  This is necessary for some of the sensors discussed below.  Arduino compatible microcontrollers also have digital input - that is they can tell if a signal is high or low (i.e. something close to GND or something close to the operating voltage - either 3.3V or 5V - that the microcontroller can handle).  Microcontrollers can also handle certain digital serial communication protocols which some sensors output.  None of the sensors I'll mention below output frequency or use serial communication.  Some industrial sensors use a 4-20mA output.  The answer to your question 1) above is that it depends on the sensor.
    • Regarding your question 2):  I'm going to exclude industrial 4-20 mA sensors but you can have a look at them.  They are generally more expensive and less common in DIY projects.
    • Regarding your question 2):  One approach is to use a Hall sensor.  See for example my review of the Infineon TLI4970-D050T4 here.  You can find many more boards with this type of sensor with an internet search of "hall current sensor".  These sensors are invasive in that they must be wired in series with the load/machine.  They require an ADC and can determine the actual current value.
    • Regarding your question 2):  I'd probably look at a non-invasive current transformer sensor first, e.g. this one from Seeed.  They require an ADC and a fairly simple voltage divider and DC offset voltage to get it in range.
    • Regarding your question 3): In addition to a reed switch, you might also consider a Hall Sensor and magnet, e.g. the Rohm Hall BD7411G I reviewed here which outputs a high or low voltage to indicate proximity.  There are many others available.
    • Regarding your question 3):  All microcontrollers have timers so it is a simple matter of timing how long the GPIO pin is high (or low depending on the logic/wiring used).  If the hall sensor or reed switch is only in the on state for less than say 1 second or however long it takes to move to the next opening then you know to ignore it.

    Hope this helps.  Again, my advice is to break this into manageable pieces.  You will more likely get engagement here on e14 with smaller chunks as well.  Maybe start with sensing current, choose an inexpensive sensor, see how it works, and make another post if there is an issue.

Reply

  • Hello 

    That is a relatively complex project for someone new to microcontrollers but doable with effort.  The best advice I can give is to break it into pieces and prototype each step before proceeding to a final build.  There are others on e14 that are more knowledgeable than me on this topic but here are some thoughts:

    • As usual, there are lots of ways to approach this and do it - what I've listed below are ideas and not necessarily the best recommendations for your project.
    • I'm going to assume you will use an Arduino compatible board as there are lots of libraries and references on the internet to do the sort of things you have outlined
    • Regarding your question1):  Most microcontrollers including at least some versions of the ESP8266 have one or more ADC pins (a means to convert an Analog signal to Digital).  This is necessary for some of the sensors discussed below.  Arduino compatible microcontrollers also have digital input - that is they can tell if a signal is high or low (i.e. something close to GND or something close to the operating voltage - either 3.3V or 5V - that the microcontroller can handle).  Microcontrollers can also handle certain digital serial communication protocols which some sensors output.  None of the sensors I'll mention below output frequency or use serial communication.  Some industrial sensors use a 4-20mA output.  The answer to your question 1) above is that it depends on the sensor.
    • Regarding your question 2):  I'm going to exclude industrial 4-20 mA sensors but you can have a look at them.  They are generally more expensive and less common in DIY projects.
    • Regarding your question 2):  One approach is to use a Hall sensor.  See for example my review of the Infineon TLI4970-D050T4 here.  You can find many more boards with this type of sensor with an internet search of "hall current sensor".  These sensors are invasive in that they must be wired in series with the load/machine.  They require an ADC and can determine the actual current value.
    • Regarding your question 2):  I'd probably look at a non-invasive current transformer sensor first, e.g. this one from Seeed.  They require an ADC and a fairly simple voltage divider and DC offset voltage to get it in range.
    • Regarding your question 3): In addition to a reed switch, you might also consider a Hall Sensor and magnet, e.g. the Rohm Hall BD7411G I reviewed here which outputs a high or low voltage to indicate proximity.  There are many others available.
    • Regarding your question 3):  All microcontrollers have timers so it is a simple matter of timing how long the GPIO pin is high (or low depending on the logic/wiring used).  If the hall sensor or reed switch is only in the on state for less than say 1 second or however long it takes to move to the next opening then you know to ignore it.

    Hope this helps.  Again, my advice is to break this into manageable pieces.  You will more likely get engagement here on e14 with smaller chunks as well.  Maybe start with sensing current, choose an inexpensive sensor, see how it works, and make another post if there is an issue.

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