Control your popcorn making from a world away
In this tutorial we will go through the build process of creating an internet connected popcorn machine with the TI LaunchPad ecosystem and off the shelf parts. The Internet of Things is an exciting subject because it encompasses the possibilities of taking many applications which are analog or mechanical in nature and connecting them up to the internet to create new life and ''intelligence'' for tired products. We can do a demonstration of this magic using a fairly innocuous device, the classic popcorn machine found in movie theaters and homes everywhere.
A popcorn machine is a device that is purpose built for the job of popping corn and in the case of a movie theater popper, storing it for later consumption. Popcorn making is a relatively simple exercise. Special popping corn kernels are the key ingredient and are easily bought off the shelf. These kernels, unlike regular corn kernels, are able to be popped when proper heat is applied. This is due to a small amount of water stored insides that heats up and the steam forces the inside of the kernel to expand out, creating the popped corn. Heat can be applied in a number of ways and you can pop corn using a stove top pot, a microwave oven, a hot air popper, and a kettle. The movie theater popper uses a kettle that is heated up with an electric heating element. Using cooking oil (a popular one is coconut oil), the inside of the kettle can get nice and hot and the popcorn can quickly pop out. Inside the kettle is a stirring mechanism to make sure the heat and oil gets distributed across the kernels. The stirrer is powered by an AC motor at the top of the machine.
For this project, we will need to identify the things we can control. In this case we have the heating element, the stirring motor, and a light bulb to illuminate the inside of the machine. All of these components use AC power, which comes from the wall outlet. For high voltage control such as 120V AC, we can use a relay to trigger each component on and off with our LaunchPad. We could keep the light bulb, but LEDs are much more fun and functional! We will mount RGB LEDs on the inside of the case that can act as interior lighting as well as flash in patterns to give us visual indications of the machine state. There are other things we can add to the machine to make it a bit cooler or more functional. We can easily add a temperature sensor to give us the temperature inside the machine or we can add a display to give us visual information like status messages. An audio source would also be a good addition to turn our popcorn machine into a jukebox or at the very least give us audio indicators about the machine’s status.
For an IoP machine, we would like to automate as much of the cooking and serving process as possible. The kettle has a tipping mechanism to help empty popcorn and unpopped kernels into the serving area. We can add a servo mechanism that utilizes a string and pulley to help us pull the handle that tips the kettle. We also want to add a way to automatically feed kernels into the kettle. We can modify the machine to add a hopper system that will allow us to feed new kernels for each batch of popcorn.
Lastly, we’ll need to add an internet connection to our machine so we can control it while on the couch or at work before we head home. We can do this using the CC3100 Wi-Fi device.
Here is the list of materials we will need for this endeavor. Most can be ordered online, but we also need to make a run to the local hardware store. You will also need your tool box handy, the required tools can cause additional cost if you don’t have them. Keep in mind this list can change depending on what features you want to incorporate into your machine.
BOM (Total Cost: ~$400)
Energia IDE: Free!
1x Popcorn Machine (Funtime 8oz Popper): Amazon $165 + free shipping
1x MSP430F5529 LaunchPad (MSP-EXP430F5529LP): TI $12.99 + s&h
1x CC3100 BoosterPack (CC3100BOOST): TI $19.99 + s&h
1x Grove BoosterPack: Seeedstudio $7.50 + s&h
2x Grove Relay: Seeedstudio $2.90 + s&h
1x Grove Temperature & Humidity Sensor: Seeedstudio 14.90 + s&h
7x Olimex 8x8 LED Matrix (MOD-LED8x8): Mouser $9.13 + s&h
2x NeoPixel Digital RGB LED Strip: Adafruit $24.95 + s&h
1x Continuous Rotation Servo: Adafruit $14.00 + s&h
1x Standard Servo: Adafruit $12.00 + s&h
1x Micro USB Cable: Free with LaunchPad
1x USB wall plug: included with many electronics products
1x AC Socket plug
Velcro Industrial Strength
With Energia, we have so many options for an MCU. Which one do we choose? Since this is a pretty complex project with multiple subsystems being connected to the LaunchPad, we’ll need something with higher performance and good access to the pins. While the CC3200 LaunchPad would be a good choice with it’s integrated Wi-Fi capability and 80MHz ARM M4 core, it doesn’t quite have enough pins to handle our requirements. Since we know from experience we’ll have an easier time with supported libraries that run on MSP430, we decided to go with the MSP430F5529 LaunchPad. This LaunchPad offers a good balance of low power consumption + performance and gives us the pin access we need. If we pair this LaunchPad with the CC3100 we’ll have the perfect processing solution for this IoT project.
The popcorn machine has two primary electrical components, the heating element for the kettle and the motor for the kettle stirrer. These components are AC driven, meaning they can be powered directly from the AC power coming from a wall outlet. In this case we have several options to control an AC circuit with a DC microcontroller. The most popular are Relays and TRIACs. A common example of a relay is a turn signal in your car. The relay turns the signal light on and off and makes a clicking noise when the switch flips. The noise is caused by the mechanical part of the relay. You may have used a TRIAC if you have a light switch in your home that is dimmable. The dimming function is enabled by the TRIAC in addition to turning the light on and off without a mechanical clicking noise. Depending on your application, relays or TRIACs may be better suited. In this case, we just need a binary on/off switch for our kettle and motor so we will go with relays. Thanks to Seeedstudio, there are some nice 3V Relays available as Grove Modules that pair well with the Grove Base BoosterPack for LaunchPad. To control the relay, we can simply digital write to the appropriate pin in Energia.
We made some small mechanical modifications to our machine so that we could attach the relays. There are many ways to go about this. What we did was buy some short AC cables and splice into them. This allows us to hook up the relay and easily connect to any open AC plug. Since AC power is very dangerous to the touch and you should use caution and safety as much as possible when building electronics, we used a plastic enclosure to cover the relay and the exposed leads. To be extra safe, never plug in your popcorn machine until you are ready to test and avoid touching any internals when the machine is powered on.
The Grove Base BoosterPack is not only nice for hooking up multiple Grove modules like we do in this project, but it also is nice connection point for our other components to our LaunchPad. We can use the Grove connectors to hook up our LED strips and servos which just require one signal pin, VCC, and GND. The BoosterPack will help us maximize our VCC and GND buses so we don’t run out of pins hooking up all this stuff! You can use standard jumper wires with female ends to hook up to the Grove Connectors. The connections can be a little bit loose since they aren’t the exact same size, but they do work together.
Adding audio cues is a fun additional feature we can add to make the popcorn machine just a little more interactive. A boring but effective way to do this is to use a traditional Piezo buzzer to play tones when different actions are happening. We can step up our game a little more though with a little analog magic and add voice to our LaunchPad! You can check out this tutorial here on the basics of how to accomplish this in Energia using WAV files. You can also add MIDI Music with this tutorial (Credit: Simon Field). We can now add voice announcements at different stages of the state machine using analog write to the appropriate pin in Energia.
For a speaker you will want to get one that is reasonably sized. We had a spare lying around from another project. We will not be able to hear very well using the LaunchPad as the primary driver (3V or 5V) so we will need to add an external power supply (9V) and a transistor or FET.
You can also incorporate a piezo buzzer to act as another type of audio indicator. We used the Grove Buzzer to beep when modes are getting changed or tasks complete. Audio can be tricky as it can require some creativity to make it sound good. It can also be hard to amplify the audio to be audible in a noisy environment. Having some type of basic audio does give the machine an improved user experience.
A hopper will make it that much easier to load in our popcorn and oil into the machine. There are two options to create a hopper, electronic or manual. For a manual hopper you basically are using gravity and a funnel to get your ingredients to the kettle. For an electronic hopper, we can use a value that can be actuated by a servo or motor. This can be tuned to pour the right amount of kernels through the system. Finding a valve that will be easy to turn with a servo is not easy. During our build we did not successfully find a good valve using PVC piping. We then decided to try a manual hopper using PVC but did not quite find the best way to mount it, so we decided to postpone this subsystem for a future upgrade. It can be easily done using PVC pipe or other common tubing and you will need to find a way to prop open the kettle lid to receive incoming kernels and oil.
As a way to make the entire process more automatic, we can create a basic electronic pulley system to help us tip the kettle and empty out any contents. We will need some string, a small pulley, a spool to attach to our servo (we used a solder wick spool), and a continuous servo (some are restricted to 180 degrees, we want 360+). The first step is to attach the spool to your servo. Use super glue to glue the spool to one of your servo attachments like the cross or circle. Let that dry for a while. Next tie the string to the kettle handle and thread through the pulley system to the top of your machine. The string will be retracted around the spinning spool, pulling the handle which will tip the kettle. You will need to tune your servo code to determine how many rotations are needed to tip the kettle and not go beyond that range.
On the software side, we will use the Servo Library. You will need to know your timing to complete the operation. This can be found out through trial and error. In industrial settings, they use a timing belt, which has a predetermined length that can provide consistency in a repeatable operation.
When building the kettle tipping subsystem using the servo, we had some trouble getting it properly calibrated. It takes quite a bit of torque to tip the kettle and servo would skip at the apex of the operation. It is recommended to use a stepper motor instead so that the operation can be more exact and repeatable. However, it may be possible to use the servo method, we just didn’t find an easy way to incorporate it, so we will add the stepper motor to a future upgrade.
The popcorn machine comes with a light bulb to help illuminate the interior and maybe double as a heat lamp. We can improve the cool factor of our machine by adding RGB LEDs to act as interior lighting. First we remove the lightbulb fixture to give us more room. There are many ways to mount LEDs inside of a project. You can use custom PCBs, wires, conductive ink, copper tape and more. We’ve elected to use NeoPixel LED strips for a nice and clean solution that we can mount to the top of our machine. NeoPixels are nice because they have an LED driver built into the LED so all we need to do is send signals from our microcontroller. One of the challenges of working with NeoPixels is they require very specific timings from the microcontroller, so just because your Energia library works on an MSP430 doesn’t mean it will work easily on something else.
To prepare your strips you will need to cut to size and then solder some hookup wire to the data in (DI) side of the strip. These pads can be tricky to solder correctly, make sure you properly separate the three wires and add a bit of solder to each of the pads before you solder the wires on. Once this is done you are ready to mount them. You can either super glue the LED strips or use some kind adhesive that can stand the residual heat from the kettle like double sided tape or Velcro. In our build we used Velcro that we super glued to the LED strips to have a tight connection but still gives us the option to swap out our LEDs at a later time. Line up your data in (DI) side with the holes in the top so you can thread more hookup wire to your LaunchPad sitting on top.
For a nice way to display text that can be seen from far away, we can add an LED sign to the front and back facade of the machine. This has a number of benefits because it is cheaper than an LCD screen, we can create a large display that can be seen and read at distance, and it is not too complicated to program. There are definitely cases where an LCD screen makes more sense and provides a better user experience, but for this machine, an LED Matrix will be more than enough. Using Velcro so we can dismount and replace as needed, we attach Olimex 8x8 LED Matrices to the front and wrap hookup wire around to the interior. It’s actually a perfect fit and mounts very cleanly. For our machine we were able to mount 7 8x8 LED sections across the top and very easily wire it to the LaunchPad inside.
The matrices we used have 5 pins: GND, DATA, LATCH, CLK, VCC. We use the 3.3V VCC from our LaunchPad to power the modules.
It could be nice to know the temperature inside of the machine. Perhaps you popped corn but now the machine has cooled down or maybe you made a lot and the temperature is quite hot inside and you need a warning to not over do it. We can add a simple temperature and humidity sensor Grove module that can drop down through a hole in the top to help us measure the internal temperature.
On the software side we can use the sample code provide by Seeedstudio which can be found on their wiki and Github.
To add Wi-Fi to our machine, we will use the CC3100 BoosterPack. This pretty much gives plug and play Wi-Fi capabilities to our LaunchPad. Using the WiFi library in Energia we can easily get connected to a local hotspot and then access any number of cloud APIs. To make our tasks super simple, we are going to use Temboo. Temboo is an API aggregator and can help act as a glue for IoT, giving us access to many popular web services. For control we can do a variety of things. Maybe we can have it be text operated using SMS or maybe we can tweet at it. This time we’ll set up a dashboard on a web page hosted on the LaunchPad. When we access this page, we can issue commands to the machine via click buttons in the browser. In this scenario, we’ll have be connected to the same Wi-Fi hotspot as the IoP Machine.
We are able to query the server for a wide variety of information. We can pull down the latest weather information, get the date and time and a number of other things. We will query the server for a time stamp and then use our real time clock locally to keep the time so we don’t need to keep pinging the server. When we aren’t popping corn, we can use the display to share tweets, stock information, or any other real time information that might be interesting.
You can find the demo code on github. If you’ve set up your machine like ours, it should just work. If not, you will need to debug each subsystem separately.
Check out other tutorials at www.energia.nu/guide!