Category: Arduino

Packaging Arduino projects

I made a post over at the popular Arduino forum on a topic where someone was inquiring about available enclosures. The community tends to respond “just 3D print one” but that’s a mistake in my opinion.

3D printing, while useful, seems pointless to me unless you’re looking for something not available off the shelf. Even then, the 3D print falls short if you need a transparent cover, or a NEMA4X /IP66 (washdown-proof) rating, or any number of other structural properties. That off the shelf $20 polycarbonate case has a lot of engineering time put into it and provides a huge amount of convenience.
As far as laser cut enclosures are concerned, I’ve yet to find one that doesn’t look completely ugly like something a 6 year-old put together for a craft class.

Seriously, burnt wood edges is not a professional look! I have seen professional enclosures for large machines made out of wood and particle board and you’d never know what the material was. When designed by an engineer who knows what he’s doing, wood can be a fantastic material.

The amateurish laser-cut “snap together jigsaw cases” all look like crap in my opinion. And that’s a pity, because you can do some great stuff with a laser cutter. It’s just that the community has apparently decided to embrace the lowest common denominator design quality.

My gotos for great cases are Polycase & Bud for plastic wall and desk mount enclosures. Polycase is great for getting your enclosures custom modified (cutouts, slots, custom printing, etc.) at reasonable prices. I also like Hammond for metal enclosures (although Bud has some nice aluminum cast boxes). Serpac or OPC for handheld/belt mount types. Altech for industrial enclosures with electrical knockouts (although Polycase is now carrying those also).

A few links:

Polycase https://www.polycase.com/

Bud https://www.budind.com/plastic_boxes.php

Small Hammond enclosures. I like these for Arduino Nano since they fit nicely and the 1551 enclosure comes in many versions http://www.hammondmfg.com/dwg9.htm

You can find these and many, many more enclosures for sale at my favorite electronics distributor, Digi-Key. Note that Amazon also carries many electronics enclosures, but I haven’t found enough of a price difference to offset not having reliable datasheets.

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Arduino Actuators

An actuator is a device that produces a mechanical action. That’s the generic description, but when people mention “actuator” in conjunction with Arduino, they will typically mean a linear actuator.

However, as we’ll see, there is much more to the actuator “family” than just the linear types.

Probably the easiest actuator type to use with Arduino is the R/C servo motor. You can connect them directly to an output pin since they have their own internal electronics.

Anything else: solenoid, linear actuator, etc., usually will require an external driver and more wiring. Although there are some linear actuators that have the same connections as servos.

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DF1201S MP3 PlayerPro & Arduino
One of my uses for this blog to is to record useful information that I (and others) might need later. This is about an annoying problem I ran into.

I’ve used the DfRobot Player Pro a couple of times in “stand alone” mode. It’s a great audio player: small, cheap, and easy to use. It also has a serial interface so it can be controlled by an arduino or microcontroller. DF Robot provides the DFRobot_DS1201S library to make this easier. However, all the examples I see online are using the playFileNum(num) command that takes an index of a file (MP3) to be played. The problem with this is that the file index depends on the order in which the file file was stored to the Player Pro’s Flash memory.

There is also a playSpecFile(String) method that takes a filename, which you’d expect is much easier and would be more popular. However, when I tried using it, it always played the same song. OK, time to debug. There is also a method in their library to retrieve the name of the currently playing file. However, when I use code like this:
```
// Play file
DF1201S.playSpecFile("one.mp3");
// Print name of file that's playing
Serial.println(DF1201S.getFileName());
DF1201S.playSpecFile("two.mp3");
// Print name of file that's playing
Serial.println(DF1201S.getFileName());
DF1201S.playSpecFile("three.mp3");
// Print name of file that's playing
Serial.println(DF1201S.getFileName());
```
It always plays the same song and to boot, I get Chinese characters displayed for the file name. Clearly, not what I was trying to play.

However, make a minor change to the filename and this works.
```
// Play file
DF1201S.playSpecFile("/one.mp3");
// Print name of file that's playing
Serial.println(DF1201S.getFileName());
DF1201S.playSpecFile("/two.mp3");
// Print name of file that's playing
Serial.println(DF1201S.getFileName());
DF1201S.playSpecFile("/three.mp3");
// Print name of file that's playing
Serial.println(DF1201S.getFileName());
```
This plays three different songs correctly and their filenames are reported accurately.

HTH everyone who’s run into the same problem 🙂

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Arduino Programming: About time

Time is probably the most commonly controlled process variable. Timers are all over the place in industrial control. Odds are, if you need some type of timer, no matter how strange, you can find it off the shelf.

Now, many of these timers used a chip usually referred to as the “555.” The LM555 originally made by (I think; someone will correct me) National Semiconductor was a very versatile device, but it was at the heart of many time-delay relays, short timing circuits, etc.

So once upon a time, if you wanted to build a basic timer, odds are you would wire up a 555 into a circuit. To build a handful, or just one, you’d use a perf board,

maybe you might use wire wrap or even dead-bug construction (my favorite!)

It would be time consuming,but maybe you had no choice because the timer had some weird requirement that no off the shelf timer had, or needed to fit into an oddly shaped space.

What does this have to do with Arduinos? Well, you can program any timing sequence into an Arduino. Say you want the heater on a commercial ironing board to come on for five seconds when the operator lowers it, a 555 does it easily. If you want the heater to come on for five seconds and when the board is raised again, a fan to blow for 10 seconds to cool the clothing, the 555 can still be used. Maybe you need two of them. But now, the Arduino becomes an easier solution. Whether you need one time sequence, or dozens, a single Arduino can be programmed to do it. When you factor in the labor of wiring a circuit board with the 555, the low off the shelf price of the Arduino makes it even more attractive.

This is the wonder of the time we live in: an off the shelf microprocessor board is now inexpensive enough to be used for logic replacement.

Amazing

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Arduino Programming: Turn water on with Arduino and solenoid valve
Arduinos are popular small microcontroller boards that have many applications. However, they’re not designed to switch loads above a few milliamps: say a couple LEDs or so. While power-driver shields do provide this capability, they also can consume more resources than you may be able to give up.

We developed a high current driver to make it easy to control a solenoid valves with Arduino. It will also control pumps and motors. With an adapter cable, it can easily connect to your Arduino, BeagleBone, Raspberry Pi or other digital controller without soldering or crimping any connections. Doesn’t get any easier than that.

The power driver board was born out of a need for controlling a 1 amp solenoid valve using an Arduino. The solenoid valve was being used to control the water flow to fill a tank automatically. Now there’s a simple way to use your Arduino or compatible to switch up to 3A at 24VDC. Two output connections (the white wires shown above) connect directly the load (your solenoid, relay, motor, etc) and the power (red, black) go to the power supply (5 -24 volts). The orange lead is used to switch on and off. This is a low-voltage (5V) control that can connect directly to a microcontroller, or development board. An onboard LED indicates when the load is switched on.

Here’s some sample code that implements a timer with an Arduino. When the pushbutton is pressed, it turns on water flow for 3 seconds
```
// This sketch demonstrates a simple timer
// A load (motor, solenoid, relay, solenoid valve is on Pin 1
// A pushbutton to trigger the timer start is on pin 2
//
// When the pushbutton is held down for more than 0.1 second 
// then released, the timer starts
// and times out after 3 seconds
//
// Timer is retriggerable: if pushbutton pressed 
// during the timeout period, timer restarts
//
// Constant definitions
#define LOOP_INTERVAL 10
#define TIMEOUT 300 * LOOP_INTERVAL
#define TRIGGER_INTERVALS 10
#define TIMER_INACTIVE -1
#define TRIGGER_PIN 0
#define OUTPUT_PIN 1

void setup()
{
  pinMode(OUTPUT_PIN, OUTPUT);
  pinMode(TRIGGER_PIN, INPUT_PULLUP);
}

void loop()
{
  static int count = 0;
  static int timer = TIMER_INACTIVE;
  // Process loop periodically
  delay(LOOP_INTERVAL);
  
  // Check trigger input
  if (digitalRead(TRIGGER_PIN) == LOW)
  {
    // Must hold down pushbutton for the entire interval and 
    // then release to trigger
    count++;
  }
  else
  {
    // push button released. Check if we should start timing
    if (count >= TRIGGER_INTERVALS)
    {
      // Turn output ON (timeout is retriggerable)
      digitalWrite(OUTPUT_PIN, HIGH);
      timer = TIMEOUT;
    }
    count = 0;
  }
  
  // If timer active, count down
  if (timer != TIMER_INACTIVE)
  {
    timer -= LOOP_INTERVAL;
    if (timer == 0)
    {
      // Turn output OFF
      digitalWrite(OUTPUT_PIN, LOW);
      timer = TIMER_INACTIVE;
    }
  }
}      
```
Let’s find out what new applications you can come up with.

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Don’t do what Donny Don’t does

Item #1: do not try to power motors from the Arduino 5 volt output pin. There, I said it.

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ChatGPT and Arduino

Unless you’ve been hiding under a particularly large rock, you must have hear of OpenAI’s chatGPT: a publicly accessible Artificial Intelligence that is surprisingly helpful. How helpful? Well, it can even be used to write Arduino code!

And that’s where the problems begin. For an experienced programmer, chatGPT is amazingly useful: it can produce custom versions of commonly-needed code in seconds. However, for a beginner, or a non-programmer, the downsides may outweigh the benefits. One of the problems with chatGPT-generated Arduino code is that it can be wrong in subtle, or even obvious ways. To someone who writes code for a living (like yours truly), these bugs are easy to find. For a neophyte, it looks fine and it’s not until they try to run it that it fails in mysterious ways. And worst of all, as good as chatGPT is at writing code, it’s terrible at debugging it. So if your Arduino code that chatGPT generated doesn’t work, you’re pretty much out of luck.

I’ve been getting more and more email from people in this particular quandary. They’ve tried using chatGPT to write code for their desperately-needed Arduino system, but it doesn’t work and they can’t figure out why.

Well, that’s why this site is here: we can fix the problem and write professional grade code that you can rely on, and best of all, it works 🙂

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Arduino time delay relay

I decided to build a time delay relay using an M5Stack unit.

Link to code

https://github.com/cedarlakeinstruments/M5-PeriodicRelay#m5-periodicrelay

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Program ESP32 without the Arduino IDE
I recently had to make a field upgrade to the software on some ESP32-based devices. I didn’t want to have to require that the operator go through the entire process of installing the Arduino IDE, download libraries, and all that not-so-fun stuff. For us techies, it’s no big deal. For a non-technical user who has tons of more important things to do, it becomes a royal pain in the butt.

So, what to do? From watching the IDE output, I could see that it called esptool.exe. A bit of research into this tool and it looked like the only problem we were likely to run into was figuring out which virtual COM port had been assigned to the device. Also, since there were a number of these units to reprogram, it needed to be efficient.

Enter the chgport command. chgport lets you change port settings, but for my purposes the most important part was that it lists the COM ports connected to the PC.

I could redirect the output from chgport to a file, then parse that file and supply esptool with the COM port of the device. After verifying this manually, I went forward and built this script.
```
set BOOT=PROGRAM.ino.bootloader.bin
set PART=PROGRAM.ino.partitions.bin  
set PROG=PROGRAM.ino.m5stack_core2.bin
set APP=boot_app0.bin

chgport > port.txt
set /p PORTLINE= < port.txt
set PORTNAME=%PORTLINE:~0,5%
echo %PORTNAME%

esptool.exe --chip esp32 --port %PORTNAME% --baud 921600 --before default_reset --after hard_reset write_flash -z --flash_mode dio --flash_freq 80m --flash_size 16MB 0x1000 %BOOT% 0x8000 %PART% 0xe000 %APP% 0x10000 %PROG%
pause
```
The name of the actual file programmed into the M5Stack device was replaced above by “PROGRAM.ino” Telling the IDE to save the compiled binary will put this file, along with the bootloader and partition configuration into your current working directory.

Next, you can see that we redirect the output of chgport to a file, then set a variable PORTLINE to the content of that file. The next line strips out the first 5 characters and stores it in the PORTNAME variable. This imposes an important requirement for using this batch script: the Arduino device must be the only, or at least the first, COM port in the file. It’s possible to work around this limitation, but it would require a more complex batch file, or perhaps even a Python script or similar.

Assuming we can successfully get the COM port, the next line calls the esptool with the necessary parameters and the device is programmed. I added a “pause” command so the user can see the result of the script before the window disappears.

There you have it. HTH!

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Ready to ship

I love it when a project comes together nicely.

M5 Stack has some really great hardware and made this project so much smoother. 12V input signal with local status displayed on screen and also communicated to App via BLE! All based on the M5Stack Tough units.

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