I thought I'd give an update.

I added four .470 capacitors in paralel, but the gun was still turning itself off. Then I added the diode, and.. it worked! The gun remains stable.

...at least.. while it was on a beefy lab power supply. It indicates that when firing the gun uses about .6 amps, and it prefers to be around 8.5 volts (6 AA batteries). 9 volts seems to be too much.

I tried to switch it to the intended portable design, with a USB PD decoy feeding into a 4A up-down adjustable buck converter.

But then it crashes again.

For example, I tried this:

• 55W steam deck USB-C PD power supply ->
• adjustable decoy set to 15 or 20 volt.
• down-converting that to 8.5v with the buck converter.

Maybe all this power converting means that it can't provide the sudden increases in power when the motor spins up?

Perhaps using a linear DC-DC converter work better? Or maybe the USB-PD decoy just can't handle it? It's a mystery.

Thanks. I'll look into it.

@ejlane Could a resistor be used for that?

I think capacitors with a blocking diode would be the right call..

Cool!

That calculation clears up so much. Really great explanation, thank you!

It seems a diode is needed either way.

The power supply runs both the Arduino the blaster itself, which means the two motors it uses. One motor spins the barrel (purely as an optical effect), and other one actually shoot out the darts.

for a hobby level project maybe simply going 10x for a few pennies more would be a good idea

Glad to hear that (other than cost) there is no problem with using a way too big capacitor. That also simplifies building up a stock :-)

So I have this huge NERF gatttling gun that I was trying to have some fun with. I wanted to be able to lock or unlock the trigger remotely based on face recognition, which is handled by a mobile phone at the front of the gun.

The problem I ran into is that whenever the gun's motors spin up then cause a power loss to the arduino. Now I could add a separate power supply for the Arduino, but it would obviously be much cleaner if it looks like a normal gun from the outside.

So I figured I needed some kind of "electrcity buffer" that would continue to provide the Arduino with stable power whenever the motors spin up.

I realised I know very little about capacitors.

• Which type do I need? Some are "aluminium high frequency". Are motors high frequency? Should I get those? Do they charge up faster?
• Is there any risk that a capacitor makes the situation worse? E.g. if it's empty and it sucks up electricity that should be going to the Arduino?
• Some go up to 400 volts. Some seem a perfect match at 5.5 volts. How do you choose what voltage rating to get? Is there a trade-off? Is it wise to go a few volts above the voltage in your system?
• I figured I wanted as many Farads as possible? So I found these capacitors with 4F. But I realised I have no idea if that's a lot. How can I compare it to, say, batteries? How long can a 4F 5.5v capacitor run an Arduino nano + radio?
• Is there a downside to having a lot of Farads, other than the cost?
• How do I make sure the energy in the capacitor is "reserved" for the Arduino? After all, the motors are on the same circuit, and could perhaps suck it dry instead?

Incredible. The "yeah it's a hobby" terrain has been left far behind.

If you want the latest developments if this addon, please use the Candle Controller instead of the Webthings Gateway. Candle is a fork of Webthings that I also work on. Going forward it's your best bet for updates.

https://www.candlesmarthome.com

I used MySensors to create a privacy friendly smart home demonstrator called Candle. Quite a few people are building it, but they may not even realise they are using MySensors.

In this project my own attention certainly has shifted a bit. Cheap Zigbee dongles and devices aid my goal of moving Candle in a more consumer friendly direction, so that people could just buy most of the parts ready-to-go, and still keep everything local. Some devices will still be MySensors devices, simply because there aren't any privacy friendly alternatives that I know of. But a temperature and humidity sensor, those use Zigbee for me now. And I'm moving the privacy features from the arduino code into the central controller instead.

Speculation about other factors:

• Practical Arduino hardware education isn't happening right now because of covid. And even there, there are so many hardware options now. Microbits, ESP32, etc.
• I've also noticed people asking about standardisation, and caring about interoperability.
• There are many more products available now. Edge cases are being catered to, e.g. gardening.

Things that might help for me:

• I really wish there was a cheap, widely available Arduino akin to the RF-Nano, but with RFM69 433Mhz. MySensors has always had range issues for me on 2.4ghz.
• The MySensors implementation doesn't make it easy for devices to describe the UI they would like. E.g. if a device is read-only or toggle-able is currently dependent on the type, instead of being a factor that can be set for each sensor type independently.

A new website with a strong focus on new users, USP's (cheap privacy & friendly, or just fun, educational and artisanal) and up-to-date examples might help.

This all may sound critical, but that's not the intention. I really dig MySensors. It's definitely in my toolbelt.

I've also used them both. Now I'm a very happy Webthings Gateway user. Try it!

[edit by nca78] fixed link, should be without www.

Perhaps this code is of interest to you. It's the Candle plant health sensor. It's got all the bells and whistles you could want, including optional support for automated irrigation.

One thing you'll notice in there is that the capacitive moisture sensors output voltages between 0 and 3. So in @rvendrame's code you may have to change the 1023 to 650, and also make sure no voltages higher than that would lead to percentages above 100%.

      int16_t moistureLevel = analogRead(analog_pins[i]);
      Serial.print(F("raw analog moisture value: "));
      Serial.println(moistureLevel);

      if( moistureLevel > 650 ){moistureLevel = 650;}
      moistureLevels[i] = map(moistureLevel,0,650,0,99); // The maximum voltage output of the capacitive sensor is 3V, so since we're measuring 0-5v about 614 is the theoretical highest value we'll ever get.

I notice in your code that the title Analog Soil Moisture Sensorx3 is too long. It can't be longer than 25 characters.

Wait, wait.. what is that USB stick with the dual antennas? Is that a dedicated MySensors gateway device?

// Ah, it's project Janus. AWESOME!

What @wiredfrank said. Don't use these unshielded PA device in the first place.

I have a MH-Z19B CO2 sensor (as part of the Candle system).

In the logs I see some strange sudden jumps between measured levels.

I don't think it's an issue with the code.

Could this be related to an internal re-calibration of the device somehow? Has anyone else seen something similar?

Or maybe the sensor is just dying?

There are also some very cheap usb-stick size SSD's now. Now sure about the long term quality, but it's.. interesting.

This 64Gb one is 15 dollars including shipping

This 128Gb one is $20.

Finally, this Kingdian one seems very popular. It's $30, but is a bit faster.

Thanks for the advice @skywatch! You're right about the distance increasing, for sure. Then again, if the voltage drops from 12v to, say, 10 volt, would that matter? The Arduino itself will still bring it down to 5, and it can handle anything between 6 and 12 as an input on the jack plug?

What do you mean with running it in a loop? Where could I learn more about that?

Has anyone bought a PineTime by chance? They are really progressing quickly, with OTA support and everything.

@dzjr I had a look at your list, and as I read through it I realised that the Mozilla WebThings Gateway really needs P1 support. So I created an addon for that.

It might make the Mozilla WebThings Gateway an option for you, although it doesn't support all the things you asked for (DMX, Modbus, APC USB).

It does have great usability, privacy friendly local voice control, and of course MySensors support.

Thanks! Ethernet cable is a great idea (since it's also used for power over ethernet it makes sense). Unfortunately I've already been donated some speaker wire. It's gauge is larger than ethernet, and it's made of copper, so I think it should be ok.

Thanks. But my apartment is only 10 from front to back. I thought that if I place the power source in the middle, then the maximum distance to an endpoint is about 5 meters. The same as the maximum length of USB extension cords.

Would you still recommend against it for those lengths?

@sincze did you manage to create a nice sketch to read out a P1 device? I'm looking for such a sketch.