What did you build today (Pictures) ?

[NeverDie]

@OldSurferDude said in What did you build today (Pictures) ?:

@NeverDie It is my understanding, though I can't wrap my head around it, that it is the length of the conductor that makes the antenna tuned to a certain frequency. If this is the case, you could run your antenna around the edge of your circular pcb which would make the effective radius only slightly bigger.

You mean like this?

I get the impression that somehow the antenna positioning relative to the ground plane might figure into it as well:

Perhaps that stands in the way of wrapping the antenna completely around the circumference? I can't claim to have any deep understanding of how antennas are supposed to be designed. In the past I noticed that TI sold a sample set of canonical antenna designs, so then you could try them all out and see what suits you: https://www.ti.com/lit/an/swra161b/swra161b.pdf?ts=1661617962454&ref_url=https%253A%252F%252Fwww.google.com%252F

[OldSurferDude]

@NeverDie That isn't what I was thinking but after a bit of research, that's better than what I was thinking. ;)

PCB antennae work better at > 868MHz(pg 7). A 2.4GHz signal should have an antenna length of 3.1cm The nRFl01 spec shows a PCB with an antenna that is about that length but I measure the board I have and the antenna is about 4.6cm(?) Here(pg 10) you'll find a design, though I'm not sure for what frequency as the length adds up to 4.03cm. As you can see, you must not have the ground plane near the antenna.

Here, RonM9 modifies an nRF24l01 making the antenna a dipole. I tried this and did show some improvement, but not the success he had. His wires were ~5.0cm, but bends them in the opposite directions at the edge of the pcb. Does that make the antenna length about 4cm?

The antenna for a longer wave length (lower frequency) will be proportionally longer.

I'd like to do the same testing as RonM9, but I've got some other pressing projects. ;)

I hope this helps your research.

OSD

[berkseo]

Now this project looks like this:
https://www.instagram.com/p/CkikRzAtECe/?utm_source=ig_web_button_share_sheet

[monte]

From left to right:

• Home Assistant server with built-in NRF24 radio and OLED display based on Orange Pi Zero
• MQTT Mysensors gateway with ESP8285
• 4 channel triac dimmer with oled display and UI for operating in standalone mode.

[TheoL]

@monte do you have a schematis for that dimmer? If so I'm interested in it

[monte]

@TheoL there is nothing special in it :) In fact it's an old design that was waiting for the code to be written for a long time. And there are some issues with it. It seems that external interrupts for zero-crossing make NRF24 ACK fail most of the time. And if I were to make another one of this, I would add some low cost mcu to do the dimming part alone. I have dimmers with EPS8266 that uses Attiny13A for triac control, but I wouldn't try to make it control 4 channels.

Also the time of Atmega328 has passed, I guess. They are marked "Not recommended for new designs" by the manufacturer and I have struggled to fit everything I wanted (UI mostly) in it's memory. I ended up disabling serial output in mysensors and everywhere else, decreasing message buffer size and scraping bytes everywhere else I could to make it work stable without crashing.
I'm not sure if I will continue to make new designs for mysensors, but I think I will use NRF51822, as they are so cheap now at aliexpress, and you can add PA LNA to help with signal strength (theoretically, I haven't tried it). Another way is to use NRF52840 for all new designs, even they are 4-5 times more expensive than 51822 but later you can write a firmware for it to use Zigbee of Thread/Matter and use the same design with new functionality.

[TheoL]

As much as I love the 328 I think I should make the change to a different board :) for me they fit my needs as I try to keep the logic in my nodes as small as possible. I have one rule though: Manual first, for actuators my nodes need to support manual control.

Thanx for the schematics, I'll have a look at. Can you control led light bulbs with this schematics?

[monte]

@TheoL this is a basic triac control scheme, so it is leading edge type dimmer. I have led bulbs, that work with it, but they are clearly marked as dimmable. The downside of these bulbs is that they are very sensible to the slightest voltage fluctuations. I have not the most stable voltage on one of my phases, so it is very visible, unlike with the incandescent bulbs, that are connected to the same power source.

[TheoL]

@monte I had a gut feeling about it, since dimmable led bulbs like trailing edge. I'll keep looking for a good 220v led bulb dimmer schematic.

[monte]

@TheoL that's not the dimmer's fault a far as I am concerned. It behaves the same way at full brightness. It's just a cheap chinese driver in it.