• RE: Most reliable "best" radio

    I think I may now finally understand the purpose of the optional S0, LENGTH, and S1 fields in the nRF52 packet frame. The datasheet gives very little insight into them, so I had previously disabled those fields just to avoid the topic altogether because it seemed so obscure. However, in trying to figure out how to send/receive packets between an nRF52 and an old-style nRF24L01+, the puzzle finally makes sense: they are there to either 1. provide a means of comparability with the nRF24L01's Enhanced Shockburst, which puts a 9-bit field in the middle of the frame:
    alt text
    or 2. allows you to roll-your-own super Enhanced Shockburst with extra bits (in which case standard nRF24L01P ESB compatibility be damned). Well, for a host of reasons, I think nRF24L01p compatability is worth enduring an extra 9 bits of airtime, so I'll go that route and configure the nRF52 accordingly now that I've inferred what those fields are meant for. 🤠

    posted in General Discussion
  • RE: Most reliable "best" radio

    @nagelc said in Most reliable "best" radio:

    Check out the Hammond 1551V1gY (vented) or 1151SNAP1GY (unvented).
    They look like they are about the same size. I've been using the vented ones for temp/humidity sensors. Not as ugly as most project boxes.

    @nagelc I ordered the white version of the vented model you referred to so that I can give it an up-close looky-loo. I also found an interesting "similar but different" vented enclosure from New Age Enclosures, though at twice the price, which I also ordered for comparison:
    alt text
    https://www.mouser.com/ProductDetail/789-P1A-151510
    With benefit of hindsight, maybe I should have started to look at possible enclosures from the get-go, because, depending on what's available, that may very well determine what form factors are even worth considering. 🤦 i.e. the project will end-up needing to fit the enclosure, probably not the other way around.

    posted in General Discussion
  • RE: 💬 backup power auto-switch circuit

    Thanks for posting the schematic. Just an observation, not a criticism: it looks as though the output voltage will sag down to the level of the logic-LOW threshold of your NOR gate before the battery voltage takes over. Depending on what the load is, maybe that's a non-issue. If, on the other hand, it turns out to be an issue, you could perhaps use a voltage divider to trigger the switch-over with less of a voltage drop seen at the load. In either case, I like the simplicity of the circuit. 👍

    posted in OpenHardware.io
  • RE: 💬 backup power auto-switch circuit

    @Abd-AlHaleem You have three options:

    1. Print it as a .pdf file. You can upload those; or,
    2. Compress the kicad file as a .rar file, but not a .zip file. That will also upload.
    3. Best option: Archive the kicad project (as a .zip file by default), and then compress that as a .rar file. That way you can upload the entire kicad project without it being rejected.
    posted in OpenHardware.io
  • RE: Most reliable "best" radio

    @nagelc said in Most reliable "best" radio:

    Check out the Hammond 1551V1gY (vented) or 1151SNAP1GY (unvented).
    They look like they are about the same size. I've been using the vented ones for temp/humidity sensors. Not as ugly as most project boxes.

    Good find! I like the vented ones, as it look like they would let out a lot of sound.

    posted in General Discussion
  • RE: Most reliable "best" radio

    Good suggestion on using a tic-tac container. It never would have dawned on me. Too bad I'm on a Keto diet, but I guess I could give the tic-tacs to my son, who doesn't need to diet.

    I may have spoke too soon that the nRF52 isn't sensitive enough to read the feedback voltage precisely enough. It turns out to have a 0.6v internal voltage reference, and it has a 12-bit ADC, so in theory it could measure in increments of as little as 0.6v/4096=0.146millivolts. Is that good enough? I really don't know, but I'm going to give it a try. The closer the piezo gets to resonance, the more the feedback voltage should shoot up. I'd be counting on it shooting up by a lot when it hits resonance. So, I just now uploaded the files to a fab for a PCB which can do those measurements, and hopefully I'll receive it in about a week. 🙂

    posted in General Discussion
  • RE: Most reliable "best" radio

    @Larson said in Most reliable "best" radio:

    @NeverDie said in Most reliable "best" radio:

    It would be nice if the system could self-calibrate the driving frequency to match the inherent resonance frequency of the buzzer.

    Perhaps an initialization User Interface selection? If the big picture is arranged and the region is only 5 Hz, then maybe a centeral default with an user option would be acceptable. Start slow, then rise in 0.25 Hz increments? If the user doesn't repond, then the default is mid-range. As in life, you can only help people so far. I think my mother tried to tell me that once.

    Caveat User (Emptor).

    You mean make it user selectable?

    I'm toying with the idea of an initial calibration using equipment not on the PCB. That's how I arrived at the optimal frequency on my prototype. However, it's unpleasant listening to the frequency sweeps. Even my wife complained about it, and she was in a different room entirely. The only upside is that it's sure to work.

    I found a good size for a shell, using a Govee temperature-humidity sensor:
    alt text
    It runs on a CR2477, so it has plenty of depth to it. Nobody seems to shell the shells though, and it would be a shame to canibalize their sensor just for the shell alone. I guess I'll have to 3D print something....

    posted in General Discussion
  • RE: Most reliable "best" radio

    What I've learned lately about buzzers, through experimentation, is that to get maximum loudness I need to drive a buzzer within about plus-or-minus 5Hz of its optimum resonance frequency. More than that and the loudness drops off precipitously. Unfortunately, manufacturing variance is probably more than plus-or-minus 5Hz, so that's a potential problem. The voltage supplied on the feedback pin of a piezo is only around 50mv, which is too low for an for an MCU to measure accurately without some kind of extra circuitry to help. It would be nice if the system could self-calibrate the driving frequency to match the inherent resonance frequency of the buzzer.

    Meanwhile, I'm switching over to an H-bridge for driving buzzers, because an H-bridge not only efficiently drains the charge that builds up on the piezo buzzer but it also effectively doubles the peak-to-peak voltage seen by the buzzer. At these low voltages, more apparent voltage means more loudness.

    When I started this project, I really didn't expect that the buzzer part of it would turn-out to require as much attention as it has! Sure, getting some amount of loudness is not a problem, but really maximizing loudness at these low voltages, while maintaining a tiny footprint and ease-of-assembly, isn't as easy as you'd think a priori.

    posted in General Discussion
  • RE: Most reliable "best" radio

    Fun to see what hobbyists can achieve when they stick to it long enough:
    I Landed A Rocket Like SpaceX – 07:05
    — BPS.space

    posted in General Discussion
  • RE: Which PCB fab do you currently like the best?

    OK, PCBway finished its fabrication. I've got this figured out now. PCBway, and probably the others as well, don't start the clock ticking when you submit your files and make payment. Instead, they start the clock ticking whenever the job gets to the MI stage of production. So, in that technical sense, PCBway made good on its 24 hour production advertisement. There's no apparent limit though on how long the job spends in either engineering pre-production, nor in how long it takes to ship the PCB's after the build is complete. The fab's don't seem to make any promises with regards to either of those, but either/both can stretch out the turnaround time. That said, it appears PCBway may be generally faster than JLCPCB, and definitely faster in tackling new orders submitted over the weekend. For those reasons, I think I'll be using PCBway going forward.

    posted in General Discussion