💬 Button size radionode

[Koresh]

@Cliff-Karlsson said:

I really hope that this board will be possible to buy soon assembled. Is the price for the new rfm69 the same as the old? (~3-4$)?

Yes, price is the same.

@NeverDie said:

Since you asked, here are some suggestions: 1. drop the resonator. It can run on the 8Mhz internal resonator just fine. 2. Drop the voltage converters. It's more power efficient to run direct from battery. 3. Keep the part count as low as possible. Less assembly means more users.

Thanks! I'l think about every point.
May be it will be worth leaving LDO footprint on the board without soldering it? In this case we can run board directly from battery. But if you want to use unregulated DC source you can cut thin jumper (jumper will no covered by solder mask) and solder LDO.

Soldered board will be as cheap as possible, I promise. So theere will be no need to assemble board :)

[NeverDie]

Well, if you're going for pre-assembly, there seems to be a much smaller atmega328p available from China. I recently received an very inexpensive pro mini with one on it. Not sure, but this photo may also show it: http://www.varesano.net/files/Image426.jpg However, on the pro mini I received it looks as though it may have been wire bonded directly to the PCB.

[NeverDie]

Here's a better photo of it, where you can actually read the markings: https://d3s5r33r268y59.cloudfront.net/0424/products/thumbs/IMG_20131014_145751.JPG.2560x2560_q85.jpg

[bjornhallberg]

I love it! More boards like this!

I would concur with using a TQFP atmega if you're not doing manual assembly anyway.

As for other requests / suggestions .... perhaps you could make a separate version which has less pins broken out and instead has room for a flash memory. Also I am still very much in favor of more extreme step-up ICs, that can take say 0.6-0.7V from a single AA/AAA and boost it to 3.3V. For some reason no one is going that route on the forum anymore and I don''t know why? Has everyone switched to lithium batteries?

[NeverDie]

@bjornhallberg
AFAIK, it's because available current (i.e. mah capacity) is the primary constraint, and there seems consensus that a booster on a single cell burns through that capacity a lot more quickly than, say, two cells and no buck or boost regulator. If constrained space is what's driving you to a single AA/AAA cell, then perhaps you could use a single 3.3V CR123 and still come out ahead? I haven't seen a direct head-to-head comparison, but I wouldn't be surprised if the CR123 were to win on both the volume/size and the battery life metrics.

[bjornhallberg]

@NeverDie Yeah you're probably right, but a CR123 is damn expensive from where I'm standing, compared to a single AA cell. I'm perfectly fine with changing batteries more frequently if it comes to that. The only thing that would sway me would be sub zero temperature performance. I'd sooner try a coin cell and see how far I'd get. I'm looking for compact solutions for mailbox alarms and the like where the sensor would need to be almost paper thin to stick to the lid of the box.

[Koresh]

@bjornhallberg
It sounds a little crazy but... we have enough space for eeprom in sot23-5 package (with decoupling capacitor!).
I've placed 24LC64 temporarily:smiley:

[NeverDie]

@bjornhallberg
You're right: a coincell would seem be a good match for a mailbox application.

[Cliff Karlsson]

@Koresh what is your guess of the price for 1-10 pre-assembled sensors?

[yury]

@hek

Does RFM69 really need to be connected to D2? Does Mysensors lib use it ?

[hek]

RFM69 uses interrupts, yes.

[scalz]

for batt/powering choice, I don't see a consensus lol! I think it really depends on goals and requirements. sometimes sensors can require some voltage, or you want less maintenance+cheaper batt etc.

• lithium AA/AAA (or alkaline but less good), cheap in packs, easy to find and great seldischarge rate. It's 2500-3000mah. Put them in // and you can double your lifetime... if no problem with footprint, you can find cheap LR14, 8000mah, not tried, but wow ;)
• Coincell, lower mah, and very variable lifteime if noname...

And booster is interesting if you control the power consumption of your system, and use an ultra efficient during very light loads.
Then, not sure if cr123 win so easily. CR123 have good selfdicharge rate in primary batt form, and it's something like 1200mah.

About the overall size of the device vs batt size etc..because booster takes more component..but when you make a device you don't use only an atmel+radio only.., you need more things, so at the end it's bigger. near the size of an AA/AAA. or use shield board style, but then it's not thin, less nice when using coincell. But I like the format of coincell, that's just not the same league...
Why I say this..because I made some experiments, and have some boards with boosters (not released yet..) and I like the TPS61098x..crazy thing, but very tiny :)
I don't want to debate..just my thought.

for rfm69, +1 for interrupts :) and if you want to optimize the power consumption in future with listenmode ;)

[Koresh]

Can anyone confirm microchip 24LC64 as eeprom (pinout is standard for sot23 eprom, so it is possible to change chip in future)? Is standard library compartible with it? Thanks!

[scalz]

@Koresh I think this eeprom has libs for arduino. but if this is for using ota with dualoptiboot and mysensors, as far as I know, it's not compatible. only jedec spi eeprom for the moment..If it's only for datastorage, I don't see problems.

[NeverDie]

I'm revising my earlier comment. Based on new experience, I wouldn't recommend using the smaller atmega328p.

[bjornhallberg]

@Koresh Where do you get the rfm69(h)w rev 3.0 from? Or is it the hc model? I can only seem to find rev 2 (?) on Ali?

[Koresh]

@bjornhallberg said:

@Koresh Where do you get the rfm69(h)w rev 3.0 from? Or is it the hc model? I can only seem to find rev 2 (?) on Ali?

You can find these modules as "rfm69hc" on Ali. Do not forget about haggling :)

I've received new version of these little boards :smiley:
Will show new soldered boards asap.

[Koresh]

Next revision :smirk:

[Koresh]

Looks perfect with new usb-ttl. :smiley: I plan to use this configuration as RFM69-USB gateway.

[alexsh1]

@koresh When are you planning to release the Eagle files for the board please?