Do you happen to have a board or two left over that I could buy from you.
I'm looking for testing this module with an external antenna before integrating it in our project (https://github.com/NathanB49/Utilipi/tree/dev_V2)
@tekka unbelievable !!! I tried with NRF24 and arduino nano, it's working like a charm !!!
If I use the same sketch, on a pro mini using one of my ftdi as serial interface the Tx don't go threw anymore !!!
Ftdi use a 1047 chip
Arduino nano use a CH340 for which I had to install a Chinese driver for it !?!? !!!!
Small update here. I've been working on the routing part. it's been years since i played with the nets, and wires on Eagles ... Oh boy, its a mess ! and while placing, moving components, i was thinking , wow, the Balun filter, the NRF24L01 are going to be impossible to hand solder correctly ! and I don't really want to buy a microscope, a $300 soldering station, ...
So I looked around and found something interesting so I post it here, if some makers don't know about it, and are afraid of SMD soldering : OSH also make stencil for you, Kapton stencil for $5 ! https://www.oshstencils.com/index.php
then it's a peace of cake or is it ? https://www.youtube.com/watch?v=1RMtOAHbfvU
Has anyone tried it before ? I'll definitely try it
So after some reading, phoning, thinking, again and again about FCC/CE Certification here is the plan.
I'm not going to go for the FCC Certification, as it's way too expensive, but I'll run the test myself for CE compliance.
When FCC needs to be done by US agencies, the CE can be self-certified : you run the tests with the appropriate tools, make sure your design respects the requirements, and if so, keep the results in case anyone asks anything.
Now pretty much everywhere, I read that if your product is CE compliant, then your chance of getting the FCC on the first run is very high. Dropping the cost to a "small" $5k or so
So first, CE self certification, and then if needed/wanted/asked/ ... FCC, IT, ... other certifications. Meaning so US selling first just Europe. Are there many US folks using Mysensors ?
To run the test, I'm working with my University which has all the tools, and knowledge to assist me. Could be an interesting project to run with some student ... will see !
So regarding the design, zero risk must be taken regarding the RF part :
I share a great guide from TI about antenna design : http://www.ti.com/lit/an/swra161b/swra161b.pdf
Now I want to try the Inverted F antenna presented in my early post, a Di pole antenna (no more Balun Filter), and Chip antenna and compare them the standard Meandered Inverted-F Antenna (MIFA) we all have on our NRF board !
Indeed what you are pointing out is the Achilles heel of the project ! I haven't mention it because I haven't done my research on the subject. Their might be some solutions I will post on that later on.
And you are right once again, I haven't investigated all the details ... **yet **
It's all a project is about, isn't it ? You have an idea, a goal, and then you investigate step by step to see whether you have a good chance of success or not. I use "good chance of success", because in every project you take some hypothesis, you take some risks, because success is never 100% sure.
At the beginning of the project, the chance of failure are very high, but its ok because the investment in very low (just time so far). And the more I'll progress, the lower the risk will be (if I did the investigation work properly) and then it will be ok to invest a little more.
It's also one of the reason why I post in here all of my project, this (all the comments, and feedback) helps me (and the Mysensors community) to evaluate the chance of success Vs the chance of failure. You guys can point out weak point and so on and so forth.
So I'm pretty glad you mentioned that, it shows me my project is of interest.
As mentioned, I will post on that specific crucial part once I'm done evaluating all of my options.
@scalz Yes, I know I'm not inventing anything, everything that I propose already exist
the only, and MAJOR difference is the price : I'm following a design to cost process. What does it means : I take available hardware/schematics : NRF, Arduino (Sensebender, and other good board), ... and I try to redesign and make it as cheap as possible.
The nrf51822 is indeed the killer, BUT it's not working yet with MySensors
And I totally agree with you, if you work in HW and if you are not focused on the future (new chip, new protocols, new project, ...) then your project life expectancy is very little
I obviously won't lunch mass production, so I'm running the process with 400 boards batch. So far, only based on hypothesis, meaning its pure fiction, meaning there is a margin of error in my calculation. The more I will progess, the more the margin of error will be important, and the better I will fine tune the final price.
And I'm pretty sure that if we talk about bigger production batch, then the cost of a simple board could be as low as a couple of $
Look at the low cost airline company, they didn't invent anything, they just optimized everything to drive cost down, and now they are very successful company.
Look at the new Raspberry Zero (produced in EU) : given away for free with a magazine, and then sold for $5 !!
I give out those example to illustrate that innovation is not always the key to success and to illustrate that the cheaper you go, the wider spread it will be ! (no need to add : if the quality is here)
And just to be clear, I'm not doing this to earn money, because low cost, and small batch are usually not big money maker.
Now clearly, if you tell me you will manufacture your Mytinycamel, and sell it under $7-10 fully equipped (board + radio) then I'll reconsider the project. and don't worry, if I didn't want to be challenged on the project I won't be here talking about it !
"Too bad we didn"t met when I started my projects..." => It's maybe not too late !? If we are after the same goal, we can maybe add our skills ...
@ahmedadelhosni Idk what to tell you, I guess Temp sensor is quite common, and fun thing to have inside and ouside.
Many people like to know what is the weather ouside, and the can also use inside temp sensor to control their heating/cooling system.
@tbowmo I will do my best to please the most ! I'm thinking about the footprint options. I'm also thinking about production option in one batch. If you think about it, in 400 boards, if you use the same Stencil, you can in case 1 populate the full board (EEPROM, temp sensors, ...), in case 2 only temp, and in case 3 the minimum. It's a minor program update to disable one or 2 ref. And then you have 3 types of complete board with three price to make everyone happy. I obviously won't be able to do that with chinese supplier, so I'll talk about that with the French supplier.
I'm actually doing all the quotation with various hypothesis because I don't have yet any design file. I'm working on it. So I have not made a choice on specific ref for the RF part (only the couple of inductance and capacitor for the impedance matching are critical). The PCB will be 1mm thick, and the cooper trace 1oz. There will be no ground plan under the antenna.
Thanks for sharing the MYSX connector, I'll take that into account too. Is there an eagle lib for it ? (I know it's standard dual row pin header, but the pin assignation could be useful to have directly via a lib)
Thanks I'll read that carefully.
@Anticimex still thinking about the ATSHA204 and the HW security vs SW security.
If you have a node with the ATSHA204, does the GW needs to have it on board to ?
BTW do you have the link to the security thread so I can update my knowledge on that side ? please
@Anticimex I'm thinking about that option too, as a back up solution if I fail with RF.
Also I think Sensebender is missing voltage regulator and connector so one can choose battery operation or other power supply
Small Update : Got the first quote for PCB and PCB assembly in china. That validates that the $7 objective of the board is feasible for 400 boards batch.
I ask for quotation the atsha204, some packaging are obsolete, which one is used on the Sensebender ? Sot23 or SOIC, or TSSOP ?
Also for size reduction, I thing I'll use the ATMEGA QFN32
Now lets do a dummy proto board for antenna benchmarking
@Anticimex not really. My first idea about this board was to say : lot of us by chinese arduino pro, NRF24L01, spend some time soldering everything together, because we are looking for the cheapest solution even if its not the most sexy one, the most secured one, ... So a lot of us, end up designing their own little board, with DIP Atmega, to have something smaller, more sexy, but not secured.
So I guess on my first thought, this board is more for all these people. Now when you start digging, and thinking about it, of course you want to add stuff to it, temp sensors, EEPROM, security.
My ultimate goal is the price, on that I won't deviate.
Then the secondary goal is size, functionality, and evolution : on that I'm open.
By Evolution, I mean that I could throw in some PCB foot print, for SI7021, or other component (on the bottom side for example) so people that want to add more functionality would be able to.
@korttoma I agree, SI7021 might not be absolutely necessary. About the size of the board, there is no way it will be the same size as sensebender ! @tbowmo did an incredible job on that board, plus he used 0402 chip which can be a cost driver for some production. I'll keep it small, but not as small at the sensebender !
@Nuubi can you explain why you need the :
FTDI USB-to-TTL Serial chip ?
mini B connector is not so used anymore (samsung cellphone use micro USB)
Because beside that, it's what I plan on doing. Oh I might add a temp sensor, but not sure yet.
Then I think it's worth having a thought about it :
EEPROM can allow OTA FW update. which is quite cool, when you what to update your node without taking everything down.
I'm not really convinced with the ATSHA204 tho
@tbowmo Thanks for shooting out some idea !
Indeed, I read the thread about the birth of the Sensebender which is actually a mine of information and thought about minimal design.
As you mention it while working on the sensebender, the RF will be the hardest part. I can add all the cool feature on the board, if you can't connect it, it's useless.
I'm still waiting for cost estimation from china, and french supplier specialized in IOT, prototyping, and small batch production.
I'm in a design to cost process, so first things first, I want to validate the cost objective from various quotation. Then I will see if I have to make hardware design choice, or if I just can't make it, ...
Here is draft 1 of the schematics.
I still haven't decided whether the temp sensors will be the famous SI7021 or for cost reason a more basic DS18b20 (about half the price of the SI7021)
For powering the board, I'm planning on having 2 solutions : direct 3.3V (bypass by solder jumper of the regulator) or 5v power supply with a Micro-B
The Antenna I found 2 design :
I'm still missing the breakout of the main pins.
But I wanted to have a first feedback / point of view : Is EEPROM critical ? Is the temp sensor absolutely necessary ? Same with the Micro USB and Voltage Reg ?
Edit : The Oscillator won't be monted but the solder pad will be here (If I have room for it), I also will remove the capa
@m26872 the most expensive is the Atmega I got a quote at $1.2, but I hope I can get it cheaper. then PCB and NRF chip will cost between $0.6-0.7. The other small SMC don't cost much. Depend now how much I'll get it manufacture for in quite small batch? But let's face it, if we can buy an arduino pro mini and a NRF24L01 module for less than $3-4 in China, then it should be easy to make an all in one board for abour $7-8. Depending on the quotation I'll get, I hope I'll be able to manufacture it in France.
@hek I'm doing this because I just love your project, and I think the cheaper you will give out people ready board, the more the mysensors communitty will grow.
Of course everything will be open! It's already all over the web, the arduino, the NRF, even PCB antenna design. I really don't mean to compete with the Sensbender, I'm really meanning to contribute somehow to the Mysensors Projet.
Dear MySensors Community,
I'm thinking on lunching a project aiming to making a cheap, compact, and less soldering solution for the Mysensors enthusiastic people. As Mysensors project is aiming at less programming
So the base line is : a $7 all in one Mysensors+NRF24L01
I know the Sensbender board is here, but you must solder a NRF module on top of it, and it's not so cheap.
In more details here is what I have in mind : (nothing new really)
I have already quoted a BOM, I'm waiting for PCB and PCB assembly quote from 2 manufacturer. I'm quite confident that this is feasible for 200 or more boards.
the main challenge here, from my point of view is wireless connectivity with chip or PCB Antenna. The rest is open source and all over the web.
Let me know your point of view.
I'll update the schematic I'm working on soon.
Really great idea @m26872 !!
I'm waiting for the V1.2 test and review before ordering some boards on DirtyPcb.
One Tip/question : have you thought on panelizing your slimnode, because we could easily fit 3 board on the 5X5 limitation ? I also think that DirtyPCB would even process the break routing to ease board separation.