💬 RFM69 Multisensor Node (CR123)
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Yes, the step converter has an efficiency, ranging from 50 to 90 % regarding the output current and input voltage.
There is also a quiescent voltage inside the converter, so the converter will ALWAYS eat some current, either when the devices are sleeping !The pros and couns should be measured : I hope we can consome "more" of the battery with the converter (till a lower battery voltage), but perhaps due to efficiency of the converter, we'll have wasted more power !
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if you want to know efficiency of your converters i put the formula there if you want ;)
https://forum.mysensors.org/post/52319 -
if you want to know efficiency of your converters i put the formula there if you want ;)
https://forum.mysensors.org/post/52319@scalz Thanks you a lot scalz, exactly what i want ;)
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Good reading for dc-dc converters when designing for low power: http://www.digikey.com/en/articles/techzone/2014/mar/the-advantages-of-pulse-frequency-modulation-for-dc-dc-switching-voltage-converters
L6920 can operate in both modes(PWM/PFM) and it will switch to PFM on light loads. The quiescent current is around 10uA in general for this device as the manufacturer promises. But and there's a big BUT: in reality a dc-dc converter will always have a drawback on battery life to some degree as stated by the other users that replied in this thread so it would be ideal to accomplish things without it. I wanted to test it in real life anyway and that's why I used in my designs. For the CR123 based board it can be bypassed using the provided smd jumpers. On the other design(CR2032) which is more critical I will provide that too in the next hw revision.
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I was about to make tests with the 2 same modules, powered by a single CR2032 coin , a boost converter (MAX1724) for one node, and nothing for the other.
Since those readings, I'm not sure that the boost converter is needed anymore.Just to prove myself and my friends that it is useless, I'll do the test, with each node waking up the same amount of times and two fresh cells (I'll have to reduce the sleeping time for the test to be quick enough...).
I'll post the results on the forum, as soon as the batteries will die, in a few month ;)
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Launch the 3D Viewer from PCBNew, then do screen-shots ;)
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yeah :) alt+3 is one off my favorites. But for example the rfm69W module and the battery holder 3D wrl-file are hand mande. I guess. Do you have a lean toolchain for this? I found so may multi-programm toolpath..
The rfm69w module was made by me in FreeCAD. Some of the 3d models are made by me when I don't find one online. You can find lots of 3d models(step files) here: www.3dcontentcentral.com and www.tracepartsonline.net. Then you need to use FreeCAD to import the kicad footprint and the downloaded 3d step model to align it with the footprint. I use the kicad stepup tools FreeCAD macro for this: https://sourceforge.net/projects/kicadstepup/. Then you can export the scaled wrl file using the macro dialog. It requires some work to get all things done but it works just fine(patience is your friend here or should be).
The big advantage of using the kicad stepup tools FreeCAD macro is that you can have both the step and wrl files in place for exporting the board afterwards for mechanical CAD integration. Because in the end you'll want maybe to do some 3d printed enclosure for the project. For now kicad stepup tools is the best friend in doing electronics to mechanical CAD exports in order to design the plastic enclosure(a big congrats to the authors for making that possible).
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Thanks for the nice rundown! I will try that.
Yes the mechanical integration is my problem. I have quite a tight case to fit a sensornode with some other parts and I am actually routing parts so I have a nice flat area on the baord
I also need to feed in my own CAD for some oddball parts. -
Thanks for the nice rundown! I will try that.
Yes the mechanical integration is my problem. I have quite a tight case to fit a sensornode with some other parts and I am actually routing parts so I have a nice flat area on the baord
I also need to feed in my own CAD for some oddball parts.I have a zipped snapshot of all the 3d step/wrl models that I used to build my projects so far. It was quite some work to gather them all and align with the footprints using the kicad stepup tools. It's not complete - still needs some more work:simple_smile: but it should help you or anyone else to get started into MCAD integration using FreeCAD and kicad stepup tools. Maybe it's not very easy to start when using free tools but hey they are "FREE" so we cannot ask for more. But the nice thing is that once you get used it will be really easy to do your stuff and to go forward. Oh and FreeCAD can be so powerful after you learn it - I was really amazed what you can do with it(it has it's quirks and downsides but once you master it - oh, well...).
There's also: https://www.onshape.com/ - pretty powerful this one too and it has more advanced features than FreeCAD but the downside is that it's a cloud based solution: it's free for public documents but you never know when they will go to paid accounts only so yeah...I don't really like the idea to depend on something that it's hosted and the application is not on my PC along with the documents that I create with it. Cloud solutions have their flexibility but you're locked and you depend entirely on that hosted service.
Ok, enough talking...I uploaded the zip file here: http://www.mediafire.com/file/kzh1l9uo40cpj1u/kicad_stepup_packages.zip
