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jpnorair

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  1. Like
    jpnorair got a reaction from abecedarian in imp.guru Droplet and 915MHz Long Range Radio to WiFi   
    This is wrong.  I won't get started about HAM and ARRL, and how they destroy innovation in the modern era.  But at least you can figure out my opinion.
     
    Lower wavelengths represent smaller particles via the wave-particle duality, more smaller particles can be produced with a given energy level, and therefore lower wavelengths propagate better through any medium.
     
    What I assume this question and answer refer-to is practice rather than theory.  In a concrete bunker, VHF will propagate through the bunker much better than UHF.  In a building with windows and doorways, there are situations where the diffractive losses of a longer wave signal will result in greater attenuation than the bouncing of shorter wave signals.  This can be very experimental and it depends a lot on physical geometry, construction materials, etc.
     
    UHF is basically 300-1000 MHz.  Planet Earth and humans are scaled geometrically such than UHF often propagates well in "real-world" environments.  But does it really propagate better than a 30 MHz signal?  That's a stretch.
  2. Like
    jpnorair got a reaction from spirilis in imp.guru Droplet and 915MHz Long Range Radio to WiFi   
    One common mistake is to assume that such a thing as a 1/4 wave resonant antenna exists.  The truth is, there must be a 1/2 wave dipole, or you must have a ground plane acting as a counterpoise to your 1/4 monopole, and this needs to be effectively 1/4 wave itself.  Alternatively, there is a loop antenna structure.  Small chip antennas are generally a capacitive load combined with an inductive load.  This can reduce the size of the antenna, but nothing comes for free.  bandwidth is usually less, and efficiency is usually less.
     
    There is all kinds of science, engineering, and clever tricks for making good, compact antennas.  Generally speaking, you want to have a 1/4 wave current distribution in your ground plane.  One thing I can tell by looking at the picture is that you will want a larger ground, or at least a cleverly engineered spiral at the edge of the PCB.  You will also want to use a 4-layer board with an internal ground layer.  I bet you are dropping 20 dB in your antenna system (13 at the very least).  For that form factor, I would estimate that -8 dB is about the best efficiency you can achieve over the 915 band, so that leaves 12 dB of room for improvement.
     
    I'm out of the office today and tomorrow, but on Thursday I will show some photos.
  3. Like
    jpnorair got a reaction from GeekDoc in New Chip Alert: The ESP8266 WiFi Module (It's $5)   
    On a sour note: Broadcom has patents that must be licensed in order to market WiFi devices in most of the world.  China does not have much in the way of patent law.  If you're thinking about building a product to sell, I would avoid this module for legal reasons.  If not, then buy a bunch -- they might not be available at this price forever.
  4. Like
    jpnorair got a reaction from spirilis in STMicroelectronics EFL700A39 Rechargeable 200um Paper Thin Battery   
    "Lithium Thin Film" is a technology, not a description (this is confusing).  It uses semiconductor manufacturing techniques to build the lithium ion battery onto a silicon substrate, so it is not flexible.  Lithium polymer technology builds the battery on a polymer substrate.  The distributor Powerstream (powerstream.com) is the best place to look for LiPoly, and I believe they distribute some thin, flexible models of LiPoly.
  5. Like
    jpnorair got a reaction from 12kman in STMicroelectronics EFL700A39 Rechargeable 200um Paper Thin Battery   
    "Lithium Thin Film" is a technology, not a description (this is confusing).  It uses semiconductor manufacturing techniques to build the lithium ion battery onto a silicon substrate, so it is not flexible.  Lithium polymer technology builds the battery on a polymer substrate.  The distributor Powerstream (powerstream.com) is the best place to look for LiPoly, and I believe they distribute some thin, flexible models of LiPoly.
  6. Like
    jpnorair got a reaction from 12kman in STMicroelectronics EFL700A39 Rechargeable 200um Paper Thin Battery   
    There was a company called "Infinite Power Solutions" that used to make a battery like this, and which pioneered the technology.  Actually, the technology was pioneered at Oak Ridge National Laboratory, but the guy from Oak Ridge founded IPS.  IPS raised enough money to build a nice factory in Colorado (I've been there!), but things didn't really work out for them.
     
    For ST to license the tech from Oak Ridge and then to spend 3 years developing it (this project has been going for 3 years, but you couldn't buy it until now), indicates to me that they have some particular customer in mind.  Maybe the ESA or something like that.
     
    My opinion of the Lithium-Thin-Film battery is that Li-Poly technology is very nearly as good, at this point, and it is a whole-lot cheaper.  For doing energy harvesting, ST is also releasing SPV1050, which competes with the BQ25504 from TI, but it is a lot cheaper.  Both of these chips work to charge Li-Poly AND Lithium-Thin-Film batteries from sources like solar, piezo, etc. I have tested all these combinations 
  7. Like
    jpnorair got a reaction from Automate in STMicroelectronics EFL700A39 Rechargeable 200um Paper Thin Battery   
    There was a company called "Infinite Power Solutions" that used to make a battery like this, and which pioneered the technology.  Actually, the technology was pioneered at Oak Ridge National Laboratory, but the guy from Oak Ridge founded IPS.  IPS raised enough money to build a nice factory in Colorado (I've been there!), but things didn't really work out for them.
     
    For ST to license the tech from Oak Ridge and then to spend 3 years developing it (this project has been going for 3 years, but you couldn't buy it until now), indicates to me that they have some particular customer in mind.  Maybe the ESA or something like that.
     
    My opinion of the Lithium-Thin-Film battery is that Li-Poly technology is very nearly as good, at this point, and it is a whole-lot cheaper.  For doing energy harvesting, ST is also releasing SPV1050, which competes with the BQ25504 from TI, but it is a lot cheaper.  Both of these chips work to charge Li-Poly AND Lithium-Thin-Film batteries from sources like solar, piezo, etc. I have tested all these combinations 
  8. Like
    jpnorair got a reaction from tripwire in STMicroelectronics EFL700A39 Rechargeable 200um Paper Thin Battery   
    There was a company called "Infinite Power Solutions" that used to make a battery like this, and which pioneered the technology.  Actually, the technology was pioneered at Oak Ridge National Laboratory, but the guy from Oak Ridge founded IPS.  IPS raised enough money to build a nice factory in Colorado (I've been there!), but things didn't really work out for them.
     
    For ST to license the tech from Oak Ridge and then to spend 3 years developing it (this project has been going for 3 years, but you couldn't buy it until now), indicates to me that they have some particular customer in mind.  Maybe the ESA or something like that.
     
    My opinion of the Lithium-Thin-Film battery is that Li-Poly technology is very nearly as good, at this point, and it is a whole-lot cheaper.  For doing energy harvesting, ST is also releasing SPV1050, which competes with the BQ25504 from TI, but it is a lot cheaper.  Both of these chips work to charge Li-Poly AND Lithium-Thin-Film batteries from sources like solar, piezo, etc. I have tested all these combinations 
  9. Like
    jpnorair got a reaction from spirilis in STMicroelectronics EFL700A39 Rechargeable 200um Paper Thin Battery   
    There was a company called "Infinite Power Solutions" that used to make a battery like this, and which pioneered the technology.  Actually, the technology was pioneered at Oak Ridge National Laboratory, but the guy from Oak Ridge founded IPS.  IPS raised enough money to build a nice factory in Colorado (I've been there!), but things didn't really work out for them.
     
    For ST to license the tech from Oak Ridge and then to spend 3 years developing it (this project has been going for 3 years, but you couldn't buy it until now), indicates to me that they have some particular customer in mind.  Maybe the ESA or something like that.
     
    My opinion of the Lithium-Thin-Film battery is that Li-Poly technology is very nearly as good, at this point, and it is a whole-lot cheaper.  For doing energy harvesting, ST is also releasing SPV1050, which competes with the BQ25504 from TI, but it is a lot cheaper.  Both of these chips work to charge Li-Poly AND Lithium-Thin-Film batteries from sources like solar, piezo, etc. I have tested all these combinations 
  10. Like
    jpnorair got a reaction from bluehash in STMicroelectronics EFL700A39 Rechargeable 200um Paper Thin Battery   
    There was a company called "Infinite Power Solutions" that used to make a battery like this, and which pioneered the technology.  Actually, the technology was pioneered at Oak Ridge National Laboratory, but the guy from Oak Ridge founded IPS.  IPS raised enough money to build a nice factory in Colorado (I've been there!), but things didn't really work out for them.
     
    For ST to license the tech from Oak Ridge and then to spend 3 years developing it (this project has been going for 3 years, but you couldn't buy it until now), indicates to me that they have some particular customer in mind.  Maybe the ESA or something like that.
     
    My opinion of the Lithium-Thin-Film battery is that Li-Poly technology is very nearly as good, at this point, and it is a whole-lot cheaper.  For doing energy harvesting, ST is also releasing SPV1050, which competes with the BQ25504 from TI, but it is a lot cheaper.  Both of these chips work to charge Li-Poly AND Lithium-Thin-Film batteries from sources like solar, piezo, etc. I have tested all these combinations 
  11. Like
    jpnorair got a reaction from Rickta59 in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  12. Like
    jpnorair got a reaction from pine in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  13. Like
    jpnorair got a reaction from Fred in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  14. Like
    jpnorair got a reaction from username in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  15. Like
    jpnorair got a reaction from bobnova in STM32L0 USB Interface   
    Small.  I'll have a prototype soon.  It will be able to fit inside a USB cable, I think.
     
     
    Possibly.  In any case, the project is to be open source, so you can add features however you want.
     
     
    I had not planned on making this into a Teensy competitor, but perhaps there is reason to do so.  I could one-up Teensy by offering multithreaded Wiring (i.e. multiple sketches running simultaneously) with automatic low-power usage in the background -- the RTOS underpinnings are already there.  This would require a couple months of my time, and therefore would necessitate a successful kickstarter.  What do you think?
  16. Like
    jpnorair got a reaction from Automate in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  17. Like
    jpnorair got a reaction from bluehash in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  18. Like
    jpnorair got a reaction from David Bender in A more efficient circular FIFO buffer   
    Ring buffers are not good solutions for fast performance.   For that, you want to use an A/B buffer.  Yes, you need double the memory, but that's the tradeoff.  To get "best of both worlds" I've found that, quite often, it is faster to do a DMA memcpy to shift the buffer (only happens when limit is reached) than it is to do the ring-buffer logic on every byte entered or removed.  On MSP430's with DMA you can move 2 bytes in 1 cycle, plus some setup, whereas all those if's probably burn 20-30 cycles for each byte entered/removed.  So do the arithmetic and figure out what is the best choice based on your buffer size.
  19. Like
    jpnorair got a reaction from bobnova in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  20. Like
    jpnorair got a reaction from RobG in A more efficient circular FIFO buffer   
    Ring buffers are not good solutions for fast performance.   For that, you want to use an A/B buffer.  Yes, you need double the memory, but that's the tradeoff.  To get "best of both worlds" I've found that, quite often, it is faster to do a DMA memcpy to shift the buffer (only happens when limit is reached) than it is to do the ring-buffer logic on every byte entered or removed.  On MSP430's with DMA you can move 2 bytes in 1 cycle, plus some setup, whereas all those if's probably burn 20-30 cycles for each byte entered/removed.  So do the arithmetic and figure out what is the best choice based on your buffer size.
  21. Like
    jpnorair got a reaction from greeeg in STM32L0 USB Interface   
    Just a note: I'm building an open source project that utilizes STM32L0 as USB-UART gateway.  This chip has some interesting attributes, and it can create a low-cost, small geometry USB interface that is also programmable.  I'm building the CDC-ACM to UART version first, then an Android version that does the necessary authentication, and then finally a USB-Ethernet version so you can telnet to it (ssh is too much overhead).
     
    The idle current will be in the area of 2uA, so it's a good USB bridge for any low power project you may have, unlike most off the shelf bridge chips which are nowhere near this.
     
  22. Like
    jpnorair got a reaction from bluehash in New Chip Alert: The ESP8266 WiFi Module (It's $5)   
    On a sour note: Broadcom has patents that must be licensed in order to market WiFi devices in most of the world.  China does not have much in the way of patent law.  If you're thinking about building a product to sell, I would avoid this module for legal reasons.  If not, then buy a bunch -- they might not be available at this price forever.
  23. Like
    jpnorair got a reaction from username in New Chip Alert: The ESP8266 WiFi Module (It's $5)   
    On a sour note: Broadcom has patents that must be licensed in order to market WiFi devices in most of the world.  China does not have much in the way of patent law.  If you're thinking about building a product to sell, I would avoid this module for legal reasons.  If not, then buy a bunch -- they might not be available at this price forever.
  24. Like
    jpnorair got a reaction from tripwire in What are you working on today/this week?   
    Note to yagi-uda builders: you can get more directivity by adding more elements to the front.  There are already two in the design above.  Just cut more wires of the same length and space them at lambda/4.
       
     
    A straight dipole or monopole will have no problem covering the entire band 2400-2500.  These antennas are 75 or 37 Ohms impedance respectively, and the RF source of this device is 50 Ohms, so this is easy.  I recommend this approach.  I also recommend experimenting with trimming the antennas and testing RSSI against a reference because the wire you use will have some inductance (and capacitance) and the best resonant length will be less than lambda/4.
     
    The bandwidth of a folded-dipole is theoretically the same as on a straight dipole, but it many designs the aperture is made wider, which decreases the efficiency a bit and changes the polarization a bit, but increases the bandwidth.  You can do the same thing with a regular dipole by constructing a "fat" dipole.  A thing called a "bowtie" dipole is a common structure.  Mainly, a folded-dipole has an impedance of ~300 Ohms, which sometimes is preferable.
     
    But any-old straight dipole should have no problem covering 10% of center frequency, which is quite fine for 2400-2500 MHz.  If you are trying to build a multi-band antenna the easiest way is to build a multi-element inverted-F monopole or perhaps a spiral antenna with multiple turns.
  25. Like
    jpnorair got a reaction from bobnova in What are you working on today/this week?   
    Note to yagi-uda builders: you can get more directivity by adding more elements to the front.  There are already two in the design above.  Just cut more wires of the same length and space them at lambda/4.
       
     
    A straight dipole or monopole will have no problem covering the entire band 2400-2500.  These antennas are 75 or 37 Ohms impedance respectively, and the RF source of this device is 50 Ohms, so this is easy.  I recommend this approach.  I also recommend experimenting with trimming the antennas and testing RSSI against a reference because the wire you use will have some inductance (and capacitance) and the best resonant length will be less than lambda/4.
     
    The bandwidth of a folded-dipole is theoretically the same as on a straight dipole, but it many designs the aperture is made wider, which decreases the efficiency a bit and changes the polarization a bit, but increases the bandwidth.  You can do the same thing with a regular dipole by constructing a "fat" dipole.  A thing called a "bowtie" dipole is a common structure.  Mainly, a folded-dipole has an impedance of ~300 Ohms, which sometimes is preferable.
     
    But any-old straight dipole should have no problem covering 10% of center frequency, which is quite fine for 2400-2500 MHz.  If you are trying to build a multi-band antenna the easiest way is to build a multi-element inverted-F monopole or perhaps a spiral antenna with multiple turns.
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