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Lightning Sensor — Parallax Forums

Lightning Sensor

g3cwig3cwi Posts: 262
edited 2012-11-08 14:14 in Accessories
This looks interesting for use with a Propellor.

http://www.ams.com/eng/Products/RF-Products/Lightning-Sensor/AS3935

I have some here but could do with some advice on mounting them to use.

Regards

Richard

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-05-16 10:04
    g3cwi wrote:
    I have some here but could do with some advice on mounting them to use.
    Mount it on a tall tower with a very pointy antenna. When the I2C bus stops working, you will know that it has "detected" lightning. :)

    -Phil
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-05-16 11:55
    Looks interesting.

    From the data sheet:
    The AS3935 uses a loop antenna based on a parallel LC resonator. The antenna has to be designed to have its resonance frequency at 500kHz
    and a quality factor of around 15. With a register setting it is possible to display on the IRQ pin the resonance frequency of the antenna as a
    digital signal with the register REG0x08[7] =1. The external unit can measure this frequency and tune the antenna adding or removing the
    internal capacitors with the register REG0x08[3:0]. It is necessary to tune the antenna with an accuracy of ±3.5% to optimize the performance of
    the signal validation and distance estimation.

    I wonder if there's any directionality with an antenna like that. Could the thing be set up to make a simple real-time map of an approaching storm?
  • Beau SchwabeBeau Schwabe Posts: 6,557
    edited 2012-05-16 15:38
    With that 30-30 rule and living in Oklahoma ... you'd miss out on all of the fun! :-)
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-05-20 17:01
    So what does an antenna for something like this look like?
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-05-21 16:45
    Phil Pilgrim (PhiPi) wrote: »
    Mount it on a tall tower with a very pointy antenna. When the I2C bus stops working, you will know that it has "detected" lightning. :)

    -Phil

    Indeed

    the one I used for my SLR was based on a optoIsolator and a AM radio ..
    not the most compact Or cute looking but it does work .
    ( the opto is a last ditch efforto to not smoke a 5 grand SLR ).


    Peter
  • Beau SchwabeBeau Schwabe Posts: 6,557
    edited 2012-05-24 12:12
    ElectricAye,

    According to the datasheet, there is no antenna, it's just a tuned coil acting purely as a magnetic pickup. When a lightning bolts strikes, think of the ionized column of air as a single wire with current flowing through it. A magnetic field is produced around that 'wire' that can be detected at a distance proportional to the strength and distance of the lightning bolt. The datasheet says that it does not detect individual strikes, but takes several strikes into account to predict an average... using this to determine the storm front, since 'most' lightning happens on the leading and trailing edge of a storm, this makes since. The stray strikes would be averaged. As far as cloud to cloud, the orientation of the magnetic field produced would be perpendicular in relation to a cloud to ground strike. As a result, the received signal would be much lower compared to the the 'average' threshold produced by the cloud to ground strikes of the approaching storm.

    Still, it seems they have gone to a lot of trouble with this IC, in what you could probably accomplish with a couple of MPF102's arranged as a differential electroscope and a little bit of software.

    http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CGUQFjAA&url=http%3A%2F%2Fwww.ams.com%2Feng%2Fcontent%2Fdownload%2F249847%2F974777%2F143418&ei=EYO-T8rmOKaC2AWj3-WbDw&usg=AFQjCNFLOM4_kP_5XB7xe_B0MGbUzS4T0A
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-05-24 12:49
    Beau Schwabe (Parallax) wrote: »
    ...

    According to the datasheet, there is no antenna, it's just a tuned coil acting purely as a magnetic pickup. When a lightning bolts strikes, think of the ionized column of air as a single wire with current flowing through it. ..

    Fascinating! I love your description of this. I'm totally clueless when it comes to RF, so 'much obliged for the explanation. Knowing it's just a coil, I feel motivated to give this a try. Oh wait... by coil, are you talking about something an inch in diameter or... does this thing have to be, like, 6 feet in diameter?

    Thanks, Beau
  • Beau SchwabeBeau Schwabe Posts: 6,557
    edited 2012-05-24 13:13
    The Coil is a tuned circuit that works in combination with a capacitor. Together the combination needs to be tuned to 500kHz.

    For calculations, checkout the "Software header" to this link:
    http://wiki.ohmspace.org/User:Bschwabe

    ...typically when I make a specific coil, I work backwards. First I find a capacitor value that I have handy... usually something less than 0.047uF.
    Then apply this formula... f = 1 / ( 2*PI* sqrt(l*c) ) ... or you can just go here ... http://www.deephaven.co.uk/lc.html

    Form there I see what frequency I need and determine an inductor value. For example... say I have a capacitor value of 0.01uF, using the formula with a frequency of 500kHz, I get an inductor value of roughly 10.1uH

    Now all I need is to determine my wire gauge, and use the "Air Core Coil Calculator" spreadsheet located at the top link under software.

    Once inside the spreadsheet, I find that the easiest air coil for me to wind is the "Special Case Multi-Layer where l equals b" ...
    Note: You should only need to fill in the 'green' fields on the spreadsheet.
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-05-24 18:50
    Beau Schwabe (Parallax) wrote: »
    ...

    For calculations, checkout the "Software header" to this link:....

    Thanks! I'll check this out.
  • g3cwig3cwi Posts: 262
    edited 2012-05-29 11:26
    I found an SMT => DIP converter for this package so all looks good.

    Cheers

    Richard
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-05-29 18:04
    g3cwi wrote: »
    I found an SMT => DIP converter for this package so all looks good....

    That's great. Do you have any links to where you're buying this stuff?
  • lostcauzlostcauz Posts: 36
    edited 2012-11-08 12:28
    I've been playing with the AS3935 Franklin Lightning Sensor IC the last few weeks. I purchased a board on tindie made by Tautic Electronics and this is a very cool sensor! It can detect cloud to ground and intra-cloud lightning at distances up to 40km. The sensor has a voltage range of 2.4 to 5.5 volts and can be interfaced by I2C or SPI. After lightning is detected, the AS3935 reports the distance to the head of the storm using an embedded lightning algorithm. There are tuning caps to ensure the antenna is set to 500kHz resonance and other configurable registers. It is also possible to output the resonance frequency on the IRQ pin. Everyone I've shown the board to wants one! I uploaded an AS3935 object to the OBEX for this sensor as well. Below is a pic of one of my tests.

    lightning.png
    lightning.png
    507 x 801 - 56K
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-11-08 14:14
    lostcauz wrote: »
    I've been playing with the AS3935 Franklin Lightning Sensor IC the last few weeks....

    Very cool. Thanks for the links.
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