Colpits/Hartley oscillator
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Posts: 46,084
Hi group.
I have need to monitor soil moisture. I have seen gypsum blocks, probes and
other things. (I work for CSIRO here in Oz and we actually have a set-up
that has 1 ton of ground plot on a balance and measures the extra weight as
moisture) The latest method I have seen and the one I am about to play with
is a oscillator circuit with a wound coil placed in the ground that
depending on the moisture changes the frequency of the circuit etc.
Has anyone played with this type of thing? I believe either BS1 or BS2 can
read a frequency. Is this so and if so what is the maximum freq?
I have need to monitor soil moisture. I have seen gypsum blocks, probes and
other things. (I work for CSIRO here in Oz and we actually have a set-up
that has 1 ton of ground plot on a balance and measures the extra weight as
moisture) The latest method I have seen and the one I am about to play with
is a oscillator circuit with a wound coil placed in the ground that
depending on the moisture changes the frequency of the circuit etc.
Has anyone played with this type of thing? I believe either BS1 or BS2 can
read a frequency. Is this so and if so what is the maximum freq?
Comments
You can measure frequency readily with PULSIN which varies in resolution
depending on the Stamp. Once you know the period of one half-cycle you can
compute the overall frequency. You can also measure a positive pulse and a
negative pulse to get a full-cycle, but it probably won't be adjacent
cycles. However, it sounds like your frequency would change little over
short times so that would probably work OK.
The other alternative would be to use COUNT but I prefer PULSIN.
If you are using a Colpits or Hartley oscillator, expect to use a Schmitt
trigger or even better a compartor set up as a zero-crossing detector
(ground one input of an op amp, feed the signal to the other end;
comparators are often open collector output, so you can use a pull up
resistor and read the output from the Stamp). This will clean up the sine
into something the Stamp can easily digest.
Regards,
Al Williams
AWC
P.S. If you need to measure 8 pulse channels at once check out our PAK-VII
http://www.al-williams.com/awce/pak7.htm
>
Original Message
> From: Peter May [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=iT_QyOfTmnwhF6pWlNJIU5n-ncS1bAThsVZiPM8dJ2AY-WVwwfb9GiIafaUKtCNrIFh4jeXraHmt5GsXa_PcQSk]manager@s...[/url
> Sent: Friday, October 27, 2000 5:40 AM
> To: Basic Stamp (E-mail)
> Subject: [noparse][[/noparse]basicstamps] Colpits/Hartley oscillator
>
>
> Hi group.
>
> I have need to monitor soil moisture. I have seen gypsum blocks,
> probes and
> other things. (I work for CSIRO here in Oz and we actually have a set-up
> that has 1 ton of ground plot on a balance and measures the extra
> weight as
> moisture) The latest method I have seen and the one I am about to
> play with
> is a oscillator circuit with a wound coil placed in the ground that
> depending on the moisture changes the frequency of the circuit etc.
>
> Has anyone played with this type of thing? I believe either BS1 or BS2 can
> read a frequency. Is this so and if so what is the maximum freq?
>
>
>
>
I would be interested in the moisture/frequency circuit. Can you send me
information or tell me where to find it?
Thank you,
Don Bannon dbannon@s...
>
Original Message
> From: Peter May [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=q2KTl5tOWVcxuHnAHCBVOs_7cyrbRU2cZguWBRYrVGWvFejW2pfS-ph4dQKe0-RfO7Ox9jkiXT6mR_F8vA]manager@s...[/url
> Sent: Friday, October 27, 2000 5:40 AM
> To: Basic Stamp (E-mail)
> Subject: [noparse][[/noparse]basicstamps] Colpits/Hartley oscillator
>
>
> Hi group.
>
> I have need to monitor soil moisture. I have seen gypsum blocks,
> probes and
> other things. (I work for CSIRO here in Oz and we actually have a set-up
> that has 1 ton of ground plot on a balance and measures the extra
> weight as
> moisture) The latest method I have seen and the one I am about to
> play with
> is a oscillator circuit with a wound coil placed in the ground that
> depending on the moisture changes the frequency of the circuit etc.
>
> Has anyone played with this type of thing? I believe either BS1 or BS2 can
> read a frequency. Is this so and if so what is the maximum freq?
>
>
>
>
>
If you are looking for a good program to do schematics and PCB's, try out
PROTEL. I have been using it here at work for years and it's great. Very
intuitive and easy to use. The price won't break you either. It is one of
the best bargains as far as professional software goes. PROTEL has a fully
functional demo disk that you can evaluate for free.
Regards,
Jon Enoch,
PCB Design Engineer,
Northern Airborne Technology,
British Columbia, Canada
Yeah not a problem. I found it in a book. I will scan the info in or if I
can find a schematic drawing package will send it that way. That is the
stage I am up to now. Looking around for a program to do schematic's and
PCB's that I can afford and justify....
can find a schematic drawing package will send it that way. That is the
stage I am up to now. Looking around for a program to do schematic's and
PCB's that I can afford and justify....
Original Message
From: Don Bannon [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=IRhlOlMBnbNKbRRj9xJFBWQnEQVqQdkFP1cvAaZacG4M97sO2JAI4MihNpudmhHm3OjUdVLR]dbannon@s...[/url
Sent: Saturday, 28 October 2000 12:32
To: basicstamps@egroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Colpits/Hartley oscillator
Peter--
I would be interested in the moisture/frequency circuit. Can you send me
information or tell me where to find it?
Thank you,
Don Bannon dbannon@s...
>
Original Message
> From: Peter May [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=1RZm3DnqREifa9zl_OskzHLYlR_ZAYJWVT9Q8ccrwTEWeD80GQUFPy7tpGIGI-zrRpDnksf36p_CksT6Cw]manager@s...[/url
> Sent: Friday, October 27, 2000 5:40 AM
> To: Basic Stamp (E-mail)
> Subject: [noparse][[/noparse]basicstamps] Colpits/Hartley oscillator
>
>
> Hi group.
>
> I have need to monitor soil moisture. I have seen gypsum blocks,
> probes and
> other things. (I work for CSIRO here in Oz and we actually have a set-up
> that has 1 ton of ground plot on a balance and measures the extra
> weight as
> moisture) The latest method I have seen and the one I am about to
> play with
> is a oscillator circuit with a wound coil placed in the ground that
> depending on the moisture changes the frequency of the circuit etc.
>
> Has anyone played with this type of thing? I believe either BS1 or BS2 can
> read a frequency. Is this so and if so what is the maximum freq?
>
>
>
>
>