Subject:
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Re: Cheap air flow sensor
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 22 Jun 1998 14:39:16 GMT
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Original-From:
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Sathe Dilip <sathe_dilip@bah.&StopSpam&com>
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Viewed:
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1166 times
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Finally I managed to put the schematic of Wind-O-meter described in the
Elektor publication in ASCII. Pl. set your reader font to something
like courier to view it properly. I have taken some liberty with the
opamp symbol to accomodate some component connections.
+5V
0--------0-------0-----------------------------------
0----)--------)-------)--------------------------------0
| | | | |
| | # # /--------)-,
| | #33K #33K / 100K | |
| | # # ,-##/##-, | |
| | | | | | | |
| _|_ | | | ,-||-0 56pF | |
# |M | | | 10K |\|5 |8 |1 | |
# |__| 0-------)-----####------| '~~'~~~~'~\ | |
#10K | | ,---0 3|+ \6__0 |
|R1 | | | | 10K | IC 3130 / | |
| | ,---0 | 0-----####--0---|- / | |
| |C | | | |/ | 2|/~~~~~~~~~~ | |
| B|/ | |/ C '-| T3 | | |
'--| T1 '-| B |\ | 10M | |
|\ B|\ T2 |E '------####----------' |
|E |E | |
BC639 | BC549C| BC549C| |
| | | 0V |
0--------0-------0----------------------------------0-
M is a 50 mA meter (collector of T1). Opamp supply connections not
shown.
T1 and T2 are maintained in good thermal contact by glueing them
together using a heat conductive adhesive. This pair is used as the
probe to check wind speed/air leaks. T2 is maintained at a constant
temperature by the opamp and T1. When wind/leak is present, the pair is
cooled - more current has to flow through T1 to maintain the temp. This
current is indicated by the meter. T3 acts as a reference diode.
The description says - A high sensitivity is obtained by making the
temp. of T2 about 5 degrees higher than its surroundings. This is
achieved by presetting the meter to give an offset of about 5 mA when
there is no wind blowing. BC 639 can be replaced by a BC 547 type. R1 is
selected so that the current through T1 is not excessive. Hope this
helps.
Dilip
Sathe Dilip wrote:
>
> Elektor had published a similar circuit for detecting air leaks. The
SNIP
> Dilip
>
> Jonathan Swaby wrote:
> >
> > Does anyone know of a cheap way to construct an air flow sensor? I was
SNIP
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Message has 1 Reply:
 | | Re: Cheap air flow sensor
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| (...) (circuit and description deleted) Neat idea! It reminds me of a simple variometer (rate of climb/sink) circuit in an old RC glider magazine. It used two small naked bead or glass encapsulated thermistors in a bridge circuit and the thermistors (...) (26 years ago, 22-Jun-98, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | Re: Cheap air flow sensor
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| Elektor had published a similar circuit for detecting air leaks. The heated transistor and another transistor acting as temp. sensor were glued together using heatsink compound. You had then to nullify/calibrate a meter at ambient temp. when the (...) (26 years ago, 16-Jun-98, to lugnet.robotics.handyboard)
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