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Home > Archive > Electrical Engineering > March 2007 > Inside my remote-sensor thermometer
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Inside my remote-sensor thermometer
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| Alex Coleman 2007-03-22, 8:25 pm |
| I have got a thermometer with a remore temperature sensor that sends
radio signals to update the base unit's display. The base unit also
has its own temperature sensor to let it display the indoors
temperature as well as the sensor's temperature.
The sender unit's antenna is a coil of wire which is about 1/4-inch
diameter and a couple of inches long. See these pics:
2_sender_B
http://www.flickr.com/photos/7472570@N06/430806010/
3_sender_(underside)
http://www.flickr.com/photos/7472570@N06/430806012/
The base unit's antenna is just a short length of wire. See these
pics:
4_thermo_(extra_panel)
http://www.flickr.com/photos/7472570@N06/430806014/
5_thermo_A (circuit only)
http://www.flickr.com/photos/7472570@N06/430806016/
TWO QUESTIONS: What is the best orientation for each of these units
so their antennas are postioned optimally? For simplicity I am
assuming no obstructions.
----
TWO MORE QUESTIONS: which component in the sender is the temperature
sensor? The sender's case seems sealed with no air vent!
Similarly, which component in the base unit is the sensor for the
indoors temperature? You can see the air vents in the base unit in
picture #4 but which component seen in close-up in #5 is the temp
sensor?
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| Brian MW0GKX 2007-03-22, 8:25 pm |
|
"Alex Coleman" <no@no-email.com> wrote in message
news:Xns98FBF17EE709F71F3M4@127.0.0.1...
>I have got a thermometer with a remore temperature sensor that sends
> radio signals to update the base unit's display. The base unit also
> has its own temperature sensor to let it display the indoors
> temperature as well as the sensor's temperature.
>
> The sender unit's antenna is a coil of wire which is about 1/4-inch
> diameter and a couple of inches long. See these pics:
>
> 2_sender_B
> http://www.flickr.com/photos/7472570@N06/430806010/
> 3_sender_(underside)
> http://www.flickr.com/photos/7472570@N06/430806012/
>
> The base unit's antenna is just a short length of wire. See these
> pics:
>
> 4_thermo_(extra_panel)
> http://www.flickr.com/photos/7472570@N06/430806014/
> 5_thermo_A (circuit only)
> http://www.flickr.com/photos/7472570@N06/430806016/
>
>
> TWO QUESTIONS: What is the best orientation for each of these units
> so their antennas are postioned optimally? For simplicity I am
> assuming no obstructions.
With the one I have (similar thing) it doesn't really matter, the coil would
suggest circular polarity
>
> ----
>
> TWO MORE QUESTIONS: which component in the sender is the temperature
> sensor? The sender's case seems sealed with no air vent!
I believe it's the round metal? component on the underside
>
> Similarly, which component in the base unit is the sensor for the
> indoors temperature? You can see the air vents in the base unit in
> picture #4 but which component seen in close-up in #5 is the temp
> sensor?
Again a guess at the white rectangular thinhie stood away form the board by
the ribbon cable.
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| Gordon Hudson 2007-03-23, 9:25 am |
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"Brian MW0GKX" <notsaying@here.com> wrote in message
news:nKEMh.13366$7l1.8910@newsfe4-gui.ntli.net...
>
> With the one I have (similar thing) it doesn't really matter, the coil
> would suggest circular polarity
Run that past me again?
A helical antenna has circular polarisation?
I don't mean a helical directional antenna for UHF, that one in the picture
is just a helically loaded antenna like you would get on a handheld radio so
its either going to be horizontal or vertical.
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| Alex Coleman 2007-03-23, 9:25 am |
| On 22 Mar 2007, Alex Coleman <no@no-email.com> wrote:
>
> I have got a thermometer with a remore temperature sensor that
> sends radio signals to update the base unit's display. The base
> unit also has its own temperature sensor to let it display the
> indoors temperature as well as the sensor's temperature.
>
> The sender unit's antenna is a coil of wire which is about 1/4-inch
> diameter and a couple of inches long. See these pics:
> http://www.flickr.com/photos/7472570@N06/430806010/
> http://www.flickr.com/photos/7472570@N06/430806012/
>
> The base unit's antenna is just a short length of wire. See these
> pics:
> http://www.flickr.com/photos/7472570@N06/430806014/
> http://www.flickr.com/photos/7472570N06/430806016/
>
> ------
>
> TWO QUESTIONS: What is the best orientation for each of these
> units so their antennas are postioned optimally? For simplicity I
> am assuming no obstructions.
>
> TWO MORE QUESTIONS: which component in the sender is the
> temperature sensor? The sender's case seems sealed with no air
> vent!
>
> Similarly, which component in the base unit is the sensor for the
> indoors temperature? You can see the air vents in the base unit in
> picture #4 but which component seen in close-up in #5 is the temp
> sensor?
>
> -------
> "Brian MW0GKX" <notsaying@here.com> wrote:
On 23 Mar 2007, Gordon Hudson <hostroute@gmail.com> wrote:[color=darkred]
>
> Run that past me again?
>
> A helical antenna has circular polarisation?
> I don't mean a helical directional antenna for UHF, that one in the
> picture is just a helically loaded antenna like you would get on a
> handheld radio so its either going to be horizontal or vertical.
>
I am the OP and I must say that I guess Brian's reply is accurate in
that it doesn't matter on which part one stands with respect to the
360 degrees of the curved part of the coil.
But even with your extra info about being similar to a handheld
device, I am still too much of a radio noobie to understand properly!
Sorry
I don't know if the ERP is at its max along the coil's axis or at
right angles to it. If it is maximal on-axis then is there anything
in radio theory which says one end of the coil's axis (eg. the free
end) in my device is better than the opposite end (ie. the attached
end)?
And don't forget my other queries about the base unit's reception!
See above.
Alex
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| Steve H 2007-03-23, 1:25 pm |
| "Alex Coleman" <no@no-email.com> wrote in message
news:Xns98FC88A12233F71F3M4@127.0.0.1...
> On 22 Mar 2007, Alex Coleman <no@no-email.com> wrote:
>
>
>
>
> On 23 Mar 2007, Gordon Hudson <hostroute@gmail.com> wrote:
>
> I am the OP and I must say that I guess Brian's reply is accurate in
> that it doesn't matter on which part one stands with respect to the
> 360 degrees of the curved part of the coil.
>
> But even with your extra info about being similar to a handheld
> device, I am still too much of a radio noobie to understand properly!
> Sorry
>
> I don't know if the ERP is at its max along the coil's axis or at
> right angles to it. If it is maximal on-axis then is there anything
> in radio theory which says one end of the coil's axis (eg. the free
> end) in my device is better than the opposite end (ie. the attached
> end)?
>
> And don't forget my other queries about the base unit's reception!
> See above.
>
> Alex
A normal mode helical will have a radiation pattern similar to a 1/4 wave
with linear polarisation, you only get circular polarisation when the
diameter is around the wavelength (Helix). In this instance the polar
diagram would be anyone's guess as its using the rest of the transmitter as
a counterpoise rather than a regular ground plane. If you want to increase
the range of the transmitter take two short lengths of wire around 18 c.m.
each. Remove the existing helical antenna and replace with one of the
wires, solder the other wire to the negative battery supply.
Steve H
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