what materials can GPS signals go through

P

Phil

Guest
Hi all,

Just purchasing a GPS receiver in chip form with aerial. I will need to put
it into some sort of weather resistant enclosure. (its going in/on the car)
The PCB measures 2inches x 3inches.

I was thinking of an old computer mouse case, sealed with epoxy resin.
Actually I was thinking of also dipping the receiver board and aerial in
epoxy resin to protect it from moisture as well.

As I do not want to stuff it up at this early stage, I though it would be
prudent to ask you guys if there is anything that might be damaged if I do
this. I know that GPS signals can be quickly attenuated with foliage and
obstacles, so any pointers appreciated. Is there a special type of plastic
required that will allow GPS signals through? Will dipping the board into
resin hurt any of the onboard inductor ratings, and offset any measurements?
Will dipping the aerial do any damage? Any other forseeable problems?

Do GPS signals go through most plastics? I might be forced to mount the
aerial inside the bumper of the car. How about fibre glass?

Regards,
Hax.
 
Definitely do not epoxy coat aerial or receiver, because it will stop
working ! Sealing into an enclosure is the way to go.

If you put plastic in your microwave oven and it doesn't get hot or melt, it
is low loss. Careful - test with short bursts at first, or you could have
nasty smoke or fire in your oven ! You could even buy a microwave - safe
food container and use that for the enclosure !

Some jiffy boxes might be OK.

Other thoughts are styrene based plastics, perspex, polyethylene and glass.

Roger



"Phil" <reply to thread> wrote in message
news:414444ef$0$15372$afc38c87@news.optusnet.com.au...
Hi all,

Just purchasing a GPS receiver in chip form with aerial. I will need to
put
it into some sort of weather resistant enclosure. (its going in/on the
car)
The PCB measures 2inches x 3inches.

I was thinking of an old computer mouse case, sealed with epoxy resin.
Actually I was thinking of also dipping the receiver board and aerial in
epoxy resin to protect it from moisture as well.

As I do not want to stuff it up at this early stage, I though it would be
prudent to ask you guys if there is anything that might be damaged if I do
this. I know that GPS signals can be quickly attenuated with foliage and
obstacles, so any pointers appreciated. Is there a special type of plastic
required that will allow GPS signals through? Will dipping the board into
resin hurt any of the onboard inductor ratings, and offset any
measurements?
Will dipping the aerial do any damage? Any other forseeable problems?

Do GPS signals go through most plastics? I might be forced to mount the
aerial inside the bumper of the car. How about fibre glass?

Regards,
Hax.
Click to expand...
 
"Phil" <reply to thread> wrote in message news:<414444ef$0$15372$afc38c87@news.optusnet.com.au>...
Hi all,

Just purchasing a GPS receiver in chip form with aerial. I will need to put
it into some sort of weather resistant enclosure. (its going in/on the car)
The PCB measures 2inches x 3inches.

I was thinking of an old computer mouse case, sealed with epoxy resin.
Actually I was thinking of also dipping the receiver board and aerial in
epoxy resin to protect it from moisture as well.

As I do not want to stuff it up at this early stage, I though it would be
prudent to ask you guys if there is anything that might be damaged if I do
this. I know that GPS signals can be quickly attenuated with foliage and
obstacles, so any pointers appreciated. Is there a special type of plastic
required that will allow GPS signals through? Will dipping the board into
resin hurt any of the onboard inductor ratings, and offset any measurements?
Will dipping the aerial do any damage? Any other forseeable problems?

Do GPS signals go through most plastics? I might be forced to mount the
aerial inside the bumper of the car. How about fibre glass?

Regards,
Hax.
Click to expand...
Don't pot the board in anything, just put it in a good sealed plastic
enclosure. Most plastics should be OK.
If you have a decent sloping front windscreen then you could get away
with mouting the box on the front dash. It would probably see more sky
than the bumper.

What's your application?

Dave :)
 
"David L. Jones" <altzone@gmail.com> wrote in message
news:459b0886.0409121652.55fe13df@posting.google.com...
"Phil" <reply to thread> wrote in message
news:<414444ef$0$15372$afc38c87@news.optusnet.com.au>...
Hi all,

Just purchasing a GPS receiver in chip form with aerial. I will need to
put
it into some sort of weather resistant enclosure. (its going in/on the
car)
The PCB measures 2inches x 3inches.

I was thinking of an old computer mouse case, sealed with epoxy resin.
Actually I was thinking of also dipping the receiver board and aerial in
epoxy resin to protect it from moisture as well.

As I do not want to stuff it up at this early stage, I though it would
be
prudent to ask you guys if there is anything that might be damaged if I
do
this. I know that GPS signals can be quickly attenuated with foliage and
obstacles, so any pointers appreciated. Is there a special type of
plastic
required that will allow GPS signals through? Will dipping the board
into
resin hurt any of the onboard inductor ratings, and offset any
measurements?
Will dipping the aerial do any damage? Any other forseeable problems?

Do GPS signals go through most plastics? I might be forced to mount the
aerial inside the bumper of the car. How about fibre glass?

Regards,
Hax.

Don't pot the board in anything, just put it in a good sealed plastic
enclosure. Most plastics should be OK.
If you have a decent sloping front windscreen then you could get away
with mouting the box on the front dash. It would probably see more sky
than the bumper.

What's your application?

Dave :)
Click to expand...
Dave,

Application is for a home made car tracker connected to a mobile phone. I
will use a picaxe microprocessor to read serial NMEA signal coming from the
GPS. The microprocessor will then transmit the coordinates through a simple
DTMF circuit via head set through to the mobile phone.

The receiver will be a DTMF decoder circuit connected to a land phone or
mobile. I might have an LCD screen on it or just one single 8 segment LED
display. The user will have to write down the coordinates as they come
through. Then its a matter of checking the coordinates with a street
directory to pinpoint the car.

Rather crude arrangement without using specialised bits such as a GSM modem
etc, but it is more for fun than anything practical. The phone will simply
be switched on all the time and set to auto answer so I don't even have to
modify the phone.

Actually this project was spawned from a post in this news group which
allerted me to this web page. http://www.radiohound.com/randgps.htm

I have just picked up a Rand Mcnally receiver on ebay for the job. I have
always been interested in GPS technology, and for a total of US$50 including
shipping to OZ, I couldn't stop myself from giving it a go.

BTW, I can appreciate the delicate nature of GPS receivers, but what exactly
will the epoxy break on the board? A member of another group stated that
heat would build up in the components, (no air flow) but I doubt that would
do much as the whole board uses less than half a watt. I was more concerned
with the inductors losing their values due to the induced resin.


Regards,
Phil
 
"Phil" <reply to thread> wrote in message news:<41453b7b$0$20584$afc38c87@news.optusnet.com.au>...
"David L. Jones" <altzone@gmail.com> wrote in message
news:459b0886.0409121652.55fe13df@posting.google.com...
"Phil" <reply to thread> wrote in message
news:<414444ef$0$15372$afc38c87@news.optusnet.com.au>...
Hi all,

Just purchasing a GPS receiver in chip form with aerial. I will need to
put
it into some sort of weather resistant enclosure. (its going in/on the
car)
The PCB measures 2inches x 3inches.

I was thinking of an old computer mouse case, sealed with epoxy resin.
Actually I was thinking of also dipping the receiver board and aerial in
epoxy resin to protect it from moisture as well.

As I do not want to stuff it up at this early stage, I though it would
be
prudent to ask you guys if there is anything that might be damaged if I
do
this. I know that GPS signals can be quickly attenuated with foliage and
obstacles, so any pointers appreciated. Is there a special type of
plastic
required that will allow GPS signals through? Will dipping the board
into
resin hurt any of the onboard inductor ratings, and offset any
measurements?
Will dipping the aerial do any damage? Any other forseeable problems?

Do GPS signals go through most plastics? I might be forced to mount the
aerial inside the bumper of the car. How about fibre glass?

Regards,
Hax.

Don't pot the board in anything, just put it in a good sealed plastic
enclosure. Most plastics should be OK.
If you have a decent sloping front windscreen then you could get away
with mouting the box on the front dash. It would probably see more sky
than the bumper.

What's your application?

Dave :)

Dave,

Application is for a home made car tracker connected to a mobile phone. I
will use a picaxe microprocessor to read serial NMEA signal coming from the
GPS. The microprocessor will then transmit the coordinates through a simple
DTMF circuit via head set through to the mobile phone.

The receiver will be a DTMF decoder circuit connected to a land phone or
mobile. I might have an LCD screen on it or just one single 8 segment LED
display. The user will have to write down the coordinates as they come
through. Then its a matter of checking the coordinates with a street
directory to pinpoint the car.

Rather crude arrangement without using specialised bits such as a GSM modem
etc, but it is more for fun than anything practical. The phone will simply
be switched on all the time and set to auto answer so I don't even have to
modify the phone.

Actually this project was spawned from a post in this news group which
allerted me to this web page. http://www.radiohound.com/randgps.htm

I have just picked up a Rand Mcnally receiver on ebay for the job. I have
always been interested in GPS technology, and for a total of US$50 including
shipping to OZ, I couldn't stop myself from giving it a go.

BTW, I can appreciate the delicate nature of GPS receivers, but what exactly
will the epoxy break on the board? A member of another group stated that
heat would build up in the components, (no air flow) but I doubt that would
do much as the whole board uses less than half a watt. I was more concerned
with the inductors losing their values due to the induced resin.

Regards,
Phil
Click to expand...
Hi Phil,
It's likely that the epoxy won't do anything except completely gunk up
your circuit so you can't touch it again if you need to. For an
experimental circuit like this avoid potting at all costs from a
simple need to repair/troubleshoot/tweak point of view.
There may be some small risk also that the potting could attenuate or
interfere with the reception properties of the antenna. You won't know
this until after you pot it, and then it's too late to remove it. That
would suck.
Heat buildup won't be an issue.

For an application like this you would typically re-encode the NMEA
stream at the receiver end and then feed into a moving map display
system like OziExplorer. The cars position then gets plotted in real
time overlayed on a street directory map - very cool. OziExplorer will
also take care of any necessary grid and datum conversion. For
instance, street directories use the UTM co-ordinate system, so if
your NMEA stream is giving you Lat/Long cordinates then your micro on
the receiver will have to convert to UTM for display. It's a pain in
the butt to convert Lat/Long to UTM manually.
You also have to watch out for the datum. Sydney street directories
still use the old AGD66 datum, whereas some other staes use the new
GDA94 (equivalent to WGS84 which is the GPS standard). Getting this
wrong can put you out by up to a few hundred meters.

If you love GPS technology then you'll have some real fun with
Geocaching, give it a go. www.geocaching.com.au and www.geocaching.com

Regards
Dave :)
 
"David L. Jones" <altzone@gmail.com> wrote in message
news:459b0886.0409131801.3cd82c54@posting.google.com...
"Phil" <reply to thread> wrote in message
news:<41453b7b$0$20584$afc38c87@news.optusnet.com.au>...
"David L. Jones" <altzone@gmail.com> wrote in message
news:459b0886.0409121652.55fe13df@posting.google.com...
"Phil" <reply to thread> wrote in message
news:<414444ef$0$15372$afc38c87@news.optusnet.com.au>...
Hi all,

Just purchasing a GPS receiver in chip form with aerial. I will need
to
put
it into some sort of weather resistant enclosure. (its going in/on
the
car)
The PCB measures 2inches x 3inches.

I was thinking of an old computer mouse case, sealed with epoxy
resin.
Actually I was thinking of also dipping the receiver board and
aerial in
epoxy resin to protect it from moisture as well.

As I do not want to stuff it up at this early stage, I though it
would
be
prudent to ask you guys if there is anything that might be damaged
if I
do
this. I know that GPS signals can be quickly attenuated with foliage
and
obstacles, so any pointers appreciated. Is there a special type of
plastic
required that will allow GPS signals through? Will dipping the board
into
resin hurt any of the onboard inductor ratings, and offset any
measurements?
Will dipping the aerial do any damage? Any other forseeable
problems?

Do GPS signals go through most plastics? I might be forced to mount
the
aerial inside the bumper of the car. How about fibre glass?

Regards,
Hax.

Don't pot the board in anything, just put it in a good sealed plastic
enclosure. Most plastics should be OK.
If you have a decent sloping front windscreen then you could get away
with mouting the box on the front dash. It would probably see more sky
than the bumper.

What's your application?

Dave :)

Dave,

Application is for a home made car tracker connected to a mobile phone.
I
will use a picaxe microprocessor to read serial NMEA signal coming from
the
GPS. The microprocessor will then transmit the coordinates through a
simple
DTMF circuit via head set through to the mobile phone.

The receiver will be a DTMF decoder circuit connected to a land phone or
mobile. I might have an LCD screen on it or just one single 8 segment
LED
display. The user will have to write down the coordinates as they come
through. Then its a matter of checking the coordinates with a street
directory to pinpoint the car.

Rather crude arrangement without using specialised bits such as a GSM
modem
etc, but it is more for fun than anything practical. The phone will
simply
be switched on all the time and set to auto answer so I don't even have
to
modify the phone.

Actually this project was spawned from a post in this news group which
allerted me to this web page. http://www.radiohound.com/randgps.htm

I have just picked up a Rand Mcnally receiver on ebay for the job. I
have
always been interested in GPS technology, and for a total of US$50
including
shipping to OZ, I couldn't stop myself from giving it a go.

BTW, I can appreciate the delicate nature of GPS receivers, but what
exactly
will the epoxy break on the board? A member of another group stated that
heat would build up in the components, (no air flow) but I doubt that
would
do much as the whole board uses less than half a watt. I was more
concerned
with the inductors losing their values due to the induced resin.

Regards,
Phil

Hi Phil,
It's likely that the epoxy won't do anything except completely gunk up
your circuit so you can't touch it again if you need to. For an
experimental circuit like this avoid potting at all costs from a
simple need to repair/troubleshoot/tweak point of view.
There may be some small risk also that the potting could attenuate or
interfere with the reception properties of the antenna. You won't know
this until after you pot it, and then it's too late to remove it. That
would suck.
Heat buildup won't be an issue.

For an application like this you would typically re-encode the NMEA
stream at the receiver end and then feed into a moving map display
system like OziExplorer. The cars position then gets plotted in real
time overlayed on a street directory map - very cool. OziExplorer will
also take care of any necessary grid and datum conversion. For
instance, street directories use the UTM co-ordinate system, so if
your NMEA stream is giving you Lat/Long cordinates then your micro on
the receiver will have to convert to UTM for display. It's a pain in
the butt to convert Lat/Long to UTM manually.
You also have to watch out for the datum. Sydney street directories
still use the old AGD66 datum, whereas some other staes use the new
GDA94 (equivalent to WGS84 which is the GPS standard). Getting this
wrong can put you out by up to a few hundred meters.

If you love GPS technology then you'll have some real fun with
Geocaching, give it a go. www.geocaching.com.au and www.geocaching.com

Regards
Dave :)
Click to expand...

Dave,

I have built the receiver last night. It shows the latitude/longitude via a
single 7 segment display. It's a crude arrangement designed to simply give
you the coordinates of the stolen car without the need for a PC. But you
have an excellent idea of using the receiver to emulate the NMEA stream into
a computer. That would open up a whole new world of options. I will be
rally driving (nothing fancy) in late 2005, and I can see that even with our
limited budget, we can still have some very good remote telemetry and
tracking features that might become very useful.

I have decided to place the GPS receiver on the back parcel shelf inside the
car. That should be enough for reasonable pickup and will stop it from
getting wet (or broken). (don't have to drill through the roof too)

I have looked into changing the format of melway maps, and if you are
interested, the following sites are excellent:

http://services.land.vic.gov.au/landchannel/content/interactivemap
http://www.ga.gov.au/nmd/geodesy/datums/redfearn_grid_to_geo.jsp


Regards,
Phil
 
"Phil" <reply to thread> wrote in message news:<414786e5$0$28804$afc38c87@news.optusnet.com.au>...
Dave,

I have built the receiver last night. It shows the latitude/longitude via a
single 7 segment display. It's a crude arrangement designed to simply give
you the coordinates of the stolen car without the need for a PC. But you
have an excellent idea of using the receiver to emulate the NMEA stream into
a computer. That would open up a whole new world of options. I will be
rally driving (nothing fancy) in late 2005, and I can see that even with our
limited budget, we can still have some very good remote telemetry and
tracking features that might become very useful.

I have decided to place the GPS receiver on the back parcel shelf inside the
car. That should be enough for reasonable pickup and will stop it from
getting wet (or broken). (don't have to drill through the roof too)

I have looked into changing the format of melway maps, and if you are
interested, the following sites are excellent:

http://services.land.vic.gov.au/landchannel/content/interactivemap
http://www.ga.gov.au/nmd/geodesy/datums/redfearn_grid_to_geo.jsp


Regards,
Phil
Click to expand...
If you want GPS and remote telemetry then it's worthwhile looking into
long range wireless RS-232 modems. You can get units which go tens of
km. That way you could simply have any commercial GPS receiver or
module with RS-232 output plugged into a wireless RS232 transmitter
and then the receiver going straight into the PC. Instant moving map
display of your car in OxiExplorer - cool. No electronics to design.
You can even have multiple channels.

Regards
Dave :)
 
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