Custom USB tyre pressure monitoring interface - Page 56

DigitalVampire · 01-31-2009, 01:11 AM

Can anyone please post the details of the original receiver antenna which came in the 3rd eye module.

I'm interested in the guage/thickness of the wire, number of turns, inner diameter of the cylinder and spacing between turns.

Lok · 02-06-2009, 10:35 AM

The original reciver uses a 433.92 MHz Helical antenna and has about 4.5 turns (6.5 inches in length). From your questions it sounds like you are trying to replace the antenna on my board, so I will give you some insider information.

. There are three types of antennas you can use for this application, Rigid Monopole, Helical, or Flexible Monopole. Rigid Monopole is like the radio antenna that sticks out of your car and it has the best reception for the three but is also not practical for this application as you require a 6.5 (+/- .25) inch antenna to stick out from the board. Option 2, the helical antenna is the next best option to the rigid monopole but in my case I was not able to find one that would fit on the original board design (Revision 2 will have a new style helical antenna on it as the board is being modified to fit it). Last but not least is your flexible monopole which is nothing but a simple non-sheilded wire (less than 8 guage). In any case the reception of the reciver is far superior than the original 3rd eye so using the flexible monopole antenna doesn't make a difference. Well I hope this little tid bit helps you out.

WuNgUn · 02-06-2009, 11:02 AM

Quote: Originally Posted by WuNgUn

Here's the mess I'm in now...any wonder why it stopped working?

Here, you can see where I moved the top pin over to the SMD resistor because the trace lifted off the PCB...

And what's worse, the bridge over the SMD in the foreground...at least, it looked like it was s'pose to bridge the SMD!

I reheated it and dabbed it with solder, but there was tension on the pin, lifting upwards, and I think it basically pulled the SMD off the board and drowned it in solder

If it's a bridged connection, is it even really needed?

I'll de-solder that front pin, clean it up and try for a re-solder to the board...

This is where I initially had a problem with the software...I think it'll detect the device plugged in and 'OK', even if the receiver isn't even soldered to the board.
So I'll have to try and get a 'learn' to know if it's functioning...
I'll report back...

I think I have the board working again...at least I hope (PC is on the bench right now)...
I used my multimeter (continuity) and checked the ground points...good.
I plugged the board in and powered it up and checked the power connection...reading 5V at R9 and reading voltage at other points of the board...
Measured the JP2 connection, and there is power coming to the board...checked further down the PCB and reading the signal there as well.
So I think I'm back up...
However, I can't test it with the sensors.
And I STILL can't keep the device installed between reboots/hibernate as it get's 'lost'...
And I still can't find the latest CF plugin

bemenaker · 02-06-2009, 02:13 PM

Back in August, someone was posting they were curious what is inside the wheel sensors, since they are potted and you can't see them. I work at a facility that manufactures circuit boards, and I can xray one and take pictures if you are interested. If someone sends me a broken one I will happily xray it and take pics to post, if this is important for any reason.

HiJackZX1 · 02-06-2009, 02:35 PM

Quote: Originally Posted by bemenaker

Back in August, someone was posting they were curious what is inside the wheel sensors, since they are potted and you can't see them. I work at a facility that manufactures circuit boards, and I can xray one and take pictures if you are interested. If someone sends me a broken one I will happily xray it and take pics to post, if this is important for any reason.

I think people somewhere in this thread posted pictures of busted up tire sensors. All I saw though was a circuit and lots of white glue. I think it was also to keep the insides from rattling.

Blues · 02-06-2009, 03:27 PM

Quote: Originally Posted by HiJackZX1

I think people somewhere in this thread posted pictures of busted up tire sensors. All I saw though was a circuit and lots of white glue. I think it was also to keep the insides from rattling.

Here's the picture from bes51659
http://www.mp3car.com/vbulletin/1265065-post793.html
http://web.comhem.se/bengt-olof.swing/TPMS.htm

DigitalVampire · 02-07-2009, 12:39 AM

Quote: Originally Posted by Lok

The original reciver uses a 433.92 MHz Helical antenna and has about 4.5 turns (6.5 inches in length). From your questions it sounds like you are trying to replace the antenna on my board, so I will give you some insider information.

. There are three types of antennas you can use for this application, Rigid Monopole, Helical, or Flexible Monopole. Rigid Monopole is like the radio antenna that sticks out of your car and it has the best reception for the three but is also not practical for this application as you require a 6.5 (+/- .25) inch antenna to stick out from the board. Option 2, the helical antenna is the next best option to the rigid monopole but in my case I was not able to find one that would fit on the original board design (Revision 2 will have a new style helical antenna on it as the board is being modified to fit it). Last but not least is your flexible monopole which is nothing but a simple non-sheilded wire (less than 8 guage). In any case the reception of the reciver is far superior than the original 3rd eye so using the flexible monopole antenna doesn't make a difference. Well I hope this little tid bit helps you out.

Thanks for your detailed response Lok...Yes I was trying to replace the flexible wire antenna with something more rigid as in the original kit. Makes sense to have a stable flex free antenna especially on Indian road conditions

mrbean_phillip · 02-07-2009, 04:37 AM

@ DigitalVampire:

I might get one of these

Exactly what we're looking for, stud mount to the case, and solder connection to the pcb.

Now, to find a supplier in Australia.

DigitalVampire · 02-07-2009, 05:18 AM

Quote: Originally Posted by mrbean_phillip

@ DigitalVampire:

I might get one of these

Exactly what we're looking for, stud mount to the case, and solder connection to the pcb.

Now, to find a supplier in Australia.

Good find Mr. Bean. If you finally source it, I'm sure you'll keep us posted.

I'm going a bit slow on the entire CarPC episode because of work commitments.

Blues · 02-07-2009, 03:36 PM

Quote: Originally Posted by mrbean_phillip

@ DigitalVampire:

I might get one of these

Exactly what we're looking for, stud mount to the case, and solder connection to the pcb.

Now, to find a supplier in Australia.

If you can use another brand than this Antennafoactor / Linx Technologies, then look here at Farnell Australia and RS Components Australia:
http://au.farnell.com/jsp/search/bro...na+whip+433MHz
http://australia.rs-online.com/web/s...antenna+433mhz
Both Farnell and RS Components has locations almost worldwide including Australia.

Farnell offers 433MHz 1/4-wave whip antennas from RF Solutions: http://www.rfsolutions.co.uk/acatalo...p_Antenna.html
You can also by these antennas online diretly from RF Solutions loacted in the UK.

RS Componnets offer 433MHz 1/4-wave whip antennas from Centurion/Laird Technologies (Centurion Wireless Technologies is now Laird Technologies): http://www.lairdtech.com/pages/produ...o-Overview.asp
Old Centurion website: http://www.centurion.com

Blues · 02-07-2009, 04:26 PM

Quote: Originally Posted by Lok

Rigid Monopole is like the radio antenna that sticks out of your car and it has the best reception for the three but is also not practical for this application as you require a 6.5 (+/- .25) inch antenna to stick out from the board.

Why 6.5 inch? Shouldn't it be 6.8 inch (17.2cm) for a 433.92 MHz 1/4-wavelength antenna?
http://www.onlineconversion.com/freq...wavelength.htm

mrbean_phillip · 02-07-2009, 04:36 PM

@ Blues: Yep, we can use anything that will work, approximately 1/4-wavelength length for optimum results.

Wavelength for 433.92Mhz is lambda=Speed of Light/fequency, thus 299,792,458/433.92Mhz = 690,893mm.

297,792,458meter/sec = 187,370miles/sec (approximate)

1/4 Wave is then 690.893/4 = 172,723mm

or, if your imperially declined, 172,723/25.4 = 6.80"

So, as long as we stick to the above rule (for optimum results), we can use any antenna tuned for this frequency.

Here's a nice one at Farnell's.

All we need to do is run a short piece of 50ohm coax from the antenna to the pcb, and make sure the ground (outer screen) is connected to the pcb ground - thanx for leaving the grounding-point on the pcb, Alok - nice touch - this gives us a few options!

edit: @ Blues: Nice calculator

I compiled my post, not seeing yours, would have saved me the manual calculations. Well, Alok's formula possibly includes the "shortening factor" when calculating antenna-lengths, but, it doesn't have a real effect at high frequencies.

So around 6.5" - 6.80" should be optimum.

WuNgUn · 02-07-2009, 04:43 PM

Is the built-in antenna that weak??

Blues · 02-07-2009, 04:49 PM

Quote: Originally Posted by WuNgUn

Is the built-in antenna that weak??

I don't know if it's too weak or not as I haven't got this system.
But a problem is probably that the car body (+metal rims) acts as a shield between the tire sensors and the receiver inside the car. This will reduce the signal strenght some.

mrbean_phillip · 02-07-2009, 05:01 PM

@ Wungun: It's a good antenna solution, if only a piece of wire - that's really all the more expensive antennas are, just encased in quality plastic.

So, Alok's antenna should work a fair bit better than the original 3rd Eye kit's......only problem for me is aestethics.....so, I will get something more decent, and mount it at glas-level, to try and overcome the wheel->cabin-barrier....if the antenna was mounted externally, even better.

But, in most cases, the new solution should work very well.....

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