Circuit Cellar Contest - RF Transponder

I work with the TDA5xxx chips and others in my day job (short-range battery-powered radio stuff is my daily bread). So I am automatically eliminated; I can't work on this project because there is too much danger of accidental disclosure of something that just happens to be proprietary technology owned by my employer. Sorry.

OK, thanks anyway. TRF6903 is the alternative. It's smaller and single chip, but the problem is the 2 4.7uH inductors, they are bigger than the RF chip. The TDAs are using only nH. So, we can't decide which one to use yet.

Why are you worried? It's possible to build a complete transceiver based on the Infineon solution on a 2-layer PCB perhaps 1.5" x 1.5".

Did you look at Melexis, by the way?

But the TDA5210 (FSK version is hard to get, for now). It's $3000 (1K) minimum order. TRF6903 is $4 each, in single. The materials in the contest has to be easy to get and the result reproductable.

Will do so.

Hello Linnix,

Thanks for the honors but I have to politely decline (involvement in a commercial wireless project).

Hello Linnix,

Check out the Taiyo-Yuden CK series. Comes in 0603 size, about 1.6mm long. If you drop one of these it's pretty much guaranteed you won't find it anymore. Pretty low Q though (20 or so). Digikey usually has these in stock. They are cheap but I doubt they'd split a reel.

As for RF transceiver chips check out Nordic Semi as well.

Yes, that would work. But for $3000 minimum order, they might be disqualified.

Correction. $300 (qty 3000) minimum. May or may not be acceptable.

Hello Linnix,

They should be more like 5c a pop for a reel. Don't know if Taiyo would sample a few. If you mention that it could get published they might.

Another option may be a really tiny toroid. For a choke the actual value usually isn't critical. For the matching network after a resonator you might get away with that by changing the capacitor value.

I think that should be OK. It would not be too difficult to source something similar.

It's in the crystal clock resonator. I am surprised that the TDA can get away with nHs, while the TRF requires uH.

Hello Linnix,

Looks like the IF filter to me, with L1/C4 doing the phase shift for the diff input. Who knows why they decided to design the TRF with a differential IF input, doesn't make a lot of sense to me. Infineon didn't do that on the TDA5210.

Never mind, TDA5200 is available in single now (digikey), since last check a few days ago. Perhaps someone is listening.

OK, TDA5100/TDA5210 will do.

Additional ideas:

A portable unit can switch between the vehicle base station and terminal base station. If it's not convienent to move the trucks to the data dump area, just move the portable unit there.

Don't the trucks all go in/out through a gate? Ideal place for a data dump zone.

Whilst I have experience with some of that field, the chance to play with an ARM (Cortex M3) would be interesting.

I hope you realise I reside in UK.

Whilst it is an honour to be considered and amongst such 'luminaries' I am currently behind on some projects due to a week of illness and the major projects (ASIC testers) are expected to last until January.

I will have to bow out due to commercial commitments.

-- Paul Carpenter | snipped-for-privacy@pcserviceselectronics.co.uk PC Services GNU H8 & mailing list info For those web sites you hate

My suggestion is to use multiple channels of frequencies centered around 315MHz. Quarter wave antenna of 250cm should be mountable on top of trucks. Using multiple transmitters with different primary frequencies, it should cover area of hundred meters.

However, you must follow FCC (or equivalent) guidelines. Namely, no other users would complaint. Or you can get a license to override other uses. This should be doable for a commerical terminal.

That would dictate the use of RTF6903 over TDA5200, for 315MHz FSK SS.

Hello Paul,

Hey, the grudges from the Boston tea party are behind us by now :-)))

IIRC the rules say that it doesn't matter where the team mates reside. That's how it should be. The only thing you guys would have to agree on is whether it's realise or realize...

Yes, 25cm, of course. I am talking to myself again.

It is amazing how many times people forget and you get the panic phone call in early hours of the morning!

Or I could say that was just a storm in a tea cup, or look at the trouble caused by the inability to make a decent cup of tea. Don't get me started on alternative namings of holidays, as I believe last Monday was the National Cock up day - somebody heading for India and missing.

I have actually taken part in Circuit Cellar comp before. It is more of realisng the geograhical spread of a team and its communications let alone hardware/software being in the right place.

The usual problem is seeing the coloUr of their money. Usually because they can't find the person authorised to sign the cheque.

I trust you realize that the only approved tea in NA is generated by a grungy tea bag immersed in tepid water for an interminable time. The result proves the Bostonians were right roughly 230 years ago. Just try to find a tea pot without a resident dormouse. If you do it will be plastic.