1 1/2 years later, and this thread gets better and better!

I was previously unfamiliar, but I liked this description...

http://web.mit.edu/6.02/www/f2010/ha...ectures/L9.pdf

http://www.rctech.net/forum/12222187-post251.html

howardcano,

LOOP CONSTRUCTION:

Use 18 AWG stranded, insulated wire. Wire must terminate as closely as possible to loop amplifier input, with minimal lead-in length. Place loop 12" above track.

9'x1' to 12'x1' : No jumpers on loop amplifier.

6'x1' to 8'x1' : Use jumper at J3 on loop amplifier.

3'x1' to 4'x1' : Use jumper at J5 on loop amplifier.



On your loop PCB, J4 is not use ? is always ON ?

Thanks

J4 is currently not used.

ok, we can delete C6 and R12 if J4 is not used on the loop amplifier.
It ' s OK ?

Yes.

Hello Howard,

Great project! i came across this from finding your transponder design thread. Now i have went through alot of it skip some pages, im no electrical engineer but i am interested in this as a low cost system for our club, we are using the Robitronics but its not very accurate and its difficult to get people to spend $45 for that transponder on top of the MyLaps RC4 they already have. We certainly cant afford a RC4 decoder.

So if i can build something affordable and hand out transponders for free or for very little charge then we can hold more races and even invite others.

1. From what i understand you have a working decoder with transponders?
2. Do you have an final plans with a list of materials? instructions?
3. Which timing software is compatible with your decoder? We use Flip Side Racing (opensource) i think that fits well with your project!

is anyone using this at a track sucessfully ?

thanks!

It's been nearly 10 months since I posted the specs, so for those who have not read through the entire thread (which is getting quite long now!), here they are:

http://www.rctech.net/forum/12222187-post251.html

Here are some answers to your questions:

1) Yes.

2) Send me your email address in a private message and I'll send all of the info.

3) Flipside and Zround.

I'll let our readers respond to your last question.

This is a very complex project, if you are not extremely knowledgeable in electronics, you'll need to enlist the help of a friend!

About the specs ok yes i remember coming across them but thanks for posting again. Yes the threads are long i read alot of it and skpped some parts so i was not sure at what stage its at.

Thanks for the quick reply, yes i am possibly able to do this but if not i have friends who are electrical engineers and others that understand electrical so i can get help.

I will PM you now with my email.

thanks!

Hi guys!
I have great news - Payalneg find encription method to determine amb/mrt transponders as is - with numbers at box!
At this weekend I plan to test this version of firmware, I'll post result ASAP.

Thats very good to hear! All of this pogress is amazing, we cant thank you guys enough!

Can the detection loop be installed under a carpet or on the carpet covered by tape? Would like to do this without a bridge.

Would the loop work with FlatWire? (taperwire) http://www.taperwire.com/

or other kind of flat wire?

thanks!

I think you'll have good luck as long as the floor isn't conductive. But even concrete can have rebar that will mess up the signal.

The gauge of wire affects the tuning slightly, but the biggest reasons I chose 18 AWG were strength, low cost, and availability. You can go thinner if you want to get the carpet to lay flatter, and you can also use ribbon cable with several conductors wired in parallel. Both of these options will likely be cheaper than any specialty wire.

thanks Howard,

Yes ribbon cable sounds like a good idea. Our carpet is directly on concrete so yes there is rebar near by, actually our track is in a basement so we are surrounded by concrete!

Can i shield the ribbon cable from the concrete floor? what could be used to do that?

thanks!

My apologies for this late response to your question.

The loop is affected by any conductors nearby, so shielding is exactly the opposite of what we want.

My advice is try it and see how it goes. If you encounter problems, you can always go back to the original loop specification.

It's time for a celebration! This thread is now 16 months old, and just surpassed 50,000 views.

Thanks to all of you for your interest. I hope you have found it fun and informative.

:tire::);):D:tire:

No problems Howard. Ok i think i will take opposite approach and build to original specs and get it working, then i can try variation under carpet.

Congrats on the 50k views and all your hard work to make this possible for all of us!

thanks!

Hi Howard,

I have not had any luck getting a hold of Flip Side Racing concerning a version for Cano, no response in Miniz forums and no contact form on website. Do you have an email for them ?

For Zround i have found. For those who want the download link here it is http://www.zround.com/download.php?list.5

what is the third software company?

thanks!

I just emailed the FlipSide software to you.

The third company requested many changes to the data sent by the decoder to match their software, and I did not pursue it further.

got the software Howard, thanks.

About the errata below, does it still apply? was the PCB design corrected in the version i am using? this is for REV B if i understand, you would have corrected this in REV C but its not tested?

"The 1uF capacitor on U2 (the 7805 regulator) was mislabeled on the schematic (duplicated “C4” reference designators), and consequentially was not included on the board. The cap should be soldered directly to U2.

The node label “3D” was misplaced on the schematic at U20A pin 3, causing the connection to be ignored. A jumper must be soldered from U20A pin 3 to U21 pin 4."

Yes, the errata still applies. If you feel you want to take the risk, you could make the corrections before you made new boards.

FYI, I just updated the spec post, as I realized it still indicated the loop amp board was untested.

Received my decoder boards! they look great. Now working on getting transponder board design updated and then made. I will start building decoder as soon as i have all the parts.

http://www.hostingforcanada.com/denn...der_boards.jpg

Somes news ?
thanks

How many messages are send by a RC4 transponder ?
RC3 preamble + "ID" message
RC3 preamble +7 status messages
RC4 preamble + ?????

thanks.

I don't know the exact number for the RC4, or even if there is one. There were many more unique transmissions than I was willing to count.

If an Rc4 has no sequence message, Payalneg, how you detect an rc4 transponder ?

Thanks.

OK,thanks, between a RC3 and RC4 sequences on a RC4 transponder, have you seen some equal bit after their preamble ?

I don't have a a dog in this hunt, but could you place a sheet of shielding material between the concrete and the carpet? Instead of shielding the loop itself?

No, the loop can't be shielded since it needs to receive the field from the transponder. It needs to be as far away from any extraneous conductors as possible. Several feet would be best.

Welcome to the thread, Snoopy!

Ok. I don't know enough about it. I was thinking of it more as shielding the concrete than the loop. Stacked as concrete, shield, loop, and carpet.
(Edit: Or if using a bridge; concrete, shield, carpet, transponder, loop.
Can shielding material be bought in sheets? Surely guys who do car stereo installations use something like that.)

I haven't chimed in, but I have been lurking. I have an RC4, but it was very hard to come by. I think the club for who can be a race director is too exclusive, too expensive, and just too difficult to get into. You and this thread. You have kicked a door open, for those who may not be loaded, but are determined or otherwise able to do it. You have made a way.

Decoders should be five or six hundred bucks. Transponders less than forty, but that is just my daydream. You are doing a good thing here. I wish I had more to contribute than my encouragement.

Test:

http://www.dropbox.com/sc/ypofh11b6f...0XiT2-XmCRbXDa

Testday at our local track with Cano_transponder and decoder.
 

Today a succesful testday at our local racetrack. We used two 4wd FG Mini's, the Cano-tranponders with the round shaped PCBA's, a decoder with miodified processor to have USB link to the laptop and to supply the decoderbox over USB. The loop is build inside two heavy rubber sheets for easy transport to other tracks.

Today a succesful testday at our local track
 

Remaing picture of testday at local track:

Many thanks for posting the photos! Your progress is very gratifying to me.

The loop inside the rubber sheets is a great idea.

Thank you Howard for your kind reply! Here some more details for the loop and the build.
It started in our kitchen on the floor because of cold temperatures during the winter period. The rubber sheets are taken from our office were we got new furniture and the anti-static mats were replaced by new onces. I took all old mats home...
I realize these mats have some kind of conductive layer, but if you think of put the loop on tarmac or (wet) sand, this also conducts. The conductance is not low-Ohmic so it should be OK. As an example I also attached a picture of how these mats look like.
I needed a wider loop as what I can build from one sheet, so I needed at least 2 next to each other. The top-layer is then attached in a way they overlap the bottom sheets. If one can get hold of rubber-sheets in the correct width, this is easier.
The wire of the loop is first stitched by thin double_sided tape and after that on both sides of the wire double_sided foam tape is applied. This secures the wire even better once the top sheet is placed. After all 3 parts of the top sheets are in place, I used stapples all around the mat to prevent the double_sided foam tape from detaching while rolling the mat during transport. Every 1cm has a stapple :-). Enjoy watch the attached pictures:

The rubber mats are stiched in such a way the result is a shallow step in the direction the cars appraoch and leave the loop. The bottom sheet is about 10cm wider at both ends so the front spoiler will not 'hook' the rubber. Here the remaing pictures:

+1 And not to mention offering a pretty good short course on high frequency electronics, RF electronics, DSP, test and debug... and many more. Lots of gems to be found in this thread!

Hi,

First some background bits : I'm together with friends runing an RC club (mainly 1/5 TT) in France (not far away from LuLuFRA). On our track, we do have an AMB type loop burried in the ground. We use it with an AMB system we borrow to other clubs when we do a race/competition on the track. As a digital electronics & SW engineer, I was looking at a cheap way to reuse that loop and do a timing system at cheaper cost than the existing MyLaps solutions...

When I did found this forum, I was amazed by the huge amount of work you guys (and especially Howard) did ! you almost made my day by providing an almost done solution... Thumbs-up to all of you.

I intend to 1/ adapt the amplifier, 2/ reuse the phase amplifier/DPD/SSC, 3/ use an STM32F4 (working there :)) and 4/ create a custom app...

I have analysed every single of your schematics, and going through the logic ones (DPD, SSC, PDS), I realized this is a very nifty piece of logic work :)

When it comes to the analog part of the design I have much more struggle especially understanding the behavior of the loop amplifier (as I said I'm more of a digital guy). What I understand, is that it is based on a pretty standard differential amp setup and the loop is connected toward the diff inputs.

I have 2 questions (at least to start :o) :
- I don't really understand what is the role of the Q5/R4/R5 part of the design.
- What do you consider as an input impedance for the diff amplifier - I need to adapt this to my AMB loop (T2FD type with 472Ohm). If I would understand the input impedance of the amp, I would be able to do the tuning (I have a good hamradio friend that can help there) ? I have done some googling and tech search but fails miserably :confused:

Keep it the very good work, and I also hope to hear back from Payalneg on the viterbi and convolutional settings he found ( may be the standard NASA backed one...). Most of my mates are having RC4 hybrid or Pure RC4

Rgds,
PyB

Welcome to the thread!

Q5 provides temperature compensation for the bias voltage for the input differential pair, Q1 and Q2. R4 and R5 feed the bias voltage to the pair, and (along with the input resistance of the transistors) establish the amplifier's input resistance.

Each transistor in the input pair runs at about 2.5mA. Assuming a beta of 100, that gives an effective small-signal input resistance of about 1K ohms each. In parallel with 2K, the result is about 660 ohms. Since there are two inputs, the timing loop sees about 1300 ohms. (At 5MHz, it's mostly resistive.) This can be padded down with the components at J3, J4, and J5 to match the loop size. The components also change the loop tuning.

The loop amplifier uses the timing loop as an inductive coil (not as an antenna) to receive the magnetic field from the transponder. The components set the loop's resonant frequency to 5MHz, with a low Q (wide bandwidth) to follow the transponder's relatively fast phase-shift modulation.

Hi guys. Sorry for delay. Busy at work.
Yes, Payalneg did good job - transponders read as is, with original amb numbers.
I don't have any details about how he did that, so you can try write to him - maybe he will answer.