Why do you use the LM319 component in 3V3 power supply instead of 5V ?
The LM319 is designed to operate with a power supply > 5V

thanks

I just finished revision B of the decoder software. The LED now blinks off momentarily after a transponder has passed under the loop. This will help during troubleshooting to make sure the loop is active. The copyright notice that is sent via RS232 on power-up contains the revision identifier.

The copyright notice can be used to check for proper operation of the serial port on the PC (using a terminal program such as PuTTY).

howardcano, Hi, can you explain the role of Q5 transistor in your amplifier's schematics?
And 2nd question - what is the maximum distance of transponder detection from the loop? Thanks.

Q5 provides a temperature-compensated bias voltage to the bases of Q1 and Q2.

The detection distance will vary depending on the location of the transponder in the car. The transponder needs to be well away from conductive materials like aluminum and carbon fiber. The maximum distance is about 2 feet.

I have updated the decoder schematic and BOM. The changes are to support FlipSide software. This software sends a message on the RS232 line into the decoder to reset the internal timestamp counter at the start of a race.

Post #251 shows the latest revision names:
http://www.rctech.net/forum/12222187-post251.html

The changes include:

R66, a 10K resistor, is replaced by D60, a 1N4148 diode.

The 221R resistor at R69 has been moved to location R68. R69 is now omitted.

MRT PTX-20 (NS) Compatibility!
 

The new MRT PTX-20 (NS) has been tested, and is compatible with the Cano decoder.

This weekend I finished my proto for the transponder, loop_amplifier and the first part of the decoder hardware. I succeeded in programming the 12F683 with code that generates the preamble and a ID, for now in a fixed delay_loop of 2mS - 4mS to give me a better way of analysing the loop_amplifier and decoder. Later I will do the random 2mS - 4mS delay.
My question: What is the expected amplitude at the Phase_Detector_Input_Amplifier when the transponder is placed in the middle of a 10'x 1' loop, assuming the transponder coil is resonant at 5MHz? I have too much noise at the output of the 74HC04. I think there is something wrong in my loop_amplifier. Anyone to feedback to me what the signal_amplitude should be with a 1:10 scope probe? Thank you.

I'm seeing about 140mV peak-to-peak at the Loop Amplifier output (J1 on the Phase Detector Input Amplifier), using a Cano transponder placed 12 inches above the center of the loop. My AMB and MRT transponders give the same level.

Hi Howard! Congratulations on an excellent project!! I really enjoyd reading you posts.

I also started with the same project 1,5 years ago, but never finished it. Now I found your thread and see that you have solved it, great job!

I would love to help you with anything that needs to be addressed. I'm a software/hardware engineer with special focus on embedded software and .NET software. Please let me know how I can contribute to this awesome project.

Regards Geir.

I'm glad you enjoyed the thread!

We've mentioned before that all of the digital circuitry (not including the microprocessor) would fit into a small, inexpensive FPGA, so maybe you'd like to do that? If so, I can send you what I've done so far with the Altera EPM3064.

cool thread.. interesting projects going on.
but I have to say I read through several pages and now my brain hurts.

This post must make Howard proud once more; After a few others already succeeded in getting a system up and running, I can now as well give you all the good news! Today we managed to get the 'valid' signal as well as the three succeeding nByte_ready pulses to read the 3 ID_Bytes into the decoder processor. The processor is not added to our board yet, that will be the next step. Having the signals available from my transponder (PIC12F683 based as original in the Howard-design), this is a very satisfying stage in the project. It means the transponder software I did is indeed doing the correct preamble and as well transmits the ID that is desired. In the below pictures I would like to share some views on the hardware I build.
Because a collegue at work is very kind and interrested in what I am doing as RC-hobby and electronics, he was so kind to tranfer the breadboard containing over 20 TTL chips into a CPLD. We have used the 40MHz from the breadboard next to the serial_data received from the loop_amplifier (74AC04 output) to create the same 'Byte_ready' and the 8 bit word that will go into the decoder_processor. This is presented in the pictures that are taken from the logic-analyser we have used to debug. For your information, the CPLD code is 57 flip_flops and fits into the Altera EPM3064. However we did not have that device on hand and used a Altera MAX II.

Here are the pictures:

I started few weeks ago on the transponder, loop_amplifier and prgrammed the PIC:

http://www.pa3exv.nl/Transponder_PA3EXV.JPG

The breadboard which I finished next:

http://www.pa3exv.nl/Breadboard_PA3EXV.JPG


A different view on the breadboard:

http://www.pa3exv.nl/Breadboard_Digiview_PA3EXV.JPG


Here the breadboard next to the CPLD board during debuging:

http://www.pa3exv.nl/Breadboard_CPLD...iew_PA3EXV.JPG

And finally two pictures taken from the logic_analyser in which the 4mS test interval of the transponder ID message is shown (Howards' ID for test purpose used)

http://www.pa3exv.nl/4mS_repeat_both_systems.JPG

http://www.pa3exv.nl/Transponder_ID_both_systems.JPG


Next thing to start working is the implementation of the random delay of 2 - 4mS in between of the transponder messages. I already found a way to acomplish this in ASM, I haven't had time yet to test it in the 12F683 PIC of the transponder. Next to this we will start on the decoder_processor. Howard already gave us some great ideas for this and from that we can write the specific message that I would like to get from the decoder to feed into the lap_counter software of my own choice (RF_Lapcounter). I have in the past already did some research what exactly is needed to use this software (post # 78). I realy like that software without digging into the ZRound and others. I found the function to couple your own picture of the car and the picture of the driver nicely done. Because we an in control ourselves, we can send out whatever message we need for our solution. That's the nice think of this open source project.
So far I enjoyed contructing and programming very much. In my daily work I never got into PIC-programming so far (despite being occupied into electronics already for over 25 years). I found this project a great drive to start with that, something I would not have started on because there was no big reason to do so. Without a good goal, someone would not start programming assembly or even learn dealing with microcontrollers.
Big thanks to Howard for the inspiration, I hope it will also help others to take that the step to start designing. Nowadays not much young people can be inspired to get away from the PC playing games. We need them in the industry!

Gerrie, PA3EXV

Thanks for reading the thread, Mo! It may not be particularly interesting for those people who are not well-versed in electronics, but it does give some idea of how these things are created.

This is fantastic! Thank you for showing us your work.

If you get around to testing and verifying the CPLD, please consider offering the design to our readers. It certainly reduces the component count and the size of the circuit board.

Assembly language is the software for hardware guys! There's nothing like it for basic "bit twiddling", and keeping code as small as possible. Now that you've had a taste of it, I'll bet that you'll find yourself thinking of all sorts of little gadgets that you can make for fun.

We have reached a milestone: This thread now has more views than the thread for MRT PTX transponders! Here's a big "THANK YOU" to all of our readers!

Hello guys!
I'm using decoder from Payalneg.
There is little problem - he is very busy now, and I need advice.
Decoder and loop work awesome, but we have 1 problem - if our loop length is greater than 10m - we have misses.
May be you can get me advice - what cable may I try as loop? What Awg I need?
Maybe can try to do new loop amplifier?

And another - what about coaxial cable? Is AMB cable will be best solution?
We need cable about 20 m length.
Or maybe we can get full loop from amb?

10m is far too long. The acceptable sizes and construction specs for the loop are here:

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

The coaxial cable should be 75 ohm. As long as the cable quality is good, it doesn't matter where you purchase it. I have updated post #251 with this information.

Thank you, Howard.
Can you explain please - specs for loop says that I need you jumper in amplifier. I have Payalneg's amplifier - it is same?

10 meter it is all length of loop. Our track is 5 meter width. And here it works fine.
The problems we have only at 6.5 meter width track.

My apologies, I thought you meant the loop was 10m wide. Now I think you meant circumference.

A 12' x 1' loop might work fine with a 5m (15') track width, as long as it is centered on the track. This is because the loop also picks up transponder signals that are slightly outside of the enclosed area.

My answers only apply to my design. You can try to send Payalneg a private message regarding his design.

It would also be worthwhile to build one of my loop amplifiers and see if that helps.

I think it possible to do you amplifier to test - I don't so skilled in electronics, but there is one guy who can help me.
But then first question - may be it need to do some changes so you loop amplifier can work on our wide outdoor track - 6.5 meters?

It's worth a try. You will need to decrease the value of C1 in the loop amplifier. The correct value will vary with the size of the loop, and I can't say what that would be. As the loop size increases, it reaches a point where it simply can't be tuned high enough (5MHz). Also, the signal levels induced in the loop from the transponders will be lower, making operation sporadic.

Please let us know of the results of your experiments, if you decide to try.

@Meag: Have you experiened the misses at evening-time, after sunset? I experience lots of interference at evening. During the daytime there is better decoding. I think the reason is the loop-amplifier is a broadband design, were only the resonance of the loop (L + C) is responsable for some filtering of shortwave radio_stations that come in after sunset. I have now noticed this for several times, not moving the loop and checking during daytime and nighttime. Tell me what you experience is.
Note: my hobbyroom (as well as the loop during tests) is at the second floor of our house. Possibly when the loop is at groundlevel, the above is less true...

We use this decoder at 4 tracks - 2 on-road and 2 off-road, and loop underground at all (2-3 sm under surface). We try race at 9 and 10 pm and all work very good.
The only problem we have - is that i said prevously - on large track where loop length 6.5-7m we have many misses. And there is no difference between ambrc, amb rc4 hybrid, cano or paylaneg's chips - on small loop all works perfect, on large - we have problems.

yes, we will try!
I'll write as soon as i get results.

This might be a problem if you are right next to a radio transmitter operating near 5MHz, but otherwise those signals will be several orders of magnitude smaller than the transponder's.

However, humidity normally increases after sunset, and if you are using a buried loop (which I DON'T recommend) then the loop tuning and sensitivity can be severely degraded.

Howard: Would you have any interest in going commercial with this? You have a design that clearly works and can be built for a fraction of the cost of a mylaps system. You and the other guys who have been working on this have done an incredible job, but constructing this system is still a bit beyond the capability of most RC hobbyists. If you were able to produce complete systems, I think you would sell quite well. As you've mentioned, the page views show there is clearly interest in an alternative transponder system. I know that the startup cost of doing a proper production run is nothing to sneeze at, but maybe a kickstarter project could amass enough funds to cover that?

Thank you for your efforts so far.

The startup cost would likely be over ten thousand dollars, which personally I do not wish to spend. I'm also not much of a businessman! The kickstart concept is interesting, and might work well, although I don't really want to be the executor.

My preference would be to partner with someone to run the business, while I remain a technical consultant. I could sell rights to the entire design (all of which I have already provided free, except for software), or simply sell programmed microprocessors to someone who wanted to produce the decoder (which is essentially a way to pay and collect royalties without the bookkeeping). Buying/selling microprocessors has the advantage that there is no up-front cost for the design for the manufacturer. Buying/selling the design has the advantage that the software doesn't disappear if I get squashed by a bus.

One of the purposes of the thread was to find a partner or company (or several!) who would produce the design. I still hope that will happen.

I hope it will too. I wish I was that guy, but I'm no businessman either. Good luck!

I would think that one of the key factors in offering an alternative decoder is being able to have compatibility with the AMB/Mylaps decoders as they are so prevelent in the Rc world now. I believe Howard's design is currently compatible with all but the true Rc4 transponders, and even was reported working with the new MRT.

I would love to see this project move forward to the commercial step, but like many others, do not know the first thing about business concepts.

I appreciate all the hard work Howard and others have done to lift this project to what it is today, and sometime in the future would love to see an alternative to Mylaps.

Compitition is good right!!!

I never provided an update after we finished our summer camp, where I tested a preliminary transponder/decoder. My previous post has pictures of the decoder which used a Lattice CPLD, PIC 18F and a FT232RL cable.

We got it to work nicely with RC cars (under a wooden ramp) and with adult go-karts on a tarmac track. For the kart track we used some vinyl flooring (as found in bathrooms) as we couldn't bury the cables. The loops for both were made from wire stripped out of an old CAT5 cable.

Since then I have done a bit more work on the CPLD side and implemented the CRC checking in hardware. I have a few other ideas to test before next year and I want to get the whole decoder onto a PCB.

Attached is a picture of our high tech track control hut. It was sunny all week but decided to pour on race day. You can just about see the black coax trailing off and the brown vinyl flooring in the background.

This is very good news!

How much interference are you encountering from the kart ignition systems?

And who had FTD?

The transponders were powered from a 9v PP3 battery and not from the engines. We run both 4 stroke and 2 stroke karts and I did not notice any problems from the engines interfering with the loop.

I think we had one case where a lap was missed but aside from this things were good. My code implemented an 8 bit CRC so incorrect detections should be improbable.

We only measure using the IOF! For RC cars we divide the young people into two groups and do team endurance racing, one lap each with total laps as the
measure. We try to tell them that accuracy is much more important than speed, but they don't always listen :)

In go-karting it was a close run thing between two of the leaders, a few hundredths of a second across a ~26 second lap. I'm working on getting the CPLD/FPGA to manage the race clock so that I can timestamp events coming out of the SPI and more accurately determine these small 1/100th second times.

All on one board sounds like a good direction.

As long as the soldering isn't too intense, have you guys considered offering this as a kit with a board, programmed ICs, and a parts list?

Might be a good way to work through a beta phase and work out the bugs before investing toward production.

All-in-one system is defenitely the way I prefer. By using the CPLD and SMT components, this is the way I work it out for me. It even already exists and is commercial available (not from me to be clear):

http://www.pa3exv.nl/All-in-one_transponder.png

Which system is this? It looks nice!

I was mostly concerned with the radiated noise from the high-tension spark plug wire and the ignition coil, as these aren't usually shielded well on a kart.

!!!!!!!

Hi Howard: The guy who sells the all-in-one system at the moment is located in Germany.
He has his webpage: www.Speed-transponder.de
The systems are manufatured on demand, delivered with a variaty of transponder solutions. Some of them run from a goldcap and can run for several hours after a 5 minute charge. Others have bigger LiPO build in. This video is in german language, hopefully pictures say more than thousand words....

h ttp://www.youtube.com/watch?v=q1rIQJ3WF9o

Thanks for the link. Interestingly, I did not find any indication that the system has been tested for emissions.

I would seriously consider having that system shipped from Germany if the price was right, but I can't find any pricing info on his site. Maybe google translate is leaving something out?

I didn't see any pricing either.

The system would require FCC certification to be sold, or sold to someone, in the USA. Other countries have their own regulations, such as CE and VDE. Of course, a few items always manage to "fly under the radar".