Hi Howard, after my version of your transponder, I'm considering making a decoder. In the thread other options have been named (arduino, fpga etc).
Do you think it's possible to decode using 'off the shelf' electronics to make the project even easier to replicate? One interesting idea was the use of a radio usb dongle. From my investigations it seems that 5MHz needs a HW modification or an upscaler to be read. Also the data received must be BPSK decoded and 'injected' in the timing software, and this can be tricky, and I don't know if freq lock is fast enough. Another option is the Papilio FPGA board that is usb connected. Making an FPGA version of your circuit would still need external R/C components for debouncing/histeresis on the preamble decoder, right? The plus would be the easier way to emulate the serial comunication and a reference open source hardware that can be bought. The only custom circuit would be the 'wing' (shield in arduino world) for the analog input/amp. Do you have any suggestion?

I don't know of any off-the-shelf devices that could demodulate the 5MHz BPSK signal, but I also would not be surprised if one existed. So far no one has mentioned in the thread that they have found one.

I think the FPGA is a great way to go. The difficult part-- the demodulator-- requires no analog components, and it should be easy to also include in the FPGA other circuits (for instance, to detect and strip the "preamble") if one desired to reduce the workload on the microprocessor. The only analog circuits necessary are the loop amp and phase detector amp, and these are very simple.

Please keep us informed of your experiments!

My mistake, I was looking at the first revision, not the digital one. Right now I'm investigating how much 'horsepower' I need and find a suitable low cost device. I'm new to FPGA, but willing to learn... The main design decision I'm focusing on is between a loop>serial interface (like your design) or something more self contained that can work in standalone mode (maybe with a wifi connection and an android app) to give personal results to multiple drivers (or do both...).

Have I sent you the zip files with the project documents?

If you (or any other reader) would like to receive them, send me a private message with your email address.

Hello everyone,

I've just discovered this thread while I was researching for lap counting systems and vehicle detectors. I would like to use a system of this kind for fpv multicopter racing, and i was wondering if the decoder loop can be mounted as a gate and if it will detect the transponders as the multicopters pass through it.

You have made a great job in this thread, and also in the transponder thread, as it helps a lot to understand how actually the system works, mostly for me the analog and RF parts of the designs.

I've seen some fpv races using the infrared based i-Lap system, but I would like to evaluate other alternatives.

Thanks for all this documented work!

Hi All

I have got the files from Howard (many thanks) and wondered if anyone out there has spare PC boards I could purchase for the decoder please

I'm glad you have found the thread to be informative.

I have never seen an FPV race, but I'll bet it's a bunch of fun!

I think the detection range of the system will be too short for any flying vehicle. If the largest loop is used, the active area would be perhaps 2x12 feet. One could also fly the FPVs through the inside of the loop, but then the loop would need to be no larger than about 5 feet square, and there would be a good possibility for colliding with it. In either case, orientation of the transponders to the loop would be highly variable, giving erratic operation.

I was thinking about flying through the inside of the loop, but 5 feet square is really narrow. Collisions are really common in this kind of races, as the circuit is usually composed of a series of gates or arcs to pass through them, but wider.
One thing that could be really useful will be that if you pass inside the loop you'll get detected, but if you pass outside you won't. Sometimes it's a bit difficult for the race judges to check this conditions to ensure that everybody is racing inside the circuit.
If a transponder pases close to the loop but it doesn't pass through it will be detected?
About the transponders orientation, it will be very variable indeed, so maybe this design won't work at all.
If I want to use a wider loop, do I have to use a lower carrier frequency? will it need a complete redesign of the analog circuit? I am not particulary interested on compatibility with other systems, so it doesn't matter if transponders or decoders from other brand don't work.

Transponders will still be detected if they pass close to, but not through, the loop.

The maximum size of the loop in the design presented here is restricted because it is used as part of a resonant circuit to filter noise out of the signal. There are other ways to get larger detection areas without going to lower carrier frequencies, but as you have surmised this requires a different (and more complicated) analog circuit. Using a lower carrier frequency has the disadvantage of less efficient radiation of the signal for a given size of transponder, and I'd guess that larger transponders are not good for your application.

An optical system seems well suited to your application. Its advantages include very small and lightweight transponders, and good isolation between different detection gates (if that is a good term to use) on the race course. But each detection gate would be much more complicated than a simple loop of wire.

If I were to design such a system, I would put two (or more) LEDs on each transponder, sending the same signal but in opposite (or orthogonal) directions, and each detection gate would be a square or rectangular frame with photo detectors mounted on the frame, all facing inward. To prevent false detection of a transponder outside the frame, the decoder would require that the transponder signal be detected by at least two sides of the detection gate. This is not as simple as it seems, because the signal would not necessarily appear at the same instant in different sides of the gate due to the random angle of the transponder.

Thank you for all the clarifications.
Looks like this system is not the suitable one for fpv racing, but if I ever need a lap system for rc cars this is the way to go for sure.

My first thought about the detection gates design was to use infrared leds and phototransistors. I have used them before for slot racing with good results and with very simple and cheap circuits.
The infrared transponder will be a really simple and small device, but the gate gets complicated as one must use an array of sensors. The i-Lap system requires the sensors to be placed every 50cm I think.
Since I would like to have all the gates that define the track "active detectors", each gate should be as cheap as possible. I will keep looking for different implementations, maybe I will be lucky enough to get an affordable one.

Hi All

I was looking at the cost of getting decoder and amp PCB's made up and the cost for multiples is not much more than for one. If there are any folks out there who want a set of PCB's to build their own decoder please post on the thread if you wish to be included in a group purchase so we can share the cost.

You're in London? So am I, and I would be interested in a PCB (or maybe even two, depending on the cost).

Cool, you are on the list :D maybe we can join forces on the build as well.

Where do you race?

I have 4 boards available, $35 ea. + shipping. I have my decoder just soldered up today, need to get a trimmer pot, and project boxes then I am ready to test.

I'm interested in PCBs as well! One or two depending on cost, and shipping to Sweden. Also transponder pcbs by Howard is of interest.

Nice one, love to hear how testing goes.

Do you have amp boards as well as the decoder PCB's?

I have done a bit of searching around on pricing and OSH Park in the USA have pretty good pricing for low volume as follows:

Their minimum is 3 pieces and more items only in multiples of three as far as I can make out.

$122.20 for 3 x Decoder PCB
$5.70 for 3 x Amp board

So a pair (decoder and amp) of PCB's comes out at around $43 which is £28 or 354 SEK plus shipping.

I work in the US a lot so can avoid UK customs duty and charge if I get them delivered to the US and I will bring them in by hand.

I will also be getting Transponder PCB's, they are $2.61 ea ($7.85 for 3) if you are interested.

loop amp pics
 

Here is my H.w.Cano loop amp board pic. I cut this on my engraving machine.
It is a little harder to solder components without a solder mask, you have to have a steady hand.

Very nice job, shame it can't do 4 layer boards ;-)

Yes, interested! A pair of decoder + amp and 3 pcs of transponder PCB's would be great. I'll PM you for details.

As well as OSH Park, there is another PCB fabricating service called ITEAD Studio (Chinese I think), I've used them for a start lights device for my local model car club.

http://www.itead.cc/open-pcb/pcb-prototyping.html

Hope this helps :)

Thanks Joe, I will have a look.

Hi Howard

Mouser are saying the MC74AC4040NG is obsolete, have you got a recommendation for a replacement please?

Cheers

G

Try the 74LV4040AN, at DigiKey:
http://www.digikey.com/product-detai...6-5-ND/1594907

Cool, many thanks.

question for Howard on jumpers
 

Howard,
Do I need all the jumpers installed on the decoder, J60,61,62,63 & 64?

I am testing maybe today I hope.

Thanks
Arnie

I like that this thread keeps continuing!

I just ran across these recently. Looks like it could be be an interesting back-end to Howard's amplifier. I'm not sure how easy the SDK is to work with, but the FPGA boards get more and more user friendly (for us mortals) with each iteration.

http://www.xess.com/shop/product/xula-200/

I like Sunstone Circuit (www.sunstone.com). Boards are priced by area. Check out their ValueProto boards. 2 Layers with masking starting at $28.

Thanks, they are a bit pricey for a 4 layer but good for reference.

All of these connections have no function at present, and may be omitted.

not testing today
 

Well maybe in a week or two I can test, I had one more chip to get, the
MC74AC4040NG, it is coming from Israel. I will post my results when done.

Got my last chips delivered and performed some testing.

I tested using putTY monitoring the com port on my serial to usb converter.

here is the results from testing 2 different PTs,
the first one is the Howard design from the transponder thread.
The second one is one of my RC4 2wire transponders.

REV B COPYRIGHT 2013 HOWARD W. CANO
CDFD4C0000F1D5
CDFD4C00011A24
CDFD4C000125B0
CDFD4C0001359E
CDFD4C00014219
CDFD4C000157EA
CDFD4C000186EB
CDFD4C00018EE7

783D8400049A5A
783D840004A61C
783D840004D859
783D840004E41C
783D84000516BE
783D840005229E
783D8400055E39
783D840005B109

I tried zround software and no success yet.
I downloaded the flipside software but don't see any configuration to use the Cano decoder.

Howard can you email me the flipside software.

Looks like success !!!

Thanks Howard for all your work.

Looking good! Email sent.

I installed the latest Flipside Racing software. (thanks Howard)

Testing software with decoder and transponders went fine, works great!
Only thing left is go out and do some "in the field " testing on the track.

Has anyone powered the decoder from a USB port, we have no mains where this is going to be used so powering from the laptop usb would be great.

Yes.

From spec post (#251):

POWER REQUIREMENTS:

12VDC @ 100mA minimum if using decoder's internal 5V regulator. Decoder is polarity protected.
Or,
5VDC @ 100mA if running directly from USB port (bypassing decoder's internal 5V regulator)-- NOT polarity protected!

Thanks Howard, I was sure I had seen it somewhere.

help connecting to zrounds
 

Has anyone success connecting to zround race manager. I have tried everything I can think of. I can run flipside just fine and using a terminal window I can see the decoder just fine with Howard's copyright notice.

You may not have the version with support for the Cano decoder. Email sent.

Does anyone have any spare boards they'd like to sell?

PM me, thanks.