Yes on both. C4 positive is the square pad, ground is the round pad. J2 square pad is ground.

Hello Howard,

I have rebuilt a second loop amplifier. Now my reading is 0.90v on the wire. I am suppose to have 1.20v as per your specs, where did i go wrong? As mentioned before i am getting 4.79v out of the decoder to the loop amp.

Still not working, no detection of transponder on the decoder.

I dont have any access to oscilloscope at the moment.

what else can be checked?

First do a visual inspection of all components. Some of them have polarities that must be observed. We've already mentioned the capacitor. Check the transistors also; emitter must go to the square pad. (You can download spec sheets for the components from Mouser or Digikey.) Reversed transistors could easily explain the voltages you are seeing (since the current gain of a bipolar transistor isn't too good when the emitter and collector are swapped!).

Next would be an inspection of all solder joints. It's pretty easy to bridge connections on the loop amp board.

Anything past that will require an oscilloscope.

Hello all,
Newbie to RCTech forum here. I am in the process of building an FPV Quadcopter, this is just an FYI. I am not an expert RCr by any stretch of the imagination. But I am very much interested in the Transponder design and Lap timing decoder Howard Cano started a while back, this is great stuff. I come from a Karting and Legends racing prep techman background and have always wanted to build an accurate DIY timing system, so I googled lap counting and timing Transponder. and the search led me to this fantastic site and very informative thread. I do have a back ground in electronics, RF and satellite comms for 25+ years. If you know anything about the Atlanta Area, you can probably deduce my previous employeer not the one that begins with M but the other one, the used to be leader in the Cable industry prior to a certain west cost company buying and selling off all parts of the once very successful company as well as releasing some very skilled engineers that pretty much made the company the leader it was in the cable world. I have some free time now and I would very much like to make myself available to help out on this project. Thanks to all for the great insight into the transponder timing world. Howard I will be sending you a PM shortly begging for whatever you have avail. on these two projects, schemos, board layouts, BOM's, theory of Operation, PC Boards, Kits, pre programmed MCu's, etc..

Regards
MAC55

Thank you Howard for the recommendations. I have looked at both boards and so far all my transistors seem to be correctly installed, i am comparing with your picture.

On the decoder board I did find i was missing 2 capacitors at C3 & C4 ! wow i cant believe I forgot those. Well no change still not working and voltage at the loop is the same.

thanks for your time.

Welcome to the thread!

We could definitely use someone to take the initiative (and make the investment!) of offering assembled devices, and it sounds like you might have the background to do it. One big hurdle and expense would be testing and compliance for emissions, which I chose not to do.

I just sent you the zip file containing all of the information from both threads.

Howard,

Thanks, received the zip file. lots of good stuff in there.


All/anyone/everyone

Does anyone know if there are any patents filed anywhere for any transponder/decoder lap timing system?

Regards

MAC55

Google returns this: http://www.google.com/patents/US20120087421

The basic concept of how their transponders work has been around for at least 25 years and should be out of protection. But thanks to our completely dysfunctional patent system, "should" doesn't enter into it. They would definitely sue anybody selling a system compatible with theirs, and they'd probably sue anybody selling a non-compatible system that was even vaguely similar. With enough money, lawyers, and patience, you could almost certainly beat them. But then you're out a whole lot of time and money.

I'm not a lawyer or a patent expert. This is just my opinion based on watching the same damn thing happen all over the tech industry and factoring in AMB's litigious (and dickish) history.

Got everything ordered to build a decoder system. Expecting to receive everything by the end of December. Will post results

Is anyone actually using this system in an offroad track? if so? for how long? Any Issues? I'm looking into building one of these but rc-demon doesn't seem to be getting it to work at all...

I will be building mine in a few weeks. If you're not in a hurry and want to wait for results. I will be making 2 systems, we have 2 offroad tracks during summer, and we will use one system for indoor, during winter ( I live in Northern New-Brunswick, Canada )

I'll be eagerly waiting for your results
Please report back!
Thanks

Have you guys had any luck decoding the new RC4 units? The three wire ones?

I have not, but I believe others have. Hopefully they will respond to you.

I built myself a little automatic pit system with an Arduino. It works fine but you have to call each person to pit once per race. If I could id each car by transponder, people could pit on their own and the system could "remember" who did their one pit stop without the race director having to call them to pit.