Hi All, hope I am posting this in the right place and I really hope someone can help me out here. I am currently working with the Sparkfun SRTR. I am also using their UHF Antenna, and their UHF Tags. I am using all of this to build a RC car race timing system. I have proof of concept done, my code is operational and is communicating just fine with the Zround race timing software. All is well and the tags are being detected as needed during bench testing.
Here is my current hardware issue. The board's PCB antenna was working great for bench testing for proof of concept. When I completed the program and moved to real world testing I then hooked up the external antenna and started doing more of a real world test. I am getting very poor range and detection rates when the tag is applied to a very exposed part of the RC car. These are 1/10 scale short course trucks. I drove very slow, right at the antenna, with the tag stuck to the front bumper completely visible and exposed. It was only when I got within an inch of the antenna did I get detection, but if I take a loose tag, and hold it between my finger I could get good readings at about 8'. I plan on moving to a ground mat antenna for the final product, but they are expensive and didn't want to purchase one unless I knew this would work to my expectations. I know very little about RFID so I really don't know where to go from here. I know the very basics of how RFID works, but that is probably what is getting me in trouble. My final plan was to stick the passive tag to the inside of the front bumper. Our lanes are approximately 8' wide, and the reader should be able to do 160 tags per second, but the most we will ever have through the antenna at one time is maybe 4.
I have the soldering done as per the tutorial from sparkfun, and am using the SRTR as a shield with their Redboard and am using a 2a external power supply to the Redboard. Am I being unreasonable to think this is going to work how I want it to? Where should I go and what should I try? Will active tags work with this reader? suggestions on active tags? I can power an active tag from the RC car, preferably. I have some larger tags I am going to try as I understand the larger tag the better chances of detection?
Take it easy on me guys, RFID is foreign to me. Thanks.
doesn't appear I have sparked anyone's interest here, but I have been working diligently on trying to research this and learn on my own and have hit a small roadblock. Apparently my first reader was faulty, the replacement reader I have is allowing the exterior antenna to work as needed but here is my newest problem still within the realm of the original post. I can now get great read rates with the original LP vertical antenna, but I can't get the range I need to cover the length of one lane. If I drive directly under the antenna within approximately the center 3rd of the entire lane I get detected every time no problem. The SRTR reader only has one antenna port. Can someone help me out with a way/advice on how to add a second antenna just for better coverage of the entire lane? The lane is approximately 8-10' wide total and only the far outside of the lane I lose the ability to detect, I have tried raising and lowering the antenna height (antenna is directly centered directly facing down over the lane) and the passive tags are on the hood of the RC cars in clear sight of the reader all going the same direction. I have very limited experience with antenna's and multiplexing. I was hoping to find a way to add a second identical antenna, but not sure how or where to start. In everything I am reading it sounds like multiplexing may be the way to go just to add a second antenna, but I don't know how and it is hard to find information (that I understand) on how MUX's work or which one is best, or if this is even the right approach. Your thoughts/Advice are definitely welcome. Thanks in advance.
The data sheet states the antenna is linearly polarized vertically, which I interpret to mean the polarization is in line with the cable connector. I expect you have the antenna unit oriented correctly with the traffic flow.
Looks like your experimentation has shown you need three systems in order to cover what you call a lane. Or perhaps two systems splitting the lane area.
Addition: Just thought more about this. Is the antenna laying flat, parallel to the land surface? Should be.
this is correct, and I have experimented with tag orientation extensively with this setup, but yes, if the antenna is mounted to a wall the vertical detection area is from antenna cable to opposing end.
for easy reference, picture a 2x4 running over the lane, like a truss, and the antenna is mounted straight down at the floor in which the trucks drive under with the tag mounted on the hood of the RC truck pointing straight up at the antenna. Depending on which way I was experimenting and the way the antenna is rotated, I have had the tag mounted front to back on the hood, and also tested with the tag mounted side to side on the hood to test and prove which way the antenna needed to be placed.
Hi Paul, just an update. I ran over 100 laps consecutively last night with the one antenna. I didn't get one missed detection as long as I was in the middle 3rd of the lane. So I can definitely say the detection rate/speed is perfect, so I think I just need to find a way to add a second antenna to be able to cover the lane width. I played a bit with adjusting the height of the antenna to try and get a bigger detection spread, but didn't really see a change in results. Do you have a recommendation for adding a second antenna to a single port reader? I was trying to read and learn about hub/splitter/combiners vs multiplexers, but just not sure which way to go to get the best result in an economical matter. I read a splitter will cut the power down to half, but the multiplexers need a GPIO interface to control the switching of the antenna. If my single antenna is getting good detection, I would think half power, and lowering them down I would still get the detection I need? Your thoughts?