How can I increase the scan distance of my NFC tag ?
I'm using NFC tags on a poster. The tags are actually behind the poster but I'd like a longer scan distance in the region of 15cm. Is it possible if I use more than one tag ?
You can't. The scan distance of an NFC tag can't be increased.
You have two options. First, use a large NFC tag (around 4cm) and place it as close to the user as possible. For example, if the poster is behind glass then try and put some padding behind the poster to push the poster towards the glass (or put the sticker on the glass of course).
Second, you can put NFC tags in an array where you put three or four of them next to each other. This will not increase the scan distance but will increase the hotspot area so the user doesn't have to be so exact. Some users who have tried this have commented that it can cause intermittent responses if the phone hits the spot between the tags and moves a little. However, on balance, it's a reasonable trick.
I have 3.5cm diameter NTAG213 that I scan with a mobile app, currently, the effective working range is about 1cm-0cm (contact), how can I improve this range?
I am not interested in writing data on tags, im only interested in range and read times. I would like faster read time and/or more range (~5cm)
There's a lot of information about NFC online but it's hard to make something out of it. From my researchs, ntag213 is about the best read range for passive tags. So what gains could be made from using say 5cm diameter tags? What if I hack my phone to make a bigger coil antenna? Would that work? Would it have enough power to work effectively?
A 35mm tag having a contact scan distance indicates something isn't right. You are correct in thinking the NTAG213 chip isn't the issue.
There's three possible issues here. First is the location of the tag. Make sure it isn't on metal or has metal too close behind it. Second, an issue with the phone - which phone are you using ? Third, it's a very low quality tag.
You shouldn't need to use a larger tag that 35mm. Our standard 29mm tags would normally be expected to provide a read range in many centimetres. You would also get no likely benefit in hacking your phone. While in theory a larger antenna would help, you'd never get the tuning right without some specialist equipment and the lack of tuning will almost certainly negate any size increase benefits.