No that’s not the sound of the 90’s mobile phone boom, it’s a reference to the problems with having a tiny chip in your hand.
So everyone want’s to see this thing in action and what it can do. The problem is that most of the devices we use RF or NFC to interface with were made to talk to something with an antenna about the size of a credit card. So the manufacturers of card readers etc. made their products to match that specification and didn’t want to go overboard because it would use more power or read things from far away and get confused about what you’re trying to read.
In the above image, you can see that the manufacturers have created 2 coils to communicate with the cards that are swiped over the printer and they’re about the same size as the card it’s trying to read. The idea is they pulse out some power which is received by the antenna in the card or chip, then that card or chip uses that power to fire up and chirp back its id number. Now this chip in my hand has a tiny little antenna on it and is hidden behind my dermal layer. On top of that, the cover on the printer put even more space between us and this means it’s really hard to get the signal to and from my chip. So what are my options?
- More power!
- Get closer.
1 is always my favourite, but means some soldering of transistors and intelligent decisions about where I’m going to route the extra power from.
2 Is the way to go in this case. But how do I get closer?
Well you’re going to need to remove the plastic covers of the card scanner, to get to what’s underneath as seen above. Now we need to keep the plastic insert with the pretty pictures and the cover, so we can’t save on space by throwing those out, but what you will notice is that the card reader has a big airspace between the antennas and the back of the plastic cover. We can jack the card reader up a bit by inserting some card or something like a booster seat, but even better is to move the antenna closer and leave the electronics behind. This results in a better power transfer and clarity as it moves the antenna away from interference. It also means I don’t have to solder anything or do any thinking. So, let’s get bending.
As you can see, I’ve taken the thicker of the 2 antenna wired coils and just separated it from the circuit a little and given it a little dog leg bend. This brings it right up against the back of the cover when it’s put back in place. So give it a whirl. Excuse the bad video.