I'm using a certain RFID reader for my project:
Unfortunately, the read range is inadequate. It is my understanding that by increasing the output power, the read range can be increased. Could I use a voltage amplifier between the RFID reader the and coil to increase the power and thus the read range?
Could I use a voltage amplifier between the RFID reader the and coil to increase the power and thus the read range?
No.
Because the coil is both a transmitter and reciever if you put in an amplifier to make the output stronger you block the recieved signal.
What range do you have and what do you need?
Although I can't remember the make, I have seen RFID tags being read off cattle at a range of 500mm to 1 metre. You might want to look at the websites of agricultural suppliers to see if any meet your range requirements and then see if you can find out whats in them.
Right now, if I hold an RFID microchip, the reader picks up the chip at a radial distance of 6". However, I want the reader to be able to pick up a microchip embedded under the skin of my cat. When reading my cat's microchip, the reader can only pick up the chip when it's about 2" from the coil. Keep in mind, this isn't a radial distance of 2".
I would like to increase this range to a 2" radial read range.
The best way is to have a physically bigger coil and tune it correctly with capacitors. This is not possible without access to an oscilloscope.
Per the data sheet of the RFID reader and the IC used in this reader (http://www.emmicroelectronic.com/webfiles/product/rfid/ds/EM4095_DS.pdf), by increasing the Q factor of the inductor, I can increase the p-p voltage of the inductor and the peak current.
Also, the Q factor can be increased by reducing the inductors resistance. What would happen in an RLC circuit if I ran a resistor in parallel to the inductor?
Adding a R into a resonant circuit will lower its Q.
Grumpy_Mike:
Adding a R into a resonant circuit will lower its Q.
Connecting a resistor in any fashion into a resonant circuit will lower its Q. Series, parallel, sideways ...
The resistance of the inductor is in its wire. To reduce that resistance, you would need to use thicker wire in re-building the inductor. Which is where as Mike says, you need to be able to calibrate your new components.
Thicker wire, or litz wire. Litz wire is made of multiple strands of very small insulated wire, usually wrapped with some kind of fabric strands. It is NOT the same as stranded wire.
The insulation melts away with the heat of a soldering iron, so you just twist and solder the ends as if it were normal stranded wire.
As you go higher in frequency, the current becomes constrained increasingly in just the skin of the conductor. So larger wire gives you more surface area, but a lot of small wires can give you a -lot- more surface area in a smaller total diameter.
But if the strands aren't insulated from each other, then it acts like a single wire with grooves cut in it, making it worse than a single piece of solid wire.
Many Qi charging coils are would of Litz wire.
Also it is not a simple matter of higher Q means higher range. There is a peak level, after that further increases in Q just reduce the range again.
Probably because too high a Q means too narrow a bandwidth.
Its called "near field" for a reason....
