Hi

I want to use the RFID Reader in Battery based application, The Reader antenna (125Khz RFID Coil) will be Switched ON for 500 milli Seconds and will be switched OFF for 2500 milli Seconds. I am using MOSFET to switch ON and Swicth OFF the antenna from the reader.
But every time the antenna is energized the peak current consumption is 25mA.
Here when i switch OFF the antenna, i want to preserve that magnetic flux in a capacitor so that same is used back when i switch ON the antenna, i would request design help in this case.
Any support and feedback would be highly appreciated.

regards

 

Welcome to AAC.

How have you decided the antenna is the reason for the peak current?

 

The purpose of an antenna is to radiate energy. You cannot get that radiated energy back.

 

A garage door or gate remote control are battery operated devices that do that.
In the remote a momentary switch allows a capacitor to charge.
The ( RF sending unit) the remote continues to work on an old depleted battery but
the momentary press and hold time will be longer duration.

 

Welcome to AAC.

How have you decided the antenna is the reason for the peak current?

I am switching ON and OFF the antenna through Solid state switch.. so every time it's Switched ON, the current peaks to energize the antenna Coil.

 

The purpose of an antenna is to radiate energy. You cannot get that radiated energy back.

Yes, i understand. but this RFID reader antenna acts like a Coil, because this works like electromagnetic induction which induces power to passive tag and gets the Card data.
I have seen some of the readers which use only in Micro Amps but not sure how they have achieved them.

 

I expect that the antenna power needed is related to the range at which the reader will operate - more power equals greater range.
Compare the range of the reader you have with the range of one using much lower power.

 

I expect that the antenna power needed is related to the range at which the reader will operate - more power equals greater range.
Compare the range of the reader you have with the range of one using much lower power.

Yes, i checked the range but it's also having very good range.... But i am looking forward to other possible option to reduce the power consumption without affecting the range...

 

If you post a schematic of your transmitter we may be able to see where power saving would be possible.

 

Yes, i understand. but this RFID reader antenna acts like a Coil, because this works like electromagnetic induction which induces power to passive tag and gets the Card data.
I have seen some of the readers which use only in Micro Amps but not sure how they have achieved them.

The polarity of the current flips 125,000 times every second. At the instant you turn it off, all the energy from the every flip except the last one is already gone. Theoretically you could recover some of energy put in since the last flip, but there is no way this could be done practically, and then it would save 1/(125000/2) of the energy which 0.00017% of the energy put in during the 1/2 second on time.

 

...i want to preserve that magnetic flux in a capacitor...

Does not compute, capacitors do not preserve magnetic flux outside that movie...

 

Does not compute, capacitors do not preserve magnetic flux outside that movie...

Yes, a flux capacitor!

 

Some people who live near a 50kW radio station antenna have their fluorescent lights make dim light all the time.

 

Some people who live near a 50kW radio station antenna have their fluorescent lights make dim light all the time.

We used fluorescent tubes to tune our VLF transmitter to the matching variometer coils for the antenna. A lot more than 50kW.

A small example:
https://www.kintronic.com/eloran-lf-and-vlf-products/