detect the precense of the body inside enclosure

[Atarek]

Hello everyone,

I have a problem and i need help,

I am designing an access control,
Generally the system go to sleep mode in order to save the battery life,

The problem is that i want the system to detect the presence of the Mifare RFID tag in order to go to wake up mode,
knowing that the electronics is to be enclosed in a metal body with a plastic cover,

What type of sensing method can be used in order to detect the presence of the tag knowing that it must be contained inside the system body described before,

Thank in advacne,
Atarek

 

[MacGyverS2000]

Your description is less than clear, but it appears you want a computerized enclosure that goes to sleep when a tag is inserted into it? If so, it seems a contact switch would be the easiest solution.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[waross]

detect the precense of the body

A friend will help you move.
A really good friend will help you move a body.
You need a really good friend.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[3DDave]

RFID tags are responders. They can't be detected passively.

 

[itsmoked]

Notice the large black plates at the stores? Those are needed to reliably detect RFID tags by powering them up remotely or at least detecting their effect. Being constrained to a single metal box with a plastic face makes that pretty hard.

There are now gesture sensors that you can use dumbed down versions of that will detect 'presence'. [URL unfurl="true"]https://www.microchip.com/design-centers/capacitive-touch-sensing[/url]

They have a 'very low power' section too.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

If the body is a cat, perhaps belonging to Mr Schroedinger, you have two options.
Sorry - that's all help I can offer.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[IRstuff]

Either way, you have to open the box to find out

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[VEBill]

Thread title: "...the body inside enclosure"

If it's "inside" the enclosure, then it's trivial to arrange an optical sensor where the LED's light is blocked by the tag when it's inserted into the enclosure.

OP: "...an access control...save the battery life..."

If this is controlling a door, then such system are typically powered from AC. So you don't worry about saving battery.

 

[jraef]

Lol Gunnar, you beat me to it![pre][/pre]


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[Skogsgurra]

Sorry for that, Jeff. Must be the time zones - we are 9 hours ahead of you. Hard to beat...

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Atarek]

Thank you everyone for your support, However,

MacGyverS2000, I'm sry for the weak description, identification is based on RFID 13.56 Mhz, the system is battery powered, so, in order to save battery life, the system goes to sleep, but it can wake up when the user wave the card in front of it.
My problem is detecting the presence of the user card?



VE1BLL, the solution i'am developing is battery powered

Thank you,
Atarek

 

[MacGyverS2000]

If you need to detect something via RF, then the system cannot completely go to sleep... something has to be paying attention. Now, there are plenty of extremely low-power micros out there that can be woken from a deep sleep via an interrupt pin, so this would be my suggestion. You could even combine this with a mechanical switch of some form to reduce the power needed by an all-electronic setup, but in the end someone still has to be "up and running".

Dan - Owner

http://www.Hi-TecDesigns.com

 

[IRstuff]

Just consider that your typical LCD watch can run 5 to 10 years continuously on.

One alternative is to use an ultra-low power presence sensor to wake up the RFID processor.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[3DDave]

The problem you have is that RFID cards transmit using energy gathered from the energy they absorb from an external radio power source. If the radio is not transmitting, the RFID card does nothing that is detectable. They only transmit when they get a proper handshake signal so a simple RF source won't work.

Feel free to post a link to the supporting information that suggested to you that this approach was possible.

 

[VEBill]

MGS2k "...woken from a deep sleep via an interrupt pin....combine this with a mechanical switch..."

Agree. Add a "WAKE" push button.

Feasible. Easy. Not very arduous for the users, considering the limitation that it's battery powered. Done.