Using Magnetic Card Reader in Low Current Application

Go To Last Post
6 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I've been researching info on magnetic card readers but documentation isn't very complete (e.g. Omron V3A-4K). I'll be using a reader in an application where a few AA batteries provide power for > 1 year so I need to keep the reader off until a card needs to be read.

I see many readers have a "card detect" or similar output and a "current save" mode. As best I can tell the card detect output is driven by a FET totem pole and current save mode puts the unit into the 2mA consumption range. If this is true then I don't see how the reader can be used in an ultra-low current application without the user pushing a button before he swipes the card, which is undesirable.

How is this problem typically solved?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I doubt that many card readers are used in that sort of situation. Most are charged daily, or even every few minutes (thinking wireless credit card terminals here). If you require ultra low current consumption, you are likely required to perform your own card detect and make sure that the reader is completely powered off when not required.

A simple micro switch connected to an interrupt pin on a low power AVR should be perfect.

-Tim

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I thought of that but I don't see a simple way to incorporate my own microswitch into the unit. Even the internal units I've looked at have the plastic molding in place where the card swipes through, making it difficult to incorporate a switch.

Other than a keypad are there other ways I should consider doing an authentication (security not being much of an issue) that can be implemented in the $20-$40 per machine range with < $5 per user?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Check this
http://www.uicworld.com/product/...

I used the MRD520A for a product here, but this guys have chips with very low power compsumption. They send samples too (or at least, they sent samples to me some years ago)
Check the three track chips

Nachus

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You could hack the card detect, and do optical with very short on-times.

You could, at least for track 2, use a VERY low power opamp in a current to voltage converter configuration, and just take the interrupt from there as a wakeup. The start sentinel should provide enough time to get awake. Then you'd have to decode the F-2F on your own, but that's not hard.

(been there, done that, revolutionized the industry..)

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Well, I have to be able to do this in an automated production environment in the thousands of units. I'm not sure how I would hack the card detect unless you're referring to somehow inserting my own optical Tx/Rx setup mechanically in the device. It doesn't seem like something I'd want to do in production.

I can't find any specs on how long it takes the card reader to start up and actually do a card read. If I detect that the card is going into the unit can it wake up quickly enough as I apply power and be ready to go when the card hits the read heads?