Tag Archives: Arduino

RFID(RDM630) and Arduino

RFID is in use all around us. If you have ever chipped your pet with an ID tag or take a look to the plastic tag in your key ring you use to enter your building, you have used RIFD. “Radio-frequency identification (RFID) is the use of an object (typically referred to as an RFID tag) applied to or incorporated into a product, animal, or person for the purpose of identification and tracking using radio waves.” Read more.

You can read RFID tags Using a RFID reader and an Arduino board. Below you can find the schematic for Connecting a RDM630serial RFID reader to an Arduino board.

RDM630 and Arduino

Pinout for RDM630

Here is the sample code that reads RFID tags from RDM630 serial RFID reader and prints them on the serial  port. You can see the results by clicking “Serial Monitor” in Arduino program. The LED blinks when the reader reads a tag.

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12V Lamp on Arduino with a reed relay

Intro

Arduino has a limited current sinking/sourcing capability (less than 40 mili Amps) on its pins. Whenever you intend to switch a device which needs high current or high voltage (like a lamp or a motor) an intermediate circuit is needed. In the simplest case this intermediate circuit is a relay.

Relays

Relay acts as a normal switch, but is triggered with a magnet rather than a handle. Here we use a special kind of relay called reed relay. Such relays come in vacuum enclosures and have excellent performance in terms of being an ideal switch. Whenever driving coils there should be a diode connected across the coil in reverse bias, so it will damp the back EMF produced. However, the relay we are using has this diode across its coils internally, so we don’t need to worry about it.

Circuit

Make the circuit below:

Select the Blink sketch (File>Examples>Digital>Blink) from your Arduino software and upload it to your board. The Lamp on the bread and the LED on your Arduino board should light up at the same time.

More info

Note that similar to any other load, relays draw current. This current can be more than what an Arduino can provide. In such cases you cannot connect the relay directly to an Arduino output. Use a transistor for the relay and a diode to protect against back EMF. Here is an example how to drive such a relay with a transistor.

An easier approach for driving high current/voltage relays is to use a relay driver such as ULN2003 or ULN2803. Here is a sample schematic how to do so (taken from this rocket project).