Many times you need to remotely control a relay, electrovalve or some other electronic or electromechanical device, and many times wirelessly. With XBee modules things become very easy. Very versatile and having small dimensions it is easy to add it to your projects.

In this demonstration the modules are set to wirelessly control two types of relays, standard and latched. To achieve this you will need to configure the analog inputs of the Xbee to digital I/O. In the given schematics the standard relay is driven by a general purpose NPN transistor T1. Some relays already have the protection diode incorporated, if not you will need to use D1 as shown.

The latch relay is driven by a hex inverter IC connected as a buffer. Each inverter changes the logic level from high to low and from low to high so you must cascade two inverters to preserve the logic level. This type of relay is activated by pulses so it needs a small amount of current. Even so the output capability of a single inverter might not be enough so the remaining inverters are connected in parallel.

On the transmitter side you have two push buttons connected between ground and the digital I/O ports of the XBee. There is no need for pull-up resistors because this is done internally in the Xbee.

This demonstration has lots of practical applications. You can connect almost anything to those relays or use the digital output of the module with a buffer to control other devices or transmit information.

Wireless Relay Control with XBee: [Link][Via]

January 19th, 2009

Ethernet relay board

Ethernet relay board

There many devices which can be controlled trough relays, like light bulbs, pumps, motorized doors, and the list can go on. Most of the relay boards available on the web are based on the serial interface, this has some drawbacks: limited distance, about 15meter based on the RS232 standard, and the new generation of motherboards lack this port. The presented board has ethernet interface using the ENC28J60 and the PIC18F4680, it also has a Real Time Circuit with battery backup, the ethernet interface beside its speed has a major advantage, the RJ45 contains a coupling transformer which is used to galvanically isolate the local electronics ground from the bus, this doesn’t mean that it will support a 230 common mode voltage, but offers protection to a certain limit.

The ethernet interface shows its full potential when comes along with a webserver, fortunately the author thought this to, he developed a simple web server which runs on the PIC, this way you can control the relays trough your network or even the internet.

Ethernet relay board: [Link]

June 17th, 2008

IR – relay control

ir-relay-control-board

Choose one key on your remote controller (from tv, video or similar), memorized it following a simple procedure and with that key you will able to turn ON or OFF any electrical device you wish. So, with every short press of that key, you change the state of relay in receiver (Ir-switch).

Memorizing remote controller key is simple and you can do it following this procedure: press key on Ir-switch and led-diode will turn ON. Now you can release key on Ir-switch, and press key on your remote controller. If you do that, led-diode will blink, and your memorizing process is finished.

IR – relay control: [Link]

27 Zone Sprinkler Controller With Pump Control

The Sprinkler controller was designed to act as a interface and controller for managing sprinkler system valves (also called zones). Those that exist either use what I consider to be unreliable protocols (X10), have a very limited number of valves (like 6 or 8), aren’t opto-isolated (i.e. just relays, pratically guaranteed to send huge transients into your automation system) or are just expensive (like $250 for 8 zones).

Currently i don’t have a lawn so I’m not too interested in this kind of projects, but i thought you might be.

27 Zone Sprinkler Controller With Pump Control: [Link]



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