Having problems connecting RELAY on arduino / homeduino

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Hello,

I have some Problems connecting a Relay to the ardunio:

I Need to Switch a 12 V device with a relay, so first i have connected VCC and GND from the relay directly to the arduino.
Then i connect the 3rd pin to D8 (also tried analog pin) to the arduino.

Then i configured pimatic using homeduino by switching PIN 8

Everything went good so Long. I restarted pimatic, and tried to Switch the pin via pimatic.
And the first 2 tries where OK, but then i got “failed to open Serial port” and i have to restart the raspberry.

Any ideas what is wrong here ? I also tried to connect the relay via external 5V device, but still got the problem on the first 2 switches.

@hyperx the “failed to open Serial port” message seems to indicate that the relay is somehow drawing power from the arduino, resulting in a reset of the arduino or to few power to communicate via the serial port.

I use a relay too, in order to control my central heating system. I have connected the GND and VCC of the relay to the power pins of the raspberry, and the switch pin to pin 5 of the arduino. I also put a transistor between it in order to amplify the signal.

@hyperx My recommendation is to either follow one of the arduino relay tutorials, e.g., http://www.electroschematics.com/8975/arduino-control-relay/ or to use a relay module which is available for about two euros, e.g. http://www.ebay.de/itm/2-Kanal-5V-Relaismodul-Relay-Board-Module-Fuer-Arduino-8051-AVR-ARM-DSP-MSP430-/181378035849?_trksid=p2141725.m3641.l6368
Typically, these modules aleady include the amplifying transistor and a flyback diode (Freilaufdiode).

@denniss17 said:

@hyperx the “failed to open Serial port” message seems to indicate that the relay is somehow drawing power from the arduino, resulting in a reset of the arduino or to few power to communicate via the serial port.

I use a relay too, in order to control my central heating system. I have connected the GND and VCC of the relay to the power pins of the raspberry, and the switch pin to pin 5 of the arduino. I also put a transistor between it in order to amplify the signal.

I have tried exactly the same way… except the “transistor” … and first it worked 2 days. But now after a couple of switches… i have the same problem again.
It seems that the relay need a lot of current some time…

You can simply connect a relay to arduino board via vcc and ground pin. I think you should use amplifier for the signal.