Re: Calling electronic experts: DIY GSM-controlled module for home appliances @kpzen, use the ULN 2803 A buffer (only 1 is needed out of the 8, maybe 2 if the coil current of the relay if coil current is >500mA - unlikely) to drive the coil of the DUMAG relay. From what you have described (+ve/ -ve/ common/ NO/ NC), the relay connections are:
1. +ive: one side of the relay coil. The 12V +ive line should be connected to this point, as also the COM point of the Buffer IC (it brings a reverse connected flyback diode in the chip into play to dissipate the negative surge of coil current switching)
2. -ive: the other side of the coil. This would be connected to the Output pin of the buffer (Pin 1C etc.). The 5V and 12V grounds have to be connected together
3. Common is the Common point of the NO/NC contact (this is not associated with the Coil). In the inactive condition of the relay (no current flowing through coil), this makes contact with the NC side
4. NO contact: Normally Open contact. The coil pulls the armature when current flows through it, connecting the Common to the NO contact; otherwise it is isolated
5. NC contact: Normally Closed contact. This is connected to Common when no current flows through relay coil, and is 'opened' or isolated when coil pulls armature
Coil +ive Common
Coil -ive NO NC
For your application, you will need to connect the Common to the Supply side (which I assume is 230V 1ph 50Hz AC), and the NO contact should be connected to the Phase line of the socket into which the appliance will be connected. A high at the Buffer Input will cause current to flow through the Relay Coil, and hence the Appliance will get power. You only have to apply 5V to the input of the Buffer (Pin 1B etc.) through which ever Port pin you connect (i.e. make that pin go high by writing 1 to it). |