Hi, What do you look for in a relay to do a specific job, What do terms mean, such as minimul voltage and stuff??
You've two sections to a relay, the activation coil and the switches. The coil comes in a range of DC voltages, eg 6v, 12v, 24v, and mains AC voltage, so first thing is to pick which you want. For any voltage there'll be a range that work, so a 12v coil might pull in the armature (the iron bit that moves) at 9v, and not overheat at 15v, so operating voltage is 9-15v. Then, once it's attracted the armature, it doesn't take as much voltage to keep hold of it, so a minimum drop-out voltage (must-release voltage) may be quoted, say 1.2v. For some jobs you may want to know how fast it can switch, so that should be in the spec. The other section is the switches, they come in various styles, same as toggle switches, SPST, DPDT, etc. They will have a voltage and current rating, for both AC and DC. They also come in various materials, like silver, gold, tungsten, etc. Some materials, like tungsten, are better for high current, some (like gold) for very low current or low voltage.
I see, So what do I need to look for in say a relay that switch a 240 voltage on by using a lower voltage???
that its rated for the DCvoltage you want use as the switching voltage (5v or 12v - I presume?) then it is rated at 230v AC and can carry the current you want. Post the ratings you need and if I have one here its yours for free !! (feel free to drop something in a kiddies charity box sometime
Then there's how you want to mount it - pcb mount or plug-in base with screw connectors. Have a look at the Maplin range to get some ideas.
OCLOCKER, cheers mate, thats brill of you. I need one that will switch on and off a 240 V system, using up to 24 volts as the switching voltage
Can you define up to 24v - most are 5-6v or 12v or 24v and whilst the range of voltages they will work at is wide I dunno if its wide enough to run a 12V one at 24v etc?
Well, what it is, its a control unit that has an options relay fitted on it. To the options relay can be fitted such things as an external light. But the options relay only allows up to 24v DC to flow through its potential free contacts (apparently) and so if an external light is to be conected the it need its own 240v power supply. So I was going to run a voltage through the option relay to another relay, so when the options relay is activated it will in turn switch on the second relay which will turn on the 240v Power supply.
