drive a small put dat
OK, I give up. What on earth is a "put dat"?
The coils of 5V relays typically require more current than a microcontroller
pin can drive, so use an NPN inverter [etc] ckt to drive the coil.
Also, you **ALWAYS** need a diode across the relay coil. They develop a large
voltage spike when switching off, related to the formula V = L di/dt. The quicker
the turnoff, ie small dt, the larger the spike.http://en.wikipedia.org/wiki/Inductor
You might also need some sort of spark quencher across the relay "contacts",
too, if you're switching any sort of inductive load.