# how many light bulb for one relay?

i've just done this tutorial: http://www.arduino.cc/es_old/Tutoriales/Rele

it works great! i've done it in a breadboard (with two 5v circuits for test) and then soldered (for just does not have 220v on a breadboard) and it works well for 1 light.

now i need more lights and i thought to make a relè for switch on/off a multiple adapter.

the thing i want to know: the pin of the relay are thin (just all other 5v-breadboard-based component) and i thought that more volts you have more bigger have to be the wire.. how many normal 220v ac light bulb can i control with one relay?

• Can you give us the relay's specifications, preferably a datasheet? – stevenvh Aug 25 '12 at 17:46

What is something to take into account is that incandescent lamps cause a high inrush current, due to the fact that their resistance is low when they're cold. That inrush current may be as high as 10 $\times$ the nominal value. For instance, a 60 W bulb will draw 60 W/220 V $\approx$ 250 mA. Inrush current will be 2.5 A, then a 10 A relay will only switch four(*) 60 W bulbs, instead of the forty one might expect.