I'm making a 12 volt appliance that uses a thermostat to switch on and off a halogen light bulb and pc fan at the same time.

I've worked out the total amperage draw of all components should be about 950 ma when used togother.

However I'm regularly breaking the 12v mains 1 amp power adapters.

So my question is do you think I could be peaking over 1 amp when the thermostat switches on both the fan and bulb at the same time??

Would it help if I just let the fan run all the time so its not starting an stopping, then just the bulb has to start from cold?

Thanks

 

Hello,

When a lamp is cold the resistance is lower, so it will draw more current at startup.

Greetings,
Bertus

 

Hi
So, do you know if the fan will draw more amps at start up compared to when its running.
Also do you know if the lamp can draw more than its 10 watt rating?
Thanks

 

Hello,

The fan startup will also draw a little more then running.
The lamp will draw much more at startup.

Electrical characteristics

Incandescent lamps are nearly pure resistive loads with a power factor of 1. This means the actual power consumed (in watts) and the apparent power (in volt-amperes) are equal. The actual resistance of the filament is temperature-dependent. The cold resistance of tungsten-filament lamps is about 1/15 the hot-filament resistance when the lamp is operating. For example, a 100-watt, 120-volt lamp has a resistance of 144 ohms when lit, but the cold resistance is much lower (about 9.5 ohms) [38] [39]. Since incandescent lamps are resistive loads, simple triac dimmers can be used to control brightness. Electrical contacts may carry a "T" rating symbol indicating that they are designed to control circuits with the high inrush current characteristic of tungsten lamps. For a 100-watt, 120 volt general-service lamp, the current stabilizes in about 0.10 seconds, and the lamp reaches 90% of its full brightness after about 0.13 seconds. [40]

This quote comes from this wiki page:
http://en.wikipedia.org/wiki/Incandescent_lamp

Greetings,
Bertus