Designing Dew Heater

[ZiHao]

So I am planning to make a dew heater for my camera len using resistors wired in parallel, then distributing them around the circumference of the lens.

Diameter of lens: 65mm

Total power output: 6W

Power Supply(powerbank): 5V, 2A, 20Ah

Resistance for each resistor: 120 Ohm

Resistor power rating: 0.25W

Power output for each resistor: 0.21W

Current drawn: 1.21A

Number of resistor required: 29

Will probably insulate the wire with tape, and wrap the resistors in cloth around the lens. Is 6W too much or sufficient for this use? Any suggestions? Thanks.

[rl]

That should be fine. You might well find less power is enough but I know how bad dew can be in the tropics...

The resistors will probably be ok but might be a little bit close to their maximum wattage. Half-watt parts are available and not much bigger physically.