| 摘要 |
An auto darkening eye protection device including a shutter assembly, a light sensing circuit, a control circuit and a power source. The shutter assembly is adjustable to a plurality of shade levels. The light sensing circuit senses light from a welding arc and providing an output indicative of the shade level at which the shutter assembly should be operated, the light sensing circuit includes a phototransistor operative to receive the light from the welding arc and produce a phototransistor output representative thereof. The phototransistor output from the phototransistor is used to form the output of the light sensing circuit. The phototransistor is configured for surface mount and has an external base connection connected to the base of the phototransistor. The control circuit is configured to receive the output from the light sensing circuit and provide a drive signal to the shutter assembly responsive to said output. The drive signal is operative to drive the shutter assembly to one of said plurality of shade levels. The power source is coupled to the light sensing circuit and control circuit for powering same. The present invention provides reduced power consumption, improved attenuation of low intensity light signals, a sharp rise time from the phototransistor in response to high intensity light, and allows implementation into a smaller sleeker eye protection device.
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