Quote:
Originally Posted by Uncle Bulgaria
Am I to assume from this that the receiver conducts when the light falls on it, and this current is amplified and converted to a voltage with one of the resistors, such that 7.5V is present on blue when the beam is unbroken?
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You can see from post 9 that everything can be contained in a small package but there is a limited space for an opaque flag to move in and out in that arrangement. Mindful of post 2, in your application there needs to be a larger working distance therefore an IR LED and an IR receiver (photo transistor or photo diode) are used.
There is a hole in your damaged pcb but assuming the switching (blue) wire is connected to the device above the hole, that would suggest an open collector switching arrangement that is provided with a voltage within the power module, so you aren't going to measure a switching voltage until that is connected. Is the pcb double sided by any chance?
Eddie