You might also try to ground the Emitter of the Photo transistor and place the load resistor in the collector side from Vcc to the Collector and measure there, A low would indicate that the Diode is turned on, A high would indicate that the voltage on the Anode is below 1.5V. I've used the NEC2501/2/4 in that manner many times with great success. If you need a high to indicate a condition, invert your sketch logic.
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