Logic high/low

[carlson]

How do I use this photo interrupter circuit

Silicon Chip Online - Circuit Notebook

at 3 volt (without relay) to pull pins 12/13 (in12/22) of this IC

BA6845FS Datasheet pdf - Magnetic Disk LSIs > FDD stepping motor driver - ROHM

low when beam blocked and high when beam not blocked.

 

[MikeMl]

I'd wire it as in the train detector, but put a second inverter after the first. That would give you the high.

If you can move the load resistor to the collector of the photo-transistor, then you can do it with only one Schmitt inverter.

 

[carlson]

Can I do it without the invertor

 

[MikeMl]

Probably not, because the transition from on/off off/on will be not be a clean logic transition, will be too slow, and because of the low-gain optointerupter, will float around near the trip-point being modulated by 120Hz incident light.

 

[carlson]

terrific ta thanks