Optocoupler puzzle

Try this: Ground pins 2 and 4. Input to pin 1 through your resistor, and output from pin 5, with 100 ohms from pin 5 to +5V.

Ed

Change the 10K to a 47K (or a 100K) and see what happens.

Tried your suggestion, and it helped a bit. What really made a difference was lowering the 1k to 200 ohms.

Remind me not to use the 4N35 for any low-power projects. ;)

Thanks, Ed.

:I dug an old 4N35 out of the junk box, and :wired it up two ways (below). : :I put ~150us pulses on pin 2, and expected :to see something similar at the output. What :I get is a scope waveform that slowly ramps :to about 2v over the 150us, before ramping :back to rest in about 20us. : :I tried changing the 1k to 500ohm, and the :10k to 1k, but it still showed a ramp. : :What the heck am I seeing, and why? : : +5v +5v : | | : .-. .-. : | |1k | |10k : | | | | : '-' '-' : | .-------. | : |--|1 6|-- | : | | | : in --|2 5|----+-- out : | | : --|3 4|-----| : | | | : '-------' gnd : : +5v +5v : | | : .-. | : | |1k | : | | | : '-' | : | .-------. | : |--|1 6|-- | : | | | : in --|2 5|----| : | | : --|3 4|----+-- out : | | .-. : '-------' | |10k : | | : '-' : |gnd :(created by AACircuit v1.28.6 beta 04/19/05 www.tech- :chat.de)

First, try reading the data sheet.

yeah I can see (with 20/20 hindsight) that it would. did you think to check the datasheet?

that's what the datasheet is for