Man/Auto schematic with 4n35


I want to switch on/off some device using a 4n35 opto-isolator and Arduino but I have some questions.
I need a “manual” way to turn on/off the device without the control of Arduino.
Can I use the base of the transistor like the schematic?
Is there a better way?

The connection to D4 is to tell arduino that the system is in Auto/Manual mode

The resistors’ values are false.

Thank you.

sorry, my english is not as good as I want

Connecting like that really removes your isolation.
Also, you say D4 but I think you mean D5 tells you the auto/manual mode.
A better way, and to keep your isolation, is to add a switch disconnecting D4 from the 4N35 pin 1 when you want to manual, and use a switch to connect pin1 to +5 via 150 ohm resistor when you want it on, and connect the Run/stop switch so it grounds on the isolated side when you want it stopped indepemdently of the arduino or the manual switch.

In this way?

Yes, you are right. D5 instead of D4

That would work also.
When Man/Auto is closed and Run/Stop is open, the Arduino is in control.
If Run/Stop happens to be closed at the same time, the arduino won’t sink more than ~35mA if it should try & take the output Low.

When Man/Auto is open, Run/Stop close & open acts the same as Arduino High/Low.

Probably get more consistent results (current flow thru the LED) if th 4N35 pin 2 goes to ground, and you move the 220 ohm resistor between D4 and the Man/Autoswitch.

Sorry, the system is more complex than the initial drawing
I need 2 signals (Forward and Return) and 3 switch (man/auto, forward and return)

Sorry again

So 2 single pole switches, and 1 double pole double throw switch.

Just to be on the really safe side, I would put a high value resistor in parallel with the LEDs, better yet on the transistor's base. It makes me chill to see totally undriven electronic "inputs"...