how can i connect 24VDC to digital input (usb 6008)

[Ondik]

hello,

how can i connect 24VDC to digital input (usb 6008), is it possible with some optocoupler?

thanks

[crossrulz]

The 6008 is a static DIO, so speed shouldn't be an issue.  Therefore an optocoupler should work.  Just make sure you get one the meets your specs.

[SnowMule]

Depending on isolation requirements, you may be able to get away with a zener diode or voltage divider.

[Ondik]

Is it possible? (in attachment..),

thanks to all..

[johnsold]

That should work. The USB-6008 has an internal 4700 ohm pull up resistor to +5 V. If you were using a device without the pull up resistors, you would need to add an external resistor.

If there is any chance the optocoupler could be connected to the 24 V circuit in reverse polarity, adding a protective diode would prevent damage to the LED.

Lynn

[Buechsenschuetz]

The solution shown should work. Anyway, using a zener diode or a voltage divider may not work properly. Many PLCs and other 24V control devices have outputs which source 24VDC when on high level and are simply switched off when on low level. A TTL compatible input will need a current sink to detect a proper low state, if the line is simply disconnected or switched off, it may be in an undefined state (detected as high level in most cases).

Of course, with the solution shown, the logic states will be reversed. I.e. the input will be in low state when the 24VDC line is on high level and vice-versa.

[Ondik]

thanks to all to yours answer..

second problem for me is analyze digital input but with 110 VAC (voltage is or not), i draw some connection with optocoupler PC814,

have any man from you some experience with this?