Want to use LabVIEW to digitally control the lighting of LED's using a 24 volt system.

[Janathan]

Would like to turn on LED's powered by 24 volts, having current limiting to about 8ma by applying a digital low to turn on the LED, and a digital hi (open) to turn it off. I have a usb 6009, which I use with my laptop, but according to the spec, it cannot exceed 5.8 volts on a digital output. I need at least 4 digital inputs and 9 digital outputs to control 9 LED's. What equipment do I need. I may have access to a desk top as well.

            Thanks, Janathan

[F._Schubert]

You'll need a 24V power supply, relays for the DO with a driver circuit (they come as ready made ICs or do them yourself with diode and transistor) and optocoupler for the DI.

Felix

[RTSLVU]

There are several ways to accomplish this. I have attached an image that shows three basic ideas

[RTSLVU]

Forgot your digital inputs

The 6009 has a +5V power output use that for your digital inputs.

[Ben]

DO to whatever...

Phoenix Contact will put together whatever you need (short of 3KV). I have used their DIN rail mounted stff since they are generally a single component solution for each output point and have built-in LEDs to let you see your output. If they don't have what you need on the shelf, they will put something together for you.

Ben

[tbob · Accepted solution]

To drive the 9 LEDs, use the ULN2003.  Google it.  You digital output feeds into the ULN2003 and its output feeds the LEDs.  You still need current limiting resistors inline withe LED.  The ULN2003 can handle 7 inputs/outputs.  So you will need two of them.  Much simpler than having 9 transistors with base resistors.

[F._Schubert]

Thanks tbob, the ULN was the driver IC I mentioned, I didn't knew the number.

I also did swap the optocoupler/relay for DI/DO. Once I had to interface a 24V machine with my NI DAQ. Galvanic isolation was a requirement, so we did need relays for the DI. For my DOs, I couldn't switch the relay (24V), so we used an optocoupler (cause you still need the 24V line for the UNL to drive a 24V relay; but I think there are relays you can operate with 5V and switch 24V). Maybe it was from phoenix as Ben mentioned, or from Wago. Make sure you get the proper voltage rating, so 5V/24V.

Felix

[Janathan]

Thanks to Felix Schubert, RTSLVU, Ben and tbob for your responses. All great ideas and easy to implement! I'm a little embarassed I didn't think of the transistors myself!

Jan

[RTSLVU]

If yo uare going to go the open collector inverter/driver IC route you might want to consider the ULN280(x) series.

http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXysuw.pdf

These are a little more convient to use as they have 8 inverters/drivers per package