24V input / output

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1

Hi everybody,

Is it possible to use netmf/gadgeteer in automation?
I See a Problem with the Input voltage which is 24vdc.

How does you fix it?
I dont want to solder. Is there a DIN rail device for it like an optocoupler?!
Why are they using PLC instead?

Thanks
Greets
Johann

2

I believe if you use the DP power module, you can use up to 30V for input power.

3

Oh Sorry. I dont mean the power supply.
Im searching for a Solution for digital Inputs.

4

Consider using an optocoupler with seperate power supply to take external inputs. Don’t know of any Gadgeteer module that has them though.

5

I found this shield. Can i use it with the 3.3v output from gadgeteer. Or is there an other Way? The input consumption is 5v.
http://www.exp-tech.de/Shields/product-200-201-207.html

I found some optocoupler and Test it this days.

Greets Johann

6

If you’re looking for low current relays, there’s a thing known as a “small signal relay” that is cheap, small, can be driven directly by a GPIO pin by most microcontrollers (use ~10mA or so), and sometimes/often have integrated diodes for suppressing the back EMF.

7

If you don’t need galvanic isolation, I’d just use a FET. Here’s a neat trick for level conversion:
[ol] Hook the FET’s source pin to the Gadgeteer pin. Hook the gate to 3.3V, and hook the drain to your 24V input/output.
Put a pull-up resistor on the 24V logic, pulled up to 24V.
Place another pull-up resistor from the Gadgeteer pin to 3.3V.[/ol]

The best part is that it’s inherently bidirectional. We use it for i2C all the time.

You can’t draw any appreciable amount of current on the 24V side (otherwise your pull-up will start drifting to ground), but that’s only a problem if your 24V stuff has a low input impedance.

8

What 3.3V FET do you use? I had a hard time finding them last time I looked…