24 VDC input circuit

[(8{)} ( .)]

Sheesh. I though this would be easy but it's not.

I wanted to be lazy so I tried to find a tried and true 24 Volt DC input circuit for my son's Arduino. The Arduino only takes 5 volt inputs so an opto-coupler should be enough to drive one. The rest of the circuit should also be simple, just a handful of parts; a cap, a resitor, a diode.

I'm looking for a circuit diagram which includes part numbers.

Any takers?

Thanks!

(8{)} .)
(Yosi)

 

[James Mcquade]

Just exactly what are you wanting to build?

when i google Arduino, there is a lot of possibilities.

regards,
james

 

[(8{)} ( .)]

Hi.

Just the simple input circuit. As I said, I know what part are in there just not the part numbers (resistor size, which opto to use, etc.)

Thanks!

 

[Lancie1]

A 24 Volt DC input circuit to drive a 5 volt Arduino input?

It seems something is missing or unexplained. It seems to me you really need a 5 volt DC power supply to drive a 5 volt input device to connect to the Arduino. Perhaps you mean how do you reduce or convert a 24 VDC supply down to 5 volts DC?

 

[(8{)} ( .)]

The simplest way is a voltage divider but I want it to be robust. There should be an RC circuit in there to debounce the input at least. I'm just looking for a standard PLC input circuit.

Thanks!

 

[keithkyll]

Google PLC Input circuit. Here's one that's simple. I would use a 2.2K (instead of 1K) resistor on the input to limit the LED (opto) current to 10 mA.
Use a Darlington output. 4N32.

 

[(8{)} ( .)]

Perfect!

Thanks!

 

[Lancie1]

I'm just looking for a standard PLC input circuit.

I did not know that there was a PLC standard input. That shows how out-of-touch I am.
Which of the standards committees adopted the 24 volt level?

If it were me, I probably would just use a 5 volt DC power supply. I have several spare 120-volt-AC-to 3, 5, 6, and 9 volt DC supplies in my junk cabinet from old broken electronic devices.

 

[(8{)} ( .)]

Lancie1, has PC now come to automation?

By standard I mean a commonly used circuit or a CUC or, oh what the hell, a Standard type input circuit.

Cheers,

(8{)} .)
(Yosi)

 

[Lancie1]

If your commonly used circuit of 24 VDC inputs was really a standard voltage, then your Ardunio would already have 24 VDC inputs. I think that a wide variety of input voltages are still used, from 12 VDC to 250 volts AC, although the trend is toward 24 volts DC.

 

[(8{)} ( .)]

Arduino is a microcontroller. The I/O pins are 5 volt. They need signal conditioning. Output (relay) boards are available that provide isolation on the output (because of the relay). I couldn't find similar input boards, although almost any kind of input imaginable is available for the Arduino, for 24VDC inputs.

Cheers,

(8{)} .)
(Yosi)

 

[Lancie1]

I couldn't find similar input boards, although almost any kind of input imaginable is available for the Arduino, for 24VDC inputs.

So if any imaginable 24 VDC input is available, why are you using a 5 volt version of the Arduino? Is it because of cost, or what?

 

[(8{)} ( .)]

The funny thing is that while it is easy to find temperature sensors, humidity sensors, motion sensors, vibration sensors, etc... all for a buck or two a piece, I couldn't find digital I/O signal conditioners (ie. the 24VDC interface).

Anyway, I bought it for my son to play with. We're investigating very low-cost alternatives to things like SMS reporting or turning on I/O or OEM type stuff (Test stand control for example). There's so much stuff that you can do with the Arduino for < 50 bux. Most definitely not a PLC replacer but there are plenty of places where it is a cost-effective solution for places where a PLC is overkill. Check it out: arduino.cc Also do a search on Ebay for compatible modules.

Cheers,

(8{)} .)
(Yosi)

 

[Lancie1]

Check it out: arduino.cc Also do a search on Ebay for compatible modules.

I checked it out. It is a very nice hobby system, based on a supply voltage of 5 volts DC. I think I would buy a 5 volt power supply (AC to 5 VDC Adapter) that would allow use of a wide variety of input switches and sensors.

Quoting from the Arduino site Overview:

It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.

 

[(8{)} ( .)]

Absolutely. Regarding the 5VDC, even if I wanted to use it I'd want to condition it, and that was the reason behind my question. The power-supply will be a 5VDC (there are 3VDC versions of the Arduino too). The problem is interfacing the I/O with existing devices which, in most of the machines I encounter now-a-days, is 24VDC, hence my reason for 24VDC.

Anyway, you can find some very interesting things that people are doing with Arduino. How about protocol translation? Check out some of the projects on YouTube as well.