Digital Input, Digital output

[Kaka]

Anybody can tell me what does digital input and output means on a thermostat controller?

[Brian_UK]

Digital Input means that the input signal changes from ON to OFF or OFF to ON.

Digital Output is the same thing, a simple ON/OFF function.

A mention of the model number would help with further answers.

[RefrigNoob]

Usually used to trigger events in the thermostat, or to have something external triggered by the thermostat. Both these are usually configurable in the thermostat.
For instance:
You may be able to configure the digital output to be an alarm. So when the thermostat has an alarm the output will close. This you can use to sound a horn or a big red light or launch a missile or something.

Or you can configure the digital input to a Manual Defrost. Then you can connect an external switch to the input an everytime you hit the switch, the thermostat will go into defrost mode.

This is not the same as RS485 communications ports on some thermostats.

[Kaka]

this means that digital input and output receive or give out on and off signal only..
it cant receive or give out 0-10V, 4-20mA, etc signal??

Can you guys give me some of the items that gives on off signal only?

[littleyapper]

yes it can take or give out 4/20ma etc.... depending on the controller and what you want to do ... all above replies are spot on ... you would really need to tell us what you have or what you want.... cheers

[Kaka]

i would want to know if i can connect a hi low pressure limit switch or a overheat protection thermostat to the digital input?

[Lowrider]

Digital signals can only be 0 or 1. Analog signals can be 0-10V, 2-10V, 0-20mA, 4-20mA or resistance.

[NoNickName]

yes it can take or give out 4/20ma etc....

No, it can't. It's digital, remember?

[RefrigNoob]

i would want to know if i can connect a hi low pressure limit switch or a overheat protection thermostat to the digital input?

Yes you can. As long as it's a pressure SWITCH, not a pressure transducer. Ditto for overheat protection SWITCH.

Then you just have to configure the digital input in the "setup" of the thermostat. In other words you have to tell the thermostat what you want it to do when the digital input is open or closed. Obviously one of the 2 states must be "normal" operation mode, and the other state is the exception. You can usually also set the "polarity" of the normal state.

For instance, a LP cut-out switch could be closed when LP is too low, and open when LP is high enough to permit normal fridge operation.

So you have to set the thermostat to interpret the digital input as a critical alarm, and you have to set it the polarity/state as normally open.

[RefrigNoob]

Have a look at this:
http://www.dixell.com/linea58/download/XR40C-D_GB.pdf
There you can see that i1P and i1F are the 2 settings I referred to. This depends of course on the thermostat you are using.

[w.l.ong]

hello KAKA,
can you tell us more what application you like to control,
also how many output and input of your system,
in here i use PLC connect to Digital temp. control,

w.l.ong