Idea feasibility

Hello, I am not a programmer by any means, but I am in a field where controllers (plc) are used heavily. I have an idea but I’m not sure if an Arduino is capable. This is an air conditioning application.

Here is what I would need:

Current sensing relay, NTC Temp probe, on board relay (low voltage) of some sort. 24vac operation.

Logic: When board senses +1amp current, it starts a timer (60 seconds) after this timer expires, it looks at ntc temperature within specified limits. If it sees temp outside the limit, the relay switches.

Is something like this possible?

When is a relay NOT a current sensing relay?

Paul

Maybe I didn’t explain that correctly. I would need an external current sensing relay, the type you clamp on a motor lead. When the motor turns on, the sensing relay “makes”.

MrRobotooo: Current sensing relay, NTC Temp probe, on board relay (low voltage) of some sort. 24vac operation.

Logic: When board senses +1amp current, it starts a timer (60 seconds) after this timer expires, it looks at ntc temperature within specified limits. If it sees temp outside the limit, the relay switches.

Is something like this possible?

Sure. You also might consider instead of a current sensing relay, an electronic approach.

have a look at Current monitoring with non-invasive sensor and arduino the sensors are available for a range of currents what will the onboard relay be switching? e.g. high volrage or current?

In a word, 'yes', it is possible.

OpenEnergyMonitor
is a link to a place that gives you the math.

CT or current sensor into the Arduino to watch for the unit drawing power.

once it reaches your threshold, you can start the timer. simple software function

once the timer times out, it can close a relay.
this relay needs to be sized for the proper load.

as a side note, I am curious as to what temperature.
there is an X/Y problem
the OP (you) rule things in or out for unknown reasons, not using common or easy things that might do the same thing.
if you already have your NTC, do you know what value ? and is it already in use for another control circuit ?

Wow, thanks for the quick replies. I’ll try to answer all of the questions here.

The working temperature range for the ntc sensor will be 30°f to 70°f. Outside this range would trigger the onboard relay (alarm).

The ntc sensor would be a 10k type 2, but any ntc would be fine as long as it can measure temperature within the working range.

The on board relay is used as an alarm relay. The current will be very low as it will be powering an alarm light (led) and small audiable buzzer.

So to recap, the arduino would look for motor current, if it senses motor current, it starts a 60 second timer. After the timer expires it looks at a ntc sensor. If the sensor goes outside the working range, the arduino switches the on board relay as an alarm. Hopefully that makes sense and clarifies things