Jan1
Posts: 42
Joined: Tue Nov 13, 2012 7:22 pm

GPIO or PLC needed

Tue Jan 05, 2016 6:30 am

I would like to control a heater ( via Solid State Relay) from a Raspberry.
My scenario would be like this
I will start a heater from a "cold" state( heater will have an ambient temperature). The temperature will reach a low temperature limit( say 190 C) and waits for me to start my temperature profile .The profile will be like this: temperature goes to 220 C, wait 20 seconds and goes back to the low temperature limit 190 C.
But the temperature will have to stay at those 190 C( low temperature limit), so the next time I will start the profile , the profile will start again from 190C(low temperature limit), not from the ambient temperature.
Is that possible with only GPIOs of Raspberry ( with using a A/D convertor) or I must use a PLC controller?
Did anyone try anything similar?
Thank you for your feedbacks

BMS Doug
Posts: 3824
Joined: Thu Mar 27, 2014 2:42 pm
Location: London, UK

Re: GPIO or PLC needed

Tue Jan 05, 2016 9:06 am

Jan1 wrote:I would like to control a heater ( via Solid State Relay) from a Raspberry.
My scenario would be like this
I will start a heater from a "cold" state( heater will have an ambient temperature). The temperature will reach a low temperature limit( say 190 C) and waits for me to start my temperature profile .The profile will be like this: temperature goes to 220 C, wait 20 seconds and goes back to the low temperature limit 190 C.
But the temperature will have to stay at those 190 C( low temperature limit), so the next time I will start the profile , the profile will start again from 190C(low temperature limit), not from the ambient temperature.
Is that possible with only GPIOs of Raspberry ( with using a A/D convertor) or I must use a PLC controller?
Did anyone try anything similar?
Thank you for your feedbacks
What do you want to use to measure the temperature?
Unless you already have a sensor then you will probably find that it is easier to buy an analogue sensor than a digital one.
If you have an analogue sensor you will need to do Analogue to digital conversion (ADC) if you wish to use a raspberry pi.

I'd probably use an Arduino, which has ADC built in and is more suited to the application.
Doug.
Building Management Systems Engineer.

Jan1
Posts: 42
Joined: Tue Nov 13, 2012 7:22 pm

Re: GPIO or PLC needed

Tue Jan 05, 2016 9:35 am

I am going to use a thermocouple K model, which is analogue, I think. I know I will have to use an
Analogue to digital conversion.Can you suggest any type?
Why do you think with Arduino it will be easier?

User avatar
joan
Posts: 14747
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: GPIO or PLC needed

Tue Jan 05, 2016 9:42 am

Jan1 wrote:I am going to use a thermocouple K model, which is analogue, I think. I know I will have to use an
Analogue to digital conversion.Can you suggest any type?
Why do you think with Arduino it will be easier?
The application (as defined) is very simple. Arduinos have built-in ADCs. Arduinos are designed for this sort of simple task, are easy to program, and launch the program automatically at power-on, and can run off low power batteries.

BMS Doug
Posts: 3824
Joined: Thu Mar 27, 2014 2:42 pm
Location: London, UK

Re: GPIO or PLC needed

Tue Jan 05, 2016 1:56 pm

joan wrote:
Jan1 wrote:I am going to use a thermocouple K model, which is analogue, I think. I know I will have to use an
Analogue to digital conversion.Can you suggest any type?
Why do you think with Arduino it will be easier?
The application (as defined) is very simple. Arduinos have built-in ADCs. Arduinos are designed for this sort of simple task, are easy to program, and launch the program automatically at power-on, and can run off low power batteries.
Exactly this ^^ reason.

With an Arduino your application would be up and running within moments of being powered on, every time, without any complicated shutdown process.
A Pi (being a full computer) will take more work to setup as the controller, require an external ADC, take longer to startup each time you use it and require a correct shutdown process.
Doug.
Building Management Systems Engineer.

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