Component for switching on Fan

mitchilin · Sep 8, 2016

Hi,

I'm building a cupboard for a Project at work that has integrated docking stations for laptops. In order for the laptops not to overheat, I am implementing a ventilation system.

I need to find a component that when a certain temperature is reached, it can send a signal to the Siemens S7-300 PLC I am using, and in turn I can turn on the ventilation.

Can someone please help me which component I need and how I can wire it up to the digital input of the PLC? I want the ventilation to turn on around 25-30 degrees C.

Thank you in advance

Ronnie Sullivan · Sep 8, 2016

How about a thermostat wired directly to the fan?

mitchilin · Sep 8, 2016

I would like to wire it through the PLC as there are other things I would like to program. For example cupbaords reach certain temperature -> fans turns on, LEDs turn on, message shows on HMI. I need some stuff to program so I have some control system to put in my presentation after I have finished the project.

mk42 · Sep 8, 2016

Normally, you would measure temperature as an analog input, and then you can process it in your program easily. Different tasks can have different setpoints, or even multiple setpoints, all off one input.

However, if you want to measure temp digitally, then it becomes a simple "is it too hot" choice, and you only get to use one temp for that, per input. Ronnie sullivan's suggestion of a Thermostat is a good one. You could probably find one that you can wire to the input instead of directly to the fan.

mitchilin · Sep 8, 2016

Thanks.

That's all I need. An analogue input would be nice but I don't have space for the module.

Thanks for your help.

BryanG · Sep 8, 2016

If you web search for 'enclosure thermostat' you will find the type of thing to use. Some need a supply + & - or L & N and then give a switched feed output. Some just need a + or an L and switch that signal out. The ones that need a full supply tend to have a smaller hysteresis between On and Off switching.

Matthew12345678 · Sep 8, 2016

what if you had a thermostat wired into a relay to turn the fan on and to give an input back to the plc...

RDS · Sep 8, 2016

Simple thermostat will work. Check with enclosure vendors, or try this link:
https://www.automationdirect.com/ad...nagement/Thermostats_-a-_Hygrostats/011479-00

timryder · Sep 8, 2016

RDS said:
Simple thermostat will work. Check with enclosure vendors, or try this link:
https://www.automationdirect.com/ad...nagement/Thermostats_-a-_Hygrostats/011479-00

I second this advice, I've used this device specifically before and had great success. You can run 24v to the contact terminal and when the thermostat reaches the temp you set it will close the contact relaying the 24v to the PLC input card. The thermostat has a built in hysteresis which will continue the fan on below the set temperature for a few degrees to prevent it from cycling on/off constantly.

Good suggestion.

mitchilin · Sep 14, 2016

That thermostat looks great, I have done some research and found this component which I think works the same way as the one suggested:

https://www.conrad.de/de/raumthermo...gramm-5-bis-30-c-renkforce-tr-93-1323079.html

The manual can be found in english with this document:

http://www.produktinfo.conrad.com/d...-RENKFORCE_RAUMTEMPERATURREGL_de_en_fr_nl.pdf

Can someone pülease confirm that I could use this with 24V instead of 230V? I don't understand how the thermostat works, does it need a voltage supply?

Thank you

RDS · Sep 14, 2016

That one will work. Pay attention to the contact ratings for the load you are connecting. The "integrated light" on this unit will not operate at 24V but it is only an option and need not be wired.

Component for switching on Fan

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