Thermostatically-controlled fan

agusano

Hello,

I need help for a project that I am carrying out.

I am using the output of a fan to drive a solid state relay. This relay activates or turns off some LEDs that do not have to be on all the time. That's why I need to have control over its on and off.

If the leds get too hot they can cause an emergency.

I have chosen to use the thermostatically controlled fans. I bought the board to be able to use a thermocouple. I have managed (using a fan to see it graphically) that it turns on from a specific temperature. But I would like it to work the other way around: that when the sensor measures a temperature higher than a limit value, the FAN OUTPUT TURNS OFF.

Could that be possible? Thank you

cosmowave

@agusano Which FW Version are you using?

Eventually you can invert it with a leading "!" in the M950 command

M950 F2 C"!Fan2" Q25000

agusano

@cosmowave I'm using RepRapFirmware for Duet 2 WiFi/Ethernet 3.2.2 (2021-02-11).

The fact is that i want to use this as a safety disconection system.

I want to do something like this:

M106 P0 H0 T70; Send this gcode to power up the LEDs but when the sensor measures 70º to force it to stop working.

In case that the system is working properly i will use the M106 P0 S0 command to turn of the relay.

cosmowave

@agusano Then, i think the best option would be to create and use daemon.g for controlling the LED's.

agusano

@cosmowave @cosmowave I will study this option.

But what worries me the most is that i want to implement this safety system because once i send this m106 p0 s255 gcode to power the leds. If the software that i use to print or my board bugs i can't manage to send the power off gcode on time. Thats why i wanted to control the temperature the led reaches once i turn them on. In that moment is when i want to control that and when it reaches hight temperature (because something on the software/board went wrong) i can turn them of without damaging anything.

cosmowave

@agusano If you'd like to be completely safe, you should consider to design a "power cut" circuit
It is possible to make a circuit with your temp sensor, a transistor and some resistors to cut the power supply of the LED's when a temp is reached.
Eventually there are complete circuits to buy on the market. Like a relais wich is controlled by a temp sensor...