For now I am not asking for code, but what things I should be considering.
I am VERY NEW to programming and what I want to do is...
On my furnace I have ducting on the inlet side pulling heat from my wood stove and circulating through the house. As the fire goes down overnight if the fan is left on it eventually circulates cooler air, so...
I am trying to make a controller for when a sensor in the wood stove duct falls below the set point it will shut off the fan. I would like to have say a 5 minute delay after the the temp falls below set point before the fan shuts off to prevent any temp fluctuations from turn the fan back on, just in case..
I have my program turning on and off LEDs with temp, Im am really struggling with the delay...
What hardware/software do You have now? Sensing the temperature of a live fire might not be like measuring boiling water.
What is the data for the fan?
Circuit diagram?
Give some more info.
20james06:
I have my program turning on and off LEDs with temp, Im am really struggling with the delay...
Thanks,
James
Since you already have the sensor in place.
Is this ducting a heat exchanger? Also are you in Europe?
What you need to do is set the "Off" temp lower than the "On" temp. maybe 5-10 degree C difference should be enough... play with it to find the perfect range. Example: So if the temp goes to 30 C then you turn off. Make the On temp higher maybe 40 C and it should not go back and forth... You don't need a delay.
Sounds good, turning fan on when temperature climbs above a certain level assuming that the fireplace is feed. Turning off at a lower temperature assuming that the fire is on the way out should work. Just trim the values…..
Look at the mills function and the sticky at the top doing several things at once - you DO NOT want to use the delay function
When the temp drops below the set point - set a bit "low-temp" ( or what ever you want to call it) - as long as the bit is set - use the mills function to make a timer - when the timer gets to 5 minutes - turn off the fan
You might consider a similar timer for the fan restart - or set the fan start temp up a bit if the no airflow causes the temperature to rise a bit
Thanks for the info so far, sorry for the lack of information in my first post, I rushed it before heading into work.. my controller is an uno by Elegoo. Programming with the arduino online editor.
I won't be directly controlling the fan, rather making the controller another contact on the fan wires at the thermostat. (A parallel setup so the furnace can cycle normally if the controller is not running the fan)
Temp sensor will be reading hot air being pulled by the fan, not reading the fire.
Still figuring out a transistor/relay setup for switching the fan.
20james06: For now I am not asking for code, but what things I should be considering.
I am VERY NEW to programming and what I want to do is...
On my furnace I have ducting on the inlet side pulling heat from my wood stove and circulating through the house. As the fire goes down overnight if the fan is left on it eventually circulates cooler air, so...
I am trying to make a controller for when a sensor in the wood stove duct falls below the set point it will shut off the fan. I would like to have say a 5 minute delay after the the temp falls below set point before the fan shuts off to prevent any temp fluctuations from turn the fan back on, just in case..
I have my program turning on and off LEDs with temp, Im am really struggling with the delay...
Thanks,
James
I did exactly the same thing in the 1970's when we lived in Portland Oregon. We put in a regular wood/coal furnace which would burn all night. So we never had a cool breeze from the oil furnace fan.
You need a similar wood burner, not a "wood stove".
Don't overdo the job. Sensing the temperature after the fan complicates things a bit. Temp reading will be wrong when fan is off. Think again if You can do things slightly different.
Anyone see an issue with using a thermocouple like the kind you see in heater units? That way you can have it connected away from the blowing air and right on to an area where you can sense temperature of the stove. You need to make some measurements and make sure you get a robust sensor or it’s in an area where it won’t burn your wires.
Just google Arduino relay tutorial and you will find many examples. You just need a transistor or mosfet to turn power on to relay to power on the fan. Just size it for the fan you’re using. Whether it’s DC or AC with a transformer.
Thanks for the mention of the thermocouple. That was my original idea and I'm not sure why I headed away from it. I agree it would be a better source and more consistent.
you would want the fan to turn ON at one temperature, say 40C and then turn off at a lower temperature, say 35C or whatever.
the gap is called hysteresis and this gap prevents a thing from turning on/off/on/off/on/off/on/off
you would need the heater to be started and producing heat before it turned on again.
lots and lots of temperature sensors for creature comfort air temperatures.
the DS18B20 is popular and super simple. can be had in a metal can for ease of installation
the BME280 offers another easy solution. requires a bit more of an enclosure as it is exposed on a ciruit board.
the temperature being measured and the maximum temperature are key in selecting the sensor.
but the concept is easy enough.
you can even data log when the temperature dropped
or the temperature every minute.
or alert your phone ......