240v Temprature Controlled Fan - First Project

Discussion in 'The Projects Forum' started by TeslaJr, Apr 18, 2012.

  1. TeslaJr

    Thread Starter New Member

    Apr 18, 2012
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    Hi Forum :)

    Im trying to build a 240 volt fan controller that kicks in above a chosen temperature selected by the user (my target temp is 25C/76F to give you a gauge). Here is a list of functionality im trying to archive


    • Activate above temp or bellow - a switch that can change the controller from activating when above selected temp, to activating when bellow a selected temp. This is so a heater could be used in winter, and then in summer. so a heat/cool switch


    • Adjustable idle speed- the controller needs to have an adjustable fan idle speed (0%-80%) when temperature is bellow currently selected temperature value.


    • Adjustable max output- When temperature gets above selection, it would be nice to not have fan go straight to 100%. so an adjustable max output dial would also be nice say 20% to 100%.


    • Temperature differential control- It would probably be bad for the fan motor if it kicked on and off ever few seconds. So once it does get above set temperature the fan should stay on until is brought it back by set amount. a triple switch with 3C or 5C or 7c would be nice choices.

    the current load will be around 200 Watts, but capacity up to 500 Watts would be nice :D

    Should i got analog dials or digital screen buttons...? What ever is simplest to archive my goals im happy with.

    I have found some products close to what i need online, but not all features in one. and i cant find any circuit thats match this, or maybe i just couldn't understand them.

    I did some electronics at school. enjoyed it, but have forgotten almost everything. I really need some help with this circuit design. I really look forward to your replies :)
     
    Last edited: Apr 18, 2012
  2. wayneh

    Expert

    Sep 9, 2010
    12,145
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    I assume this is an AC fan?

    It sounds to me like you need a proportional speed control, meaning the fan will speed up as the temp gets farther from the target. This almost eliminates a simple "thermostat" (on/off) approach. I say almost, because you could still have a multi-level thermostat setup. But that may not be much simpler to setup than a proper proportional controller.
     
  3. TeslaJr

    Thread Starter New Member

    Apr 18, 2012
    5
    0
    Hi wayneh :)

    Thanks so much for your reply and suggestion. Yeah that sounds smart! fan building speed if temperature does, as long as it outpaced the increase in temp to keep it on target that would be perfect.

    Yep fan is AC.


    I feel bad i dont have more to offer like a ruff diagram of a circuit, but ive kinda just jumped in the deep end here and hoping to learn a lot on the way.

    Here are some products that are close to what i want, but not quite right.

    This unit is pretty good but no limit on max fan speed perhaps it uses your idea though so might not be necessary.. also cant reverse it to turn on bellow temp and turn off above temp for heating. EXPENSIVE too :(

    Edit: unit bellow would be pretty close to perfect, reverse feature would be nice but if we could come up with the same functionality as unit bellow it would do the job.

    http://www.growerssupply.com/farm/s...01&productId=162278&pageId=ItemDetail&isDoc=N

    This next one has the reverse feature but is 120 volt, and doesnt have an idle speed setting. its important i have some airflow even if im bellow temperature, but have the ability to set idle to 0%/off if needed. Notice this unit also has a temp setting for both night and day which is kinda unnecessary for my purposes

    http://www.newegg.com/Product/Produ...7-_-Garden+++Patio-_-Quantum-_-9SIA02D08B6077
     
    Last edited: Apr 18, 2012
  4. wayneh

    Expert

    Sep 9, 2010
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    I have to admit ignorance of AC motor speed control. It has always confused me. Maybe an expert will jump in soon.

    But it occurs to me that even a cheap table fan has 3 or 4 speeds with a selector switch or switches. It would not be too hard to develop a DC circuit to control a few relays, simulating the switches. But maybe you already have a motor without this capability?
     
  5. TeslaJr

    Thread Starter New Member

    Apr 18, 2012
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    0
    Thats ok thanks for trying mate. maybe we can both learn from this thread :D
     
  6. TeslaJr

    Thread Starter New Member

    Apr 18, 2012
    5
    0
  7. wayneh

    Expert

    Sep 9, 2010
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    While you're waiting for help it would be good to post details about your fan motor.
     
  8. TeslaJr

    Thread Starter New Member

    Apr 18, 2012
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    Thanks again for you imput mate :)

    This is the same fan for sale on ebay. Made in china somewhere no doubt and cant really find any detailed specs on it http://www.ebay.com.au/itm/6-INLINE-...item35b5c6c0fb

    I dont fully understand what your asking. Use relays to step up the speed with DC switches? I dont have a speed switching feature on my fan unfortunatly. But its more the auto ramp up above set temp that interests me most, and being able to set a custom idle speed.
     
  9. wayneh

    Expert

    Sep 9, 2010
    12,145
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    The limited specifications listed there are not encouraging - no hint of variable speed. I think you'll need to know more about the motor before you can design (or even choose) a controller for it.
     
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