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Smart implant to control fan based on DS18B20


k1s21
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Question

Hello I've been trying to get a fan running triggered by temperatures measured by DS18B20 probes.

 

The Fan is 12V and according to the spec needs max 0.08A, so I tried first a 12V 1A PSU to power both, but by the time i was wired up it had only 10.5 V at the fan connection.  I tried another PSU, this time 12V 1.5A but only 10.8V at the fan connection - not sufficient to make the fan spin.

 

If the maximum current on the outputs is 150mA, why is the fan's 80mA / 0.96W not being received through the Smart Implant ?

 

The wiring from the PSU to the Smart Implant is 2cm.  From the implant to the fan is 1 metre (using the cable supplied with the PSU ~12-14 AWG I thnk)

 

 

 

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Edited by k1s21
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@k1s21

I ask, do you have a DC motor? It can be an AC motor. Are you sure it's DC?
Is it some type of PC fan? Send the exact type.
Is the fan only two-wire? Doesn't need a PWM folder?
Some fans also come with a thermistor that actively controls the speed-based temperature(it inserts its own resistance into the circuit).
it's weird that doesn't get move with such a small drop voltage. In practice, different voltage dividers are made to slow down the fan speed and these then turn more slowly even at 5V.
Do you have a Stabilized 12V DC power supply?
I suggest the following procedure:
Connect the fan to the power supply only - is it spinning? If so, disconnect the DS18 sensors from the SI and connect the SI to the power supply - is the fan rotating?

Edited by Martin_N
Edit: i wrote some bad words
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  • Hello Martin,

    Thanks for your reply 

    Yes the fan (Noctua NF-A20 PWM) works fine when plugged in directly to a 12V 1A supply (or 12V 1.5A) - I don't know if they're "Stabilized" - they came with IP cameras

     

    As a PWM fan it has 4 wires but only the two for +ve and -ve are connected (I haven't got any of the supplied "Low Noise" adapters connected.  The 2x DS18B20 and smart implant are all powered from the same PSU

     

    Disconnecting the DS18B20s would mean de-soldering (some tidy work ;) ) .  Do you think the tiny electrical demand of the probes is causing that voltage drop?

    Edited by k1s21
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    @k1s21

    I assume you tried to measure with an ohmmeter that the SI outputs are switching. Isn't there a mistake in my own performances? Check this first.
    It could happen that a short circuit on the circuit passed through the output. (for example by connecting a wire on a fan). Then the fan survived, but the SI output remained as a fuse ... :(

    The power supplies to the cameras are stabilized, so the drop in voltage will be a mystery. In addition, at a given current, a fairly large cross-section (small AWG) of wire to the fan and a short distance should be practically no accommodation.
    I assume that you have used a black wire for - and yellow wires for + on the fan.
    If so, disconnect the fan from the SI and connect only the wires that switch the SI output.
    Is it spinning? ... No = look for a problem in the power supply or fan.
    Yes = return the wires to SI, but the interchange is between them (I think there are no relays, but optocouplers and something doesn't work like me).

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    I think you are overloading the smart implant. The fan will have an inrush current of many times the steady state current of 0.08A. When the fan it not spinning it will try to draw this high current and you may damage the smart implant.  The way to get around this is to have the smart implant drive a slave relay, and the relay then drives the fan.

     

    Post back if this solves your issue!

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    Unless your Smart Implant is defective, running your fan should work.
    Have you measured how much current your fan draws when you run it directly against the voltage adapter?

    How do you trigg the output?

     

    I tested this with a three speed fan on a UBS that has the same performance as the Smart Implant and the fan was able to run at all three speeds.

    (UBS with mini relay CPC1008N)


    Low speed 72 mA (starting current 94 mA)
    Medium speed 112 mA (starting current 150 mA)
    High speed 148 mA (starting current 200 mA)

     

    Edited by RH_Dreambox
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  • Inquirer
  • Well,

     

    I've discovered that the fan never draws more than 0.15A 

    Yes, the Smart Implant outputs are switching.

    It seems Output 1 delivers 12V but Output 2 only 10V.

     

     

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    @k1s21

    Really interesting information. Did you measure the voltage empty or with the fan connected?
    It really looks like a damaged output. Be that as it may, I believe that the fan should run slower even at 10V.
    When you state that the current does not exceed 0.15A, I understand that it is close to value. So it depends on what measuring instrument you use. If you don't have True RMS, you don't have to catch a peak that exceeds just 0.15A.

    If you know that the SI is really damaged, try to disassemble it and take a picture of it from the inside. Unfortunately, I do not have any and I would be interested in the internal construction. According to some models, it should be different from the Universal Binary Sensor.

     

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  • I measured it empty with the -ve electrode on the output screws and the +ve at the power input.

     

    The current draw I see is simply looking at the multimeter screen as I switch power on until after a second or so it settles down to 0.08A. 

     

    I'm not inclined to open it if is defective, in case I can return it under warranty. Unfortunately not much help from Fibaro support.  Simply a short message: "Output 1 and output2 don't deliver any voltage. It's a dry-contact/ Potential free"

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    I found a picture of SI. Although it looks more like a model than a photo, I can already make a picture.

    From what I can see, this is not "dry contact" in the true sense of the word - it's more of a relay contact term.
    I understand that the output may appear this way, the optocouplers and SSR relays are similar and always switch some minimal voltage.
    There are really used optocouplers that galvanically separate the circuits. There will still be protective diodes for the outputs on the underside of the SI.
    I've never thought about it, but depending on the internal connection, it may depend on how you connect the entire circuit.
    If you now switch +, try changing the connection and switching -.
    I'm guessing the diode was damaged.

     

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