A partial approach to quietening noisy PCs can additionally be to reduce the pace of interior cooling lovers. Low-cost fan speed controllers are available, however they continuously hire inefficient, heat-generating linear regulators and include no temperature remarks mechanism. This concept makes use of a with no trouble available, cheap in-car cell phone charger. The majority of these use common circuitry and require only minor amendments to function as efficient fan speed controllers complete with temperature feedback. Most in-car chargers are based on the nicely-known MC34063 DC-DC switchmode IC.
When used for charging cell phones, the open-circuit output voltage is in most cases set to between 7V and 9V. This is carried out with a easy voltage divider across the output, the centre level of which joins to the feedback input (pin 5) of the MC34063. To make the output voltage var-iable with air temperature, first exchange the higher resistor of the divider with a four.7kΩ resistor in collection with a four.7kΩ trimpot. The decrease half of the divider is then changed with a 470Ω resistor in sequence with a 500Ω NTC thermistor. These prices are simplest a information and may additionally be diverse to suit totally different thermistor and fan types.
Efficient Fan Speed Controller Circuit Diagram
Note that component lead size should be minimised to avoid introducing noise into the remarks circuitry. Getting the best fan beginning voltage is a topic of trial and error. The prices shown on the circuit supply a beginning voltage of about 6.8V at room temperature however trimpot VR1 can be utilized to lift this voltage as vital. The output can then upward thrust to about 10V if the interior temperature upward viasts sufficiently. The 4.7kΩ resistor can be reduced to three.9kΩ and VR1 adjusted to give a lower beginning voltage if the fan pace is still too excessive at 7V. After operating for one hour or so, the fan voltage as set with the help of the interior case temperature thermistor on my PC settled at 7.4V.
Suitable chargers are to be had from Oatley Electronics, Cat. No. 2D0074. They’re presently listed at $5 for two, which is less than the associated fee of the MC34063 ICs alone! Data on the MC34063 can also be downloaded from www.onsemi.com and a useful construction aid is to be found at www.nomad.ee/micros/mc34063. Finally, note that now not all chargers have an output filter capacitor put in. Typically, this is a 220µF 10V or 16V electrolytic sort. To save just a few cents, the producers every so often go away this component out, relying on the mobile’s battery to operate the filtering process. If this element is missing from your charger’s PC board, it will have to be put in ahead of the availability is used.
http://www.ecircuitslab.com/2011/08/efficient-fan-speed-controller.html
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