Help with overcoming heat problem in big adaptable box

Discussion in 'The Projects Forum' started by bowlingo, Mar 4, 2012.

  1. bowlingo

    Thread Starter Member

    Jun 29, 2011
    162
    0
    Hi all,

    I have a 420 x 380 x 180mm big adaptable box with a hinged lid that I wish to put various pieces of kit inside.

    I am trying to configure the power supplies that go into this box so there is as little heat as possible.

    I need 1 x 24V 2A power supply within the box

    And I need to power the following that will be 12V...

    8 x 1.8A (at full torque)motors = 14.4 Amps

    2 x small bilge pumps = 5 Amps

    Smoke alarm mA's

    Water sensor mA's

    12V relay mA's

    The easy way would be to put a 12V 20A power supply within the unit i.e one of these

    http://www.ebay.co.uk/itm/DC-12V-20..._Measurement_Equipment_ET&hash=item1c2306c69e

    But I am concerned about the level of heat these power supplies can give off.

    Another option might be a 5A power supply with the 2 x pumps on, smoke alarm, water sensor and relay on

    And a 12V sealed lead acid battery on the motors. The motors will only have to go on for about 120 seconds on a daily basis so maybe I can put a battery on it i.e

    http://www.batterymasters.co.uk/Pro...attery-(L(mm)-W(mm)-H(mm)-97-48-55)_1750.aspx

    With a charger permanantly connected to it i.e

    http://www.batterymasters.co.uk/Product-Yuasa-SLA-Charger-12v-300-mAh,-YCP03A12_1856.aspx

    I would use a relay to break the wire going between the battery and the motors i.e switch

    Any ideas on how I calcualate what battery will be suitable for the 14.4A draw, what charger etc and if it will overcome the potential heat issues?

    Thanks
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,984
    3,223
    It's a little confusing to understand what you all have in the box and what is out of the box. :confused: Can you post a diagram?
     
  3. bowlingo

    Thread Starter Member

    Jun 29, 2011
    162
    0
    The water sensor is in the box, the relay is in the box. The pumps, motors and smoke alarm are external to the box and plugged in on leads. I will have one 230V power lead going into the box and everything coming out of the box again on plugs/sockets. The 24V 2A power supply is powering a PH/CF transmitter, one of these

    http://www.ebay.co.uk/itm/Olimex-PIC32-PINGUINIO-OTG-prototype-PINGUINO-board-PIC32MX440-/270911284305?_trksid=p3284.m263&_trkparms=algo%3DSIC%26its%3DI%26itu%3DUCI%252BIA%252BUA%252BFICS%252BUFI%26otn%3D21%26pmod%3D220946159148%26ps%3D54

    and one of these

    http://www.ebay.co.uk/itm/Olimex-pa...al_Components_Supplies_ET&hash=item3f10ebeada

    and a 20 input/ 20 output/ 4AD input custom made I/O board

    The guy designing and coding the control side of the system (above boards) has told me the 24V 2A power supply is fine for the boards and ph/cf transmitter

    I am trying to design the 12V power supply side so it dosent get to hot inside the enclosure as I dont want to drill a load of holes in it

    Thanks
     
  4. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    I'd just go for the 20A supply. A 20A switch mode supply will generate about the same amount of heat as a 5A one if they are both supplying the same (under 5A) current.
    Assuming an efficiency of 90% it will only be about 7W at 5A

    <ed> Apparently the efficiency is 80%, but 14W in a box that size still won't heat it up too much
    http://translate.google.co.uk/trans...arch?q=ky-240w-12-l&hl=en&safe=off&prmd=imvns
    </ed>
     
    Last edited: Mar 4, 2012
  5. bowlingo

    Thread Starter Member

    Jun 29, 2011
    162
    0
  6. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    Yes, the heat will be about the same. You can get an idea of how warm it will get if you put a desk lamp with an energy saving light bulb in the box, they tend to be around 10-15W.
     
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