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Robot cooling — Parallax Forums

Robot cooling

FRC2370FRC2370 Posts: 128
edited 2012-10-24 19:59 in Robotics
Built a chair robot to drive around on. The hardware (Arduino, power board, jaguar speed controllers) is sealed on the bottom with plastic panels to keep dust out, but today during testing I noticed that the jaguars, after checking the data logger, had temperature faults. There's no where for the exhaust from the jags to go, so would putting a set of 120mm case fans on top to push the air out be a bad idea?
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Comments

  • kwinnkwinn Posts: 8,697
    edited 2012-08-25 15:46
    Nope, it's a good idea, although it draws extra power from the battery. For battery powered equipment it is a good idea to mount parts that dissipate a lot of power to the inside wall or brace of the metal enclosure if possible. That way heat can be removed without using fans.
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-25 16:40
    Well odds are the fans would run on the arduinos pwm ports, and its running on a
    marine deep cycle battery. But which fans do you think would suit a heavy power robot best? I was looking at Thermaltake AF0032 fans
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-25 18:49
    The fans don't need any special connection. Just a regular old toggle switch will work.

    However you mount the fan try to make sure it is not working against the Jags' fans. Also, try to create a nice flow through your compartment so that fresh air is drawn to the jags then exhausted out.
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-25 18:54
    Well, Im planning on putting one in the front with a filter (so dust doesnt get in), and an exhaust fan out the back. Im borrowing a friends fan for testing and it would seem that it runs happily on a pwm output without any code, just the power and ground
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-25 19:12
    Can you explain what this pwm output is?
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-25 19:15
    Pulse Width Modulation. On the board of education, its the 4 ports in the top with a black, a red, and a white wire. Red is 5V+, black is Ground, and White is data (modulated pulses) Its enough to run the van because on the arduino its 12v
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-25 20:15
    So what you are really doing is plugging the fan into the power and ground - no pulse width modulation involved, right? It sounds to me like it is not running on pwm output at all. The fact that there is an i/o pin there too is irrelevant since it is not being used.

    I think it is misleading to refer to the three conductor cables as "pwm cables" and any port that they plug into a "pwm port" since neither is limited to pwm only usage, yet that is pervasive amongst FRC folks.
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-25 20:18
    Well the fans im going to be running are PWM enabled so they can be run through temp sensors. And for the record, do you have something against FRC?
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-25 20:58
    FRC2370 wrote: »
    Well the fans im going to be running are PWM enabled so they can be run through temp sensors.

    Are you sure that the fans are PWM enabled? The third wire is commonly used for reading RPM, it is not PWM.
    And for the record, do you have something against FRC?

    The record will show that I am a mentor for FRC team 1899.

    http://www.boeing.com/Features/2011/05/bds_first_robotics_5_9_11.html
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-25 21:01
    The manufacturer says PWM enabled. And sorry bout that accusation then.
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-25 21:24
    I can't think of what is special about a "PWM enabled" fan. Any motor by default is PWM enabled. It is a bit like saying that it is "off" or "on" enabled. It is probably just reassurance to the purchaser that it will work when being driven by PWM.

    My overall point is that the ports on the BOE (probably true for Arduino too) are not "PWM" ports. Yes, you can send a PWM signal over them but they can be used for other things as well that are definitely not PWM. To call them PWM ports is misleading.
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-08-26 07:38
    * for the record I was a mentor too for BCR 294..


    for the fan Be carfull some times the Fan will stall.. The issue is there is switching going on in a brush less fan . this Can be confused by a PWM in at the Wrong Freq ( Beat Freq kind of issue ) Throw a cap accross the fan leads .smoooooth that thing ..
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-26 07:41
    How much voltage does the fan need?
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-08-26 08:23
    12V ...... so in that range.
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-26 08:54
    So should it be connected to the pdb directly or still off of a 3 pin connector on the arduino?
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-08-26 09:54
    If it was me. Run it right off a 12V rail . so the PDB wil be OK .

    What is your Pack voltage ?
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-26 10:02
    Pack voltage?
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2012-08-26 10:32
    W9GFO wrote: »
    My overall point is that the ports on the BOE (probably true for Arduino too) are not "PWM" ports.

    For the Arduino, while you can bit-bang crude PWM on any pin, the board in fact does have dedicated pins for hardware PWM. On the Uno (differs between boards) these pins are connected to three hardware timers; each timer provides PWM for two pins.

    So, ignoring the other material brought up in this thread -- and just to provide clarification for lurkers -- on the Arduino Uno there are six specific pins capable of hardware PWM, while the rest are not. These pins can also be used for ordinary digital I/O, and in some cases (and typical for the Arduino) double-up with other hardware capabilities that are likewise hardwired. For example, one of the PWM-enabled pins, pin 3, can also serve as one of two external hardware interrupts.

    -- Gordon
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-08-26 10:32
    what batts does your device run on?
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-26 10:36
    The 12V 17A battery that FRC uses. Running 2 of them - decided to ditch the heavy marine battery
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-26 20:37
    So how would I build and install the 12V rail to 2 or 3 fans?
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-08-27 08:29
    Rail Bus feeder ... Its all the same.

    The term rail to rail Op Amp .

    EG your PC ( 0r mac ) has a 12V rail 5V 3.3V and so on .

    so your battt hits a breaker right . Per FRC standards . then hits a distribution point . with fuses that feed spikes and victors .... remember I am OLD FRC pre 09 .


    Those " wires" can be considered buses or rails.......


    think of it as the main street in a town .... the main Drag.... that is the Main Bus or main rail for a givin voltage ..

    To run the fans parallel them.....
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-27 10:21
    So how should they be connected? Since they have 3 pin connectors
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-08-27 12:58
    Black is GND . there is a yellow and a red ..... the red is V 12V




    If in doubt use a 9 V to power one up ........

    got a photo of the fan ??
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-27 13:36
    This is the fan. Not sure on the model. How is this gonna get wired into the PDB with the little 3 pin connection?
    Photo on 27-08-2012 at 16.33.jpg
    Photo on 27-08-2012 at 16.33.jpg
    640 x 426 - 80K
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-27 21:36
    On Wednesday I'll be installing the fans on the robot. Im using a set of ThermalTake Thunderblades (1800 RPM, 72.6 CFM, Blue LEDs) for intake, and a set of the fans that my team got in the Kit of Parts for 2012 (2,800 RPM, 120 CFM) for exhaust, since my mentors helping with the project. Any idea how the fans should be set up on the chassis?

    0612121710b.jpg


    Keep in mind the battery will be sitting on top of the robot once the lexan is installed.
    0612121710b.jpg
    1024 x 768 - 114K
  • Peter KG6LSEPeter KG6LSE Posts: 1,383
    edited 2012-08-28 02:55
    CUt off that plug .. wire to here Attachment not found.

    and I see you are missing a breaker or fuse or some normal way to switch the REAL power ...
    ( a tip use a 100A " red key " 1/4 turn RV batt disconnect ) 9 USD or so at any auto store..
  • FRC2370FRC2370 Posts: 128
    edited 2012-08-28 07:15
    This was a slightly older picture. The electrical system is perfect now. Any idea where the fans should be installed?
  • HumanoidoHumanoido Posts: 5,770
    edited 2012-09-06 08:45
    Cycle it with a can of directed freeze activated with either a solenoid or servo. I experimented with this on the Big Brain and it worked really well for coolant supply source and real time chip enhancements.
  • FRC2370FRC2370 Posts: 128
    edited 2012-09-06 08:53
    So how would this work installation wise?
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