Fans

Technical Electrical
1

Rookie Team 3992 here;

A few questions:

  1. What do you guys usually use the fans for? Circuits? Motors? Etc?
  2. How do you mount your fans?
  3. Is hooking them up to electrical similar to a motor where neg and pos switched around will cause them to rotate in reverse? Or will that fry them?

I’m not at our warehouse right now, so I’m only asking from memory; perhaps they have black & red wires to aid attachment.

2

You can do just fine without using any fans at all. Typically you’d want to use them if your electronics there is low air flow across your electronics. I only used them once a few years ago when we had an enclosed electronics box. The fans are basically just small motors, so you can reverse the polarity without harming them. You can even control the speed just like you would a motor, if you wanted to. Mounting really depends on what sort of space you have, but be careful of pulling in small particulate (i.e. metal shavings) that can harm your electronics, especially if you are using Jaguars.

3

I ask mainly because of a thread that was posted about the RS775 motors getting too hot in the CIM-U-LATOR gearbox; I planned to hook up a fan to that.

4

The lager fans won’t reverse. You can touch them to a battery to play with them. There are arrows on the sides showing which way the air should flow. Like they said ^ you should only need them if you enclose your electronics.

5

That’s true, most fans are designed to be used a certain direction, but I would think they’d still reverse and be less effective. I haven’t used them in a few years though.

If your motors/gearboxes have good airflow I would think they would be okay, but if you still feel like you need fans, as long as they are positioned in such a way that they increase the airflow across the motor they will help. Know that you have to provide power separate from the motor power for these. Typically a relay would be used here. I seem to remember hooking mine up directly to the PD board just to be always on, but I’m not entirely sure that’s legal…

6

MJ,
Most DC fans now in use are actually high efficiency multiphase motors. They do not drive backwards. They are singular direction with the fan rotation and air flow clearly marked on the body of the fan.

7

Thanks for the info! I haven’t used fans for a while so I guess I remembered wrong.

8

We put them in the bag with all of the fans from previous years kits. Eventually, we might get enough to make a hovercraft.

9

The quiet high speed fans are probably brushless, in which case the internal electronics establishes the direction. If the only interface to the outside world is the power supply, then reversing the polarity will not make the fan spin in the reverse direction.
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10

With arms & things powered by 3 1/2 CIMs and Globe motors.

11

We usually use a small fan to cool down a compressor if we have one.