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Old 03-02-2007, 04:31 PM   #165
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Join Date: Mar 2007
Hard Hat Fan Ventilation Modification

Halfway through my project I searched the Net for understanding how to wire the batteries. I came across your site. Very cool to see someone else with the same idea, work or play.

I eventually found someone to answer my question but I felt compelled to share this for the beginners like me trying to understand electricity.

By putting batteries in series (positive of one battery to negative of another battery) you increase the voltage. If I put two 9-volt batteries in series I will have 18 volts of electricity. Think of voltage as water pressure in a hose. If you had too much water pressure you could blow out a sprinkler. If you have too much voltage for a fan you can fry the fan.

By putting batteries in parallel (positives of batteries together and negatives of batteries together) you increase the current. If I put two 9-volt Duracell batteries in parallel I will have 580 mA (580 milliAmps = .5 Amps) x 2, because there are two batteries which would equal 1160 mA. This would allow my 12 volt, 1.9 watt, 158 mA fan to run for about 7 hours. That would double the time of one battery. Think of current as the volume of water going through the hose. If you double the size of the hose connecting to the same sprinkler, you'll get double the time because the sprinkler still only uses so much water.

I think that's pretty clear. Please add to it if anyone sees something wrong or misunderstood above.

So here was my idea...

Hard Hat Fan Ventilation Modification

Note: MSA does NOT approve of altering the hard hats, nor storing ANYTHING in them.

It's the middle of summer and you are up on the roof shingling. The sun is just beating down on you and sweat is just pouring off you like a pregnant nun in confession. You are told you have to wear a hard hat even though nothing but blue sky is above you.

I have access to a bunch of old computers and I removed one of the little 12 volt, 2" x 2" fans that cool the heat sink of the processor. They are only about 1/2" thick so there is plenty of room above the webbing. First I placed the fan in the hard hat and marked the area that I wanted. I took it out and drilled a bunch of 1/4" holes in the area where the fan would be. Using electrical tape I secured and sealed the fan into the hardhat. It is important that a seal is made with the electrical tape for proper airflow to take place.

I purchased a 9-volt battery, a 9-volt battery snap and a small switch. A 9-volt battery will produce around 600 mAh (milliAmp hours) of current. The fan only needs about 7 volts to run and uses about 150 mA of current. This will allow the fan to run for about four hours through the really hot part of the day. I can feel a slight cool flow of air up over my head. I decided to have the fan pull the air up through the hard hat and take the heat of my head up and out. Works great with very little noise and it is also very unnoticeable from the sides and back of the hard hat. I mounted the battery with electrical tape and ran a switch under the bill for quick and easy powering off and on.

Last edited by GeneXian : 03-04-2007 at 03:16 PM.
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