Voltage question

[Sskyhawk]

Hey Guys,

After reading a thread by Spartan-K22 http://www.405th.com/showthread.php/5436-Tutorial-Fan-Installation?highlight=ventilation+system+helmet I decided to buy the stuff to make the fans, and it worked out pretty well. However one thing I wanted to try and fix was the amount of voltage. The fan is a 12v fan, but I am only using 9v batteries. Now I am no electrician, but my thinking would be I could use 3 fans at 12v and 4 batteries at 9 volts for an equal 36 volts, that way I could maximize the power of the fans. Like I said, this makes sense to me, but i have no training in electronics besides to hook up the red wires to the red wires, and black to black, so I wanted to make sure that this wouldn't be an issue.

Thanks for all your help!!!

 

[Techmagos89]

orrr you could drop the voltage down via resistors if your running a series circuit.

 

[Macattack64]

That will work if you hook it up in sequence.
Basically like this:

 

[Vigilnt sniper]

or if you are looking to use only one or two fans you can place a "STEP-UP Transistor" inbetween the battery and your fan. this will increase the voltage giving you more power from the same battery.

 

[Sskyhawk]

That will work if you hook it up in sequence.
Basically like this:

Wow Awesome Diagram! I love all the support from everyone on the site and I appreciate all the help!! Thanks so much!!!

 

[Macattack64]

You'll also probably need a switch too. You can put that on the long red between the battery and the fan.

You're welcome. ^_^

 

[Vigilnt sniper]

actualy i would recomend putting it on the black lead instead of the red one, being that power comes directly from the negative lead it would make more sence to do so as it would cut off power from the batteries.

 

[Shadow Of Intent]

I'm in the same position as you, and my first thought was to use a 9v battery and two AA sized 1.5v batteries. This would give me the 12v if connected in series, but more importantly, you should check if it actually provides sufficient airflow. I hooked up a 9v battery to a set of 4 AA 1.2v rechargables from my cordless screwdriver, giving just over 14v, and even that wasnt very powerful, even less so once it has to drag air in through a small set of vents and mesh in the front of the helmet. You may also want to read up on internal resistance... I think 9v batteries have a very high internal resistance, so the current from a 9v battery may be lower than 6 AA batteries, but don't take my word for it.

I may try using 2 9v batteries to reach 18v. I know that upping it to 150% the stated voltage may burn out the fans, but they are relatively inexpensive, and most components factor in an extra 50%, or certainly 25%. I'll let you know how it goes if it is successful!

 

[CoolC]

Keep it simple. Just attached 9V battery to 12V. It will just work fine. The fan will not turn at high speed, but it turns enough to keep the air circulate in the helmet. Actually having a lower speed helps minimize the fan sound. I installed 4 fans on 4 helmets using 9V and never had any problem.

Here is one crude installation on my first helmet.

 

[ventrue]

actualy i would recomend putting it on the black lead instead of the red one, being that power comes directly from the negative lead it would make more sence to do so as it would cut off power from the batteries.

That's completely wrong.

 

[Satchmo III]

Keep it simple. Just attached 9V battery to 12V. It will just work fine. The fan will not turn at high speed, but it turns enough to keep the air circulate in the helmet. Actually having a lower speed helps minimize the fan sound. I installed 4 fans on 4 helmets using 9V and never had any problem.

This is the simplest method since a 9V battery has enough voltage to move a typical 12V computer fan (this is what Spartan-K22 did in his tutorial). I agree with CoolC's thinking that the idea is to get air circulating which doesn't necessarily require the full speed of a fan to accomplish.

If you wanted to run two fans from one 9V battery this is possible also if you wire the fans in parallel as shown below (9V is supplied to each fan this way, but since two fans are drawing amperage from the battery, the battery life will be half as much as with one fan running). With the fans in parallel (instead of in series) should one fan fail the other will still be operational.

If you wanted to deliver the full 12V to each of the fans (or one fan if you don't require two) you could add two AA batteries or two AAA batteries (either two would supply 3V if in series) in series with the 9V battery...though then you'd have to mess around with two different battery types which might be inconvenient.

Instead of concerning yourself with supplying the full 12V to the fan(s) you may wish to consider adding a second 9V battery in parallel with the first in order to extend the length of time before you'd have to switch out the batteries. This is what I did for my Mark V(b) helmet (http://www.405th.com/showthread.php/30987-Noble-six-build-work-log-(Satchmo-III)?p=538123#post538123). This is but a suggestion.

Good luck with your build!

Also, you might want to try to post singular questions like this in appropriate help (sticky) threads. This is a perfect question for the electronics help thread (http://www.405th.com/showthread.php/26853-quot-Help!-quot-for-Electronics) where discussions like this are common. This way the question is asked in a relevant area and new threads are kept to a minimum.

 

[CoolC]

That's completely wrong.

Ventrue. You probably might want to explain why he is wrong.

 

[ventrue]

Ventrue. You probably might want to explain why he is wrong. In the electrical world, red and black are the same wires. It would not cause any interuptions in the electrical current. The red and black (plus Green/Brown) are just indicators of which ones are live/hot, or ground.

The underlying message was rather: "Don't reply if you don't know". But yes, I should explain: A switch does not cut off the power flow from the battery, it stops the flow of electrons between a battery's two sides. It's completely irrelevant where you put the switch, as long as the two sides aren't connected when the switch is open.

 

[CoolC]

The underlying message was rather: "Don't reply if you don't know". But yes, I should explain: A switch does not cut off the power flow from the battery, it stops the flow of electrons between a battery's two sides. It's completely irrelevant where you put the switch, as long as the two sides aren't connected when the switch is open.

Maybe it is just me. I read the original response a few twice and I couldn't figure out what he was referring to. So instead of making an ass of myself, I removed some of my response.

I agree with you on the flow of current. The switch functions as a floodgate. It connects two current together regardless where you put it.

 

[Sskyhawk]

Once again guys thanks for all the responses and suggestions, I appreciate all the help!!!

 

[Vigilnt sniper]

ventru why do you make it your duty to counter my every suggestion? it doesnt matter yes however i prefer and was taught to place a switch on the negative lead. if you have a problem with that call up my now dead high school electronics teacher and complain to him about it. if what i said was basically a fee-sable option then nothing more needs to be said. seriously your constant countering of my suggestions is starting to irk me.

 

[ventrue]

ventru why do you make it your duty to counter my every suggestion? it doesnt matter yes however i prefer and was taught to place a switch on the negative lead. if you have a problem with that call up my now dead high school electronics teacher and complain to him about it. if what i said was basically a fee-sable option then nothing more needs to be said. seriously your constant countering of my suggestions is starting to irk me.

You overestimate my interest in your person.

 

[Vigilnt sniper]

well then stop bashing my every "SUGGESTION" because that is what they are SUGGESTIONS and telling me i am wrong all the time. i did not tell a lie. simply that it made more sense to me to place them there as that is how i was taught. then you come along and tell me i am wrong as you have three or four times today alone. get the eff off my back.