Led And Fan Wiring Schematic

[Mavrick]

I thought I would start putting back into the community I have learned a great deal from. I may not be the best or the fastest at modeling, however i'm rather fluent when it comes to electronics.



So, here's the circuit diagram and parts list for the helmet electronics system I plan to use.



This is my Schematic. Please dont reproduce for sale. If you feel you arent capable of making one, PM me and we'll arrange something.

It has been simulated using the following components. I will compile a "shopping cart" and price once i find the cheapest supplier.



1 8.4v Battery Pack

2 5v DC Fans. 1 X 1 X .4" 5V @ 50mA.............$14.95 each (from jameco.com)

4 High Output LED 3700 mcd @ 3.5vf & 20mA If.....$1.35 each (from jameco.com)

2 68ohm @ 5% 1/4w resistors......................$0.00 Can be picked up from any local radioshack or electronic parts store. Usually packaged in an assortment

1 LM7805T 5v Fixed Voltage Regulator.............$0.25 (from jameco.com)

1 100 uf electrolitic capacitor..................$0.00 Can be picked up from any local radioshack or electronic parts store. Usually packaged in an assortment

1 10uf electrolitic capacitor....................$0.00 Can be picked up from any local radioshack or electronic parts store. Usually packaged in an assortment

1 100nf capacitor................................$0.00 Can be picked up from any local radioshack or electronic parts store. Usually packaged in an assortment

2 SPST Switches..................................$0.00 any switch you're comfortable using. Since the power consumption is low, voltage requirements are null.

1 small PCB board 2" x 2" to give yourself room..$2.00 - 4.00 depending on your source. standard size for mounting components.



Total mA consumption is instantaneous ~ 220mA. Depending on your 8.4v power source, if you choose something along the lines of 1700mAh; you guessed it, 8 hours without having to recharge.



Circuit description:



One switch to power the 4 LEDs. There resisters are used to pull down the voltage to allow for the 3.5v forward voltage for each series.

One switch to power the two fans. I've used a 5v Fixed Voltage regulator as most fans are either 5v or 12v. The voltage regulator wont output correctly if the voltage is below 7.5v. It boasts up to 1 amp continuous, however, the two fans i've chosen only use 50mA each. The capacitors are to help the fans during start up as thats when they'll pull the most current.



I decided on an 8.4v NiMH battery simply because its rechargeable. There are literally thousands of configurations available so finding one to fit a helmet will not be an issue! I also chose this because it allows for expansion. Unlike a 9v battery which usually keeps a charge of 500mAh.



I've chosen two fans because i plan on one pulling air from the outside and one pushing the hot air out. The fans operate at 24db so they are relatively quiet as well. If it works out that a single fan is adequate, then the other will be removed. However, we all know how hot rooms for of people can get so thats why i've started with two.



Unfortunately, my progress is slow as i'm currently working on my biceps in the couple hours of time i have a night. Once complete, i will move to the helmet so i can create a working model to show off. I might actually switch to a flat type LED as most of those can give a much higher luminosity. I'll have to wait for the finished helmet to figure that out though.



Hopefully i've helped someone out!



Marshall

 

[JEDI THERON]

Very nice! I think I can create one using your diagrame. I am electronics illiterate so I must ask, what type of battery(s) is the 8.4v? Is this two AA or AAA?

 

[Mavrick]

Actually the 8.4v is 7 1.2v rechargable cells. For regular throw away batteries, the voltage is 1.5v per cell. At that, it would be 9v total and your R1 and R2 resistor values would change to 68ohms. Everything else would remain the same.



The size, AAA, AA, 2/3C, D, etc. Is not the voltage, its the capacity of the battery (in mAh)



I usually get my batteries from www.onlybatterypacks.com.



They come as small as you need. for 2200 mAh, depending on how big your helmet is and how long you will have the system on.

http://www.onlybatterypacks.com/showitem.asp?ItemID=10650.9 = 2200 mAh. = ~10 hours of continuous use with fans and LEDs.



Or if thats too big

http://www.onlybatterypacks.com/showitem.asp?ItemID=10638.9 = 1000 mAh. = ~4.5 hours of continuous use with fans and LEDs. Its a very small pack.



I do recommend making your battery pack removable and using DEANS connectors! The mini tamiya really suck.

 

[Loess]

Very nice! I think I can create one using your diagrame. I am electronics illiterate so I must ask, what type of battery(s) is the 8.4v? Is this two AA or AAA?

I believe he means you'd use an 8.4 volt battery pack, like this.





Thanks for the schematics! I've been meaning to get some fans in my ODST helm, but I'm only a tinkerer with electronics, I would have been reduced to jamming a 12v pack in there with two fans, and desperately hoping for it to work passably well.

 

[Mavrick]

No problem man, the thanks goes to the community who inspires me!

ALL SOLDERING IS DONE ON BOTTOM SIDE.



NEVER Directly solder "+" and "-" together. If you must cross, use an insolated wire.



All Colored Box outlines are for remote items. Use DEANS connectors to connect to LEDs, Battery, and Fans.

The bright red lines are on board soldering.

Dark red lines are insulated wire bridges.

"C2" Capacitor does not have a polarity, meaning there is no + or - terminals.



When done building, cover exposed solder with an insolation to prevent shorts.

 

[Masterchief1977]

just wondering what kind of fans are we talking about here? like what size where do you get them?

 

[Mavrick]

just wondering what kind of fans are we talking about here? like what size where do you get them?

The information is listed in my first post.



The fans are 1" x 1" x .4". (20mm x 20mm x 10mm). I quoted the fans from jameco.com at $14.95 each.



Each fan must be 5v and draw no more than 50-60mA each. Anything more than that and i recommend that the voltage regulator be heat sinked and bench ran to monitor temperature. If heat sinked, it can output up to 1A. The voltage regulator has thermal and overload protection, however if run too hot for too long, it will fry.

 

[Masterchief1977]

The information is listed in my first post.



The fans are 1" x 1" x .4". (20mm x 20mm x 10mm). I quoted the fans from jameco.com at $14.95 each.



Each fan must be 5v and draw no more than 50-60mA each. Anything more than that and i recommend that the voltage regulator be heat sinked and bench ran to monitor temperature. If heat sinked, it can output up to 1A. The voltage regulator has thermal and overload protection, however if run too hot for too long, it will fry.

Duh Im blind sorry. So basically small computer fans would probably work.

 

[Robbymrodriguez]

Hey Mavrick, what do you think of these chips? Do you think they could be used to cool without drawing too much juice? It could make for real AC inside the helm.

 

[Mavrick]

Hey Mavrick, what do you think of these chips? Do you think they could be used to cool without drawing too much juice? It could make for real AC inside the helm.

peltier plates are really cool, but the downside is that while one side freezes, the other becomes extremely hot! Also, the voltage that they require is over 15v so that would be one huge battery pack. The 80watt small one runs at 16.1v. Thats just shy of 5 amps. to run it by itself it would take a 5 amp hour battery pack....which is massive.



Masterchief. Yeah, or similar to a google fan found in airsoft/paintball masks. Whichever you choose, make sure it lists the voltage and current draw so you can guestimate your battery useage as well as heatsinking the voltage regulator.

 

[thegeek]

The only problem I see is that you might be running the LEDs a bit hot... The 47 ohm resistors that you propose will run the lights at almost 30mA. if you use a 70 ohm LED your LEDs will last longer at the rated 20mA. That is assuming that you are still using a 8.4V source. Also according to my calculation the resistors will only need to disapate 28mW of power so you can use 1/8 or 1/16 Watt resistors very easily you can even go surface mount!!!

 

[Toby]

Nice schematics, but if I were you, I'd lower the battery voltage to ~5V. I haven't hat the time to do calculations, but my idea is the following: The fans draw more current than the LEDs (2x 50 mA > 4x 20 mA). The voltage regulator is wasting a fair amount of the power (as heat no less), more than some more resistors for parallel LED configuration would. So bringing the circuit to 5V would be more efficient. Now I know that you can't make up 5V with 1.2V cells, but using 4.8V-4.6V, you can use smaller resistors for the LEDs and the fans will only spin slightly less fast. You could use 8 cells in 4x 1.2V blocks, doubling your time.



I hope I've got all this right, maybe someone can back me up here

 

[Mavrick]

The only problem I see is that you might be running the LEDs a bit hot... The 47 ohm resistors that you propose will run the lights at almost 30mA. if you use a 70 ohm LED your LEDs will last longer at the rated 20mA. That is assuming that you are still using a 8.4V source. Also according to my calculation the resistors will only need to disapate 28mW of power so you can use 1/8 or 1/16 Watt resistors very easily you can even go surface mount!!!

I made my calculations based off of the max inrush current of the LED. If just going by the average 20 mA (if) then an 68 ohm resistor would work. It would dissipate 32mW. I'm a little rusty with electronics so thats why i suggested a bench test first.

The voltage regulator is wasting a fair amount of the power (as heat no less)

it uses 4-8mA.

So bringing the circuit to 5V would be more efficient. Now I know that you can't make up 5V with 1.2V cells, but using 4.8V-4.6V, you can use smaller resistors for the LEDs and the fans will only spin slightly less fast. You could use 8 cells in 4x 1.2V blocks, doubling your time.

The problem with using rechargables is that the battery discharge is not linear. Meaning, as the battery drains, so does the pack's voltage. The fan would be underpowered throughout the whole time moving less CFM than it was rated for. With a higher voltage pack, the voltage regulator makes sure that the fans always see 5v.

 

[Wolf96]

love the post and the info, unfortunate for me, my specialty is surveillance and camera schems and hate dealing with the electronic side. As my helmet Im working on will have at least 4 LED's and hopefully some fans if I can find the room, Im going to need input like this to help me wire and power these. So Ill keep checking back until I finally understand what all you electronic masters are talking about.



Wolf Out

 

[Kasinator]

This has been a real big help. Now I can really put some serious hardware on my suit!

 

[Mavrick]

Hopefully i can post a bench test vid of it next weekend.

 

[Toby]

You're incorrect. Each LED doesnt use 20mA. Each pair is in series and both pairs are in parallel. That means 20mA per side.

Run at 5V, each LED would use 20 mA, series would not be possible

The problem with using rechargables is that the battery discharge is not linear. Meaning, as the battery drains, so does the pack's voltage. The fan would be underpowered throughout the whole time moving less CFM than it was rated for. With a higher voltage pack, the voltage regulator makes sure that the fans always see 5v.

I also realize the battery conundrum, but I know from 12V fans that they work nearly as good at 9V (also less noise). So even 4V for a 5V fan would probably still be okay. Still, if the voltage regulator doesn't use that much power, my original assumption is not valid and your solution is definitely the more constant one for batteries.

 

[Loves hina]

Wow, its great to see somthing like this posted on the forums. I see you being alot of help to some people. Im not much for electronics right now, especially considering the only thing i learned in my Physics class (Pre-AP none the less) was basically the difference between a linear and non-linear circuit (i already knew and most the class didnt understand it at all). so I have a freind or two who have a bunch of experience on the matter who can do this stuff for me. I have a few fans from a couple old comps set aside, about 4-5 fans in all. Some on the power source or a couple small ones on the old procesors. great tut and info btw.

 

[Mavrick]

Run at 5V, each LED would use 20 mA, series would not be possible

it was a miscalculation on my part and my original post will be edited to show the correct resistor values and total current draw of the circuit.

I also realize the battery conundrum, but I know from 12V fans that they work nearly as good at 9V (also less noise). So even 4V for a 5V fan would probably still be okay. Still, if the voltage regulator doesn't use that much power, my original assumption is not valid and your solution is definitely the more constant one for batteries.

but whats wrong with spending .25 cents and drawing 8 more mA for a guaranteed 5v? All i was trying to do was add a little more stability rather than hooking a fan straight to a battery. Its a little extra circuitry for fans that will be running at almost the same speed at the efficiency they were designed for. I'm putting all this time into trying to make a really nice suit and so i'd like the electronics to match. If no one wants to use it, thats fine. I just thought i'd offer my ideas to the community.

 

[thatdecade]

The problem with using rechargables is that the battery discharge is not linear. Meaning, as the battery drains, so does the pack's voltage. The fan would be underpowered throughout the whole time moving less CFM than it was rated for. With a higher voltage pack, the voltage regulator makes sure that the fans always see 5v.

I was skeptical of the v reg too, but this is very well put explanation. I love the option to use a rechargeable battery. One less thing to worry about.





I have a question about the fan you chose. I'm looking at the product page on jameco for a 1 inch 5V fan. The specs say it pushs 1.8 cfm.

Do you have one of these fans on hand? This number seems very low and wouldn't make much airflow.