Just built my first voltage regulator

[TyRex]

Ok, first off.......I've found that this setup is almost the perfect combination of parts(I tried many), because it allows the full range of fan speed to the full range of the pot.

parts:
10k linear pot(radioshack # 271-1715)
NPN transistor(TIP3055) (radioshack # 276-2020)
heatsink(radioshack # 276-1368)
heatsink grease (radioshack # 276-1372)
wire/perf board

The nice thing about this transistor is that it can handle 10 amps at the collector, which is plenty for even the most 'power hungry' collection of fans, if cooled properly that is. I've tested it out on 2 120mm high velocity fans each pulling 1.2 amps. The heatsink was hot to the touch, but being that the maximum operating temp of the transistor is 150C, it could still handle more. Also, this setup only sees a voltage drop of .3v.

When I turned the pot all the way to max resistance, the fans slowed to the point of absolute silence. If the fans are turned on while the pot is at full resistance, the fans will not turn unless a little more voltage is given to get them going. This is how you can tell this is the best pot for this setup.

On too construction......On a transistor, there are 3 pins, the collector(pin2), the base(pin1), and the emitter(pin3). Solder one end of the pot to the collector(2), and the middle of the pot to the base(3). Solder a lead(red wire) to to the collector(2). Finally, solder a lead(black wire) to the emitter(3).

Now just apply some HS grease and bolt on the heatsink, thats it.
And yes, you need the heatsink for heavy(as in above 1a) amperage loads.

Enjoy all......


oh, and one more thing, I have no idea how efficient this is. Anyone good at calculating efficiency percentages, please post it......

 

[Hoot]

That's a great circuit, but believe it or not, there is an even more simple one. You need the same linear pot, but a different power transistor TIP-34 (RS # 276-2027), no heatsink or circuit board. That particular transistor is a PNP as opposed to the TIP3055 which is an NPN. The difference is that you put the PNP on the ground side as opposed to the hot side of the fan. Here's where it gets neat. The tab of the TIP-34 has a hole in it. You simply mount it to any available hole in your case chassis with a screw and nut. That mount provides the electical return path to the PSU minus rail. You connect the fans plus lead to the +12V rail and its minus lead to the transistor pin designated as the emitter and place the linear pot between the pins corresponding to the base and collector. The case mount, besides acting as an electrical return path, doubles as the heatsink. If you want to, you can put a dab of heatsink grease between the transistor and the spot on the case where you mount it. It does not matter whether you use the white stuff or some left over Arctic Silver. The area around the hole where you mount it to should not be painted. Behind the front panel, there are typically plenty of holes in the chassis that will accomodate a number 6 or 8 screw.

Hoot

EDIT

I mispoke when I called the transistor a TIP34. It is an MJE34, which equates to a TIP42.

 

[TyRex]

that's even better, takes up less space since there's no need for a heatsink..........I'll give that a go next......thanx for the advice

 

[Shroomer]

THis is a wonderful thing! I was going to get some expensive fans or get a Nexus, but this is much more fun than either one.

How many watts have you thrown at this hoot? If I get a 151 CFM 120mm Delta will I blow the thing up?

PS! BGmicro has the PNP for .89 and the pot for .99 (Mini) 1.50(STD)

Radio Shack is 1.50 for PNP and 2.50 for pot(std)

 

[TyRex]

yeah, radioshack is usually the most expensive place to buy any part......I had 2 131CFM 120mm fans running on the transistor i used. The specs for that transistor are better, so i would say it could easily handle that fan

 

[jlin453]

Any pictures?

 

[eobard]

Any pictures?

Ditto.

Also let's not forget another factor in deciding where to get your parts: Radio Crap's % of compotency. If your luck with them is anything like mine, you'll be making an average of 2 return trips to get parts that actually work for each initial trip to their store to get the parts in the first place.

 

[SuperDave1685]

ok. I searched for a post like this for a while. I got the money for the parts in the first setup listed, as thats the one that seems to make the most sense to me.... pardon me, but I'm not a very electrically-inclined person. Could someone please xplain this a little better? I mean i think I know what I'm doing, but i think i just need a little more thourough explination and maybe a picture or two? That would be of ENORMOUS help!! Thanks a lot!!

 

[TyRex]

here's a crude drawing

 

[TyRex]

ok, wheres a good place to upload pictures?

 

[AcEmAsTr]

whats a voltage regulator? obviously it regulates the voltage(dont even think about it all u smartasses ) but what exactly?

 

[jlin453]

whats a voltage regulator? obviously it regulates the voltage(dont even think about it all u smartasses ) but what exactly?

IF you have a loud fan, you can make it quieter by decreasing the voltage. That's how the 12-7V mod works. Instead of 12V, the fan gets 7V.

 

[jlin453]

ok, wheres a good place to upload pictures?

Email them to me and I'll post the pics in this thread.

[email protected]

 

[AcEmAsTr]

www.lycos.co.uk they r 1337 for pictures, too many popups and ads for website tho

 

[TyRex]

sent to jlin.....

 

[jlin453]

 

[TyRex]

ok, now i see a mistake i made, after its up.......... the pin labels are in reverse so pin 1 is pin 3, and pin 3 is pin 1. pin2 is still the same......

PS. thanx for posting it jlin.......

 

[Shroomer]

That pic would be for the NPN setup, right? If not, I don't follow.

Here is a pic I drew for the PNP circuit. Hoot, make any corrections if needed.

Pic

 

[Hoot]

No corrections needed Shroomer. That pegs it perfectly. About all that comes to mind is in the interest of good technical design to add a disc ceramic .01 uf capacitor between the base and collector if you mount the potentiometer away from the area where the transistor is mounted. That TO-220 transistor can handle a lot of current. I'd wager that it can handle more axial fans than you would care to put in your case.

Hoot

 

[Shroomer]

Careful what you wager, hoot...

My new idea is to get the most freakin powerful fans I can find and tone them down with this.

Note: Why the cap if the pots will be far away? I was thinking of mouting the transistors in my power supply and running a new hole and grommet for the wires which would lead to the front panel.

Also: Can the connection point be on the POTs or the transistors? I'd think the most convenient spot would be on the POTs.