Making high power fan controllers - guide

[zbarnes]

Well, I hooked up ye ol' circuit, and the fan ran but didn't vary speeds when I turned the TT pot up and down. Measure it again with the ohmmeter, and found out it was dead. So I took it apart, and guess what? I found the third leg. It was heatshrinked over. So now I have to replace it. Which stinks, but it looks like a pretty standard pot, so hopefully I'll be able to find one that will fit in its place.

I'm gonna shoot for a 10k pot, since that's what it was, and everything is supposed to work out that way. But if you think I should get a different value, let me know.

Thanks again

 

[Ven0m]

In original scheme, there are smaller pots used, but if you have the second one of around 50k, 10k on the first will be ok. I've checkecked that with simulator and it worked. Unfortunatl,y I haven't got these 2 transistors in list, ut they seem to be good too.

 

[Susquehannock]

Cool guide Ven0m.

 

[Stoanhart]

Does anyone know any good sites to get you aquainted with circuit diagrams? I tried googling, but all I found were pay university courses, books, and instructional videos. I found that kind of strange, since this is exactly the kind of info that is usually incredibly easy to find on the net.

I'm not a coplete noob when it comes to this stuff, but some of the diagrams on pag1 of this thread are a little overwhelming. And I hate buying parts and never finishing a project...frustrating and expensive. So I want to familiarise myself a little more before attempting this.

 

[Ven0m]

Unfortunatly, I don't know such site, but there are some programs for designing circuits. Most of them have free demo versions, so you could try.

 

[Stoanhart]

Well, now that I look at them again, they are not so bad. I have been looking at diagrams to build a headphone amp, and after making some sort of sense of those, these seem easy.

I actually only have 2 question left.

1) what are those angles arrows coming off of the side of the pots? Why does R1 have 3 lines connected to it, and R2 only has 2? I though pots only had 1 input and 1 output, not 3 connectors like a transistor

2) Many diagrams I have seen (not this one), have large triangles with many wires connecting to them, each wire with a number. I am assuming those are chips, and the numbers represent pins. Is that correct?

Thanks.

 

[Shroomer]

1: a POT ALWAYS has 3 lines coming off of it. A Rheostat has only 2. One line is the wire that swipes the carbon on the inside, and the other 2 are each end of the carbon (or other resistive material). Basically as you change the dial, you change the resistance between the lead with the arrow and each end. One end begins to have greater resistance and one has lower. You can choose to use only one end of it in a circuit if you wish.

R2 is there to set a minimum resistance to that leg of R1 and thus set the minimum speed of you fan. It can be substituted with just a resistor or nothing at all if you like.

2:Yes, to the best of my knowledge, you are correct.

 

[Ven0m]

That's overvolting controller scheme I designed some time ago, it's not tested with no guarantee that it will work or will not burn your computer , use at your own risk.
Only for the brave ones If someone has enough knowledge, could he suggest some useful changes?

It's with added controller, should allow up to around 20v off MOLEX. Click the pic to enlarge it.

 

[squasher]

well I am making my first for my fan.
So I have the psu molex 12v-resistor-tranistor-fan?
So yellow wire to resistor to tranistor to fan black?
and red wire to fan red?

 

[Ven0m]

well I am making my first for my fan.
So I have the psu molex 12v-resistor-tranistor-fan?
So yellow wire to resistor to tranistor to fan black?
and red wire to fan red?

I'm lost, can't understand it at all. Just read scheme carefully and if you're not sure about something, make some pic and we'll check it.
However if you're trying to decide between 1-transitor and 2-transistor controller, go for 1 only if you think that 2 is "really that complicated". 2-transistor is much better and kickstart will allow you running fans at lower speeds.

 

[squasher]

The 12v lines goes to resistor then to transistor then to fan, and the ground goes right to fan

Edit:
Its too hard to see here is the real one
http://www.im4ges.net/im4ges/trsimages/fan.GIF
Edit #2 wait you can see it now, ill leave the link there anyway
Edit#3 whoa dang you can not see it well any more lol

 

[Ven0m]

nonono
Notice that pot doesn't go in line with transistor, just links its base to 12v rail. Bipolar transistors have 3 pins - Collector, Base, Emittter.
Generally transistor is used not to let all electricity go through pot, but only a small part. I think that it's easier to see on 2-transistor controller. If you still want to make 1-transistor controller, maybe enlarge pic t osee more details...

 

[squasher]

I know that I am being a n00b here, but I am having some real trouble understanding this.
Can somebody just make a paint picture of how to make a two tranistor controller?

 

[squasher]

Bump

 

[Stoanhart]

you just bumped a sticky

 

[squasher]

Hehe, lol forgot about that.

 

[NickF]

Was experimenting with my own variable fan speed controller about 2 years ago, using a Basic Stamp microcontroller as the heart of this system, I hooked up several radioshack thermistors (one for cpu, hd, case temp) I can calculate what the temp of each thermistor by running 5v through it and then polling to see how long it took to charge a cap of know value.

After determining the temp at various locations, I output PWM to a power transistor which controls the fan speed of the various fans, and also reports system temps via a serial LCD module. Works fairly well, I don't have any circuit diagrams as I kludged this together. This system is able to control the fan speeds depending on the actual temp at the thermistor in real time, no twisting pot's, it does all the work.

 

[L337 M33P]

Unfortunatly, I don't know such site, but there are some programs for designing circuits. Most of them have free demo versions, so you could try.

Circuitmaker 6 student version

/thread

 

[Lat]

i actually use circuitmaker too in my ecet program, so yeah, i can vouch for it

 

[AlabamaCajun]

You can pick up 10 of 2N4919 power trans for $3.50 at Jameco.
http://www.jameco.com/webapp/wcs/st...toreId=10001&catalogId=10001&productId=126380
These handle 6 to 7 watts with heatsink, enough for most single fans or 2 if they draw less than 0.2 amps @12V. I plan to use them to build a controller for 2 fans and a PIC for reading 2 fans speed on 2 digit displays and 2 temp sensors with colored descrete LEDs.