automated fan circuit

[Aardil]

I talked with Perry (Dam I mentioned his Name!! )
Working on getting a schemematic for fan circuit. At this point he is rather reluctant to give it out, but I will keep working on him.
The good news:
I can build these boards for single fan single temp probe using mostly Rad shack components.
If there is enough interest I can move to phase 2 and start producing the mainboards designed for this application ( a real printed board not the Rad shack jumper mess like I am currently using.
If there is enough interest ( I only need about 6 people to break even ) I can build these boards and send them out the door for 35 bucks.
This would cover my cost as far as materials, board etching and of course Perry's ( Dam did it again ) time and knowledge.
This is not a sales pitch
only trying to see if there is enough interest to even fool with the idea.

Trust me I have more than 35 bucks tied up in mistakes so I feel this would be a fair price for a automated fan control and yes it does have pots to set the start up temp and fan votage.

The phase 2 boards would require a bit of tweaking on my end to ensure they work so I would need a few weeks of R&D to make sure they are done correctly.

I can and will tell you that Perry (Dam a third time) is a designer and builder of car audio amps that do use a temp controled fan circiut. So he is not new to the game.

Let me know if you are interested
Aardil

aardil@cox.net

I hope I have not broken any rules with this post if I have please remove this thread.

[Puzzdre]

Working on getting a schemematic for fan circuit. At this point he is rather reluctant to give it out, but I will keep working on him.

Oh yeah, please do...

The schematic would be very very nice, not to mention the pic of the PCB if possible...

[Aardil]

This is the Rad shack version of the control module, 2 things to remember:

1. This is a dual control 3 sensor board so it has alot of jumpers that are not nessary for a single control unit.
2. All I have is a video camera so the clarity is not that great.
Sorry

Aardil

[Ecradda]

so what exactly does this do?

[Aardil]

OK
Here is a ruff drawing of what is happening


The Temp probe is placed on anything you are trying to check temp at. Return line, Rad, Cpu block. Remember that the unit is only sensing temp NOT giving you a LCD or LED readout. The probe is a referance point for the board.

Pot #1 is a variable pot, by increasing or decreasing the setting you can have the Fan come on at higher or lower temp settings. AGAIN you must use an additonal thermometer If you are trying to get it to turn on at a specific temp.

Pot #2 controls fan speed, also a variable pot. Once you have determined when you want the fans to come on you would adjust the Pot #2 so that the fan starts turning as soon as the Pot#1 reaches its predetermined temp setting. Increasing the Pot #2 Will make the fan reach 12 volt output faster, Decreasing Pot #2 will make the fan start out at around 6 volts and as temp rises on Temp probe pot #2 will increase the voltage to the fan untill 12 volts is reached.
At the same time, as the point of temp probe cools the fan will slow down until it reaches the point of less than 6 volts where the fan will basically stop. ( takes about 6 volts to get the fan moving and it will stop turning when power drops to about 5.75 volts.

So in recap:
Being totally Variable you set the point at where the fan will start to come on and then set the fan speed as far as how fast you want it to climb to 12 volts.
Thus Totally automatic Variable Speed Fan control Circiut.

Hope this makes it a bit clearer.
Aardil

[punish3r]

Here's one of the few fan controller circuits I like (Mainly because it doesn't require the purchase of a ranged thermistor)



For a little clarity on the components: Q1 doesn't HAVE to be a BD140, just about any power transistor that'll sink what your fan draws +10% is a good choice. I'm running somewhat small fans, so my transistor is a 6.5W design. Of note on this transistor, please heatsink it. It will get warm with use. For those who don't know, the odd symbol for D2 designates a Zener Diode, and since the writer of this original schem was australian, 220R for R5 and 10R for R6 designate 220 ohms and 10 ohms respectively. Kind of reminds me of the confusion with the people who thought 2.3k and 2k3 were different values but I digress...
The 'Diode Sensors' are basic 1N4004 diodes, available... Well, anywhere really.

I got the circuit idea originally from Elliot Sound Products in Australia. This is their original graphic, so I hope they don't mind too horribly that I'm posting it here. It's a decent, simple design. Albeit, it has no voltage control to the fan, but considering the location of the fan within the circuit, it would be of no consequence to wire in a voltage controller.

All components, except possibly the uA741 should be available from your local Rat Shack.

[Puzzdre]

Whoa! The ESP site! I really like the site, I've built a dolby surround 'decoder' with his schematics two yrs ago... It worked really nicely (still does, just not using it no more )...

This could be used with a relay instead of fan, so the relay can power the fan(s) on 7V for quieter operation...

And that 741 opamp, I guess if it is available locally here where I live, then it's surely available ANYWHERE... Think that price here is about 0.5 Euro or less...

Good thinking punish3r!!!

[jag_e_fattig]

whats the adress to the esp site?

[MadDogMe]

I'd prefer Aardils one that increases the fan voltage/speed as the temp gets hotter,rather than an ON/OFF jobbie . if I was US side I'd be very interested, would'nt be too bothered about the LED~bar readout myself, maybe just a single LED to show it's 'kicked in'?...

[Puzzdre]

jag: here
http://sound.westhost.com/projects.htm

[Brians256]

Nice idea, Aardil! There are some really neat ideas here, but I think that there are going to be two classes of response.

First group of people will want to do it themselves. There are other designs that are better in some ways. For instance, does your design turn the fan full on and full off when it reaches the highpoint temperature? How much hysteresis does it have (we don't want the fan turning on and off constantly as it hovers around the setpoint)? Does it use PWM to allow very low fan speeds and high efficiency or does it use linear regulation that is smoother but puts out more waste heat?

The second group is probably smaller. They find the idea neat and want to get one because they don't have the time and/or expertise to do it themselves. Truthfully, you have a good price for what you are offering, I believe.

[airspirit]

I think this is a cool idea, though I've never understood the whole variable fan thing. It's like my PSU; it has variable temp controlled fans controlled by the system temps, but what happens if my GPU gets hot, for instance? I'm tempted to just chop the logic off of them (die 3vil circuits!!!), and wire them in 5V constant to get the same relative silence but with better constant functionality. The problem with a fully variable system is that I've actually watched my fans spin down to almost nothing because the PSU isn't working hard, but my system temps go through the roof because suddenly there isn't decent airflow. By the time the heat gets to the PSU, the system temps are over 50C.

If I may make a suggestion, (if it would be possible), it would be nice to be able to set a minimum system voltage for the loop, allowing your fans to run constantly at 5V-7V, but ramping up if the temps get above a certain mark. That would be VERY useful, indeed, and might draw some serious attention in the fan-cooler crowd, since this would be a virtual godsend.

[Since87]

punish3r,

I looked over that schematic. Depending on the fan load, the 10 Ohm resistor (R6) is going to limit the voltage to the fan(s) substantially. For example if the fan load is 0.5 Amps at 12 Volts, the max voltage the fans will get with that circuit is 8.5 Volts.

It appears the only purpose for R6 is to protect the transistor from excessive current draw through the capacitor at power-up. I'd be inclined to replace R6 with a 2 Ohm 10 Watt resistor and use the TIP120 transistor available at Radio Shack. (It has an 8 Amp peak rating.) This would get the maximum voltage to around 11V.

You might be able to get away with throwing out R6 and C1 altogether. Many brushless "DC" fans draw current in pulses though, so the cap is probably a good idea.

[Aardil]

OK you guys are in trouble now
Here is a few of the answers to the questions you are asking about.
These are direct quotes from Perry ( Dam it, did it again!! )

Brians256 :
For instance, does your design turn the fan full on and full off when it reaches the highpoint temperature? How much hysteresis does it have (we don't want the fan turning on and off constantly as it hovers around the setpoint)?

Answer :
Hysteresis doesn't come into play because it's a variable speed controller. If it was simply on/off, then hysteresis would be a factor.

Brians256 :
Does it use PWM to allow very low fan speeds and high efficiency or does it use linear regulation that is smoother but puts out more waste heat?

Answer :
It uses PWM to allow variable speed with good efficiency and to avoid having to use a large
heatsink for the switching transistor.

Airspirit :
If I may make a suggestion, (if it would be possible), it would be nice to be able to set a
minimum system voltage for the loop, allowing your fans to run constantly at 5V-7V, but ramping up
if the temps get above a certain mark. That would be VERY useful, indeed, and might draw some
serious attention in the fan-cooler crowd, since this would be a virtual godsend.

Answer :
This would be easy to do with the addition of one more potentiometer.

Airspirit :
worried about spiking temperatures due to slow or no fan cooling.

Answer :
Since the water is continually circulated, the thermistor would sense the increase in temperature and would start the fan as soon as it was needed (assuming that it was set up properly). The change in fan speed for a change in temperature is adjustable (as is sensitivity and the set point).

MadDogMe :
maybe just a single LED to show it's 'kicked in'?...

Answer :
Easily doable. It would involve another inexpensive IC set up as a comparator. You would set it to come on when the fan was turning a certain speed (you'd have to calibrate it for your particular fan).

[airspirit]

I agree, if the thermistor was bathed in the coolant, the setup you currently have is ideal. I was playing devil's advocate for the strictly air cooled crowd. Honestly, they may be your biggest market. I can't imagine an air cooler that has already gone half deaf not wanting some relief that wouldn't cause system meltdown.

[Ecradda]

you should make them custom for people. but i was wondering if it can handle alot of fans, like 5 120mm's, and a couple of 40-60mm's.

[Aardil]

Ecradda:

Custom is a very expensive word

one off pieces tend to raise the cost of something that you would think should be 10 bucks to upwards of 100 bucks. Not saying this is the case here but I have done custom work before and had it done for me, overall it doesnt justify the price.

To the best of my knowledge the curent control board is set up to handle only one fan per board, by changing a few components it may be able to handle 2 maybe 3 but not sure on that.

The good news is since all the boards run off 12 volt circiutry you can add more boards to control more fans, I dont see this as a big problem since most PSU's and MB's support several fans

[Aardil]

Just a sneak preview

Phase 2 board proto type

[Brians256]

I'm looking forward to seeing the production version where it could be really quite small! That's such a small component count that it could really be convenient to install.

[airspirit]

You can use as many fans as you want provided that the power draw isn't too high, and if they all are identical, the settings will be the same throughout the daisy chained fans. Hook too many up and you'll cook his board (fire fire cha cha cha). You can't have each fan controlled seperately in this manner.

I assume I'm not talking out my ass, since I'm basing that off of inspecting your design, though please correct me if I'm wrong.

[Aardil]

I stand corrected.
I was not thinking of running the fans in series ( was thinking paralell ).
Also The Boss says the board will support mutiple fans. but at some point a Heat sink would be required.
I am not sure of how many fans it will support as we are doing testing this week on Phase 2 board to try and nail down the specs.

Aardil