The Fanbus

Sorry, I am used to stuff like 4.3K and such

 

<the monkeys eyes reflect understanding now>

Thank you very much

 

Standard European way, but I think, as with metrication, the States are lagging.

The idea is to get rid of the decimal point and use the minimum number of digits for greater clarity on schematics, so instead of 0.01uF use 10nF or just 10n.

Maplin are only half-way there, on one page they'll list 0.0022uF, on the next 2.2n; 2n2 would be the preferred way.

Electronic Circuit Symbols & Notations

 

To start with 4.3k and 4k3 are the same and wen u have loads of

resistors ur gonna need ur resistor colour code
(the first person to tell me the full colour code will win nuffing but its fun aint it)

if u r going to build a electrobus use the Sw Pot Lin 10kSw Pot Lin 10k maplin code FW42V and connect from the top of R1 and top of R3 to th on off connnectors of the pot i hav a ruff circuitlay-out

and if u don't no all redy the knobs are maplin code YR65V

 

First... I'm an electronic dunce. I have, however read the Fanbus article over and over.

My plan is to make an electrobus, using the Meggitt 17PCSA103MC19P Push-Push Pots. (RS # 377-4782), as suggested my Macro. (They are hard to find... can't find Meggitt in Canada/US. Will order from UK).

Some questions.

1) How hot do the heatsinks get? Will enclosing in a project box cause them to get too hot? (I was thinking of using a CD-ROM casing to host the front panel, project box, and a few other project boxes for other stuff.

2) Rather than switched variable/full, I was thinking of switched temp. controlled/variable (since the loss is so small in Macro's circuit, cranking the pot would have almost the same result as full). How about the abiltiy to select either, via jumpers?

I see the temperature control in your PWM Bus article. How difficult would it be to incorporate into the electro-bus?

I am leaning towards 2 LEDs -- blue in the knob for variable, stealth fibre one in faceplate for temp controlled.

What's the most practicle way to get some real dimming (range, I suppose) going on the the LED's? Is the multiple diodes in series with the LED (I think suggested by CPemma in another thread -- no search available, sorry!) the most practicle method?

Thanks,

Mark.

 

A heat-sink must be able to lose heat, otherwise it will get hotter & hotter till something fails.

The diode led dimming method is now here.

A common method is to feed the led with a variable duty-cycle square-wave (ie a PWM signal) but that's more complex than a few diodes. But if you wanted the led to dim reasonably while the controlled voltage went all the way to zero (rather than just to 6v or so) the diode system wouldn't work.

 

Understood. Because of this, I am still concerned about placing everything inside to CD-ROM casing. Next to nil airflow would mean that heatsinks would be ineffective.


I looked up the "RN79L" heatsink (Maplin) that Macro suggested in the electrobus article. Web page at Maplin's describes it as 50 mm, 9.5 degrees C/Watt.

I just received my orders from Maplin and Farnell. Would prefer not to have to pay all that duty/shipping/brokerage again. In my digikey catalog, there are loads of heatshinks available for the TO-220 package. The listed specs range from .5W to 17W, from 4 to 140.5 Thermal Res C/Watt. What should I be looking for?

I'm thinking I need horizontal, to allow it to fit in the old CD-Rom casing. But what other specs should I be looking for?

Macro describes his electrobus as 4 to 12 volts. Would the diode system be OK then? Would it be the "best" method of dimming the LED's?

Thanks.

Mark.

 

Even with half-a-dozen typical fans, a 25degC/W heat sink will stay fairly cool. If you want to work out the needed spec for your fannage, sums are here.

But would you ever run your fans at 4v? I'd try raising your diodes/led Vf to 6v-7v and see if it works to your satisfaction.

 

Was going to ask the same thing. So please could somebody with more electronics knowledge than I have give a short answer? Replacing a resistor with a thermistor of suitable value would do the job???

 

No problem with this regulator, it will take high value resistors (like common thermistors) in the control chain, unlike a 317T.



Swap R2 for a 10k thermistor.

Make the pot a 47k preset, R1 also 47k (or use a 100k preset and don't bother with a fixed R1, as in the diagram below from a datasheet)

Join the green wire (one end of pot) and the mauve wire (pot wiper)



Tweak the preset pot to get a minimum safe fan speed under cold conditions.

btw, macroman, the links for the article sections are still awry, I found a monitor mod on the electrobus page

 

Which links? The all work for me?

 

On the start page http://bit-tech.net/article/52, the links at the bottom.

(1) OK

(2) 7-12v bus http://bit-tech.net/article/3 ... Sorry, no can find in the database...

(3) Rheobus http://bit-tech.net/article/4 ...ditto

(4) Electrobus http://bit-tech.net/article/5 goes to the monitor mod.

 

Just tried it and they all work.
Were have you copied those links from?

 

The white links at the bottom of the page. The RHS side-bar menu links work OK.

The same links at the bottom of http://bit-tech.net/article/52/1 are OK, just http://bit-tech.net/article/52 wrong.

 

I can't find a problem - they all work. Have you tried refreshing/clearing your cache?

 

I can't seem to find MIC29302BT in US sites such as Digikey and mouser. Does anyone know if it uses a different product code?

 

Very refreshed, I'll wipe the cache and lose all my pr0n, but the faulty code I'm seeing is

 

Strange, you're right about the source code but it worked for me and the link was correct in the status bar when hovering the mouse over the link? Bizzare.

Anyway edited now - try it.

Thanks for the heads up

 

http://www.arrow.com/newproducts_sub_cat/1,2586,Voltage_Controllers,00.html list it.

29302 is 3A max, similarish alternatives are MIC29152BT (1.5A max, same pin-out, cheaper) or MIC2941ABT (1.25A, different pin-out)

 

So I can keep my pR0n...