Suppression of (electrical) noise from CH Thermostat

why not use a pot (potential devider) to slow the fan down ?

Martin Warby

Do you mean insert a resistor in series with the fan - so that it *always* runs at at least low speed - and use the stat to by-pass the resistor when max cooling is required?

Would that work with this type of motor?

Wouldn't contact noise from the stat still get into the system?

On a mains fan? Not to mention the fact that the dumped power ends up as heat and the power dissipation required is a bit above your average variable "pot", which generally aren't mains rated either...

I guess you could use a suitably rated wirewound resistor, slowing the fan down will help the noise, indeed just taking 10% of the speed will make quite a difference.

Suppresion of the stat, 0.1uF in series with 100R across the contacts. Either as suitably rated components or a contact suppressor like Maplin RG22Y. Note the Specification part of that items description appears blank in my browser check the device is mains rated...

Use the correct fan, you can get them with internal / external thermisters and this regulates the fan speed.

I was thinking of a pot (a variable resistor looks like

connect outer 2 tags to supply connect inner tag to +ve lead of fan connect -ve led of fan to -ve lead on outer 2 tags

Simply turn the pot till the desired speed is obtained

Martin Warby

DOH should have read post more throughly thought it was a DC fan but was using a mains rated thermostat.I agree using a pot would be a BAD idea in the circumstances.

I think if normal DC fans aren't powerful enough to cool the system then the general airflow in the case needs to be considered

Martin Warby

Thanks. Could you please point to a specific area on the Ebuyer site - there's a lot of stuff to wade through!

I've had one or two "funnies" with the computer in the past which look as if they might be DC power related - so I'm trying to avoid loading the internal power supply any more, even though it has been uprated.

Until you see smoke and smell burning

Have you looked at the power rating of a normal pot?

Many thanks Dave - looks like just the thing. I think the RG22Y is mains rated. I captured the picture from the Maplin website and blew it up - and although it's not wonderfully distinct, I'm pretty sure it says 250VAC on it.

In message , Set Square writes

You could always go for water cooling, quite a few of them about nowadays

It sounds like you have some fundamental problems to sort out

I have a desktop 2 gig machine with 4 HDs, a gig of memory, quality graphics card etc in a case with poor ventilation, no problems with it cutting out with overheating

see my earlier post I had not realised it was a mains fan (I presumed it was running from the 12V DC line).

Martin Warby

Sorry. You're looking for the "case mods" section. I think then the misc subsection. For example, I've got a 4 channel fan speed controller for 3.99. And 5 (sleeve bearing) 120mm fans for 72p each. (that are remarkable in that they will reliably start down at 2.4V, so can be run from the 3.3V line, in almost absolute silence.)

Thanks - but does any this stuff work with a *mains* voltage fan - which is what I've got?

Even then, you're pushing it

No. DC fans are pretty cheap, and may be more suitable, as they can be slowed down easily, whereas AC ones would require more complex electronics.

I think the idea is that at 72p, you could possibly purchase a new DC one?

Christian.

True - but I've just invested rather more than that in a nice mains fan, with proper bearings - so that it doesn't make a lot of *mechanical* noise like cheap fans do.