NSY: True, it is complex, having total amount of four components :lol: . Hehe. Although I said unnecessary complexity I didn't say it was complex. But I get your point. The reason is also that I was able to do the PCB extremely small by not adding the extra transistor. Money is not an object, the s...

This sounds a bit odd. Implies SLM non-linearity. Was this repeatable with more than one fan? Several? How about dfferent mic positions? (not distance) I should have added that I used the Coolermaster fan for these last measurements and its sound level was anything but consistent at any distance. I...

One thing I was wondering about recently, is it not worth testing the noise of fans inside a PC, rather than hanging independently? Surely there could be certain fans which vibrate like mad when attatched to a chasis but are quiet otherwise. Id like to see a conclusive, be-all-and-end-all analysis ...

I wonder how the manufacturers measure the flow. Because looking at their datasheets even the slightest increase in pressure on the positive side reduces the flow. By placing a duct on either side of the fan you would introduce a pressure drop that will make the measurements less accurate. I know we...

1. I live in sweden so the measurements were taken between 00:00-02:00. I don't know the lower limit of the B&K and it doesn't say so in the manual either. The manual states that it has a dynamic range of 60 dB and then you configure the maximum value to be measured. In this case i chose 60 dB as th...

Well I did some experimenting today. I measured the noise of a fan at a distance of 0.125 m and 0.25 m. The results were 27.4 dbA at 0.25 m and 34.1 at 0.125 m. So a difference of 6.7 dB not exactly 6 dB but fairly close. See my post in the Fan & control forum were i present all measurements. http:/...

Today I measured the noise produced by different fans. The noise was measured using a Bruel&Kjaer 2231 SLM. This is an instrument in the $6000 range so I'm thinking it should be fairly accurate. What is not so accurate is the environment in which the measurements were performed ( my apartment). I re...

One thing you can do though is measure at say 25 cm then subtract 12 dbA from the measured value. I'm not sure how accurate this is but I intend to some experimenting later on tonight. I have borrowed an SLM from the company I work at. The problem is as you say the background noise. In my apartment ...

What kind of hose? In particular what diameter? Cos the cross section of the pipe needs to be as large as possible so as to reduce drag, otherwise the back pressure on the fan will reduce the CFM considerably. I didn't even get that far. I just ran the fan alone. It was 230 VAC fan so I used a tria...

It's difficult to say which will be quieter between a lot of large slow moving fans or a few fast ones. Because if you have say for instance two fans at 21 dBA the resulting noise will be 24 dBA. So it's a trade-off between flow and noise and number of fans. I remember a while back I was looking at ...

Clamrade: You are correct. Driving a small fan like the L1A will probably not be a problem with a 1/4 W pot. I'm using it to control slightly larger fans. TerryW: I can't see that happening. The fan voltage will always follow the base voltage minus the Vbe drop unless the base current becomes excess...

Yes it would. However it must be rated at a higher wattage than a normal potentiometer. These are often referred to as rheostats and tend to be rather expensive. That's why I use the above circuit.

Well I did some experimenting with two 4.7 V zeners in parallel in series with a single 5.6 Ohm resistor. Then I measured the temperature of both zeners. They were fairly close although one diode got slightly hotter than the other. This indicates that they dissipate about the same amount of power. S...

Johnkenyon Actually I don't think it's recommended to connect more zeners in parallel because they all have a slightly different voltage. A 4.7 V zener for example may differ from 4.4 V to 5.0 V. This will make the current sharing unequal. Although I'm not sure to which extent. In this case it might...

Every time you double the distance the noise decreases by 6 dB. So if you measured 24 dB at 1 m you will get 18 dB at 2 m and 12 dB at 4 m and so on. So in your case the measurement at 1.2 m will equal a bit over 23.5 dB at 0.5 meters.

I'm using circuitmaker to do the simulations ( which uses the Pspice engine) and eagle layout editor to do the schematics. Have you tested it yet? I only had a 1k NTC thermistor which because of the current through it heated itself thus making the fan spin slower even if the thermistor got hotter de...

That's a good idea powergyoza, using a zener instead. I think the circuit below might work. It seems to be working in the simulator atleast. http://www.efd.lth.se/~e99hh/temp.gif Again, I have not tested this ciruit in reality which means there is a chance something will fry. So test this at your ow...

Hi, I am new to these forums so its possible this has been posted before. I just wanted to share the way that I control the speed of my fans with the simple circuit posted below. I use this instead of a rheostat because i found them too expensive and I had all the components for this circuit lying a...

I am not sure what you want to do but the way I understand it is that you want to be able to limit the lower and upper voltage the fan receives. I am assuming that you have some knowledge in basic electronics. What you could do is to connect a diode from the drain on the FET to the 5 V supply. You c...