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No, it will not increase past its set point. However, it will continue to decrease.Quote:
Originally posted by bluesfusion
So? If the pots you've used keep turning after you've reached the max limit, does the resistance also keep on increasing forever? lol. :rolleyes:
What I said was perfectly correct.
There's no need to get cocky, I'm stating something that I'm aware of from experience. Not to argue.
What he is saying is that by picking too high of a resistance your Effective range is only a fraction of the available rotation of the POT.Quote:
Originally posted by CrawlingEye
Just so you know, there is no '10-12 degrees of turn to adjust' ever. In all the VR's I've used, they'll keep turning even after you've reached their maximum limit.
i.e. You need a 15ohm POT but instead use a 200ohm POT - If your fan speed will vary only from 0-15 ohms on the POT then the rest of the range will cause an inperceivable change to the fan speed.
Also if your POT keeps turning after you've reached max/min then your using a clutch type which is fairly uncommon for large power POTs.
Hmm, well I looked on an online store and found one that may work- It's rated at 15 ohms, 15 watts. Think that will be okay? And also, will that allow me to fully vary the speeds?Quote:
Originally posted by bluesfusion
Ok. 12V, 1.1 Amps. Plugging this into my exact calculations, I get -
Pot resistance around 15 ohms and Pot wattage about 3.5 Watts.
You definitely need a safety margin on the wattage. Find the highest wattage pot you can find which has max resistance around 15ohms.
At a minimum I'll recommend a Pot rated at - 15 ohms, 5 watts.
Here's the link
Quote:
Originally posted by Mrfreddio55
Hmm, well I looked on an online store and found one that may work- It's rated at 15 ohms, 15 watts. Think that will be okay? And also, will that allow me to fully vary the speeds?
Here's the link
Yeah the higher the wattage, the better for safety. Higher wattage doesn't make any difference to the control. So the 15W pot is great. :)
The value I gave you - 15 ohms - will let you vary the voltage at the fan from 12V to 5V. Your fan may be able to run at lower voltage than 5V, but 5V is good enough to have a big reduction in speed and noise compared to 12V.
If you want full optimum control, once you get the fan you can experiment or find out the exact starting voltage and then refer to this graph for a 12V, 1.1Amp fan to get the pot resistance needed to get control over the full range of the fan. The way you use this chart is look at the red curve. On the left side Y-axis, choose the fan starting voltage, go horizontally to the red curve and then vertically to the X-axis where it will show you the resistance of the pot needed.
For your fan, I chose 5V as the starting voltage cause most fans run at 5V properly. Then the resistance of Pot needed is about 15 ohms. If your fan starts at 4V a pot of 22ohms will give you maximum control, etc.
http://home.attbi.com/~bluesfusion/fanpot.jpg
Actually since I have the spreadsheet set up, I can generate a selection chart for other current fans as well. Just choose the curve which applies to your fan, select a starting voltage and read the pot resistance off the x-axis. :)
http://home.attbi.com/~bluesfusion/potselection.jpg
Thanks for all the help guys :)