I want to change the speed of a DC motor(12V,2000RPM) using a pot and operate a table fan(where I've replaced its AC motor with DC).Now the problem is I get a regulated output at o/p of 7812 but not after connecting the pot(10k)!
Need ua help guys!
Thanks!
How to change speed of dc motor using potentiometer
dc motorfanpotentiometervoltage-regulator
Related Solutions
Normally a potmeter has three connections. The middle is the wiper which moves over the resistive path, from the left pin to the right one when rotating clockwise. Swap the left and right pin and you should be OK. Important: be sure that it's a logarithmic potmeter instead of the regular linear ones.
edit
I read that the resistance increases if you rotate clockwise, and that you want the reverse. I don't know what the surroundings of the potmeter look like, but for a volume control you normally want to increase the resistance (between the left pin and the wiper) when rotating clockwise. If for some reason you want the reverse you don't want a logarithmic potmeter, but an anti-logarithmic one, which is much rarer.
If I understand you correctly, you want to adjust things so the range only covers between ~30% and ~60% of the current range.
Let's say the output voltage from the pot wiper is currently 0-10V, here is a circuit to alter it to 3.3V to 6.6V (so 33% and 66% of original range):
The 10kΩ pot is represented by the two resistors in the dotted rectangle.
Output simulation with pot swept from 0 to 10kΩ (x-axis, output voltage on y-axis):
You can make it even easier to fine tune by using a 10-turn pot.
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Best Answer
LM317:
To use your 10K pot you can use it for R2 and change R1 to 1.2K ohms. It will not work correctly without the fan connected because the load current will be too low for the LM317 to regulate.
Adjustment range (with fan connected) should be 1.25 to around 12V, assuming at least 14V in. Check it doesn't get too hot- you might have to add a heatsink or bolt it to something- at least you have a fan to cool it.