I'm building a homebrew stir plate and I'm having potentiometer issues; the 25 ohm potentiometer I bought doesn't turn the fan down enough. This is how I wired things initially:
+>rocker switch>potentiometer(25 ohm)>fan
- >fan
So then I added various amounts of resistance (10-200+ ohms) in series with the potentiometer and this slowed the fan down, but reduced the range of the potentiometer to the point that it seemed to be a fixed resistor. So I connected the resistors in parallel with the potentiometer, which slowed the fan to a lesser degree and also reduced the range of the potentiometer. Here's a schematic:
________________>resistor (10-200+ ohms)>
+ >rocker switch>_______________________>fan
________________>potentiometer (25 ohm) >
- >fan
After that, I decided to connect two 25 ohm potentiometers in series. They didn't slow the fan much or speed it up much either. I also connected a 50 ohm potentiometer and it acts like a switch. It allows no current to flow until the very top of its range, then it's fully open.
I'm using a 12V 300MA power supply, which it what the fan is rated for. Any ideas on what to try next? I've read many previous posts about wiring homebrew stir plates, but I haven't found a solution.
One more thing, the rocker switch I would like to use has a lighted LED and four terminals. The top two are oriented horizontal to one another and the bottom two vertical. The top two are labeled +/-. I haven't been able to get this switch to work as I'm used to the three-terminal kind. Any ideas on this? This is how the terminals are arranged:
+ -
_?
_?
+>rocker switch>potentiometer(25 ohm)>fan
- >fan
So then I added various amounts of resistance (10-200+ ohms) in series with the potentiometer and this slowed the fan down, but reduced the range of the potentiometer to the point that it seemed to be a fixed resistor. So I connected the resistors in parallel with the potentiometer, which slowed the fan to a lesser degree and also reduced the range of the potentiometer. Here's a schematic:
________________>resistor (10-200+ ohms)>
+ >rocker switch>_______________________>fan
________________>potentiometer (25 ohm) >
- >fan
After that, I decided to connect two 25 ohm potentiometers in series. They didn't slow the fan much or speed it up much either. I also connected a 50 ohm potentiometer and it acts like a switch. It allows no current to flow until the very top of its range, then it's fully open.
I'm using a 12V 300MA power supply, which it what the fan is rated for. Any ideas on what to try next? I've read many previous posts about wiring homebrew stir plates, but I haven't found a solution.
One more thing, the rocker switch I would like to use has a lighted LED and four terminals. The top two are oriented horizontal to one another and the bottom two vertical. The top two are labeled +/-. I haven't been able to get this switch to work as I'm used to the three-terminal kind. Any ideas on this? This is how the terminals are arranged:
+ -
_?
_?