So I've gotten into homebrewing and a common project is to build your own stir plate to help stimulate a yeast starter for a new batch of beer. The concept is fairly simple; you put magnets on the hub of a computer fan, add a power switch and a potentiometer to control the fan RPMs, and allow the spinning magnets to spin the stir bar in whatever your vessel of choice is.
I've ordered some parts to make one of these myself, but I've made it a little more complicated for myself and I'm struggling to understand whether or not all of these parts are going to cooperate together. My parts list includes:
- On/Off Switch
- 5mm Red LED (to be used as an on/off indicator):
- 2.1 mm Panel Mount Barrel Jack
- 680 Ohm Resistor (ran a calculator to see what I needed to power the LED, not sure I got these right):
- LED Panel Mount (to clean up the installation on the box):
- 30 W Adjustable Voltage AC/DC Power Supply:
- 20k Ohm Potentiometer (salvaged from old computer fan controller)
- 120 mm Computer Fan
I have three primary concerns:
1. How do I wire up the LED to the power switch so that it comes on when I switch the switch on? I understand the need to have a closed circuit loop, but do I put this on a separate loop from the pot and fan? Will adding in the 680 ohm resistor kill the power to my fan?
2. Is this 30 W power supply going to work with this system? I was looking at the math on the potentiometer and I saw that they have a "power rating" generally between (.25 and 2 W). Am I going to fry the pot with this power supply? Is there something else I need to add in to avoid this problem?
3. Is a 20k potentiometer way too large of a resistance spectrum? Most of my reading has said that a 1k pot is better for this application (more control because of a wider usable spectrum) but I just happened to have this 20k one that came from a fan controller in an old PC. Seems odd that they'd use a 20k if it wasn't suitable for the job, but maybe it's not the best choice?
Thanks in advance for any help y'all can offer! I'm trying to learn to read these circuit diagrams, but I'm struggling to understand how they relate to the actual hardware.
I've ordered some parts to make one of these myself, but I've made it a little more complicated for myself and I'm struggling to understand whether or not all of these parts are going to cooperate together. My parts list includes:
- On/Off Switch
- 5mm Red LED (to be used as an on/off indicator):
- 2.1 mm Panel Mount Barrel Jack
- 680 Ohm Resistor (ran a calculator to see what I needed to power the LED, not sure I got these right):
- LED Panel Mount (to clean up the installation on the box):
- 30 W Adjustable Voltage AC/DC Power Supply:
- 20k Ohm Potentiometer (salvaged from old computer fan controller)
- 120 mm Computer Fan
I have three primary concerns:
1. How do I wire up the LED to the power switch so that it comes on when I switch the switch on? I understand the need to have a closed circuit loop, but do I put this on a separate loop from the pot and fan? Will adding in the 680 ohm resistor kill the power to my fan?
2. Is this 30 W power supply going to work with this system? I was looking at the math on the potentiometer and I saw that they have a "power rating" generally between (.25 and 2 W). Am I going to fry the pot with this power supply? Is there something else I need to add in to avoid this problem?
3. Is a 20k potentiometer way too large of a resistance spectrum? Most of my reading has said that a 1k pot is better for this application (more control because of a wider usable spectrum) but I just happened to have this 20k one that came from a fan controller in an old PC. Seems odd that they'd use a 20k if it wasn't suitable for the job, but maybe it's not the best choice?
Thanks in advance for any help y'all can offer! I'm trying to learn to read these circuit diagrams, but I'm struggling to understand how they relate to the actual hardware.