Hello everyone!
I registered for this forum to pick someone's brain for a small electronics project I am working on.
I am currently trying to design a DIY magnetic stir plate, like those used in laboratory settings for mixing solutions, etc. The stirring action in my project is to come from a small neodymium magnet mounted on the axis of rotation of a 12V DC pulse-width modulated PC fan - as the fan spins, so will the magnet, creating a rotating magnetic field to act upon a stir bar placed in any containers above the plate.
One key aspect of the project is to have fine control over stir speed, and therefore control over fan rotation speed. I know that pulse-width modulation (and other voltage regulation techniques) of the fan's DC operating voltage is hazardous to the fan's internal circuitry and such, but also has very poor control over fan speeds as the duty cycle approaches 0% and 100%.
Therefore, I have planned on implementing a separate PWM control circuit (outputting a signal to the fan's dedicated PWM input pin) to control fan speed.
The fan requires 12V supply for operation, and the PWM circuit requires 5V supply, outputting a signal between 5V (100% duty cycle), and 0V (0% duty cycle) to the fan, to adjust fan speed. I had planned on containing all the circuitry in a nice stained wooden cigar box I had lying around, functioning essentially as a black box - a simple control knob to adjust the duty cycle of the fan, contained in an elegant package.
My question is this - how can I elegantly have two different voltage supplies coming into the box, to power these two circuits? I have some experience with dabbling in circuitry on various projects, but cannot for the life of me figure out how to accomplish this as elegantly as possible (I really don't want to have to run two wall-wart type AC adapters into the case).
Any help that can be provided would be greatly appreciated. Thanks!
I registered for this forum to pick someone's brain for a small electronics project I am working on.
I am currently trying to design a DIY magnetic stir plate, like those used in laboratory settings for mixing solutions, etc. The stirring action in my project is to come from a small neodymium magnet mounted on the axis of rotation of a 12V DC pulse-width modulated PC fan - as the fan spins, so will the magnet, creating a rotating magnetic field to act upon a stir bar placed in any containers above the plate.
One key aspect of the project is to have fine control over stir speed, and therefore control over fan rotation speed. I know that pulse-width modulation (and other voltage regulation techniques) of the fan's DC operating voltage is hazardous to the fan's internal circuitry and such, but also has very poor control over fan speeds as the duty cycle approaches 0% and 100%.
Therefore, I have planned on implementing a separate PWM control circuit (outputting a signal to the fan's dedicated PWM input pin) to control fan speed.
The fan requires 12V supply for operation, and the PWM circuit requires 5V supply, outputting a signal between 5V (100% duty cycle), and 0V (0% duty cycle) to the fan, to adjust fan speed. I had planned on containing all the circuitry in a nice stained wooden cigar box I had lying around, functioning essentially as a black box - a simple control knob to adjust the duty cycle of the fan, contained in an elegant package.
My question is this - how can I elegantly have two different voltage supplies coming into the box, to power these two circuits? I have some experience with dabbling in circuitry on various projects, but cannot for the life of me figure out how to accomplish this as elegantly as possible (I really don't want to have to run two wall-wart type AC adapters into the case).
Any help that can be provided would be greatly appreciated. Thanks!
