I was hoping for a section for DIY electronics, but couldn't find anything like that.
So since this project is for aimed at being able to control PWM pumps like the 35X or new PWM version of the D5 from a normal variable voltage fan controller I figured the Water Cooling section was the best place for this thread.
As many of you know, a lot of my builds feature some custom electronics that make them unique and special.
All of my builds with PWM pumps have custom PWM controllers to set the pump speed manually, or be able to switch it to mobo control.
I got some PM's recently asking about being able to control a PWM pump from a fan controller, and one suggested a circuit that's been around for a while, that after giving it some thought, seemed adaptable as a base to work from.
Here's the link, the second one down is the one of interest:
I was already planning to use the new Lamptron CW611 controller in the "Mix 'n Match" NZXT 630's builds, so being able to use a pair of 35X's in a setup where I could switch control between manual or mobo speed control and control by the CW611 seemed like a cool idea.
One thing I've learned from building several iterations of DIY PWM controllers, is that you have to build them so that you have a fair amount of trim control for the minimum % and the max % points.
You typically don't want to run a pump down below 15 to 20% or so, and most are at max speed by 70% to 75%.
It's nice to have trim pots set up so that the main speed control runs the pump from the minimum desired speed to the max speed over all of its range, not just a small portion somewhere near the middle of its range. . . ..
And to make it more fun, not all pumps, D5 / 35X are the same, and PWM fans are different yet, as to how they react to the PWM %.
The key part of the circuit that makes it adaptable to voltage control, is the voltage divider network R3, P1, R4, which controls the trip point of the LM311 comparator.
With the circuit set up, it was easy enough to measure what voltage was needed to reach 100% duty cycle, and what voltage threshold was required to rise above 0%.
Knowing what the 0 to 100% duty cycle voltage span is, allowed me to set up a finely adjustable voltage divider network to convert the variable voltage from the fan controller down to a range equal to that span.
The small problem is that the fan controller output starts at 0V, while the 0% duty cycle voltage is about 2.2V.
To solve that problem, I made a finely adjustable voltage divider network and a non-inverting summing amplifier to add the first 2.2V, so that the swing of the fan controller output can swing the PWM from 0 to 100%
In the pic below, the smaller rear protoboard has the fan controller output voltage divider network on the far right, with the "base level" voltage divider network just to its left.
The IC to the left of the dividers is a dual unity gain buffer that feeds the summing amp in the IC to its left. Also in that IC is the unity gain buffer for the manual speed control circuit's voltage output.
The larger front protoboard, is essentially the circuit in the schematic pic, with a LM339 quad comparator IC in place of the single LM311, as the output of the right NE55 IC needs additional conditioning.
The trim pots at the far left are for the 0% and 100% adjustments.
The trim pot on the lower board is the frequency trimmer.
This pic shows the speed control and the switch for fan controller or manual speed control operation.
Here it is set up on my electronics bench: . . .It's in manual mode and set at about 12% as a minimum:
Here's ~95%, and you can see that the frequency is right at 25KHz:
Here's 50%, notice the frequency stays right at the 25KHz mark:
Close up of what I have set as the minimum %:
Here's some pics with the PWM being controlled by the Aerocool X-Vision (display position 4)
Here's 100% . . . full speed on that fan of 1100 rpm 11.9 volts out from the X-Vision:
~70% . . . 11.0V out from the X-Vision . . ..1000 rpm:
~40% . . . .5.6V out from the X-Vision 600rpm
~20% . . . 3.9V out from the X-Vision . . . . . 600rpm
Next phase is to solder it up on some perfboard.
Not sure yet whether I want to go to the trouble to design a pcb for it yet.
Hope you like my project,