DDC 12V Speed control built and tested

[Hansfragger]

Hello everyone. I started with a modified DDC 12V pump and purchased a 15W ceramic rheostat from Frozen CPU. I fabricated a simple L bracket out of aluminum for mounting. Then leads were soldered on, heat shrink and sleeving applied, and appropriate molex connectors(1 male, 1 female) added to insert between pump molex connector and power supply molex connector. The pump is installed in my external radiator setup with 1/2" ID hose. The voltages were read at the molex after going through the rheostat with a Fluke 177 multimeter. As I do not have any accurate temperature or RPM measuring equipment, the temp readings will merely give a reference to different RPM vs temp results. I used a digital stand alone thermometer to measure ambient temperature. It has a claimed accuracy of +/-2 degrees F.(If you believe that want to buy some swampland in Florida?). CPU temps were taken from the built in sensor in my ABIT IC7G MAX2 mb. Pump RPM readings were also taken from the mb by plugging the speed sensor wire from the pump into the CPU fan header. These last 2 measurements were displayed on-screen with ABIT EQ.
Ambient temp - 81.5F
RPM -------- Voltage ----- CPU Temp ----- Rheostat body temp
3515 _____ 12.05 ______ 116 __________ OK
3375/3515_ 11.50 ______ 116 __________ OK
3245______ 10.88 ______ 116 __________ OK
3125______ 10.69 ______ 116 __________ OK
3013______ 10.26 ______ 117 __________ OK
2812/2909__ 9.68 ______ 118 ____ Almost too warm to hold
2721/2636__ 8.96 ______ 118 ______ Too warm to hold
2163/2220__ 7.75 ______ 118 ______ Too warm to hold

No reading, _ 7.25
pump would not run.
There was a small perceivable difference in noise coming from the pump at the lower RPM's. Also the noise of the liquid flowing through the system seemed to be a little lower.

[iakovl]

realy nice
maybe u should make a water block for the reho (just an idea :P)
then u can make the pump do low volt without the reho to be to warm