| Had some time this afternoon to spend on prototyping the electric water pump controller. I previously acquired a Davies-Craig controller from John Paul Beckman for use with my water pump project, but unfortuantely that controller is only rated at 7.5Amps maximum. At full duty, my pump is pulling as much as 20amps, which it will likely never see this kind of duty cycle but, the Davies-Craig unit isn't going to cut it. This gives a little insight into how much water this pump must be moving if it can pull as much as 20A and the Davies Craig pumps are claimed to flow as much as 20 gallons per minute at 7.5Amps. Here's the pump:
 I have run this pump on the engine now several times and brought the engine up to some elevated temperatures - 240 degrees was the highest I let it go to test that there were no leaks in the system and that the water pump was properly sealing up. This pump moves enough water that with the radiator cap off, it almost sloshes water out of the hole. Further bench testing will be done to ensure longevity as well as get an accurate measurement on its flowrate. I used a circuit design that I located through a google search and did some modification to it of my own for use in this application. The original circuit uses a 555 timer to generate a duty cycle pulsetrain with variable duty dependent on a potentiometer (that's a "knob" for the non-electrical folks). With a little modification using a 100K thermistor and a 250K potentiometer in series, the circuit was transformed into a temperature dependent duty cycle with the ability to calibrate it for proper pump speed. I also built a seperate high-current driver circuit using the NTE2985 MOSFETs (these are actually just some I had laying around as they are the same driver MOSFET in our fuel pump controllers), which can handle 30A a piece. I used four of these babies to help distribute the current across more components to help with heat dissipation and longevity. This is just the prototype I etched and laid up, so excuse the spartan appearance of it all. 
The Workbench:
 This controller will ultimately be engineered on a single board and fit into a nice housing to go along with the electric water pump itself when it comes available. Not sure at the moment what the complete kit will cost, but as always, I'll do my best to make it an economic upgrade. I also put together a short video of the operation of this setup in the kitchen - with the wife's permission and help, of course. She makes an excellent camerawoman. :) (Right Click, Save As...)
[ http://ashspecz.com/Image%20Gallery/Electric%20Water%20Pump/Video/HPIM0563.mpg ]
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AshsZ-II Ultimate Street Z Progress: EWP Controller - 
