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Location:
Terrigal
Registered:
May 2002
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Electronic gurus
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Tue, 05 October 2004 11:45
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Hi all, need some help from the electronics gurus out there.
I'm working out a way to improve the function of a craig davies electric water pump.
At the moment its wired up to ign + so takes ages awhile for the engine to warm up and creating un-necessary wear on the pump.
There is a controller box for it based on water temp, but the big problem with this is the pump doesn't spin until the water is at a certain temp and the temp sensor isn't inside the engine so the temp sensor never sees an accurate water temp because the water isn't flowing.
So... my idea is to create a simple circuit that works something like that :
ign + switches on a relay that powers the pump with a resistor inline so the pump only runs very slowly, say maybe supply it with +4v or so.
Then i'll have a temp sensor switch, like the thermo fan switch on/off switch (90 degree on, 85 off, or so). This will switch on another relay and supply the pump with +12v.
So does that sound ok ?
What size resistor would I need to cut 12v down to 4v or so. Can I get a variable resistor so I can select how many volts the pump gets so I can get it just spinning enough to flow water past the temp sensor?
When the relay connected to temp sensor switches on and supplys the 12v to the pump, what effect will that have on the other circuit with the resistor etc? Should I put a diode after the resitor, but before the pump, and have the 12v switch after the diode so the power cant flow back to the resitor and other relay?
I hope that makes some sense..
Thanks
Joel
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I supported Toymods
Location:
melbourne
Registered:
June 2002
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Re: Electronic gurus
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Tue, 05 October 2004 11:55
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joel, you will have problems with the resistor idea, i cant remember why, but it isnt just a matter of sticking a resistor in series with the water pump, something to do with huge current going through the resistor.
if you wanted to do this, it would be easier using PWM (pulse width modulation) but i dont know how to do this either.
where is the temperature sender? if it was in the head i would be happy with that, but it might not be.
could you just have it so the pump turns on like 2 minutes after you start the engine or something?
hope i have given you more answers than questions, i fear i havent.
good luck!
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Location:
sydney
Registered:
March 2003
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Location:
Land of Oz
Registered:
June 2004
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Re: Electronic gurus
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Tue, 05 October 2004 12:19
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Hi,
Resistors are okay, but a little crude. They will get hot, unless you get a big wattage unit and consume power - ie generate heat. Better idea is to have a voltage regulator to supply lower voltage. You'll need a TO3-case regulator 'cos I'm sure the pump will pull a few amps. You can adjust the voltage output by changing the resistor values for the regulator. THese are just ordinary 1/2W resistors and won't run hot - though the reg will get warm under load, so better use a heatsink.
The PWM idea is good also. I think Jaycar had a speed controller kit, based on PWM for electric drill motors and it handles a few amps. So, you could use that kit as is - just leave the speed knob (when you decide what speed you want the motor to turn) on the one setting, or replace the pot for the speed control with a fixed resistor - once you've established the speed you want.
seeyuzz
river
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I supported Toymods
Banned User
Location:
Brisbane
Registered:
May 2002
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Re: Electronic gurus
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Tue, 05 October 2004 12:27
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Sideshow has the right idea. Use a/some oem fuel pump resistor packs to do the job.
But are you sure that the EWP controller doesnt run the pump slowly like you are wanting to do? I'm sure they. Or at least they used to 
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Electronic gurus
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Tue, 05 October 2004 12:35
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there is a number of ways you can do this really. both river's and sideshow's suggestions would work fine, but it really depends on what lengths you want to go to to control the speed of this little puppy.
An LM317 (T03 type) would work fine, with a thermostat controlled switch going between high and low speeds. Using the River suggestion of this, coupled with the simple Jaycar temperature switch kit would do exactly what you want.
Otherwise you can go the path of the resistor banks like sideshow said. Its probably what i would do as it's cheap, works, and simple. Not exactly perfect but it works.
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Electronic gurus
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Tue, 05 October 2004 14:05
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Or you can get really keen and build something that varies the speed of the pump with temperature i.e. connect the temp sensor to the voltage regulator/PWM circuit. Of course that requires a bit more playing around 
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Location:
Terrigal
Registered:
May 2002
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Re: Electronic gurus
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Tue, 05 October 2004 23:43
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Thanks everyone for all the suggestions! Looks like I have a few options here to look at more indepth.
Just to answer a few of the questions...
The engine is a very custom job and yeah the temp sensor for thermo fan, engine temp guage, and water pump, have all ended up in a alloy pipe that exits the rear of the head and goes to the radiator. They are probably 20cm + away from the engine so really need water flowing past them to get accurate readings.
I cannot believe the craig davies pump controller does not do what i'm trying to setup. I've talked for ages to their tech support department and they swear blind that the pump doesn't spin at all until the sensor starts to see a rise in temp. I reckon that is crazy and it should spin slowly then increase in speed as temp goes up.
So we actually own a $300 controller for it, but it proves quite useless. All it seems to be is a fancy thermo fan style switch. And it uses a stupid probe you have to put into the water pipe that never seals correctly. Be much nicer with a screw in sensor.
I'll have a good read over all the suggestions  thanks again!
Probably will have some more questions once I decide what path to take
Cheers
Joel
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Location:
Terrigal
Registered:
May 2002
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Re: Electronic gurus
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Tue, 05 October 2004 23:50
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| Quote: |
Thanks again for the reply. NO TROUBLE
My understanding was regardless of the temp at the sensor (even if it is cold), the pump should work at a slow speed? So the sensor would get an accurate coolant temp coming out of the engine. NO
Or does the sensor have to be a certain temp before the pump will spin at all? YES - ABOUT 70C
Thanks
Joel
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That is a section of an email that went back and forth to Craig Davies tech.. Craig Davies answers are in CAPITALS.
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Location:
Terrigal
Registered:
May 2002
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Location:
townsville NQLD
Registered:
February 2004
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Re: Electronic gurus
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Wed, 06 October 2004 01:05
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hi,
you could always hook a few brake light bulbs in series, that will reduce the power and not get to dangerously hot. u can have it under the bonnet somewhere or in the wheel well. this will be cheap and really effective. and then when the temp sensor relay cuts in, it 'shorts' the bulbs and puts the pump up too full power.
homemade electronics is the go
give it a go, u got nuthin to loose
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Location:
Terrigal
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 02:04
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The more i've been thinking, maybe the jaycar DC motor speed controller is the way to go to get it running at a slow speed, and then let the craig davies controller do its thing once it warms up. Can anyone see a problem with this?
The craig davies controller is designed to control the speed of the pump to keep the coolant at a set temp. So the jaycar kit will just keep it spinning slowly so the craig davies temp sensor gets an accurate reading.
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Toymods Club Treasurer
Location:
Sydney
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 02:21
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Is the temp sensor before or after the thermostat?
If its after, then it will be getting the right temp to start to pump as the engine gets closer to operating temp.
The thermostat will only open to allow the water to pump after its hot enough, so there's no point in the pump working if its going to push against a closed thermostat.
If its before the thermostat, it won't get a proper reading till after the thermostat is open, as its only reading the radiator temp, not the engine temp.
Or have I got this all backwards?
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Location:
Terrigal
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 02:27
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Well it doesn't actually run a thermostat anymore, because basically the speed of the pump is meant to control the temp of the engine.
It goes something like this :
Bottom radiator hose - electric water pump - into engine (into gutted mechanical pump) - water out of engine - into pipe that goes back to top radiator hose (this pipe is what holds all the temp sensors).
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Toymods Club Treasurer
Location:
Sydney
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 02:40
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I see.
So you're saying that if the pump isn't working, the temp sensor isn't going to see the required temp until all the coolant in the engine has heated & transfered the heat up the pipe to the sensor.
Does a thermostat fully seal or do they let some coolant past? Mind you they also right at the engine.
If you could mount the sensor closer to the engine I think the controller should work.
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Location:
Terrigal
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 02:50
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| Quote: |
So you're saying that if the pump isn't working, the temp sensor isn't going to see the required temp until all the coolant in the engine has heated & transfered the heat up the pipe to the sensor.
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Yeah thats exactly it. We found that when the pump turned on, also the thermo fan as its switch is in the same place, the temp guage (again sensor is in this same pipe) jumped straight up to over 105 degrees.
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Toymods Club Treasurer
Location:
Sydney
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 03:00
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Sounds to me like you need to move some sensors.
The rad fan one should be close to, or in, the radiator.
The pump switch should be near, or in, the engine.
The one for your dash guage I'd leave where it is.
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I supported Toymods
Location:
Australia
Registered:
November 2003
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Re: Electronic gurus
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Wed, 06 October 2004 03:04
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| wagonist wrote on Wed, 06 October 2004 10:40 |
Does a thermostat fully seal or do they let some coolant past? Mind you they also right at the engine.
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FYI, when you put an EWP in, you remove the thermostat.
The controller becomes the thermostat.
But a thermostat lets through a very small amount of water while fulled closed.
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 03:13
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First... how much current does the pump draw??
Im thinking itll be a LOT.
Because of this, the light bulb idea and LM317 idea probably wont work.
Using resistors would, but they would be huge and would need to be bolted to the chassis or radiator to act like a heatsink so they dont cook.
PWM is the best idea, but you may have problems with this too.
There is a good chance the motor will need above 60% power to startup, after this you can then slow it back down.
Unless your tricky with electronics, youll need to do this with somthing like that Jaycar PWM Controller kit with a knob on the dash you rotate to full when you start the car and then back off.
I could see this being rather annoying, and you also actually wouldnt know how fast the pump was turning until your engine heats up.
You could also forget to turn it up later and cook the engine.
So i think you should just use it the stock way, or find someone that can build a controller for you that will do it properly.
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Location:
townsville NQLD
Registered:
February 2004
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Re: Electronic gurus
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Wed, 06 October 2004 04:07
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of course the light bulb idea will work. if need be, hook up 4 (5amp) light bulbs in parralel and the resistance will be very high. i predict if you hook up 10 5amp bulbs in parralel, u would be able to start the car.
the good thing is that its totally variable. also cheap too!!
do you kno how many amps the pump draw??
say the pump uses 10 amps, put 2 5amp bulbs in parrel. this should equal the power being used by the pump and slow the pump to half speed. in crease the no. bulbs in parralel and you in crease the speed (lower resistance being taken up by the bulbs).
but its all up to you
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Location:
Land of Oz
Registered:
June 2004
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Re: Electronic gurus
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Wed, 06 October 2004 05:38
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Hi,
And you can place the lightbulbs around the front of your grille like the "Kit" car. It'd save you having to put in neons!
When your car lights up like a Xmas tree you'll know the pump is starting. 
seeyuzz
river
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Location:
sydney
Registered:
March 2003
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Location:
Terrigal
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 06:02
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Hey Jim, this isn't actually my car but a mates.
Basically it was a hybrid job with a starion block and vr4 twin cam head and the water pump wouldn't fit anymore and had heaps of problems trying to get one to fit and getting a ribbed belt etc..
So he decided to fit electric water pump instead.
He has an Autronic SMC so can we use it to control the water pump?
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Location:
sydney
Registered:
March 2003
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Re: Electronic gurus
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Wed, 06 October 2004 06:13
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ok
now it makes sense
it wouldnt be to hard to set up with the autronic
have a relay that switches from one pole to another
relay off it sends 12 thru resistor to pump
autronic turns on relay then switches to other pole and supplies 12v to water pump
u dont have ot make it complicated
if u drill a tiny hole in the thermostat this will help some water circulate and not build up pressure too much before thermnpostat opens
plus the water circulation will help water pass over the temp sensors for the autronic
then if u runout of outputs on autronic the best thing to do is put a thermo fan switch in thermostat housing
i have a list of different thermo fan switches
all diff threads and temps they turn fans on
i think its better toi run autronic to do water pump and fan switch to do thermo fans
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Location:
Terrigal
Registered:
May 2002
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Re: Electronic gurus
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Wed, 06 October 2004 06:38
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Ok cool so still need a relay and resistor to cut the power down?
Yeah the fan is running off a switch, the autronic isn't controlling this.
So what output on the autronic do I use?
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Location:
sydney
Registered:
March 2003
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Re: Electronic gurus
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Wed, 06 October 2004 07:22
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just use aux output for fan
but instead of fan run it to relay
and make it turn on at say 70 and off at 130 so it never turns off
or if u want it to turn fast and slow more regularly make it fast at 90 slow at 85
which means on at 90 off at 85
the resistor is easiest way to do this
without have to buiold some device
make it simple and u will get less hassles
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