It's controlled by motherboard with a 4 wire header. I don't want to crack the pump open.Maybe.
What kind of a Controller did the Pump come with ?
Do you have all the Specifications for the Motor and the PWM Circuitry ?
Is the PWM Controller separate from the Pump-Motor ?
Can you get inside the Pump-Motor,
modify it,
and then insure a perfect re-Sealing of the Housing ?
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100% PWM can also be Ground.You can always use a valve to control the flow. If you're restricting the flow excessively you can use a Tee to let the pump run without making it work too hard while some of the flow can go to the height you desire.
Now, will your pump run at full speed where it was formerly controlled by PWM? Yes. PWM is Pulse Width Modulation. Assuming you can vary the PWM from 0% to 100% - ask yourself this - what is 100% PWM? Is it not 12V all the time? So what's the difference between PWM @ 100% and 12V unrestricted?
Can I connect a potentiometer to VCC and GND of the pump?100% PWM can also be Ground.
Standard understanding of PWM is that the top of the square wave (metaphorically speaking) is the positive voltage. Yes, it COULD be the negative leg, but generally PWM isn't thought of that way. But I understand what you are saying.100% PWM can also be Ground.
That's probably unlikely. The pot will act as a voltage divider, meaning it has to be able to handle the load of the pump and as a load itself it must be rated in watts to handle that much current. Suppose you have a 10K pot: At 12 volts, that pot will draw 1.2mA and 14.4mW. That's not a small pot. While 14 milli watts is not a lot, most trim pots I've ever worked with are too small to handle that much power.Can I connect a potentiometer to VCC and GND of the pump?
You can but it would not work nearly as well as pwm. When controlling power delivered to the pump with a pot, the drop from full power to half power requires the pot to heat up from the other half of the power (the power not used by the pump). In PWM, at half power, the power is literally off for half the time and on half the time. No energy needs to be absorbed or lost - there is simply no power consumed for half the time.I am making an indoor fountain with an old 800 L/H AIO pump. Will the pump run full speed without the signal, like fans? if so, can I hook a potentiometer to the 12v adapter to adjust the height of the stream?
Should I pull pin 4 high and floating, low and floating, or high and low?Why not just use PWM?
You could build a simple PWM module that could drive the pump with a 555, and in turn you can control the 555 with a pot.
Just keep in mind that the PWM signal might need to be 5 volts just as all PWM fans are, and higher voltage could damage it.
Simple build...regulator...555...few other parts, plus the pot.
Look up Noctua white paper for more info on the PWM specs.
Pretty sure the pump would work like a PWM computer fan does. Read this - "Pulse-width modulationShould I pull pin 4 high and floating, low and floating, or high and low?
I must confess my ignorance but what is an old 800 L/H AIO pump?I am making an indoor fountain with an old 800 L/H AIO pump.