Two Pumps- One Controller?

fenner408

fenner408

New member
Joined
Jan 8, 2009
Messages
79
Im wanting to run two pumps off of my Snow stage 2 controller (vc100). has anyone done this? Will the controller handle the amp draw of the two pumps?
 
i was just asking snow this myself ..it ha to be totally custom deal...depends on the controller they told me..best call em
 
dieselbeef said:
i was just asking snow this myself ..it ha to be totally custom deal...depends on the controller they told me..best call em
Click to expand...

I talked to them and they said it could possibly but he wasn't sure.


just run 2 relays to take the load off of the controller
Click to expand...

It is a progressive controller though. If I used relays they pumps would be on/off right?
 
I imagine they progressively control with a PWM signal? You can use a solid state relay if the PWM frequency is low enough (below ~100/1000 hertz). If the frequency is above that, which is common when controlling electric motors, then your mileage with solid state relays will vary. If you can't make it work with a solid state relay, then you can use some sort of transistor based amplifier or find another PWM that has a frequency input. But those are wonky ways to do it.


Does the pressure really stay that constant when they progressively ramp the pump, or does it drop off right with flow rate?
 
Last edited:
I asked Snow, they wouldn't tell me what their PWM frequency was, but they said it was "always changing" and that their controller would control up to 12 amps.


Who wants to look at their Snow controller output with an oscilloscope?
 
Begle1 said:
I imagine they progressively control with a PWM signal? You can use a solid state relay if the PWM frequency is low enough (below ~100/1000 hertz). If the frequency is above that, which is common when controlling electric motors, then your mileage with solid state relays will vary. If you can't make it work with a solid state relay, then you can use some sort of transistor based amplifier or find another PWM that has a frequency input. But those are wonky ways to do it.



I asked Snow, they wouldn't tell me what their PWM frequency was, but they said it was "always changing" and that their controller would control up to 12 amps.
Click to expand...

Your talking spanish to me man. :bang
 
You're gonna have to learn electro-spanish fast to do what you want.

Wouldn't it be easier to use PWM to control two solenoids progressively and have the pump spec'd for enough flow to feed both paths? Seems easier that trying to PWM two pumps simutaneously. Simple pressure circuit to control pump on/off like an electric pressure washer. Modulate the valves.
 
Or just use more valves...

Two valves gives you three stages; first on- second off, first off- second on, first on- second on

Three valves gives seven stages. First on, second on, first and second on, third on, third and first on, third and second on, all three on.

Four valves gives fifteen stages.

Binary baby.


Or you can buy one of these. I'm just waiting for the exchange rates to get better. I've been waiting four years and it keeps moving in the wrong direction.
 
Last edited:
yeah but then you have non linear delivery rates, which is what I thought you were questioning when considering PWM on two pumps.
 
Non-linear?

#1 flows 1 LPM, #2 flows 2 LPM and #3 flows 4 LPM.

#1=1
#2=2
#1+#2=3
#3=4
#1+#3=5
#2+#3=6
#1+#2+#3=7

Looks pretty linear to me... You'll need to get creative with your control system, but ons and offs are more reliable than something infinitely progressive. And who really needs more than 7 stages?


"PWM" stands for "pulse width modulation" or "pulse width modulator"; it's a square wave signal that turns something on and off at a certain frequency. A 25 hertz PWM signal turns something on and off 25 times per second. If it's at 100% duty cycle, then it's always on. If it's at 50% duty cycle, then it spends as much time on as it does off. A good PWM will let you put whatever duty cycle you want onto a valve. Certain valves need different frequencies, and they're really sensitive to it; NOS ProShots work between 20-80% duty cycle at 25 hertz, above that and they tend to not open at all an above it they tend to not close at all. But they're variable within that duty cycle range. ProShots at 25 hertz sound badass.

A solid state relay acts like a regular relay, only it has no moving pieces so it can flip really fast and doesn't wear out nearly as quick. If you're using 25-35 hertz PWM signals, you can use solid state relays to control as many amps as you want for cheap.

When it comes to controlling a motor, you aren't really limited by frequency; usually the higher the frequency the smoother the control. Typically PWM's are used on motors instead of valves, and the frequency can be well into the kilohertz.

There is another way of controlling a valve with a PWM, which is to use it at high frequencies and actually hold the plunger half-way or quarter-way open at any given time, instead of totally opening it and closing it many times a second. OEM's do this all the time for pressure regulators or idle air controllers, and it lets a valve last a long time instead of wearing it out within a few hours, but it requires a feedback loop of some sort to be able to dial the plunger to exactly where it needs to be.

When you end up using high frequencies, amplifying the available amperage becomes a more expensive proposition than using solid state relays. You need to use amplification transistor doodads like what CNC machines and industrial robotics use, which I know little about other than that they're expensive.
 
Last edited:
Did you ever figure out the fuel system you were proposing for your 1st gen?
 
The one that switched between high and low pressure inputs.

And by non linear I meant not finitely variable. 1lpm then jump then jump. Not that there is a need for either. I would like to see the analog logic circuit for 3 pumps and variable output flow.
 
You must log in or register to reply here.
Back
Top