3-wire Idle Control Solenoid

[DerekAE86]

I'm a little confused how the 3-wire solenoid setup works behind the scenes because the help file seems to indicate opposite of the software settings.

The help file says to wire the common pin to power, the pin that closes the valve when ground is applied to Aux1 and the pin that opens the valve to Aux2. Then set the Active State in the software to High.

That doesn't make sense straight up because the PWM Aux are outputs Active High or Low (on) and Floating (off), right?
So that means it would switch between High and Floating. So if the common pin is also High (14v) then nothing would happen?

The next thing that's odd is when you select the 3-wire solenoid in the software Aux1 gets named "Open" and Aux2 "Close". Which is the opposite to the help file.

So my guess is when "3-wire Idle Solenoid" is selected the "Active State" no longer means High or Low, it's always Low - it just inverts the duty cycle instead. (eg: commanding 80% low duty when set to "Active Low" would command 20% low duty when set to "Active High". That way if you accidently wired it backwards you can just swap it in software like the help file says.

Though then I'm left with the question - how exactly does the idle control operate in 3-wire mode?
Assuming the "neutral state" of the solenoid is 50% open. Low on Aux1 opens it further, Low on Aux2 closes it further.

Is it a constant "tug of war" between the two outputs?
ie: 80% would command 80% low duty on Aux1 and 20% low duty on Aux2
and 30% would command 30% low duty on Aux1 and 70% low duty on Aux2

Or does only one side operate at a time?
ie: 90% would command around 75% low duty on Aux1 and nothing on Aux2 (floating)
15% would command nothing on Aux1 (floating) and around 65% low duty on Aux2
and 50% would command nothing on either output (both floating and valve in neutral state)

 

[Adamw]

Wire as per the help file with aux 1 active state set to high and it will work correctly.  In reality it doesn't matter anymore which way you wire the valve, if it works in the wrong direction just flip the active state setting.  

Active state does not change the drive type from lowside to highside, it only changes whether the aux 1 output is high or low when active.  Aux 2 is always doing the opposite of aux 1. 

So, with active state set to high and an idle valve command of 100% you will have 100% high on Aux 1 and 100% low on aux 2, 100% of the current will be flowing through the open winding so the valve will be 100% open.  If you command a valve position of 25% then Aux 1 will be high for 25% of the cycle time (low for 75% of the cycle time), aux 2 will be low for 25% of the cycle time (high for 75% of the cycle), you have 25 % of the current flowing through the open winding, 75% of the current flowing through the close winding, the valve will be 25% open.  

I agree the pin labels for the runtimes confuse the issue, I assume this was probably originally done based on low-side drive outputs active state defaulting to low. 

[koracing]

If you ever get the chance, plug one in while it's unmounted where you can see the flapper movement.  Then set the base position up and down and watch it move.  The spring loaded flapper nominally sits in a "center" position, and one side pin has to be grounded to get it to move toward fully open, and the opposite pin needs to be grounded to move toward fully closed.  Because two outputs are used to allow the full range of movement, they have to work in equal and opposite unison the way @Adamw describes.  

That said, I really wish there was a setting in the link to command fully closed when on boost.  It never drops below minimum duty cycle in the idle settings unfortunately.  You can make a 3D base position table to get close, but it's a feature I would like to see added.

[DerekAE86]

6 hours ago, Adamw said:

Active state does not change the drive type from lowside to highside, it only changes whether the aux 1 output is high or low when active.  Aux 2 is always doing the opposite of aux 1. 

 

6 hours ago, Adamw said:

I agree the pin labels for the runtimes confuse the issue, I assume this was probably originally done based on low-side drive outputs active state defaulting to low. 

Yep I think this was what I was getting caught up on. The confusion between Lowside/Highside drivers and what's considered "Active" in the software.

It clears it up though. Thanks.