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fuel transfer controller, revisited

 
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ceengland7(at)gmail.com
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PostPosted: Wed Sep 18, 2019 7:28 am    Post subject: fuel transfer controller, revisited Reply with quote

Hi guys,

In my homebuilt project, I have aux tank(s) that must be pumped to the main
tank for engine supply, on an engine that uses automotive style high
pressure injection with a regulator return line to the main tank. (Personal
preference vs the complexity of a 4-selection duplex valve)

Thought I'd tap the brain trust for how best to execute an idea for an
automated fuel transfer controller. Liquid level controllers are readily
available now, but most I've found are almost 'too clever' for what I want,
using simple bare wire for probes in a water tank. What I'd like is a
controller that could look to the variable voltage seen by our typical fuel
gauges/EFISs from 'standard' Stewart Warner type resistive sensors for
level sensing, instead of separate probes, optical sensors, etc.

For my AFS engine monitor circuit, the tank sensor, according to AFS:
'It will be pulled up to ~4v. So with the 40-240Ω you will see 0.1 to 1.0V
.'

Since the sensor goes to 40 ohms at full and is referenced to ground, That
means 1.0 V at empty, and 0.1 V at full. ( I suspect that this is fairly
typical for gauges using SW resistive sensors.)

So my idea of an ideal circuit is this:

*An *adjustable* setpoint for pump turn-on, when voltage *rises* to say,
0.6V, and pump turn-off when voltage *falls* to say, 0.2V (to avoid
overfilling the tank). I'd consider the adjustable feature to be essential,
due to variations in float arms, tanks, supply voltage to the sensor/gauge
(might be 14V in some cases), etc. *A 'nice to have' additional feature for
others would allow inverting the voltage measurements, since some
installations might expect the resistive sensor to be at 240 ohms when full


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ceengland7(at)gmail.com
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PostPosted: Wed Sep 18, 2019 7:31 am    Post subject: fuel transfer controller, revisited Reply with quote

OOPS; forgot an important point:
Since the device will operate in parallel with an existing gauge (or input to an EFIS), the voltage sensing circuit obviously needs to present a relatively high impedance to avoid affecting the existing measurements.
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On Tue, Sep 17, 2019 at 10:25 PM Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:

Quote:
Hi guys,
In my homebuilt project, I have aux tank(s) that must be pumped to the main tank for engine supply, on an engine that uses automotive style high pressure injection with a regulator return line to the main tank. (Personal preference vs the complexity of a 4-selection duplex valve)
Thought I'd tap the brain trust for how best to execute an idea for an automated fuel transfer controller. Liquid level controllers are readily available now, but most I've found are almost 'too clever' for what I want, using simple bare wire for probes in a water tank. What I'd like is a controller that could look to the variable voltage seen by our typical fuel gauges/EFISs from 'standard' Stewart Warner type resistive sensors for level sensing, instead of separate probes, optical sensors, etc. 
For my AFS engine monitor circuit, the tank sensor, according to AFS:
'It will be pulled up to ~4v. So with the 40-240Ω you will see 0.1 to 1.0V .'

   

Since the sensor goes to 40 ohms at full and is referenced to ground, That means 1.0 V at empty, and 0.1 V at full. ( I suspect that this is fairly typical for gauges using SW resistive sensors.) 
So my idea of an ideal circuit is this: 
An *adjustable* setpoint for pump turn-on, when voltage *rises* to say, 0.6V, and pump turn-off when voltage *falls* to say, 0.2V (to avoid overfilling the tank). I'd consider the adjustable feature to be essential, due to variations in float arms, tanks, supply voltage to the sensor/gauge (might be 14V in some cases), etc. A 'nice to have' additional feature for others  would allow inverting the voltage measurements, since some installations might expect the resistive sensor to be at 240 ohms when full.
Any thoughts on a simple circuit to do this? Every off-the-shelf controller I've found uses switches, triggers, etc, instead of voltage comparators. The two most common ICs are the LM324 (using one section as an oscillator to generate a low voltage AC to excite the probes), and a 555 timer IC (much simpler circuit, but no provision for voltage sensing for trigger).
Thanks for any thoughts,
Charlie
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Joined: 28 Mar 2008
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Location: Riley TWP Michigan

PostPosted: Wed Sep 18, 2019 7:52 am    Post subject: Re: fuel transfer controller, revisited Reply with quote

Charlie, a search on the internet found this thread:
https://forum.allaboutcircuits.com/threads/voltage-controlled-switch.63998/


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PostPosted: Wed Sep 18, 2019 9:03 am    Post subject: fuel transfer controller, revisited Reply with quote

Charlie,

Believe your approach is too "clever". For example, your specifications have no way to turn off the pump when the aux tanks are empty and the mains are low. Nor is there any way to turn on the pump when the fuel sensor fails.

Suggest a simple push button activated timer circuit that stays on for about 20% of the aux tank capacity is a simpler, more reliable approach. See the May issue of Kitplanes for a detailed description of such a circuit and how to use it.

Or a simpler version of the same circuit can be found at the Glassair Owners Association website under the tag "fuel".

If you don't have access to these on-line drop me a note and I can email you the source files.

I also have a manuscript for a gadget that correctly detects net fuel flow in a return line installation. Cost: about $2.00 in parts plus the flow transducers.

Tom Kuffel
kuffel(at)cyberport.net (kuffel(at)cyberport.net)
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PostPosted: Wed Sep 18, 2019 11:10 am    Post subject: fuel transfer controller, revisited Reply with quote

Are the AUX tanks higher than the main? At the wing tips vs. root, for instance?
If so, get rid of the electronics completely. Put a float controlled valve on port on the main tank, and have it fed from a low point on the AUX tank.


On Wednesday, September 18, 2019, 11:29:11 AM EDT, Charlie England <ceengland7(at)gmail.com> wrote:




Hi guys,
In my homebuilt project, I have aux tank(s) that must be pumped to the main tank for engine supply, on an engine that uses automotive style high pressure injection with a regulator return line to the main tank. (Personal preference vs the complexity of a 4-selection duplex valve)
Thought I'd tap the brain trust for how best to execute an idea for an automated fuel transfer controller. Liquid level controllers are readily available now, but most I've found are almost 'too clever' for what I want, using simple bare wire for probes in a water tank. What I'd like is a controller that could look to the variable voltage seen by our typical fuel gauges/EFISs from 'standard' Stewart Warner type resistive sensors for level sensing, instead of separate probes, optical sensors, etc.
For my AFS engine monitor circuit, the tank sensor, according to AFS:
'It will be pulled up to ~4v. So with the 40-240Ω you will see 0.1 to 1.0V .'



Since the sensor goes to 40 ohms at full and is referenced to ground, That means 1.0 V at empty, and 0.1 V at full. ( I suspect that this is fairly typical for gauges using SW resistive sensors.)
So my idea of an ideal circuit is this:
An *adjustable* setpoint for pump turn-on, when voltage *rises* to say, 0.6V, and pump turn-off when voltage *falls* to say, 0.2V (to avoid overfilling the tank). I'd consider the adjustable feature to be essential, due to variations in float arms, tanks, supply voltage to the sensor/gauge (might be 14V in some cases), etc. A 'nice to have' additional feature for others would allow inverting the voltage measurements, since some installations might expect the resistive sensor to be at 240 ohms when full.
Any thoughts on a simple circuit to do this? Every off-the-shelf controller I've found uses switches, triggers, etc, instead of voltage comparators. The two most common ICs are the LM324 (using one section as an oscillator to generate a low voltage AC to excite the probes), and a 555 timer IC (much simpler circuit, but no provision for voltage sensing for trigger).
Thanks for any thoughts,
Charlie
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PostPosted: Wed Sep 18, 2019 11:16 am    Post subject: fuel transfer controller, revisited Reply with quote

On 9/18/2019 10:52 AM, user9253 wrote:
Quote:


Charlie, a search on the internet found this thread:
https://forum.allaboutcircuits.com/threads/voltage-controlled-switch.63998/

--------
Joe Gores

Thanks for the link, and the reminder. I've been away from active

electronics work for so long, I'd completely forgotten about comparator
circuits. I'll do some more research on that path; I'd like to have
independently adjustable trigger points via trim pots, and a variation
on that circuit might allow it. The site looks like it could be useful
for a variety of other projects, as well.

Charlie

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PostPosted: Wed Sep 18, 2019 11:29 am    Post subject: fuel transfer controller, revisited Reply with quote

On 9/18/2019 12:00 PM, The Kuffels wrote:

Quote:
 Charlie,
 
Believe your approach is too "clever".  For example, your specifications have no way to turn off the pump when the aux tanks are empty and the mains are low.  Nor is there any way to turn on the pump when the fuel sensor fails.
 
Suggest a simple push button activated timer circuit that stays on for about 20% of the aux tank capacity is a simpler, more reliable approach.  See the May issue of Kitplanes for a detailed description of such a circuit and how to use it.
 
Or a simpler version of the same circuit can be found at the Glassair Owners Association website under the tag "fuel".
 
If you don't have access to these on-line drop me a note and I can email you the source files.
 
I also have a manuscript for a gadget that correctly detects net fuel flow in a return line installation.  Cost: about $2.00 in parts plus the flow transducers.
 
Tom Kuffel
kuffel(at)cyberport.net (kuffel(at)cyberport.net)

Hi Tom,

I appreciate the warning, since any of us can get lost in the weeds (get too clever). In this case, though, I already have a 'no fuel present' optical sensor in the supply line to the transfer pump(s). I was afraid my initial narrative would get so long that I didn't try to describe every detail; only the specific function that I'm having trouble finalizing. I also intend manual switch control to both stop and start transfers if problems develop.

Thanks for the link to the Glassair site for the timer circuit; a simple timer has always been 'plan B'. I do have a subscription to Kitplanes (all homebuilders should, in my opinion), so I'm good there.  I'd love to see your return flow compensation circuit, though it's not an issue for this particular installation (flow sensor is downstream of the regulator bypass). I'd be *really* excited if you could do it for $2 without the need of an extra $150 flow sensor. Smile
If you don't mind sending it, my email address is
ceengland7(at)gmail.com (ceengland7(at)gmail.com).

Thanks,

Charlie
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PostPosted: Wed Sep 18, 2019 11:45 am    Post subject: fuel transfer controller, revisited Reply with quote

Not high enough to matter; it's an RV-7 with 'wet wing' leading edge tanks outboard of the mains. About 3 lbs weight gain total for the tanks themselves & fuel lines, plus the weight of redundant Facet transfer pumps in the fuselage.

The -7 is acro-qualified, but not with fuel weight in the outboard sections of the wings. I've probably seen all the various tank building and transfer methods, and none of the passive transfer methods I've seen so far give me any confidence in being able to positively empty the aux tanks and know that no fuel will get back out there even when the main is full. The passive methods of transfer that I've seen also depend on the cap on the main tank being totally fuel tight (not a universal certainty with Van's caps) because the higher aux fuel will try to exit the main's cap when both are full. In addition, some of the schemes depend on re-arranging the vent system so that the main's vent ties to the aux outlet, and the aux supplies the vent for the whole system. I can't get comfortable with messing around with the vent system, either, regardless of acro issues.

The alternative engine is a radical enough change, so I tried to keep the actual fuel delivery path as close to 'stock' as possible, with the only mod to the fuel delivery main tank being its return line.

Charlie

On 9/18/2019 2:07 PM, Ernest Christley wrote:

Quote:
Are the AUX tanks higher than the main?  At the wing tips vs. root, for instance?


If so, get rid of the electronics completely.  Put a float controlled valve on port on the main tank, and have it fed from a low point on the AUX tank.




On Wednesday, September 18, 2019, 11:29:11 AM EDT, Charlie England <ceengland7(at)gmail.com> (ceengland7(at)gmail.com) wrote:




Hi guys,


In my homebuilt project, I have aux tank(s) that must be pumped to the main tank for engine supply, on an engine that uses automotive style high pressure injection with a regulator return line to the main tank. (Personal preference vs the complexity of a 4-selection duplex valve)


Thought I'd tap the brain trust for how best to execute an idea for an automated fuel transfer controller. Liquid level controllers are readily available now, but most I've found are almost 'too clever' for what I want, using simple bare wire for probes in a water tank. What I'd like is a controller that could look to the variable voltage seen by our typical fuel gauges/EFISs from 'standard' Stewart Warner type resistive sensors for level sensing, instead of separate probes, optical sensors, etc. 


For my AFS engine monitor circuit, the tank sensor, according to AFS:
'It will be pulled up to ~4v. So with the 40-240Ω you will see 0.1 to 1.0V .'

   

Since the sensor goes to 40 ohms at full and is referenced to ground, That means 1.0 V at empty, and 0.1 V at full. ( I suspect that this is fairly typical for gauges using SW resistive sensors.) 


So my idea of an ideal circuit is this: 


An *adjustable* setpoint for pump turn-on, when voltage *rises* to say, 0.6V, and pump turn-off when voltage *falls* to say, 0.2V (to avoid overfilling the tank). I'd consider the adjustable feature to be essential, due to variations in float arms, tanks, supply voltage to the sensor/gauge (might be 14V in some cases), etc. A 'nice to have' additional feature for others  would allow inverting the voltage measurements, since some installations might expect the resistive sensor to be at 240 ohms when full.


Any thoughts on a simple circuit to do this? Every off-the-shelf controller I've found uses switches, triggers, etc, instead of voltage comparators. The two most common ICs are the LM324 (using one section as an oscillator to generate a low voltage AC to excite the probes), and a 555 timer IC (much simpler circuit, but no provision for voltage sensing for trigger).


Thanks for any thoughts,


Charlie


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Joined: 04 Nov 2018
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PostPosted: Thu Sep 19, 2019 7:01 am    Post subject: Re: fuel transfer controller, revisited Reply with quote

We went around a closely related topic on homebuiltairplanes.com a while back. I have a similar system, and I am electing to simply run one of two Facet pumps all the time to keep the header (main) tank full. The header (main) tank is only vented back to the source tank through a duplex valve, so yes, it is circulating fuel. I view having any additional switches, logic, timers, fuel level sensors, etc in the loop as being less reliable than running one pump with another in reserve. Having 150 miles worth of fuel in the header feels pretty good too.

Thread is https://www.homebuiltairplanes.com/forums/threads/transfer-pumps-and-fuel-system-configuration.30820/

There are others on there that I started about details of fuel systems, but they seem off topic for this thread.

Good luck

Bill


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PostPosted: Thu Sep 19, 2019 9:36 am    Post subject: fuel transfer controller, revisited Reply with quote

On 9/19/2019 10:01 AM, wsimpso1 wrote:
Quote:


We went around a closely related topic on homebuiltairplanes.com a while back. I have a similar system, and I am electing to simply run one of two Facet pumps all the time to keep the header (main) tank full. The header (main) tank is only vented back to the source tank through a duplex valve, so yes, it is circulating fuel. I view having any additional switches, logic, timers, fuel level sensors, etc in the loop as being less reliable than running one pump with another in reserve. Having 150 miles worth of fuel in the header feels pretty good too.

Thread is https://www.homebuiltairplanes.com/forums/threads/transfer-pumps-and-fuel-system-configuration.30820/

There are others on there that I started about details of fuel systems, but they seem off topic for this thread.

Good luck

Bill
Hi Bill,


I think that technique has a lot of merit in a lot of situations, but as
I mentioned in another post, my plane is acro-capable, and I need to
preserve the ability to *know* that the auxs are empty for acro. Another
factor is that in this plane, two of the three auxs will almost never
have fuel in them (only for extended out/back legs with no refueling).

I'm trying to keep the fuel-delivery tank as close to 'as designed' as I
possibly can, and still be able to use auto style fuel injection and get
aux fuel to it.

Thanks,

Charlie

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Joined: 11 Oct 2019
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PostPosted: Sun Oct 13, 2019 9:30 pm    Post subject: Re: fuel transfer controller, revisited Reply with quote

The controller refers to a master device that changes the wiring of the main circuit or the control circuit in a predetermined order and changes the resistance value in the circuit to control the starting, speeding, braking, and reversing of the motor. It consists of a program counter, an instruction register, an instruction decoder, a timing generator, and an operation controller. It is the "decision-making body" that issues commands, that is, completes the coordination and direct operation of the entire computer system.
Controller model (AD8311ACBZ-P7)


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PostPosted: Mon Oct 14, 2019 7:15 am    Post subject: fuel transfer controller, revisited Reply with quote

At 12:30 AM 10/14/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "MasterKang" <WilheminaSuazoTJF(at)yahoo.com>

The controller refers to a master device . . .

<snip>

Not a registered member of this list.
Ignore as SPAM


Bob . . .


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