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Simple sequencing using common 5-pin auto relays

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Gilles

Joined: 16 May 2020
Posts: 33

Posted: Wed Aug 09, 2023 12:10 am Post subject: Simple sequencing using common 5-pin auto relays

Le 09/08/2023 Ã  03:13, user9253 a       Ã©critÂ :

     

      	  Quote: 	
		          	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com> (fransew(at)gmail.com)



You are right Matt.  I did not read your original post carefully enough.

You wrote, "mounting one as a toggle switch sideways that can be pulled towards a guarded starter button. . . "

I think that is the best solution instead of complicating the circuit with relays or electronic timers.  

My 912ULS also requires 3 hands to start.  One hand pulls the choke, one hand turns the start key.  It starts within 2 seconds. 

Then I have to push the choke in and lock it while simultaneously advancing the throttle.  It is not easy, but doable.



	
     	
     



          

Hello all,     

This conversation rang a bell.     

In 2016-2017 I was asked to design the electrical architecture       for a 912 IS installation in a light aircraft they intended to       certify with EASA.     

To avoid the multiplicity of switches I proposed the use of a       rotating key selector for the Rotax complicated start sequence,       with a spring loaded "starter engage" position. The electronic       lane and pump test switches were spring loaded to avoid any pilot       error.     

[img]cid:part1.C3ng0M7d.NioiV3cn(at)free.fr[/img]     

The start power was automatically disconnected as soon as bus       power exceeded ~13V, and is now managed by the single lever       system.     

This setup was accepted by the EASA certification team without       any problem.     

FWIW

          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

iF8cAFeZ3BCtBynp.jpg

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_________________
Best regards,
Gilles
http://contrails.free.fr

Voyager

Joined: 30 Jun 2020
Posts: 77

Posted: Wed Aug 09, 2023 3:39 am Post subject: Simple sequencing using common 5-pin auto relays

Hi Gilles,



I understand the separate emergency power switch and am doing that also.  I understand pumps and momentary start for starter engage.  However what is the run position for? Does run activate the start power?  If that is the case, what turns off the start power after engine start? Separate logic behind the scenes?  Is this switch commercially available or proprietary to the company you worked with?

Matt



Sent from my iPad



 	  Quote: 	
		  On Aug 9, 2023, at 4:12 AM, Gilles T <gilles.thesee(at)free.fr> wrote:



ï»¿                   Le 09/08/2023 Ã  03:13, user9253 a       Ã©crit :

     

      	  Quote: 	
		          	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com> (fransew(at)gmail.com)



You are right Matt.  I did not read your original post carefully enough.

You wrote, "mounting one as a toggle switch sideways that can be pulled towards a guarded starter button. . . "

I think that is the best solution instead of complicating the circuit with relays or electronic timers.  

My 912ULS also requires 3 hands to start.  One hand pulls the choke, one hand turns the start key.  It starts within 2 seconds. 

Then I have to push the choke in and lock it while simultaneously advancing the throttle.  It is not easy, but doable.



	
     	
     



          

Hello all,     

This conversation rang a bell.     

In 2016-2017 I was asked to design the electrical architecture       for a 912 IS installation in a light aircraft they intended to       certify with EASA.     

To avoid the multiplicity of switches I proposed the use of a       rotating key selector for the Rotax complicated start sequence,       with a spring loaded "starter engage" position. The electronic       lane and pump test switches were spring loaded to avoid any pilot       error.     

<iF8cAFeZ3BCtBynp.jpg>

     

The start power was automatically disconnected as soon as bus       power exceeded ~13V, and is now managed by the single lever       system.     

This setup was accepted by the EASA certification team without       any problem.     

FWIW

          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

Gilles

Joined: 16 May 2020
Posts: 33

Posted: Wed Aug 09, 2023 4:27 am Post subject: Simple sequencing using common 5-pin auto relays

Le 09/08/2023 Ã  13:38, Matthew S.       Whiting a Ã©critÂ :

     

      	  Quote: 	
		                Hi Gilles,       

       

       I understand the separate emergency power switch and am doing         that also. Â I understand pumps and momentary start for starter         engage. Â However what is the run position for? Does run activate         the start power? Â If that is the case, what turns off the start         power after engine start? Separate logic behind the scenes? Â Is         this switch commercially available or proprietary to the company         you worked with?

       

       

     	
     



          

Hello Matt,     

Out of memory - it's been 6-7 years - the idea was positions 2,3,       4 would have "start power" activated. 

          

Pos 3 hasÂ  pumps + Lanes activated.     

So the "Run" position is pump + lanes and is the "normal" flight       position.

          

Pos 4 activates the starter motor and energizes the correct pump       as specified by Rotax.     

I had a British firm manufacture a couple of keyswitches as per       my specs in order to wire the prototype.

          

Yes a simple comparator circuit was designed to disconnect "start       power" once the engine alternator charges. In case of failure,       Rotax assured me that there was no drawback running an entire       flight with "start power" still connected.

          

[img]cid:part1.Gh6IqqET.5N0TE7WF(at)free.fr[/img]     

Pump and lane test switch are momentary.

          

The idea was to avoid any pilot error or omission in the pump or       lane sequence.     

Hope this helps

          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

wM80ABDJmdd67mHZ.jpg

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_________________
Best regards,
Gilles
http://contrails.free.fr

Voyager

Joined: 30 Jun 2020
Posts: 77

Posted: Wed Aug 09, 2023 4:47 am Post subject: Simple sequencing using common 5-pin auto relays

Gilles,



Your design is very much like what I am trying to achieve in my home built, but with COTS parts and not having to build custom hardware.  I am trying to essentially automate out the gymnastics that Rotax failed to engineer out of their engine start sequence.  I am still amazed they havenâ€™t done that as a computer controlled engine could easily drive the appropriate sequence and make starting a Rotax as simple as starting a car.

I have searched and not found an available switch like you describe which seems odd given the growing popularity of the Rotax engines.

Matt



Sent from my iPad



 	  Quote: 	
		  On Aug 9, 2023, at 8:29 AM, Gilles T <gilles.thesee(at)free.fr> wrote:



ï»¿                   Le 09/08/2023 Ã  13:38, Matthew S.       Whiting a Ã©crit :

     

      	  Quote: 	
		                Hi Gilles,       

       

       I understand the separate emergency power switch and am doing         that also.  I understand pumps and momentary start for starter         engage.  However what is the run position for? Does run activate         the start power?  If that is the case, what turns off the start         power after engine start? Separate logic behind the scenes?  Is         this switch commercially available or proprietary to the company         you worked with?

       

       

     	
     



          

Hello Matt,     

Out of memory - it's been 6-7 years - the idea was positions 2,3,       4 would have "start power" activated. 

          

Pos 3 has  pumps + Lanes activated.     

So the "Run" position is pump + lanes and is the "normal" flight       position.

          

Pos 4 activates the starter motor and energizes the correct pump       as specified by Rotax.     

I had a British firm manufacture a couple of keyswitches as per       my specs in order to wire the prototype.

          

Yes a simple comparator circuit was designed to disconnect "start       power" once the engine alternator charges. In case of failure,       Rotax assured me that there was no drawback running an entire       flight with "start power" still connected.

          

<wM80ABDJmdd67mHZ.jpg>

     

Pump and lane test switch are momentary.

          

The idea was to avoid any pilot error or omission in the pump or       lane sequence.     

Hope this helps

          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

Gilles

Joined: 16 May 2020
Posts: 33

Posted: Wed Aug 09, 2023 6:59 am Post subject: Simple sequencing using common 5-pin auto relays

Le 09/08/2023 Ã  14:46, Matthew S.       Whiting a Ã©critÂ :

     

      	  Quote: 	
		                Gilles,       

           

       Your design is very much like what I am             trying to achieve in my home built, but with COTS parts and             not having to build custom hardware. Â I am trying to             essentially automate out the gymnastics that Rotax failed to             engineer out of their engine start sequence. Â I am still             amazed they havenâ€™t done that as a computer controlled             engine could easily drive the appropriate sequence and make             starting a Rotax as simple as starting a car.

       

           

       I have searched and not found an available             switch like you describe which seems odd given the growing             popularity of the Rotax engines.

       

       

     	
     



          

Hi again, Matt,     

No doubt the whole sequence can be automated with an Arduino or       something. Some factories already did that, but I personnally have       some preference for hard wiring and "human" sequencing when it       comes to the engine. And automation means electric power and not       always obvious failure modes and mitigation.

          

Having a modular keyswitch wired for a given sequence seems       pretty standard for some suppliers, and only cost a couple of       dozen bucks, quid or whatever      

At the time Rotax IS builders were proud to advertize their neat       rows of several switches, cleverly located so you can pull one       while pushing on the other. Like other Diesel aero engines, like       starting a locomotive.     

A pilot error waiting to happen...     

This is how they adapted the proposed principle, as viewed on a       production aircraft at Friedrichshafen     

[img]cid:part1.01pqU4D7.NT2CZw00(at)free.fr[/img]     -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

Jva5jc3uRCye5RHK.jpg

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_________________
Best regards,
Gilles
http://contrails.free.fr

Voyager

Joined: 30 Jun 2020
Posts: 77

Posted: Wed Aug 09, 2023 7:10 am Post subject: Simple sequencing using common 5-pin auto relays

Well, when every firing of your spark plugs and fuel injectors is running off a computer, I am not too worried about the computer controlling a couple of simple functions at engine start.  



Matt



Sent from my iPad



 	  Quote: 	
		  On Aug 9, 2023, at 11:06 AM, Gilles T <gilles.thesee(at)free.fr> wrote:



ï»¿                   Le 09/08/2023 Ã  14:46, Matthew S.       Whiting a Ã©crit :

     

      	  Quote: 	
		                Gilles,       

           

       Your design is very much like what I am             trying to achieve in my home built, but with COTS parts and             not having to build custom hardware.  I am trying to             essentially automate out the gymnastics that Rotax failed to             engineer out of their engine start sequence.  I am still             amazed they havenâ€™t done that as a computer controlled             engine could easily drive the appropriate sequence and make             starting a Rotax as simple as starting a car.

       

           

       I have searched and not found an available             switch like you describe which seems odd given the growing             popularity of the Rotax engines.

       

       

     	
     



          

Hi again, Matt,     

No doubt the whole sequence can be automated with an Arduino or       something. Some factories already did that, but I personnally have       some preference for hard wiring and "human" sequencing when it       comes to the engine. And automation means electric power and not       always obvious failure modes and mitigation.

          

Having a modular keyswitch wired for a given sequence seems       pretty standard for some suppliers, and only cost a couple of       dozen bucks, quid or whatever      

At the time Rotax IS builders were proud to advertize their neat       rows of several switches, cleverly located so you can pull one       while pushing on the other. Like other Diesel aero engines, like       starting a locomotive.     

A pilot error waiting to happen...     

This is how they adapted the proposed principle, as viewed on a       production aircraft at Friedrichshafen     

<Jva5jc3uRCye5RHK.jpg>

     -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

Gilles

Joined: 16 May 2020
Posts: 33

Posted: Wed Aug 09, 2023 7:22 am Post subject: Simple sequencing using common 5-pin auto relays

Le 09/08/2023 Ã  17:09, Matthew S.       Whiting a Ã©critÂ :

     

      	  Quote: 	
		                Well, when every firing of your spark plugs and           fuel injectors is running off a computer, I am not too worried           about the computer controlling a couple of simple functions at           engine start. Â        

       

     	
     



          

As long as your chips are as robust, redundant and proved as       theirs and you performed the same amount of tests and failure mode       analyses 

          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

_________________
Best regards,
Gilles
http://contrails.free.fr

Gilles

Joined: 16 May 2020
Posts: 33

Posted: Wed Aug 09, 2023 8:00 am Post subject: Simple sequencing using common 5-pin auto relays

Le 09/08/2023 Ã  17:38, Alec Myers a       Ã©critÂ :

     

      	  Quote: 	
		          	  Quote: 	
		  --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com> (alec(at)alecmyers.com)



This is prime territory for an 8-bit PIC microcontroller. Code that is only 30 lines long is easy to test, and the hardware already exists in the billions.



	
     	
     



          

Some ultralight manufacturer did that and was approved by EASA.     

That said, after chatting with the designer at Fried 2018 I       didn't get a clear idea of what was doing what in the sequence.     

Maybe old fashioned pilot preferences, a bit like having a       microcontroller managing the trims during flaps maneuvering when       trim forces are light, or having electric flaps when manual would       do the same, etc.     

For instance my digitally regulated soldering iron is a pain to       adjust and loses settings, when I could have ordered the manual       potentiometer version doing the same, just quicker      

I'm not against electricity and automation as a means to an end,       but I hate wondering "what's it doing now?"     

That said I'd be much interested in having details on Matt's       final realization.

          



          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

_________________
Best regards,
Gilles
http://contrails.free.fr

Voyager

Joined: 30 Jun 2020
Posts: 77

Posted: Wed Aug 09, 2023 8:23 am Post subject: Simple sequencing using common 5-pin auto relays

I agree that a small microcontroller would be a decent solution, however, my coding skills are more than a decade rusty and it would take me far more time to get up to speed again than it is worth.  And the reality is that the system would likely not be maintainable down the road.



I am going with a momentary switch and push button starter with separate switches for the lanes and fuel pumps.  On paper, it seems like my three relay and one diode solution will work and this will allow me to use the momentary toggle switch to latch the relay holding start power until the starter is engaged.  The starter relay will then take over the provision of start power as well as engaging the starter.  Once the starter push button is released, the start power should also release.

If this works great, if not, I will simply hold the momentary toggle while pushing the starter button and plan to mount them close together so that one hand can hopefully actuate both.  This is my fall back solution.

Matt



Sent from my iPad



 	  Quote: 	
		  On Aug 9, 2023, at 12:02 PM, Gilles T <gilles.thesee(at)free.fr> wrote:



ï»¿                   Le 09/08/2023 Ã  17:38, Alec Myers a       Ã©crit :

     

      	  Quote: 	
		          	  Quote: 	
		  --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com> (alec(at)alecmyers.com)



This is prime territory for an 8-bit PIC microcontroller. Code that is only 30 lines long is easy to test, and the hardware already exists in the billions.



	
     	
     



          

Some ultralight manufacturer did that and was approved by EASA.     

That said, after chatting with the designer at Fried 2018 I       didn't get a clear idea of what was doing what in the sequence.     

Maybe old fashioned pilot preferences, a bit like having a       microcontroller managing the trims during flaps maneuvering when       trim forces are light, or having electric flaps when manual would       do the same, etc.     

For instance my digitally regulated soldering iron is a pain to       adjust and loses settings, when I could have ordered the manual       potentiometer version doing the same, just quicker      

I'm not against electricity and automation as a means to an end,       but I hate wondering "what's it doing now?"     

That said I'd be much interested in having details on Matt's       final realization.

          



          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Wed Aug 09, 2023 8:50 am Post subject: Re: Simple sequencing using common 5-pin auto relays

How about this circuit? I am not necessarily recommending it, but I think that it does what you want.

Rotax Start Relay.png

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Joe Gores

Gilles

Joined: 16 May 2020
Posts: 33

Posted: Wed Aug 09, 2023 9:32 am Post subject: Simple sequencing using common 5-pin auto relays

Le 09/08/2023 Ã  18:22, Matthew S.       Whiting a Ã©critÂ :

     

      	  Quote: 	
		                I agree that a small microcontroller would be a           decent solution, however, my coding skills are more than a           decade rusty and it would take me far more time to get up to           speed again than it is worth. Â And the reality is that the           system would likely not be maintainable down the road.       

           

       I am going with a momentary switch and push             button starter with separate switches for the lanes and fuel             pumps. Â On paper, it seems like my three relay and one diode             solution will work and this will allow me to use the             momentary toggle switch to latch the relay holding start             power until the starter is engaged. Â The starter relay will             then take over the provision of start power as well as             engaging the starter. Â Once the starter push button is             released, the start power should also release.

       

           

       If this works great, if not, I will simply             hold the momentary toggle while pushing the starter button             and plan to mount them close together so that one hand can             hopefully actuate both. Â This is my fall back solution.

     	
     



          

IIRC, "start power" is for powering the electronic lanes and       pumps until the engine alternator takes over. In my experience it       took some time until the engine was "autonomous".     

I would advise to try and make it physically impossible for a       pilot to take off with the pump or lane switches in the wrong       position.     

It happened to a buddy pilot who sometimes visits here, with the       914 infamous two-pump fuel system.     



          

BTW it occurs to me that I might have provided some background to       the choices I mentioned.     

The goal of the design team was certification of their project -       which they finally obtained - and in my experience certifying       means convincing "your" system or structure expert that he won't       be sued should something happen with your setup after he approves       it.     

So sitting with him I had to demonstrate how things wouldn't go       hairy if my little "Start power" device failed.      	  Quote: 	
		         

Fail to close => engine won't start.No crash.            

Fail to open => no incidence on engine as guaranteed by         Rotax. Safe continuation to destination.     	
     

On the other hand the engine/instruments "expert" didn't allow       the cute little digital backup instruments my partners liked and       they had to resort to classic steam gauges.     

And the clever optical low level fuel sensor had to give way to a       mechanical switch and idiot light due to the requirement to       analyse the 3rd party device and 5V power supply.     

Of course the above are constraints a homebuilder or ultralight       manufacturer isn't subject to.     

FWIW

          



          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

_________________
Best regards,
Gilles
http://contrails.free.fr

Voyager

Joined: 30 Jun 2020
Posts: 77

Posted: Wed Aug 09, 2023 10:15 am Post subject: Simple sequencing using common 5-pin auto relays

I would have to review the docs to be 100% sure, but I believe you are correct.  Start power is just to bootstrap the engine until the internal generators take over.  If my recollection is correct, the engine first uses generator B (the larger one) which is supposed to be online by 1500 RPM.  I have never started a Rotax, but others say the engine fires and gets to 1500 almost before you can release the starter switch.  I believe it then switches to generator A which is the one that runs the engine autonomously from the airframe, including separate ground.



If my memory from the Lockwood course is correct, this will be detected when the system voltage jumps from battery voltage to generator voltage as once generator A takes over the engine from generator B, generator B starts supplying power to the airframe and thus the voltage jump.  However, I believe the need for start power is long past by then.  Others with actual Rotax engine start experience will have to confirm as I am going solely on my course and reading of the manuals and have no real world experience yet with operating a Rotax.

My airplane is a homebuilt so certification isnâ€™t an issue, however, as a retired CS/EE/SE, I tend to design and build to a fairly high standard as that is simply my predisposition.



Sent from my iPad



 	  Quote: 	
		  On Aug 9, 2023, at 1:34 PM, Gilles T <gilles.thesee(at)free.fr> wrote:



ï»¿                   Le 09/08/2023 Ã  18:22, Matthew S.       Whiting a Ã©crit :

     

      	  Quote: 	
		                I agree that a small microcontroller would be a           decent solution, however, my coding skills are more than a           decade rusty and it would take me far more time to get up to           speed again than it is worth.  And the reality is that the           system would likely not be maintainable down the road.       

           

       I am going with a momentary switch and push             button starter with separate switches for the lanes and fuel             pumps.  On paper, it seems like my three relay and one diode             solution will work and this will allow me to use the             momentary toggle switch to latch the relay holding start             power until the starter is engaged.  The starter relay will             then take over the provision of start power as well as             engaging the starter.  Once the starter push button is             released, the start power should also release.

       

           

       If this works great, if not, I will simply             hold the momentary toggle while pushing the starter button             and plan to mount them close together so that one hand can             hopefully actuate both.  This is my fall back solution.

     	
     



          

IIRC, "start power" is for powering the electronic lanes and       pumps until the engine alternator takes over. In my experience it       took some time until the engine was "autonomous".     

I would advise to try and make it physically impossible for a       pilot to take off with the pump or lane switches in the wrong       position.     

It happened to a buddy pilot who sometimes visits here, with the       914 infamous two-pump fuel system.     



          

BTW it occurs to me that I might have provided some background to       the choices I mentioned.     

The goal of the design team was certification of their project -       which they finally obtained - and in my experience certifying       means convincing "your" system or structure expert that he won't       be sued should something happen with your setup after he approves       it.     

So sitting with him I had to demonstrate how things wouldn't go       hairy if my little "Start power" device failed.      	  Quote: 	
		         

Fail to close => engine won't start.No crash.            

Fail to open => no incidence on engine as guaranteed by         Rotax. Safe continuation to destination.     	
     

On the other hand the engine/instruments "expert" didn't allow       the cute little digital backup instruments my partners liked and       they had to resort to classic steam gauges.     

And the clever optical low level fuel sensor had to give way to a       mechanical switch and idiot light due to the requirement to       analyse the 3rd party device and 5V power supply.     

Of course the above are constraints a homebuilder or ultralight       manufacturer isn't subject to.     

FWIW

          



          -- 

       Best regards

       Gilles

       http://contrails.free.fr

       http://lapierre.skunkworks.free.fr

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