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IVO Prop current limiter
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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jul 09, 2017 8:26 am Post subject: IVO Prop current limiter

At 12:45 PM 7/8/2017, you wrote:

  	  Quote: 	
		  Sorry - defective iPhones and all that.



 Possible simplifications to consider: 



 - If youâ€™re using a PIC maybe you could dispense with the current limiter. If you sense the current the PIC can send the FET high impedance within a few microseconds. 	


    The motor's current profile is rather trashy.

    Without active current limiting, you'll have

    motor inrush currents during spin-up.



    As I recall the mechanical details of this

    product, the prop-pitch mechanism has soft

    stops that will compress as the mechanism

    approaches limits causing the motor current

    to ramp up toward stall current.



    The original design goal was to tolerate a

    deliberate opening of the prop pitch circuit

    breaker . . . which is a rather slow device . . .

    on the order of hundreds of milliseconds.



    All this electron/silicon herding does is

    get us a more predictable, solid state

    replacment for the thermal breaker. The

    current limiter adds one transistor

    and one resistor and offers a predictable

    upper bound on stall current.



 

   Bob . . .

paulf(at)hughes.net
Guest

Posted: Sun Jul 09, 2017 5:43 pm Post subject: IVO Prop current limiter

Eric - See Bob's redesign.  I was in the process of writing code       for your drawing when Bob sent his note. I now have a version of       the software written (but not tested!) for both versions of the       hardware, so you just need to let me know which one you want to       pursue.     

Paul

          

     On 7/9/2017 11:06 AM, Robert L.       Nuckolls, III wrote:

     

      	  Quote: 	
		                At 08:59 AM 7/8/2017, you wrote:

       

        	  Quote: 	
		  The software that Bob         describes         would be pretty simple to write for the PIC12F683 chip, the same         chip we         used for the wig-wag open source project.  I'll volunteer to         contribute the software if someone wants to pursue Bob's         hardware design         using a PIC chip instead of the Arduino as an open source         project. 	
       

         I'm up to my eyeballs in a couple of development

         efforts along with juggling domestic duties . . .

         but if someone wants to brassboard this project,

         I'll volunteer to package it into a readily

         duplicated product.

       

         I've posted a proposed schematic of the controller

         at                http://tinyurl.com/ybbtw6dp

       

         A minimalist approach to packaging would

         look something like this. The fat power transistor

         would be on the bottom, heat transfer surface down.

         This would facilitate using airframe for heat-sinking

         like our schottky e-bus diode did. The connector

         would be 15 pin.  The ECB footprint would be about

         1.25 x 1.75 inches.  The 'kit' would look something

         like this except that the 700-2-7 switch is

         missing.

       

       

       

       

       [img]cid:part2.D1EE81D6.29A720F5(at)hughes.net[/img]

       

       

         Oh yeah, had a gray-matter fart while crafting the

         schematic. The software can get MUCH simpler.

       

         On power up, the initialization CLEARS the LIMIT

         LATCH and removes gate drive from the clamping

         fet.

       

         The analog input is monitored for amplitude greater

         than 0.5 volts; greater than 0.5 seconds whereupon

         the LIMIT LATCH is SET, gate of clamp fet goes

         high and removed drive from the current limit fet.

       

         An excursion below 0.5v will reset the LIMIT

         TIMER.

       

         After limit time out, the condition is sustained

         until next power-down/power-up event.

       

         I need to keep my head down on some more pressing

         tasks for the next 10 days or so. You guys can

         shepherd this along in the mean time.  

       

           Bob . . .

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Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Sun Jul 09, 2017 6:06 pm Post subject: Re: IVO Prop current limiter

 	  paulf(at)hughes.net wrote: 	
		  Eric - See Bob's redesign.  I was in the process of writing code for your drawing when Bob sent his note.  I now have a version of       the software written (but not tested!) for both versions of the hardware, so you just need to let me know which one you want to pursue.



Paul 	




Paul,



I was just composing a post to ask Bob a couple of questions in that vein.  Stand by while I sort that out and we'll press ahead shortly.



One question for you: am I correct in assuming that PIC outputs are push-pull (that is, when low, they actively pull to ground)?



Thanks,



Eric

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jul 09, 2017 7:12 pm Post subject: IVO Prop current limiter

At 09:06 PM 7/9/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>

 paulf(at)hughes.net wrote:

 > Eric - See Bob's redesign.  I was in the process of writing code for your drawing when Bob sent his note.  I now have a version of       the software written (but not tested!) for both versions of the hardware, so you just need to let me know which one you want to pursue.

 > 

 > Paul

 Paul,

 I was just composing a post to ask Bob a couple of questions in that vein.  Stand by while I sort that out and we'll press ahead shortly.

 One question for you: am I correct in assuming that PIC outputs are push-pull (that is, when low, they actively pull to ground)?

  The general purpose outputs are active pull-up/pull-down.

  A bit more robust in the pull down as I recall . . .

  Yes  the output will pull down to less than 0.6 v with a 8.5mA

  source.

 [img]cid:7.1.0.9.0.20170709220122.020de7f0(at)aeroelectric.com.0[/img] 

  Input will pull up to within 0.7 of Vdd with a 3.0mA sink

 [img]cid:7.1.0.9.0.20170709220122.020de7f0(at)aeroelectric.com.1[/img] 

   Bob . . .

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Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Sun Jul 09, 2017 7:33 pm Post subject: Re: IVO Prop current limiter

Paul / Bob,



One more question: with respect to GP3/MCLR, should it be left floating, pulled up to Vdd, or have an RC power-on-reset circuit?



Eric

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Sun Jul 09, 2017 7:58 pm Post subject: Re: IVO Prop current limiter

Bob,



I have a few questions/comments about your drawing (http://tinyurl.com/ybbtw6dp):



A.  The big current limit MOSFET is going to be in one of three states:



1. Fully on: The pilot has moved the switch, the PIC is powered on, and LIMIT LATCH is released, allowing motor drive voltage to pull up the MOSFET's gate through the 1k resistor.  Rds(on) is at minimum value and dissipation is negligible (less than 1/4W).



2. Fully off: The PIC sees >=0.5V for >0.5 sec on LIMIT SENSE.  LIMIT LATCH goes high, turning on the 2N7000, which pulls the MOSFET's gate to ground.  Dissipation is zero.  [0.5V = 7.5A motor current.]



3. Linear region: Motor current has spiked to >9A, causing the sense resistors and 2N3904 to regulate the MOSFET's gate to hold the 9A level.  Dissipation is high, but LIMIT LATCH will trip in 0.5 sec max, dropping it to zero.



So, it seems to me that unless we worry that the pilot will continue to cycle the switch in the stalled direction with the limit light illuminated, we don't need to be too concerned with heat sinking the MOSFET.  Your thoughts?



B.  You're powering the PIC from the motor drive voltage, but you mentioned in your reply to Alec Myers that this is likely to be a "trashy" rail.  Your new schematic only uses this rail to power the PIC and pull up the current limit MOSFET's gate.  Could we eliminate the two 1N4001 diodes and the wires linking them to the switch, and instead bring in a constant supply on a single wire from the bus side of the switch?  Is there some benefit to turning the PIC on and off with the prop switch?



C.  Your current sense resistor is shown rated at 2W.  I've calculated 2.4W dissipation at 6A motor current, rising to 3.75W at 7.5A and 5.4W at 9A.  I used three 0.2R 3W resistors in parallel to get 0.066667 ohms at 9W.



D.  The 2N7000 that switches the TRAVEL LIMIT light can tolerate Vds=Vdg=60V.  What is the 24V Zener diode doing?



Cheers,



Eric

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 10, 2017 4:18 am Post subject: IVO Prop current limiter

At 10:59 PM 7/9/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>



 Bob,



 I have a few questions/comments about your drawing ( http://tinyurl.com/ybbtw6dp ( http://tinyurl.com/ybbtw6dp)):



 

 A.  The big current limit MOSFET is going to be in one of three states:



 1. Fully on: The pilot has moved the switch, the PIC is powered on, and LIMIT LATCH is released, allowing motor drive voltage to pull up the MOSFET's gate through the 1k resistor.  Rds(on) is at minimum value and dissipation is negligible (less than 1/4W). 	


   yes



 

  	  Quote: 	
		  2. Fully off: The PIC sees >=0.5V for >0.5 sec on LIMIT SENSE.  LIMIT LATCH goes high, turning on the 2N7000, which pulls the MOSFET's gate to ground.  Dissipation is zero.  [0.5V = 7.5A motor current.] 	


   yes



 

  	  Quote: 	
		  3. Linear region: Motor current has spiked to >9A, causing the sense resistors and 2N3904 to regulate the MOSFET's gate to hold the 9A level.  Dissipation is high, but LIMIT LATCH will trip in 0.5 sec max, dropping it to zero. 	


   yes . . . 



 

  	  Quote: 	
		  So, it seems to me that unless we worry that the pilot will continue to cycle the switch in the stalled direction with the limit light illuminated, we don't need to be too concerned with heat sinking the MOSFET.  Your thoughts? 	


   the fat fet needs some heat sinking but

   just enough thermal mass to keep the silicon in

   limits during the trip time-out interval. Generally,

   a metallic mounting base is enough. There's a cartoon

   of the board layout below . . . the fet is on the bottom

   of the board with heat-sink surface facing down to

   contact mounting surface. This is something to be

   explored in development . . . see if you can deliberately

   smoke one!



 



  	  Quote: 	
		  B.  You're powering the PIC from the motor drive voltage, but you mentioned in your reply to Alec Myers that this is likely to be a "trashy" rail.  Your new schematic only uses this rail to power the PIC and pull up the current limit MOSFET's gate.  Could we eliminate the two 1N4001 diodes and the wires linking them to the switch, and instead bring in a constant supply on a single wire from the bus side of the switch?  Is there some benefit to turning the PIC on and off with the prop switch? 	


    The current signal will be trashy but the supply

    voltage comes from the bus (low impedance source).

    The precision shunt zener combined with the 10uf

    Vdd capacitor will offer us a very clean source

    of power for the pic.



 



  	  Quote: 	
		  C.  Your current sense resistor is shown rated at 2W.  I've calculated 2.4W dissipation at 6A motor current, rising to 3.75W at 7.5A and 5.4W at 9A.  I used three 0.2R 3W resistors in parallel to get 0.066667 ohms at 9W. 	


    Good eye, I wired 4 x .24 ohms in parallel as you can see

    below . . . while marginal for continuous operation

    at this dissipation level, half-second intervals

    will be no sweat . . . or should I say no smoke?



 



  	  Quote: 	
		  D.  The 2N7000 that switches the TRAVEL LIMIT light can tolerate Vds=Vdg=60V.  What is the 24V Zener diode doing?

 	
   Yeah . . . probably not really necessary . . . just

    a carry-over from my DO-160 qualification days

    when I was obligated to put some protection on all i/o

    lines designed to clamp off very low energy, 300v

    spikes. In practice, that zener can probably

    be left off. 



    Here's how the board layout shaped up . . .



 [img]cid:.0[/img]



 

 

   Bob . . .

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alec(at)alecmyers.com
Guest

Posted: Mon Jul 10, 2017 4:38 am Post subject: IVO Prop current limiter

If for any reason the PIC crashes (cosmic rays? It does happen) when the motor reaches its limit the FET will sit in an intermediate impedance state dissipating high power for an indeterminate length of time, possibly long enough to be emit the magic smoke. Without adequate heat sinking for the FET the PIC software should use appropriate watchdog timers and brown-out protection to minimize this risk. This is more of a problem if the PIC is powered from the 12v rail because it will be operational for effectively unlimited time before the timer is called into operation. If the PIC is powered from the motor command voltage this risk is much reduced as the PIC run time begins only when the motor is first powered. 

The motor supply for sure is going to be trashy but PICs are designed to run in very unclean environments. I agree that clean rails are better than dirty ones but you could clean the motor supply rail with a simple RC network too.

 	  Quote: 	
		  On Jul 10, 2017, at 8:17 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		  3. Linear region: Motor current has spiked to >9A, causing the sense resistors and 2N3904 to regulate the MOSFET's gate to hold the 9A level.  Dissipation is high, but LIMIT LATCH will trip in 0.5 sec max, dropping it to zero. 	
  yes . . .

ceengland7(at)gmail.com
Guest

Posted: Mon Jul 10, 2017 6:00 am Post subject: IVO Prop current limiter

Just out of curiosity, wouldn't a Polyfuse, similar to what's used in a car's electric window circuit, do what you're after? They're available up to 14 A ratings.

http://www.mouser.com/Search/Refine.aspx?Keyword=polyfuse

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 10, 2017 6:22 am Post subject: IVO Prop current limiter

At 07:36 AM 7/10/2017, you wrote:

  	  Quote: 	
		  If for any reason the PIC crashes (cosmic rays? It does happen) when the motor reaches its limit the FET will sit in an intermediate impedance state dissipating high power for an indeterminate length of time, possibly long enough to be emit the magic smoke. 	


   That's true . . . but if we were going to do

   a reliability study for a PIC chip in a 

   high hazard application, we would find

   that the chip itself is probably good for

   10 to the minus bazzilion failures per

   operating hour. Given that this chip operates

   only seconds per flight hour, I think a

   high degree of confidence is not misguided. 



  	  Quote: 	
		  Without adequate heat sinking for the FET the PIC software should use appropriate watchdog timers and brown-out protection to minimize this risk. 	


   . . . but if the chip goes TU . . . what's

   the probability that built in safeguards are

   operating?



  	  Quote: 	
		   This is more of a problem if the PIC is powered from the 12v rail because it will be operational for effectively unlimited time before the timer is called into operation. If the PIC is powered from the motor command voltage this risk is much reduced as the PIC run time begins only when the motor is first powered. 	


   Exactly . . .



  	  Quote: 	
		  The motor supply for sure is going to be trashy but PICs are designed to run in very unclean environments. I agree that clean rails are better than dirty ones but you could clean the motor supply rail with a simple RC network too. 	


   The power supply configuration depicted has

   been used on products fully qualified under

   DO160 stresses for trash.  The 5v rail

   is very precise, rigid and clean.



 

   Bob . . .

paulf(at)hughes.net
Guest

Posted: Mon Jul 10, 2017 6:47 am Post subject: IVO Prop current limiter

For this application, if we go with Bob's most recent design, I suggest 

we leave GP3/MCLR float.  Unless we plan to use the MCLR function, I'll 

disable it in software making GP3 a "normal" input (I put normal in 

quotes because I can't do a weak pull up on GP3). I've had issues in the 

past with that pin unless I software disable it.



Bob answered your other questions, and way better than I could!!



Paul

On 7/9/2017 10:33 PM, Eric Page wrote:

 	  Quote: 	
		   



 Paul,



 One more question: with respect to GP3/MCLR, should it be left floating, pulled up to Vdd, or have an RC power-on-reset circuit?



 Eric





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=470839#470839

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 10, 2017 6:53 am Post subject: IVO Prop current limiter

At 08:59 AM 7/10/2017, you wrote:

  	  Quote: 	
		  Just out of curiosity, wouldn't a Polyfuse, similar to what's used in a car's electric window circuit, do what you're after? They're available up to 14 A ratings.

  http://www.mouser.com/Search/Refine.aspx?Keyword=polyfuse 	




   Probably. The advantage here is the limit annunciator

   light that would be very slow if it didn't illuminate

   until the pollyfuse warms up and operates.



   The disadvantage is that assuming you DID hold a command

   at the limit until the fuse operates, you would not be

   able to drive out of that limit until the fuse cools

   off . . . 



   We looked at polyfuses on three separate occasions

   at Lear and Beech over the years . . . aside from

   exploiting the benefits of inrush limiting on incandescent

   lamps (NTC devices), there wasn't enough going for them

   to encourage a development program. They're designed

   to install inside some piece of hardware. We would

   have to enclose and terminate the things to make them

   an airframe component.



   To be sure, the price is right!



 

 

   Bob . . .

alec(at)alecmyers.com
Guest

Posted: Mon Jul 10, 2017 7:02 am Post subject: IVO Prop current limiter

Maybe Iâ€™m misunderstanding: If I read it right, the design calls for the PIC to run whenever the bus is powered, i.e. during the whole flight. PICs do crash and suffer brownouts: thatâ€™s why they have built-in brownout protection and watchdog timers. If these events only happened every bazillion years, Arizona Microchip wouldnâ€™t waste the silicon. 

So when you say seconds per flight: the timer is called for for only seconds per flight, but the PIC is running through a do-nothing loop for the entirety of the rest of the flight. If that loop locks up at any time (and it will do so invisibly) then the timer wonâ€™t operate when called for. Again - if watchdog timers were *not* needed, the facility would not be embedded in the silicon.



 	  Quote: 	
		  On Jul 10, 2017, at 10:22 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  At 07:36 AM 7/10/2017, you wrote:  	  Quote: 	
		  If for any reason the PIC crashes (cosmic rays? It does happen) when the motor reaches its limit the FET will sit in an intermediate impedance state dissipating high power for an indeterminate length of time, possibly long enough to be emit the magic smoke. 	
   That's true . . . but if we were going to do   a reliability study for a PIC chip in a    high hazard application, we would find   that the chip itself is probably good for   10 to the minus bazzilion failures per   operating hour. Given that this chip operates   only seconds per flight hour, I think a   high degree of confidence is not misguided.   	  Quote: 	
		  Without adequate heat sinking for the FET the PIC software should use appropriate watchdog timers and brown-out protection to minimize this risk. 	
   . . . but if the chip goes TU . . . what's   the probability that built in safeguards are   operating?  	  Quote: 	
		   This is more of a problem if the PIC is powered from the 12v rail because it will be operational for effectively unlimited time before the timer is called into operation. If the PIC is powered from the motor command voltage this risk is much reduced as the PIC run time begins only when the motor is first powered. 	
   Exactly . . .  	  Quote: 	
		  The motor supply for sure is going to be trashy but PICs are designed to run in very unclean environments. I agree that clean rails are better than dirty ones but you could clean the motor supply rail with a simple RC network too. 	
   The power supply configuration depicted has   been used on products fully qualified under   DO160 stresses for trash.  The 5v rail   is very precise, rigid and clean. 

   Bob . . .

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Mon Jul 10, 2017 7:17 am Post subject: Re: IVO Prop current limiter

Thanks for all the quick replies.  I think I have all the info I need to bang out a second revision to this schematic and wiring diagram.  I'll see if I can get it done today.  Then if everyone's happy with it, I'll start on a PCB layout.



Eric

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 10, 2017 8:11 am Post subject: IVO Prop current limiter

At 10:02 AM 7/10/2017, you wrote:

  	  Quote: 	
		  Maybe Iâ€™m misunderstanding: If I read it right, the design calls for the PIC to run whenever the bus is powered, i.e. during the whole flight. 	




   No, only while the command switch is calling

   for change of pitch.



  	  Quote: 	
		  PICs do crash and suffer brownouts: thatâ€™s why they have built-in brownout protection and watchdog timers. If these events only happened every bazillion years, Arizona Microchip wouldnâ€™t waste the silicon. 	


   Brownouts are EXTERNALLY generated events

   caused by sagging supply voltage. The power

   supply configuration shown will maintain operable

   Vdd levels on the PIC to LESS than 10V on the

   ship's bus . . . which means that the airplane

   has a lot bigger problems than a malfunctioning

   prop-pitch controller.



  	  Quote: 	
		  So when you say seconds per flight: the timer is called for for only seconds per flight, but the PIC is running through a do-nothing loop for the entirety of the rest of the flight. 	


   Not so. Vdd is generated through a diode OR

   input that routes MOTOR(+) power to the

   regulator . . . power that is present only

   while the switch is calling for prop pitch

   motion.



 

  	  Quote: 	
		   If that loop locks up at any time (and it will do so invisibly) then the timer wonâ€™t operate when called for. Again - if watchdog timers were *not* needed, the facility would not be embedded in the silicon. 	


   Do the FMEA . . . suppose you were tasked with

   CREATING a situation that would confuse/damage

   the PIC, how would you go about it? Can you

   demonstrate the condition(s) on the bench?



   Assuming such an experiment is successful, what

   is the probability of that condition occurring

   in the aircraft?



   



 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 10, 2017 8:20 am Post subject: IVO Prop current limiter

At 09:43 AM 7/10/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Paul A. Fisher" <paulf(at)hughes.net>



 For this application, if we go with Bob's most recent design, I suggest we leave GP3/MCLR float.  Unless we plan to use the MCLR function, I'll disable it in software making GP3 a "normal" input (I put normal in quotes because I can't do a weak pull up on GP3). I've had issues in the past with that pin unless I software disable it.



 Bob answered your other questions, and way better than I could!!



 Paul 	




 I've updated the schematic with pin numbers and chip

 labels that conform to the ECB layout below.



 ECB files are posted also . . .



 See  http://tinyurl.com/yby3waw6



 



  [img]cid:7.1.0.9.0.20170710111139.05cadfa0(at)aeroelectric.com.0[/img] 



 

 

   Bob . . .

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alec(at)alecmyers.com
Guest

Posted: Mon Jul 10, 2017 8:26 am Post subject: IVO Prop current limiter

Ok, so I'm advocating for a design change that's already part of the design. My bad.



On Jul 10, 2017, at 12:11, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:

  No, only while the command switch is calling

  for change of pitch.

Dennis Glaeser

Joined: 10 Jan 2006
Posts: 53
Location: Rochester Hills, Michigan

Posted: Mon Jul 10, 2017 8:26 am Post subject: Re: IVO Prop current limiter

 	  kfav8r wrote: 	
		  The DPDT switch is mounted in the panel (in my case), along with the red and green LEDs.

For the Arduino setup, I have the relay and the current sensing module in a box behind the panel, and the arduino placed nearby.

On my Arduino layout drawing, the right side is from one of Bob's original drawings. He included the 10 Amp circuit breaker there, since that is what is delivered with the IVOProp.

For wiring, I used 16 AWG for any wires handling prop motor current; that is the size delivered with the prop.

My name is Doug Garland, but true credit goes to Dennis Glaeser for starting this discussion years ago, and, of course, Bob. 	


All I get credit for is asking the question: what would it take to make the IVO 'dummy proof' to save the gear box     The rest is all Bob...



It took me 2 tries to build a working version of Bob's 'original' design.  What a blast, working on something designed just for me (at the time)!

Fortunately I didn't have any issues with it working reliably for the couple of years I used it.  I moved 'up' to an MT prop, and sold the IVO - hopefully it is still working for the new owner.

What you guys are doing now is a testament to the ingenuity you all have, and the amazing technology available today - at even more amazing prices!!

 

I remember when I started doing research in prep for building my RV7A (in 2004!!), and discovered the AeroElectric list (and Vans AirForce).  Wow! 

My plane has been flying for over 9 years now, and I still follow all these forums and continue to expand my education, and stay amazed at all of the talented folks involved who are willing to share their time, effort, and knowledge, with Bob solidly at the head of that line.



Dennis Glaeser

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 10, 2017 9:34 am Post subject: IVO Prop current limiter

 	  Quote: 	
		   

 I remember when I started doing research in prep for building my RV7A (in 2004!!), and discovered the AeroElectric list (and Vans AirForce).  Wow! 

 My plane has been flying for over 9 years now, and I still follow all these forums and continue to expand my education, and stay amazed at all of the talented folks involved who are willing to share their time, effort, and knowledge, with Bob solidly at the head of that line. 	


    What you're describing is what I call "back of the

    napkin germination, evolution and perfection of

    an idea". The most elegant solutions are most often

    the amalgamation of time and talents in a demonstration

    of spontaneous order.



    I have had several jobs where this kind of collaboration

    and refinement of ideas took place . . . automatically.

    The most fun jobs I've had the pleasure to hold.



    I think Burt told us during the Mojave roll-out that Voyager

    was conceived on the back of a napkin (or perhaps an

    envelope) at a local beanery. Now I'm never without my

    favorite back of the napkin design tool . . .



  http://tinyurl.com/ybum6b78



    . . . for decades, some of the most exciting germinations

    over tacos at Connie's El Mexico cafe were frustrated

    by ball-points that plowed holes in the napkins. Wetting

    your finger in salsa is a poor substitute.  I discovered

    these pens a few years ago. They draw cleanly and damage

    free on the cheapest of napkins. I now carry two . . . one to

    'talk' with, the other to give away when my partner(s) in

    contemplation are impressed with the utility of the tool.



    In our case, the 'napkin' is a modern collection of applications

    and byte-thrashers, not the least of which is Matt's

    servers. But what we do here has roots in antiquity. It

    is in the finest traditions offered up by the likes of

    Kettering, Edison, Johnson, Beech, Rutan, VanG, et. als.



 



 

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jul 10, 2017 7:11 pm Post subject: IVO Prop current limiter

I proofed the ecb layout I posted. I'll get some

 made. I'll have 5 or so boards to 'share' with

 anyone who wants to participate in beta-testing

 the hardware/software. Boards should be in

 about Wednesday.



 

   Bob . . .

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