Matronics Email Lists :: View topic - Designing a circuit question

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Designing a circuit question
Goto page 1, 2 Next

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

Dennis Glaeser

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

Posted: Sat Apr 17, 2010 3:03 pm Post subject: Designing a circuit question

I have an in flight adjustable IVO prop.  What I’d like to have is a light that indicates when I get to the flat pitch ‘stop’ – without adding rings and brushes.  

For those who aren’t familiar with the IVO, the adjustment is made by a motor driving a jack-screw that moves a collar which torques a rod embedded in the blades.  There are no electrical stops, just a rubber washer at each end of the run.  When the collar hits the end, the motor stalls.  The rubber washer provides a softer stall which is a bit easier on the gears driving the jack screw.  A 10A CB is the ultimate ‘stop’.  Not elegant, but it works.  

On the ground, before starting the engine, it’s easy to verify the prop is in fine pitch by listening to the motor.  The problem is before landing, when I’d like to have the prop in fine pitch, it has to be done by guess and feel, or just hold the switch until the CB pops – which is not a good thing to do on a regular basis.  

So, what I’d like is a circuit that can sense an amperage spike – going over 9A would be perfect – and turn on a light (LED of course   The ramp up to 9A is steep – goes from 5-6A to 9A very quickly (if that helps).  

I can build the circuit, I just don’t know how to design it.  

   

Thanks in advance,  

   

Dennis Glaeser  

   

        [quote][b]

ainut(at)hiwaay.net
Guest

Posted: Sat Apr 17, 2010 4:12 pm Post subject: Designing a circuit question

There is a little IC with three pins that you could put in circuit with 

the system. It tells you the amperage passing through it. IIRC it's 

about $6. I can look up the part number on the ones I have here somewhere...



David M.

Dennis & Anne Glaeser wrote:

 	  Quote: 	
		  

 I have an in flight adjustable IVO prop. What I’d like to have is a 

 light that indicates when I get to the flat pitch ‘stop’ – without 

 adding rings and brushes.



 For those who aren’t familiar with the IVO, the adjustment is made by 

 a motor driving a jack-screw that moves a collar which torques a rod 

 embedded in the blades. There are no electrical stops, just a rubber 

 washer at each end of the run. When the collar hits the end, the motor 

 stalls. The rubber washer provides a softer stall which is a bit 

 easier on the gears driving the jack screw. A 10A CB is the ultimate 

 ‘stop’. Not elegant, but it works.



 On the ground, before starting the engine, it’s easy to verify the 

 prop is in fine pitch by listening to the motor. The problem is before 

 landing, when I’d like to have the prop in fine pitch, it has to be 

 done by guess and feel, or just hold the switch until the CB pops – 

 which is not a good thing to do on a regular basis.



 So, what I’d like is a circuit that can sense an amperage spike – 

 going over 9A would be perfect – and turn on a light (LED of course 

  The ramp up to 9A is steep – goes from 5-6A to 9A very quickly (if 

 that helps).



 I can build the circuit, I just don’t know how to design it.



 Thanks in advance,



 Dennis Glaeser

mdnanwelch7(at)hotmail.co
Guest

Posted: Sat Apr 17, 2010 4:54 pm Post subject: Designing a circuit question

Dennis,

 

  I have the exact same IvoProp setup.  They make an option for this function, if I'm not mistaken.

  

   I just went to their website, and checked out what they had.  They call it a prop speed govenor.  Cost is $320.

  

   Yeah, I'd love to build one of these, too!!  If anyone can come up with a design, I could build it!!

   Maybe there could be a line of LEDs that reflect the currect load in each direction of travel.   

  

 Mike Welch

 

   

 From: glaesers(at)wideopenwest.com

To: AeroElectric-List(at)matronics.com

Subject: Designing a circuit question

Date: Sat, 17 Apr 2010 19:01:38 -0400

  .ExternalClass p.ecxMsoNormal, .ExternalClass li.ecxMsoNormal, .ExternalClass div.ecxMsoNormal {margin-bottom:.0001pt;font-size:11.0pt;font-family:'Calibri','sans-serif';} .ExternalClass a:link, .ExternalClass span.ecxMsoHyperlink {color:blue;text-decoration:underline;} .ExternalClass a:visited, .ExternalClass span.ecxMsoHyperlinkFollowed {color:purple;text-decoration:underline;} .ExternalClass span.ecxEmailStyle17 {font-family:'Calibri','sans-serif';color:windowtext;} .ExternalClass .ecxMsoChpDefault {;} (at)page Section1 {size:8.5in 11.0in;} .ExternalClass div.ecxSection1 {page:Section1;}    

I have an in flight adjustable IVO prop.  What I’d like to have is a light that indicates when I get to the flat pitch ‘stop’ – without adding rings and brushes. 

For those who aren’t familiar with the IVO, the adjustment is made by a motor driving a jack-screw that moves a collar which torques a rod embedded in the blades.  There are no electrical stops, just a rubber washer at each end of the run.  When the collar hits the end, the motor stalls.  The rubber washer provides a softer stall which is a bit easier on the gears driving the jack screw.  A 10A CB is the ultimate ‘stop’.  Not elegant, but it works. 

On the ground, before starting the engine, it’s easy to verify the prop is in fine pitch by listening to the motor.  The problem is before landing, when I’d like to have the prop in fine pitch, it has to be done by guess and feel, or just hold the switch until the CB pops – which is not a good thing to do on a regular basis. 

So, what I’d like is a circuit that can sense an amperage spike – going over 9A would be perfect – and turn on a light (LED of course   The ramp up to 9A is steep – goes from 5-6A to 9A very quickly (if that helps). 

I can build the circuit, I just don’t know how to design it. 

  

Thanks in advance, 

  

Dennis Glaeser 

 

 	  Quote: 	
		  



-List">http://www.matronics.com/Navigator?AeroElectric-List

ronics.com

ww.matronics.com/contribution



	
 		 	   		  The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail.  Get busy.  [quote][b]

Dennis Glaeser

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

Posted: Sat Apr 17, 2010 7:51 pm Post subject: Designing a circuit question

Mike,



I've seen their speed governor on their website, but don't know how well it

works. Making a decent speed controller is more involved and expensive than

I want.  

All I really want is a 'limit sensor' for the pitch stops.

Some IVO owners have installed an ammeter, which is an option but I'm hoping

for something simpler - just a light.



Dennis



----------

Mike Welch (mdnanwelch7(at)hotmail.com)

Date:

    

Sat Apr 17 - 5:54 PM

Dennis



  I have the exact same IvoProp setup.  They make an option for this

function if I'm not mistaken.

  I just went to their website and checked out what they had.  They call it

a prop speed govenor.  Cost is $320.

  Yeah I'd love to build one of these too!!  If anyone can come up with a

design I could build it!!

  Maybe there could be a line of LEDs that reflect the currect load in each

direction of travel.   



Mike Welch

Dennis Glaeser

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

Posted: Sat Apr 17, 2010 8:00 pm Post subject: Designing a circuit question

David,



Can the IC do any switching based on the amperage it senses?



Dennis



------------------

From:  David (ainut(at)hiwaay.net)



There is a little IC with three pins that you could put in circuit with 

the system. It tells you the amperage passing through it. IIRC it's 

about $6. I can look up the part number on the ones I have here somewhere...



David M.

ainut(at)hiwaay.net
Guest

Posted: Sat Apr 17, 2010 8:43 pm Post subject: Designing a circuit question

Not this one.  That would have to be another circuit.  A $1 

microprossesser could handle a $17 relay to do that job.



David



Dennis & Anne Glaeser wrote:

 	  Quote: 	
		   



 David,



 Can the IC do any switching based on the amperage it senses?



 Dennis



 ------------------

 From:  David (ainut(at)hiwaay.net)



 There is a little IC with three pins that you could put in circuit with

 the system. It tells you the amperage passing through it. IIRC it's

 about $6. I can look up the part number on the ones I have here somewhere...



 David M.

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sun Apr 18, 2010 5:23 am Post subject: Re: Designing a circuit question

Dennis,

How about this circuit designed by Bob N?

http://www.aeroelectric.com/articles/Failure_Detection_and_Annunciation.pdf

You would have to experiment with the number of turns of wire to wrap around the reed relay.  I have reed switches and can bring one to the EAA meeting if you need it.

Joe

_________________
Joe Gores

doug.ilg(at)verizon.net
Guest

Posted: Sun Apr 18, 2010 7:04 am Post subject: Designing a circuit question

Just to be clear, if all you want to do is light an LED (the original plan), there's no need for a relay.  Any of those $1 microprocessors should be able to drive a normal LED directly off an output pin.  Of course, if you're going to the trouble of putting together this sort of circuit, making it control a relay to take the power off the motor would be a fairly easy add-on.

 



Doug Ilg

Grumman Tiger N74818, College Park Airport (KCGS), Maryland

Challenger II LSS LW (N641LG reserved) - kit underway at Laurel Suburban (W18)



---

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 18, 2010 11:14 am Post subject: Designing a circuit question

At 06:01 PM 4/17/2010, you wrote:

 	  Quote: 	
		  I have an in flight adjustable IVO prop.  What 

I’d like to have is a light that indicates when 

I get to the flat pitch ‘stop’ – without adding rings and brushes.

For those who aren’t familiar with the IVO, the 

adjustment is made by a motor driving a 

jack-screw that moves a collar which torques a 

rod embedded in the blades.  There are no 

electrical stops, just a rubber washer at each 

end of the run.  When the collar hits the end, 

the motor stalls.  The rubber washer provides a 

softer stall which is a bit easier on the gears 

driving the jack screw.  A 10A CB is the 

ultimate ‘stop’.  Not elegant, but it works.

On the ground, before starting the engine, it’s 

easy to verify the prop is in fine pitch by 

listening to the motor.  The problem is before 

landing, when I’d like to have the prop in fine 

pitch, it has to be done by guess and feel, or 

just hold the switch until the CB pops – which 

is not a good thing to do on a regular basis.

So, what I’d like is a circuit that can sense an 

amperage spike – going over 9A would be perfect 

– and turn on a light (LED of course   The 

ramp up to 9A is steep – goes from 5-6A to 9A very quickly (if that helps).

I can build the circuit, I just don’t know how to design it.


	


    The reed switch sensor Joe mentioned is worthy of further

    thought. You could also build a simple constant current

    generator set for something less than the CB trip current.

    By watching for the voltage to spike across the generator

    could light an LED to indicate end-of-travel and stop using

    the CB as an operating indicator.



    I'm just getting ready to head for Wichita but I'll noodle

    the idea on the way up. I can perhaps publish something later

    this evening.



    Bob . . .

Dennis Glaeser

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

Posted: Sun Apr 18, 2010 2:46 pm Post subject: Designing a circuit question

Doug,



It may be clear to you, but you've got to do better than that to be clear to

me 

I understand the concept, but need a circuit diagram, and which $1

microprocessor to use.

I agree that once I know how to turn the LED on, adding a relay is straight

forward.  Have to admit I hadn't thought of that.  I have to think about it

and decide if it is worth the extra complexity and parts - vs. just me just

letting go of the switch...



Dennis



----------------------

Just to be clear, if all you want to do is light an LED (the original plan),

there's

no need for a relay.  Any of those $1 microprocessors should be able to

drive a normal LED directly off an output pin.  Of course, if you're going

to

the trouble of putting together this sort of circuit, making it control a

relay

to take the power off the motor would be a fairly easy add-on.

Doug Ilg

doug.ilg(at)verizon.net
Guest

Posted: Sun Apr 18, 2010 5:35 pm Post subject: Designing a circuit question

Dennis,



I'm not really the right person to give lessons on microprocessors.  All that I've done is to implement simple schematics and programs that I found on the 'net.  (A quick search for "PIC16" should find some sites with projects for that popular line of microprocessors.)  I know from that that you can drive an LED directly off an output pin with an appropriate resistor.



My point was to tell you that the relay that was referred to is not necessary for your original purpose (to light an LED).  It would be useful to actually interrupt current to the motor, if you chose to do that.



Maybe the person who originally suggested using a microprocessor can give you better advice on how to use those. 



Doug Ilg

Grumman Tiger N74818, College Park Airport (KCGS), Maryland

Challenger II LSS LW (N641LG reserved) - kit underway at Laurel Suburban (W18)



---

BobsV35B(at)aol.com
Guest

Posted: Mon Apr 19, 2010 3:42 am Post subject: Designing a circuit question

Good Morning 'Lectric Bob,

  

 This discussion of controlling a circuit by noting the change in power  consumption has gotten me to think a bit and that is always dangerous.

  

 My electrical knowledge is miniscule, but I can generally understand the  principles once they have been explained by you and the other good instructors  on this list.

  

 I have the desire to know when fuel stops flowing from one tank to another  tank via an electric pump. 

  

 In other words, I would like to know when all of the fuel from a tank has  been transferred.  My transfer system uses a Facet plunger style pump and  as the tank runs dry, the sound of the pump changes.

  

 Unfortunately, I can only hear the pump running when I am parked on the  ground with my engine shut down. I have tried to monitor the total system  amperage load to see if I could detect the change when a tank runs dry, but the  load seems to oscillate enough that I cannot pick it up via that instrument. I  am using an E.I. VA-1A to monitor the alternator output. 

  

 Is there a simple and, hopefully, economical way to measure the amount of  current it takes to drive the pump or is there a better way to tell when fuel is  no longer being transferred? I have thought of using a pressure gauge in the  fuel line, but maybe it would be easier to measure the change in current draw of  the fuel pump?

  

 Facet says that the pump can be run dry for a short period of time, but  they will not specify how long that time can be!

  

 I hate to run my pump when it is operating dry. An indicator light to tell  me it is running dry would sure be helpful. <G>

  

 Any help available is sincerely appreciated.

  

 Happy Skies,

  

 Old Bob

  

 Downers Grove, IL

 Stearman N3977A

  

  In a message dated 4/18/2010 2:14:46 P.M. Central Daylight Time,  nuckolls.bob(at)aeroelectric.com writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: "Robert L. Nuckolls, III"    <nuckolls.bob(at)aeroelectric.com>



At 06:01 PM 4/17/2010, you    wrote:

 	  Quote: 	
		  I have an in flight adjustable IVO prop.  What 

Iâ€™d    like to have is a light that indicates when 

I get to the flat pitch    â€˜stopâ€™ â€“ without adding rings and brushes.

For those who arenâ€™t    familiar with the IVO, the 

adjustment is made by a motor driving a    

jack-screw that moves a collar which torques a 

rod embedded in    the blades.  There are no 

electrical stops, just a rubber washer    at each 

end of the run.  When the collar hits the end,    

the motor stalls.  The rubber washer provides a 

softer    stall which is a bit easier on the gears 

driving the jack screw.     A 10A CB is the 

ultimate â€˜stopâ€™.  Not elegant, but it    works.

On the ground, before starting the engine, itâ€™s 

easy to    verify the prop is in fine pitch by 

listening to the motor.  The    problem is before 

landing, when Iâ€™d like to have the prop in fine    

pitch, it has to be done by guess and feel, or 

just hold the    switch until the CB pops â€“ which 

is not a good thing to do on a    regular basis.

So, what Iâ€™d like is a circuit that can sense an    

amperage spike â€“ going over 9A would be perfect 

â€“ and turn on    a light (LED of course   The 

ramp up to 9A is steep â€“ goes    from 5-6A to 9A very quickly (if that helps).

I can build the circuit,    I just donâ€™t know how to design it.


	


    The reed switch    sensor Joe mentioned is worthy of further

    thought. You could    also build a simple constant current

    generator set for    something less than the CB trip current.

    By watching for the    voltage to spike across the generator

    could light an LED to    indicate end-of-travel and stop using

    the CB as an operating    indicator.



    I'm just getting ready to head for Wichita but    I'll noodle

    the idea on the way up. I can perhaps publish    something later

    this evening.



    Bob . . .  ========================= Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


  [quote][b]

deej(at)deej.net
Guest

Posted: Mon Apr 19, 2010 6:47 am Post subject: Designing a circuit question

On 04/19/2010 07:39 AM, BobsV35B(at)aol.com wrote:



 	  Quote: 	
		   I have the desire to know when fuel stops flowing from one tank to

 another tank via an electric pump.


	


	How about an optical in-line fuel sensor?



http://www.pillarpointelectronics.com/ufstkit.html

<http://www.pillarpointelectronics.com/ufstkit.html>



-Dj



-- 

Dj Merrill - N1JOV

Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Grumman Yankee Driver N9870L - http://deej.net/yankee/

ainut(at)knology.net
Guest

Posted: Mon Apr 19, 2010 7:03 am Post subject: Designing a circuit question

For simplicity's sake, look at the Arduino.  For more detailed 

information, start at Freescale's (formerly Motorola) sites.



David

Doug Ilg wrote:

[quote] 



 Dennis,



 I'm not really the right person to give lessons on microprocessors.  All that I've done is to implement simple schematics and programs that I found on the 'net.  (A quick search for "PIC16" should find some sites with projects for that popular line of microprocessors.)  I know from that that you can drive an LED directly off an output pin with an appropriate resistor.



 My point was to tell you that the relay that was referred to is not necessary for your original purpose (to light an LED).  It would be useful to actually interrupt current to the motor, if you chose to do that.



 Maybe the person who originally suggested using a microprocessor can give you better advice on how to use those.



 Doug Ilg

 Grumman Tiger N74818, College Park Airport (KCGS), Maryland

 Challenger II LSS LW (N641LG reserved) - kit underway at Laurel Suburban (W18)



 ---

sean(at)stephensville.com
Guest

Posted: Mon Apr 19, 2010 7:57 am Post subject: Designing a circuit question

I've also had fun playing around with this to help learn the basics.



http://www.nerdkits.com/

On 4/19/10 9:32 AM, David wrote:

[quote] 



 For simplicity's sake, look at the Arduino.  For more detailed 

 information, start at Freescale's (formerly Motorola) sites.



 David

 Doug Ilg wrote:

> 

>

> Dennis,

>

> I'm not really the right person to give lessons on microprocessors.  

> All that I've done is to implement simple schematics and programs 

> that I found on the 'net.  (A quick search for "PIC16" should find 

> some sites with projects for that popular line of microprocessors.)  

> I know from that that you can drive an LED directly off an output pin 

> with an appropriate resistor.

>

> My point was to tell you that the relay that was referred to is not 

> necessary for your original purpose (to light an LED).  It would be 

> useful to actually interrupt current to the motor, if you chose to do 

> that.

>

> Maybe the person who originally suggested using a microprocessor can 

> give you better advice on how to use those.

>

> Doug Ilg

> Grumman Tiger N74818, College Park Airport (KCGS), Maryland

> Challenger II LSS LW (N641LG reserved) - kit underway at Laurel 

> Suburban (W18)

>

> ---

BobsV35B(at)aol.com
Guest

Posted: Mon Apr 19, 2010 10:45 am Post subject: Designing a circuit question

Good Afternoon Dj,

  

 That sounds like just what I need! 

  

 Unfortunately, I want to use it on a certificated airplane.  I will  check it out.

  

 Thanks much for the information.

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 4/19/2010 9:48:46 A.M. Central Daylight Time,  deej(at)deej.net writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: Dj Merrill    <deej(at)deej.net>



On 04/19/2010 07:39 AM, BobsV35B(at)aol.com    wrote:



 	  Quote: 	
		   I have the desire to know when fuel stops flowing from one    tank to

 another tank via an electric pump.


	


    How    about an optical in-line fuel    sensor?



http://www.pillarpointelectronics.com/ufstkit.html

<http://www.pillarpointelectronics.com/ufstkit.html>



-Dj



--    

Dj Merrill - N1JOV

Glastar Sportsman 2+2 Builder #7118 N421DJ -    http://deej.net/sportsman/

Grumman Yankee Driver N9870L -  ===============================================

_-=   = Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


  [quote][b]

user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Mon Apr 19, 2010 11:24 am Post subject: Re: Designing a circuit question

I wrapped 25 turns of 20awg magnet wire around a magnetic reed switch.  I was surprised at how well it works.  Less than 1/2 amp is enough to close the switch.  Very few turns of wire will be required for Dennis' application of turning on a light when motor current exceeds 7amps.

Joe

Ref: http://www.aeroelectric.com/articles/Failure_Detection_and_Annunciation.pdf

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Apr 21, 2010 6:58 am Post subject: Designing a circuit question

Hi Bob, and everyone else following this thread... 



 I have an even simpler solution, possibly costing significantly less, using the hotly debated poly-fuse. Simply put a 6A or 7A one in series with the motor, with an LED+resistor across it. When the fuse trips, the LED is energised... In it's normal state, all the current travels through the low impedance fuse, and 'none' through the LED+resistor path. No heatsink required! However, there is the problem of securing everything and making sure vibration doesn't age the soldered joints prematurely. 



     I considered this. This is the control philosophy

     for most cars on the electric window-risers. It's

     certainly simple and reliable. They are relatively

     slow acting devices and it would take some experimentation

     to get the right device. Also, once they've tripped, it

     may take 10 seconds or more for them to cool off enough

     to reset. So once the light comes on, you would have

     to wait for sufficient cooling to come off the stop.

     But if that operating mode meets design goals,

     it's certainly an option.



 Does the current limiting characteristic you mention literally limit the current to the pitch motor? My guess is it does (at least somewhat), which is why the N-fet becomes a cabin heater. 



     But it's a heater only while you are in the current limited

     mode. i.e. against the stop and the light is lit. Only a second

     or so at a time (reaction time to release the switch after

     the light comes on).



 I'm thinking that the electrical paths from the switch to the N-fet, and path from the N-fet to the ALSRJ resistor to ground need to be capable of 10A, but the other wiring will see much less. 



 How would I 'adjust for desired limit' on the ALSRJ resistor to go up to say 8A? How did you calculate or estimate that value? How sensitive would you anticipate that to be? 

     

     The current limit calibration is a function of voltage

     drop across the low value resistor and the base-emitter

     turn-on voltage for the clamp transistor. Assuming 0.6

     volts turn-on and 0.1 ohms, we get about 6 amps. I would

     'trim' the set point to higher values by paralleling the

     0.1 ohm resistor with another, higher value.



 The reason I ask is that the load on the motor does increase as the pitch on the blades approach the high (and low) pitch limits, before the mechanical stop is reached. The mechanism is literally twisting composite blades, they don't rotate in bearings like 'regular' adjustable blades. I may have to adjust the current limit to be sure I can get the blades close enough to the pitch limits for my purposes. My rough measurement of current (reading a clamp on meter) indicates a pretty good knee in the curve at around 8A. 6A may be close enough, only testing will tell. 



     Exactly. Adding a 0.5 ohm resistor in parallel would

     raise the set point to abut 7.2 amps. Adding another

     .5 ohm raises it to 8.4 amsp, etc.



 Finally, how would you compare this circuit to the reed switch approach that Joe Gores proposed, from a standpoint of repeatability of sensing the target amperage, and the ability to make adjustments to get to the desired target (number of winds and wire size selection)? 

    

    The reed switch would only light the light, it would not

    eliminate using the "breaker-trip" as the ultimate limit

    switch. In the stone-simple category of solutions, the

    polyswitch suggestion has some merit.



 

 Related question. How is the amount of heat sink area calculated? I 

 assume it is based on the amount of energy converted to heat. Where can 

 I find the info to determine what size heat sink is required. Does the 

 electrically insulating material also thermally insulate the component 

 and affect the design of the heat sink? 



    Heat sinking is an interesting and not really complicated

    discipline. It comes with two primary design goals to consider.

    They might be characterized as the "marathon" and "100-yard dash"

    modes for thermal management.



    A heat sink's ability to keep a semiconductor cool is a

    combination of thermal mass and surface area available

    to reject heat. In the case of CONTINUOUS duty operation

    like the linear dimmer modules, surface area and air

    flow are the driving considerations. In our intermittent

    duty application (1 second at each end of stroke), we

    can use a heat sink that is horribly undersized for 

    continuous duty as long as total thermal mass is sufficient

    to keep the transistor junction from fusing in the

    few seconds per operation and sufficiently space to allow

    cooling for the next cycle.



    I didn't do a calculation for the suggestion that was

    mostly an experience-based recommendation.



    There's a lot of data available on the 'net that

    speaks to continuous duty heat sink sizing and the

    insulating, thermally conducting washers used to

    electrically isolate the device from the heat sink.



    Intermittent duty sizing is not so common although

    it's easily estimated. It's a thermal rate-of-rise

    study that accounts for junction to sink thermal

    resistance + thermal inertia of the heatsink

    where we consider the specific heat of the material

    and it's total mass. I think I've got some words

    that discuss that process somewhere, I'll dig around.



    In any case, for this application, we don't need

    to design a heat-sink that allows the transistor

    to operate in an extended "cabin heater" mode.



    Bob . . .     [quote][b]

mdnanwelch7(at)hotmail.co
Guest

Posted: Wed Apr 21, 2010 10:41 am Post subject: Designing a circuit question

'Lectric Bob,



 



  I REALLY like your circuit design regarding the IvoProp motor.  In fact, I'm planning on building one, seeing as how I have an IvoProp...with the motor.



 



  If I understand the process correctly, by pushing the dpdt switch, when the motor sees 6 A current, the LED will light up.  Let go of the dpdt switch quickly, and you're in like Flynn.



 



  Here's my question:  would it be much of a challenge for the motor to lighten multiple LEDs (in both directions), as it cycles from 0 to 10A?  Of course, you'd want two separate circuits indicating if you're headed to flat pitch...or steep pitch, or some method to insure you're twisting the prop in the correct direction you intended to.



 



  Wouldn't this design I'm asking about be essentially an analog version of a current meter?   Example:  say you're at zero pitch, and you cycle toward steep pitch.  As the motor's current draw increases, it could light a 1A LED, then a 2A LED, a 3A LED, etc, etc.



Same process for the other prop twist.



 



  If a guy had this type of design he could routinely set his prop pitch to a known LED position to achieve maximum value of a variable pitch prop.  He could adjust his engine and prop (LED) to a known performance characteristic.....i.e......engine rpm 4750, pitch in the steep direction #5 LED.



 



  Thanks for your ideas!



 



Mike Welch



BTW.  I built that copper tape groundplane antenna.  It works great so far, but I'm waiting on the bnc connector/PL 259 adapter for the SWR meter to adjust it correctly (Radio Shack Friday's delivery)!!  



 



 

 		 	   		  

_________________________________________________________________

The New Busy is not the old busy. Search, chat and e-mail from your inbox

Dennis Glaeser

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

Posted: Wed Apr 21, 2010 4:42 pm Post subject: Designing a circuit question

See my comments after the ----->'s below...

    

RE: RE: Designing a circuit question

From: Mike Welch 



I REALLY like your circuit design regarding the IvoProp motor.  In fact I'm

planning on building one seeing as how I have an IvoProp...with the motor.



If I understand the process correctly by pushing the dpdt switch when the

motor sees 6A current the LED will light up.  Let go of the dpdt switch

quickly and you're in like Flynn.

------->

Yup!  Not only does the LED illuminate, the current to the motor is limited,

so it may stop before reaching the physical stop if twisting the blade is

loading the motor enough.  That's why I was asking about adjusting the

trigger amperage. We don't want the circuit limiting the pitch too much.

-----------------



Here's my question:  would it be much of a challenge for the motor to

lighten multiple LEDs (in both directions) as it cycles from 0 to 10A?  Of

course you'd want two separate circuits indicating if you're headed to flat

pitch...or steep pitch or some method to insure you're twisting the prop in

the correct direction you intended to.

----------> 

The light will come on whenever the trigger amperage is reached as you note

above.  Direction (toward high or low pitch) depends on which way the switch

is moved.  Bob's circuit sees current in the same direction all the time,

the switch is where it is reversed for the motor.

----------------------



Wouldn't this design I'm asking about be essentially an analog version of a

current meter?  Example: say you're at zero pitch and you cycle toward steep

pitch.  As the motor's current draw increases it could light a 1A LED then a

2A LED a 3A LED etc etc.

If a guy had this type of design he could routinely set his prop pitch to a

known LED position to achieve maximum value of a variable pitch prop.  He

could adjust his engine and prop (LED) to a known performance

characteristic.....i.e......engine rpm 4750 pitch in the steep direction #5

LED.

-------->

A number of IVO users have put an ammeter in the circuit to do what you

suggest by simply reading the meter instead of watching LEDs. Direction is

which way you move the switch, the ammeter works the same in both

directions.

-------------



Same process for the other prop twist.

---------->

No, the current to the switch is always in the same direction.  You'd have

to put something on in the lines to the motor to be able to sense which way

the motor is being driven.

-------------



Dennis Glaeser

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours Goto page 1, 2 Next
Page 1 of 2

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum