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Off Delay Cabin Light

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user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Tue Jun 03, 2014 2:35 am Post subject: Off Delay Cabin Light

The July 2014 issue of Kitplanes Magazine has an article by Jim Weir describing a circuit to delay turning off a light after the master switch is shut off.

http://www.kitplanes.com/issues/31_7/builder_spotlight/aero_lectrics_july_2014_21035-1.html

There is no power wire connected to Vcc pin 8 of the 555 IC.  Was a wire inadvertently left off or will the circuit work as drawn?

Joe

Courtesy Light Delay Off.JPG

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Joe Gores

ceengland7(at)gmail.com
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Posted: Tue Jun 03, 2014 4:24 am Post subject: Off Delay Cabin Light

Perhaps it's been fixed; the online version has the connection.

On Tue, Jun 3, 2014 at 5:35 AM, user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:

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

  

 The July 2014 issue of Kitplanes Magazine has an article by Jim Weir describing a circuit to delay turning off a light after the master switch is shut off.

 http://www.kitplanes.com/issues/31_7/builder_spotlight/aero_lectrics_july_2014_21035-1.html

 There is no power wire connected to Vcc pin 8 of the 555 IC.  Was a wire inadvertently left off or will the circuit work as drawn?

 Joe

 

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 Joe Gores

 

 

 

 

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 http://forums.matronics.com/viewtopic.php?p=424276#424276

 

 

 

 

 

 

 

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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Sun Jun 15, 2014 8:20 am Post subject: Re: Off Delay Cabin Light

I checked the printed paper issue and the online issue and they are both incorrect. The 555 should be wired to Positive of the keep-alive bus. Likewise the op amp should be eliminated and a 0.01 uF capacitor installed in the trigger line.



It plain to see that Jim Weir loves op amps. I prefer simpler designs and hope to publish one here soon, using no ICs and only six basic parts. It will do a "slow-fade dim-out".



ps: it is entirely possible that the Cmos 555 will operate with no power connection. Cmos circuits are known to do that since their power requirements are almost zero. But I don't think it was done on purpose.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jun 15, 2014 9:31 am Post subject: Off Delay Cabin Light

 	  Quote: 	
		  ps: it is entirely possible that the Cmos 555 will operate with no 

power connection. Cmos circuits are known to do that since their 

power requirements are almost zero. But I don't think it was done on purpose.


	


   Yeah, did a delayed off circuit mucho moons ago

   using schmidt-trigger cmos gate array driving

   power MOSFET . . . supported the timer with

   a big tantalum to keep the time active after

   the 'control' signal went low.



   Works good.



   Bob . . .

rnjcurtis(at)charter.net
Guest

Posted: Sun Jun 15, 2014 10:05 am Post subject: Off Delay Cabin Light

 	  Quote: 	
		  

 It plain to see that Jim Weir loves op amps. I prefer simpler designs and 

 hope to publish one here soon, using no ICs and only six basic parts. It 

 will do a "slow-fade dim-out".


	




        Eric,



        It might be nice to consider designing this so that

        it can be turned on and off normally while the

        master is on and then come on for a delayed

        period when the master is shut off.



        Just a thought before the design gets finalized.



        Roger

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Wed Jun 18, 2014 2:10 pm Post subject: Re: Off Delay Cabin Light

 	  Quote: 	
		  I prefer simpler designs and hope to publish one here soon, using no ICs and only six basic parts. It will do a "slow-fade dim-out". 	
 



As promised, here is a basic Sexy Slow-Fadeout  Cabin Light that is very rugged and very simple. I uses only six basic parts.



The main high-current switch is a LM395 Indestructible Power Transistor, but any number of other NPN power transistors would do just fine. The timer stays on for about R x C seconds, which here is 32 seconds. You can change this as you like preferably with a higher-value resistor (because it's easier).



The transistor needs some heatsinking if you want it to dim a very big bunch of LEDs. But some experimenting will determine what you need.



Two notes: 



1) The previous "De-Slumpifier" also works well for this task, and you don't need any "keep-alive" bus. 



2) Cree sells 200/lumen per watt white leds now, so don't be stuck with the antiques ones if you can use these.

Lamp Fade Out Timer.pdf

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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

RnJCurtis(at)charter.net
Guest

Posted: Wed Jun 18, 2014 3:05 pm Post subject: Off Delay Cabin Light

Eric,  



my computer says Page not found when I try to open the attachment.



Roger

user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Wed Jun 18, 2014 3:21 pm Post subject: Re: Off Delay Cabin Light

Thanks Eric, the download worked for me.

_________________
Joe Gores

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Thu Jun 19, 2014 5:26 am Post subject: Re: Off Delay Cabin Light

Rumen asked two things that I should have mentioned.



The mysterious resistor is the LED current-limiting resistor. Since I don't know what LEDs you are using I can't specify it, but basically the resistor is:

R=((Vbus ) -- LED Voltage drop--1.2V) /amps you want the LEDs to run at.



This should work at 28V too. with a 35V capacitor. 



You can use an amazing number of LEDs here in series/parallel, but when they turn off and the final appearance is difficult to predict without a bench test. So plan on that.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

ceengland7(at)gmail.com
Guest

Posted: Thu Jun 19, 2014 6:28 am Post subject: Off Delay Cabin Light

On 6/18/2014 6:21 PM, user9253 wrote:

 	  Quote: 	
		   



 Thanks Eric, the download worked for me.



 --------

 Joe Gores



Heads up;
	




The link does not work if access is attempted from an email. It does 

work if access is attempted from the forum.



I normally read Matt's lists via email, & couldn't load the link. I 

clicked on the 'read the topic online' link, let that page load in my 

browser, and then downloaded the drawing using the link in the browser page.



Charlie

rnjcurtis(at)charter.net
Guest

Posted: Thu Jun 19, 2014 6:28 am Post subject: Off Delay Cabin Light

 	  Quote: 	
		   The mysterious resistor is the LED current-limiting resistor. Since I 

 don't know what LEDs you are using I can't specify it, but basically the 

 resistor is:

 R=((Vbus ) -- LED Voltage drop--1.2V) /amps you want the LEDs to run at.



 This should work at 28V too. with a 35V capacitor.



 You can use an amazing number of LEDs here in series/parallel, but when 

 they turn off and the final appearance is difficult to predict without a 

 bench test. So plan on that.


	




        Eric,



        another thing you might consider is connecting the

        capacitor to the common on the switch and be able

        to select either +12V or Ground.  This would give

        you the ability to use it as a delayed turn off or have

        the option of instant shut off.  No extra components,

        just rewire the switch.



        Roger

user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Thu Jun 19, 2014 8:14 am Post subject: Re: Off Delay Cabin Light

A diode may be required in the main 12 Volt wire.  If the light is on and then the master switch is shut off, other aircraft loads will be in parallel with R1 and short it to ground, thus no delay.  If the light switch is turned on after the master switch is shut off, then there is no power available to turn on the transistor.

Here is the desired the desired functionality as I see it:



If the light switch is on and the master is on, then the light should stay on.



If the light switch is on, when the master is turned off, the light should stay on for a while and then shut off automatically.



If the master has been off and then the light switch is turned on, the light should come on for a while and then shut off automatically.



If the light switch is off, the light should be off.



Perhaps a new microprocessor-controlled product with the above features would sell.

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 19, 2014 8:15 am Post subject: Off Delay Cabin Light

At 06:21 PM 6/18/2014, you wrote:

 	  Quote: 	
		  



Thanks Eric, the download worked for me.


	




   The LM395 is an interesting part for linear operations

   but it's not a very good switch. The full-ON saturation

   voltage for this part is about 1.5 volts. An alternative

   on Eric's theme would use a simple MOS-Fet . . .



http://tinyurl.com/mtnd86d



   In the full-ON state, voltage drop across the FET

   would be quite low . . . millivolts. When given

   command of the cabin light during the delay-OFF

   operation, the light would stay full-ON until the

   transistor begins to loose conduction as the gate

   voltage falls. Assuming conductivity over a gate voltage

   decay from 4 to 2 volts, the time constants shown on

   the diagram will offer delay on the order of 1 to 2

   minutes. Your results may vary . . . fiddle with the

   size of the 1M resistor to achieve your design goals.

   Bigger resistor - longer delay.



   I can't imagine any LED cabin light needing more than

   a couple hundred mA of operating current. The LED dome

   lights in my truck only run 120 mA and are plenty

   bright. At these current levels, no heat-sinking for

   the FET is necessary . . . bolting it to the box

   that houses the assembly will be plenty of heatsink

   for up to several amps of controlled lamp load.



   The only time the transistor dissipates significant

   energy is during the dimming interval. All other times

   it is full-OFF or full-ON and dissipates no significant heat.

   Bob . . .

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