---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 06/19/14: 13 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:32 AM - Re: Off Delay Cabin Light (Eric M. Jones) 2. 07:28 AM - Re: Re: Off Delay Cabin Light (Charlie England) 3. 07:28 AM - Re: Re: Off Delay Cabin Light (Roger & Jean) 4. 09:15 AM - Re: Off Delay Cabin Light (user9253) 5. 09:15 AM - Re: Re: Off Delay Cabin Light (Robert L. Nuckolls, III) 6. 10:08 AM - fuse link to replace fuse in low current applications? (Charlie England) 7. 10:48 AM - Re: LED Ghosting (user9253) 8. 11:27 AM - Re: fuse link to replace fuse in low current applications? (Robert L. Nuckolls, III) 9. 12:02 PM - Re: Re: LED Ghosting (Robert L. Nuckolls, III) 10. 01:16 PM - Re: Re: LED Ghosting (Fisher Paul A.) 11. 01:49 PM - Re: fuse link to replace fuse in low current applications? (Charlie England) 12. 02:36 PM - Re: fuse link to replace fuse in low current applications? (Sacha) 13. 05:50 PM - Re: LED Ghosting (donjohnston) ________________________________ Message 1 _____________________________________ Time: 06:32:35 AM PST US Subject: AeroElectric-List: Re: Off Delay Cabin Light From: "Eric M. Jones" 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 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=425127#425127 ________________________________ Message 2 _____________________________________ Time: 07:28:08 AM PST US From: Charlie England Subject: Re: AeroElectric-List: Re: Off Delay Cabin Light On 6/18/2014 6:21 PM, user9253 wrote: > > 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 ________________________________ Message 3 _____________________________________ Time: 07:28:16 AM PST US From: "Roger & Jean" Subject: Re: AeroElectric-List: Re: Off Delay Cabin Light > 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 ________________________________ Message 4 _____________________________________ Time: 09:15:32 AM PST US Subject: AeroElectric-List: Re: Off Delay Cabin Light From: "user9253" 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 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=425132#425132 ________________________________ Message 5 _____________________________________ Time: 09:15:56 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Off Delay Cabin Light At 06:21 PM 6/18/2014, you wrote: > >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 . . . ________________________________ Message 6 _____________________________________ Time: 10:08:34 AM PST US Subject: AeroElectric-List: fuse link to replace fuse in low current applications? From: Charlie England I'm installing an 'alternative engine' using a fuel/ignition controller driving automotive style injectors & coil-near-plugs. My first draft for power distribution included individual fuses & B+ lines to each coil pack and to the injectors, to avoid one coil or injector failure taking out multiple the coils or injectors. Given the rarity of coil/injector failures, it seems reasonable to eliminate the multiple joints (along with weight & wiring complexity) of multiple fuses, & just use soldered-in fuse links instead of filling a fuse block with fuses. What say you? Thanks, Charlie ________________________________ Message 7 _____________________________________ Time: 10:48:23 AM PST US Subject: AeroElectric-List: Re: LED Ghosting From: "user9253" Resistors can make the oil pressure LED the same brightness as the others under one set of conditions. But when the conditions change (reduced dimmer voltage) the brightness of all LEDs will no longer be the same. The only way for all LEDs to have the same brightness under all conditions is if each circuit has the same components. A relay can be used to switch the oil pressure LED to make that circuit the same as the other LEDs that use mechanical contacts. Here are possible relays to use: http://tinyurl.com/pt9yd6v or http://tinyurl.com/o3g77dc or http://tinyurl.com/q28mku6 Another option is to modify the other LED circuits to match the oil pressure circuit. Adding a diode to those other circuits might do the trick. The only way to find out is to try it. The relay is a sure thing but costs more and is harder to install and is less reliable then a solid state solution. Diodes may or may not work but are very inexpensive and easy to install. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=425139#425139 ________________________________ Message 8 _____________________________________ Time: 11:27:36 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: fuse link to replace fuse in low current applications? At 12:07 PM 6/19/2014, you wrote: >I'm installing an 'alternative engine' using a >fuel/ignition controller driving automotive >style injectors & coil-near-plugs. My first >draft for power distribution included individual >fuses & B+ lines to each coil pack and to the >injectors, to avoid one coil or injector failure >taking out multiple the coils or injectors. > >Given the rarity of coil/injector failures, it >seems reasonable to eliminate the multiple >joints (along with weight & wiring complexity) >of multiple fuses, & just use soldered-in fuse >links instead of filling a fuse block with fuses. It's a juggling act for risk. Your assessment appears sound. I think I'd use butt-spliced links and put the wires under the legacy 'fire sleeve' but that's a process detail. What size wires make up your feeders to the loads? Bob . . . ________________________________ Message 9 _____________________________________ Time: 12:02:08 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: LED Ghosting At 12:47 PM 6/19/2014, you wrote: Resistors can make the oil pressure LED the same brightness as the others under one set of conditions. But when the conditions change (reduced dimmer voltage) the brightness of all LEDs will no longer be the same. Quite true. Stings of led's driven in parallel from a common dimmer will vistually track each other only when all the strings are identical. From a pure physics perspective, LED light output is proportional to the current in the device . . . for values at or below the device's rated operating point. The only way for all LEDs to have the same brightness under all conditions is if each circuit has the same components. A relay can be used to switch the oil pressure LED to make that circuit the same as the other LEDs that use mechanical contacts. Here are possible relays to use: http://tinyurl.com/pt9yd6v or http://tinyurl.com/o3g77dc or http://tinyurl.com/q28mku6 The quest for intensity tracking between the various indicators is purely a matter of average current through the devices. Suppose the annunciator panel featured in the start of this thread had two LEDs in some slots, and single LEDs in others. It's entirely possible that they could be made to appear identical at some level of illumination by juggling their series resistors . . . but a bit of pencil whipping of the numbers will show that as supply voltage is reduced, the current through a series string of 2 LEDs will fall off faster than for a single LED. The use of a relay to energize an LED string to emulate the performance of an oil pressure switch isn't the issue. For all practical purposes, hard contacts and transistors produce the same behavior when turned ON for any given level of 'balanced' illumination. The variances of configuration don't come into play until the illumination is adjusted to some new value. This is why duty cycle switched dimming works so well for mixed configurations of LED illumination. When you duty-cycle switch the LED, peak light output remains constant while the eye integrates a reduced average energy into a perceived level of brightness that will be more uniform across mixed configurations. I wrote the spec for a mix illumination dimmer control for the Gates Piaggio GP-180 program where the design goal was to dim 5v incandescent, 28v incandescent and and 115vac electro-luminescent from a single knob. Nobody stood up and offered a proposal for that spec (about 1985). With micro-controllers and lookup table driven power supplies, it could be done today but not easily back then. Joe is right, unless the constellation of illumination sources have the same configuration, they will not track each other well with simple adjustment of applied voltage. Bob . . . ________________________________ Message 10 ____________________________________ Time: 01:16:32 PM PST US From: "Fisher Paul A." Subject: RE: AeroElectric-List: Re: LED Ghosting I'm confused by this thread. Back to the original issue - why is it important that all of the LEDs in the annunciator panel have the same brightness? Don't you just need to know if any particular one is on or off? Aren't they used to indicate a problem? I would hope that during most flights they would all be off. And if more than one of them was on, I certainly wouldn't be worried about one being brighter or dimmer than another - I'd be busy looking for a place to land! I do appreciate the electronics discussion about the physics of getting them to the same brightness. I just don't understand why that is important in this use case. Paul A. Fisher RV7A N18PF -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Thursday, June 19, 2014 2:01 PM Subject: Re: AeroElectric-List: Re: LED Ghosting --> At 12:47 PM 6/19/2014, you wrote: Resistors can make the oil pressure LED the same brightness as the others under one set of conditions. But when the conditions change (reduced dimmer voltage) the brightness of all LEDs will no longer be the same. Quite true. Stings of led's driven in parallel from a common dimmer will vistually track each other only when all the strings are identical. From a pure physics perspective, LED light output is proportional to the current in the device . . . for values at or below the device's rated operating point. The only way for all LEDs to have the same brightness under all conditions is if each circuit has the same components. A relay can be used to switch the oil pressure LED to make that circuit the same as the other LEDs that use mechanical contacts. Here are possible relays to use: http://tinyurl.com/pt9yd6v or http://tinyurl.com/o3g77dc or http://tinyurl.com/q28mku6 The quest for intensity tracking between the various indicators is purely a matter of average current through the devices. Suppose the annunciator panel featured in the start of this thread had two LEDs in some slots, and single LEDs in others. It's entirely possible that they could be made to appear identical at some level of illumination by juggling their series resistors . . . but a bit of pencil whipping of the numbers will show that as supply voltage is reduced, the current through a series string of 2 LEDs will fall off faster than for a single LED. The use of a relay to energize an LED string to emulate the performance of an oil pressure switch isn't the issue. For all practical purposes, hard contacts and transistors produce the same behavior when turned ON for any given level of 'balanced' illumination. The variances of configuration don't come into play until the illumination is adjusted to some new value. This is why duty cycle switched dimming works so well for mixed configurations of LED illumination. When you duty-cycle switch the LED, peak light output remains constant while the eye integrates a reduced average energy into a perceived level of brightness that will be more uniform across mixed configurations. I wrote the spec for a mix illumination dimmer control for the Gates Piaggio GP-180 program where the design goal was to dim 5v incandescent, 28v incandescent and and 115vac electro-luminescent from a single knob. Nobody stood up and offered a proposal for that spec (about 1985). With micro-controllers and lookup table driven power supplies, it could be done today but not easily back then. Joe is right, unless the constellation of illumination sources have the same configuration, they will not track each other well with simple adjustment of applied voltage. Bob . . . ________________________________ Message 11 ____________________________________ Time: 01:49:07 PM PST US From: Charlie England Subject: Re: AeroElectric-List: fuse link to replace fuse in low current applications? On 6/19/2014 1:26 PM, Robert L. Nuckolls, III wrote: > > > At 12:07 PM 6/19/2014, you wrote: >> I'm installing an 'alternative engine' using a fuel/ignition >> controller driving automotive style injectors & coil-near-plugs. My >> first draft for power distribution included individual fuses & B+ >> lines to each coil pack and to the injectors, to avoid one coil or >> injector failure taking out multiple the coils or injectors. >> >> Given the rarity of coil/injector failures, it seems reasonable to >> eliminate the multiple joints (along with weight & wiring complexity) >> of multiple fuses, & just use soldered-in fuse links instead of >> filling a fuse block with fuses. > > It's a juggling act for risk. Your assessment appears > sound. I think I'd use butt-spliced links and put the > wires under the legacy 'fire sleeve' but that's a > process detail. What size wires make up your feeders > to the loads? > > > Bob . . . Design size *could* be as small as 22ga (actually, 20ga would be adequate for a single feed to power 4 ignition coils). The injectors get 22ga to each injector. I'd like to feed each coil & injector with 22ga, but realize that the 4-step-smaller criteria for the link is tough to achieve (26ga link). In the 'Book', it mentions a 4-6" length for the fuse link. Any reason not to go a bit shorter, with the link and an inch or two of the heavier wire under the 'fire sleeve'? Thanks, Charlie ________________________________ Message 12 ____________________________________ Time: 02:36:35 PM PST US From: "Sacha" Subject: RE: AeroElectric-List: fuse link to replace fuse in low current applications? > I think I'd use butt-spliced links Bob, just curious, would solder splices also be acceptable? ________________________________ Message 13 ____________________________________ Time: 05:50:41 PM PST US Subject: AeroElectric-List: Re: LED Ghosting From: "donjohnston" FisherPaulA(at)johndeere. wrote: > I'm confused by this thread. Back to the original issue - why is it important that all of the LEDs in the annunciator panel have the same brightness? Don't you just need to know if any particular one is on or off? Aren't they used to indicate a problem? I would hope that during most flights they would all be off. And if more than one of them was on, I certainly wouldn't be worried about one being brighter or dimmer than another - I'd be busy looking for a place to land! > > I do appreciate the electronics discussion about the physics of getting them to the same brightness. I just don't understand why that is important in this use case. > > Paul A. Fisher > RV7A N18PF > > -- Valid question. The master warning panel (I should probably refer to it as an annunicator panel) also has indicators for when the fuel pump is on and pitot heat is on (those indicators are amber where the low oil pressure, door unsafe, etc. are red). So you're flying along at night and you have the pitot heat or fuel pump on. The LEDs are rather bright so you dim the indicators. Once you dim those LEDs to a comfortable brightness, that low oil pressure LED will not illuminate at all. Hopefully tomorrow I will be able to get the voltage readings requested. I also got the MOSFET today so I'll give that a go as well. 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