---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 08/23/17: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 09:15 AM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury) 2. 10:37 AM - Re: Non-aero app: 120/240 AC through 24vdc switch? (user9253) 3. 10:53 AM - Product Review - Voltmeter (Robert L. Nuckolls, III) 4. 01:29 PM - Re: Product Review - Voltmeter (C&K) 5. 01:44 PM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury) 6. 02:42 PM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury) 7. 04:57 PM - Re: Z-31 questions (Robert L. Nuckolls, III) 8. 04:57 PM - Re: Non-aero app: 120/240 AC through 24vdc switch? (user9253) 9. 08:39 PM - Re: Re: Non-aero app: 120/240 AC through 24vdc switch? (Robert McCallum) ________________________________ Message 1 _____________________________________ Time: 09:15:21 AM PST US Subject: AeroElectric-List: Re: Non-aero app: 120/240 AC through 24vdc switch? From: "jonlaury" Joe and Charlie, The switch controls an electronic lamp ballast driving two 75W UVC producing. I don't know if that is inductive or resistive load. Steady state amperage is 800ma And found this white paper(excerpt) on electronic ballasts. : "Design Considerations for Electronic Ballasts Inrush currents at turn-on, produced from some electronic ballasts can cause premature relay contact failures. These inrush currents can be much higher than those experienced with traditional tungsten or magnetic ballast loads because many electronic ballasts employ large energy storage capacitors. Such capacitors can charge up to 400V for a 277V line voltage, and will briefly draw high current from the line to achieve this voltage. As mentioned above, these typically short inrush currents can climb as high as 100 times the nominal operating levels. . Type of Load Inrush Current vs. Steady State Current Incandescent Lamp 10 - 15x Fluorescent or HID Lamp with Magnetic Ballast Up to 15x Electronic Ballast (Capacitive Load) Up to 100x The inrush current magnitude and duration depends upon the value of the capacitance (measured in F), along with circuit and power distribution network impedances. This current may weld relay contacts and other switching devices or possibly fuse semiconductors. " Below is an excellent, graphic explanation of how fluorescent lamps work. It describes a building magnetic field during start up that is collapsed to produce an inductive kick. Is that the smoking gun? http://www.edisontechcenter.org/Fluorescent.html Read this topic online here: http://forums.matronics.com/viewtopic.php?p=472092#472092 ________________________________ Message 2 _____________________________________ Time: 10:37:15 AM PST US Subject: AeroElectric-List: Re: Non-aero app: 120/240 AC through 24vdc switch? From: "user9253" Switches can bounce when closing. If the inrush current is 80 amps (100 times normal) then that explains why the 5 amp switch is prematurely failing. A switch rated at 15 or 20 amps would last longer. A double pole switch might help also. Connect the two halves of the switch in parallel. That will divide the current between the two sets of contacts. While the switch is bouncing, maybe one half will be closed while the other half is closed. Or maybe not. Anyway, a bigger double pole switch should last longer. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=472097#472097 ________________________________ Message 3 _____________________________________ Time: 10:53:38 AM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Product Review - Voltmeter A few weeks back we had some discussion about digital voltmeters. I opined that the 'net sources for such devices were legion but expressed some warm fuzzies about easy to mount, easy to wire, good performance and, of course, cheap! Found this guy on eBay http://tinyurl.com/ycrez6hh Ordered in a couple to play with. They seem meet all the qualifications for warm fuzzy status. Both articles were within 0.1 volt of true at 14.2 volts. They mount in ROUND holes and wire in with 1/4" fast-ons. At $8 each, they're not expensive. The only potential down side is sun-light viewability. Bob . . . ________________________________ Message 4 _____________________________________ Time: 01:29:23 PM PST US Subject: Re: AeroElectric-List: Product Review - Voltmeter From: C&K Yes I have to shield those with my hand to read them on outdoor equipment but they seem durable and are available even cheaper and with free delivery if you don't mind the wait from overseas. Ken On 23/08/2017 1:52 PM, Robert L. Nuckolls, III wrote: > > > A few weeks back we had some discussion about > digital voltmeters. I opined that the 'net > sources for such devices were legion but > expressed some warm fuzzies about easy to > mount, easy to wire, good performance > and, of course, cheap! > > > Found this guy on eBay > > http://tinyurl.com/ycrez6hh > > Ordered in a couple to play with. They > seem meet all the qualifications for > warm fuzzy status. > > Both articles were within 0.1 volt of > true at 14.2 volts. They mount in ROUND > holes and wire in with 1/4" fast-ons. > > At $8 each, they're not expensive. The only > potential down side is sun-light viewability. > > > Bob . . . > > ________________________________ Message 5 _____________________________________ Time: 01:44:23 PM PST US Subject: AeroElectric-List: Re: Non-aero app: 120/240 AC through 24vdc switch? From: "jonlaury" Joe, Would installing a flyback diode across the Line (diode banded end) and Load terminals on the switch snub the inductive spike? Aesthetically, I'm partial to the switch I'm using. It may have a DPDT cousin, but not sure. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=472110#472110 ________________________________ Message 6 _____________________________________ Time: 02:42:49 PM PST US Subject: AeroElectric-List: Re: Non-aero app: 120/240 AC through 24vdc switch? From: "jonlaury" Joe, Your idea re splitting the load on a DBDT is the right direction for a po' boy solution. I looked at Crydom Zero-Cross relays for my app but they're pretty expensive. Going to look at hi amp latching relays too. This from Crydom, mfgr of Solid State Relays re Zero-Cross relays: Electronic Ballasts typcially do not present an inductive characteristic, so an inductive spike at turn-off is not the issue n your application. Rather they are more like "switching" power supplies and present more of a capacitive characteristic, particularly on power up. The inrush current at turn-on can be many times the normal load current for a few milliseconds, especially if the power happens to be applied at the peak of the AC sine wave. That is what is likely causing your switch to stick on when you try to turn it off. You're thought of using a zero-cross SSR is actually the way to go, but not for the turn-off. Rather it ensures that the AC line power is connected at the zero-cross point of the AC wave, minimizing the inrush current to the (essentially) "discharged" capacitive circuitry of the electronic ballast. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=472112#472112 ________________________________ Message 7 _____________________________________ Time: 04:57:01 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Z-31 questions At 09:12 PM 8/20/2017, you wrote: >Whoa, Bob, that's one heckuva story! Thanks for explaining. I had >thought that the ground power jacks in my old Cherokees had been >hardwired to the bus but, not having the wiring diagrams handy, I >did not know for sure. Everybody has their own ideas. I looked through some early Cessna 100 series drawings and found for the most part, ground service was the 3-terminal, AN2552 receptacle with only the two fat terminals utilized to hook ground power right to the battery. C177 1968-75 moved ground service power to the bus with diode in pilot terminal to guard against reversed polarity on ground cart. In the C310 circa 1974, the ground power was AN2552 with a ground power relay energized from the pilot terminal and tied right to the bus. 1998 A36 uses AN2552 with diode in pilot terminal for reverse polarity protection. External power goes right to the battery. It would be interesting to know the narrative for design decisions in each case. It was kind a deja-vu reading through the electrical system narratives on the single engine Cessnas. Can't be absolutely sure after all these years but I wrote a lot of that stuff back then and the writing style seems very familar. Bob . . . ________________________________ Message 8 _____________________________________ Time: 04:57:02 PM PST US Subject: AeroElectric-List: Re: Non-aero app: 120/240 AC through 24vdc switch? From: "user9253" Since the problem is inrush current to charge a capacitor, not inductive generated current, a diode is not going to help. I see two possible solutions: limit the inrush current or use a switching device that can handle the current. The switching device can be a bigger switch or a mechanical relay or a solid state relay. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=472113#472113 ________________________________ Message 9 _____________________________________ Time: 08:39:15 PM PST US From: Robert McCallum Subject: Re: AeroElectric-List: Re: Non-aero app: 120/240 AC through 24vdc switch? The only function of a diode would be to explode when connected in either direction across the 240VAC Bob McC > > ---------- Original Message ---------- > From: user9253 > Date: August 23, 2017 at 7:56 PM > > > > Since the problem is inrush current to charge a capacitor, not inductive > generated current, a diode is not going to help. I see two possible solutions: > limit the inrush current or use a switching device that can handle the > current. The switching device can be a bigger switch or a mechanical relay or > a solid state relay. > > -------- > Joe Gores > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=472113#472113 > > > > > > > > > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.