---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 08/27/22: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:43 AM - Re: Re: flyback diode across fuel pump (Bob Verwey) 2. 06:03 AM - Re: flyback diode across fuel pump (user9253) 3. 06:18 AM - Re: Re: flyback diode across fuel pump (C&K) 4. 06:19 AM - Re: Re: flyback diode across fuel pump (Alec) 5. 06:39 AM - Re: Re: flyback diode across fuel pump (Charlie England) 6. 07:23 AM - Re: Re: flyback diode across fuel pump (Alec Myers) 7. 08:23 AM - Re: Re: flyback diode across fuel pump (Charlie England) 8. 11:40 AM - Re: flyback diode across fuel pump (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 01:43:11 AM PST US From: Bob Verwey Subject: Re: AeroElectric-List: Re: flyback diode across fuel pump Why the cap Joe and not just a diode? On 26 Aug 2022 17:20, "user9253" wrote: A diode won't hurt anything as long as the banded end is connected to positive. Van's RV-12 schematic shows an optional 22,000 microfarad capacitor across the fuel pump. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=507781#507781 ________________________________ Message 2 _____________________________________ Time: 06:03:48 AM PST US Subject: AeroElectric-List: Re: flyback diode across fuel pump From: "user9253" > Why the cap Joe and not just a diode? I don't know. Perhaps a capacitor helps to reduces interference to the aircraft electrical system. Maybe Bob N will reply. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=507793#507793 ________________________________ Message 3 _____________________________________ Time: 06:18:29 AM PST US Subject: Re: AeroElectric-List: Re: flyback diode across fuel pump From: C&K My thoughts are that a diode with a finite voltage drop does nothing for quieting noise from the pump that is less than that finite voltage drop (usually 0.6 volt for silicon diode). Comutated motors put some hash on the supply line. I'm not aware of it typically causing problems but a capacitor should help quiet such noise somewhat. Ken On 27-Aug.-22 9:03 a.m., user9253 wrote: > > >> Why the cap Joe and not just a diode? > I don't know. Perhaps a capacitor helps to reduces interference to the aircraft electrical system. Maybe Bob N will reply. > > -------- > Joe Gores > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=507793#507793 > > ________________________________ Message 4 _____________________________________ Time: 06:19:46 AM PST US From: Alec Subject: Re: AeroElectric-List: Re: flyback diode across fuel pump Used to be capacitors were cheaper than diodes, I think. Sent from my iPhone > On Aug 27, 2022, at 09:04, user9253 wrote: > > > >> Why the cap Joe and not just a diode? > > I don't know. Perhaps a capacitor helps to reduces interference to the aircraft electrical system. Maybe Bob N will reply. > > -------- > Joe Gores > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=507793#507793 > > > > > > > > > ________________________________ Message 5 _____________________________________ Time: 06:39:23 AM PST US From: Charlie England Subject: Re: AeroElectric-List: Re: flyback diode across fuel pump Diodes used as arc suppressors are pennies each. They 'bleed off' the large voltage spikes that happen when contacts open and load is suddenly removed from a circuit. Capacitors wired as power supply 'filters' typically exist to smooth variations in DC levels. They store energy during low demand, and give it up when demand causes voltage to sag below their charge state. Those variations can come from the 'ripple' in rectified AC supply voltage, or from variations in DC loads. The obvious example of (huge) variation in load would be the starter, causing 'brownouts' of electronic devices, other examples are inrush current to incandescent lamps, DC motors, or for a more repetitive example, a Facet pulse pump (though I wouldn't have expected the draw of a Facet pump to have a significant effect on DC bus stability). Charlie On Sat, Aug 27, 2022 at 8:22 AM Alec wrote: > > Used to be capacitors were cheaper than diodes, I think. > > > Sent from my iPhone > > > On Aug 27, 2022, at 09:04, user9253 wrote: > > mail.com> > > > > > >> Why the cap Joe and not just a diode? > > > > I don't know. Perhaps a capacitor helps to reduces interference to the > aircraft electrical system. Maybe Bob N will reply. > > > > -------- > > Joe Gores > > > > > > > > > > Read this topic online here: > > > > http://forums.matronics.com/viewtopic.php?p=507793#507793 > > > > > > > > > > > > > > > > > > > > =========== =========== =========== =========== =========== > > ________________________________ Message 6 _____________________________________ Time: 07:23:31 AM PST US From: Alec Myers Subject: Re: AeroElectric-List: Re: flyback diode across fuel pump On Aug 27, 2022, at 9:38 AM, Charlie England wrote: >Diodes used as arc suppressors are pennies each. They are, now. ________________________________ Message 7 _____________________________________ Time: 08:23:43 AM PST US Subject: Re: AeroElectric-List: Re: flyback diode across fuel pump From: Charlie England On 8/27/2022 9:23 AM, Alec Myers wrote: > > > On Aug 27, 2022, at 9:38 AM, Charlie England wrote: > >> Diodes used as arc suppressors are pennies each. > They are, now. How far back do you want to go? I ran a computer repair business in the 1970s/80s/90s, and they were pennies each back then. Electrolytic caps big enough to work as legit power supply filters were a lot more expensive back then, too. -- This email has been checked for viruses by Avast antivirus software. www.avast.com ________________________________ Message 8 _____________________________________ Time: 11:40:57 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: flyback diode across fuel pump At 09:57 PM 8/25/2022, you wrote: > > >Someone on VAF suggested putting a flyback suppression diode across >fuel pump leads like we do with contactor and relay solenoid coils. >This was re an automotive fuel pump like SDS/EFII/Airflow Performance/Walbro. > >What say Bob et Al? Did the author cite a noise problem which was mitigated by adding this component? I'm mystified by any assertion of added value. Rotary pumps powered by pm motors have no 'flyback' event. PutPut pumps like the Facet devices have electronically driven solenoids that 'cock' a compression spring. A cruise through the genealogy of exemplar patents for such pumps . . . https://tinyurl.com/2e6mmzyr . . . illustrates commonly applied technology for mitigating flyback energies in these devices that include resistors, diodes and capacitors as part of the designs dating back over 30 years. I'm curious as to the history of the thread. Bob . . . Un impeachable logic: George Carlin asked, "If black boxes survive crashes, why don't they make the whole airplane out of that stuff?" ------------------------------------------------------------------------------------- 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.