---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 05/22/23: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:11 AM - Re: Re: Which Oil Pressure Switch? (Robert L. Nuckolls, III) 2. 04:38 PM - Overvoltage Protection for Rotax 9-Series Engines (Eric Page) 3. 06:50 PM - Re: Overvoltage Protection for Rotax 9-Series Engines (user9253) ________________________________ Message 1 _____________________________________ Time: 08:11:13 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Which Oil Pressure Switch? At 04:30 PM 5/20/2023, you wrote: > >Thanks Bob. >Sounds like your plan is exactly what I'm looking for. Not sure I >fully understand what's going on though. >You lost me at "I've sketched out an adapter circuit that would >interface the square wave output of your >tachometer pickup to the hour-meter." :) I can follow the diagrams basic >wiring, but still need some time in a dark corner to figure out the rest. >Slightly above my elctronical knowledge level. >I would happily accept/appreciate whatever you could come up with out of >your junkbox. Surely we can do some type of horse-trading to make it >worth your while. >Thanks again, >Shawn Very well sir. I'm mindful of the fact that this forum is populated with a diversity of experience and skills. It was not my wish that you grasp the gritty details of my proposal. But publishing the 'details' affords opportunity for those interested and willing to add the them to their personal bag of tricks. I'll scrape off a bit of space on the workbench and hammer this thing together. Bob . . . //// (o o) ===========o00o=(_)=o00o======== < Go ahead, make my day . . . > < show me where I'm wrong. > ================================ In the interest of creative evolution of the-best-we-know-how-to-do based on physics and good practice. ________________________________ Message 2 _____________________________________ Time: 04:38:55 PM PST US Subject: AeroElectric-List: Overvoltage Protection for Rotax 9-Series Engines From: "Eric Page" In a forum thread that I started in October 2021 about using a Rotax 912iS on my Kitfox, there was some discussion about my use of crowbar overvoltage protection (OVP). In that thread, Joe Gores asked, "Can it be designed to just open the relay without blowing a 1 amp fuse?" It turns out that, yes, it can. After several prototypes, I have a non-crowbar OVP Module for Rotax 9-series engines. See the attached PDF document. The oscilloscope screen capture shows its performance. Each horizontal division is half a millisecond (0.0005 sec) and each vertical division is 10V. The yellow trace is bus voltage (it starts at ~14.5V) and the purple trace is the output driving the relay coils (this trace is inverted; the relays are closed when the trace is at zero and open when it's above zero). When the bus voltage jumps to 40V, there's a ~3 millisecond delay (a time lifted from Bob's design, to prevent very short transients from causing nuisance trips), then the relay coil drive drops out (purple trace rising). Once tripped, the module latches in the tripped state, holding the relays open, which isolates the engine's stator feed from the regulator input. The module also flashes an indicator LED on the instrument panel and sends an alarm signal to an EFIS/EMS input. The trip voltage is adjustable and is set at 16.3V (another value lifted from Bob's design) but I used 40V for the test to demonstrate that the module can survive an overvoltage event (it's designed to survive 60V). The module adds pilot control of the charging system, a feature lacking in the Rotax wiring diagrams. The 912/914 manuals specify a B-lead circuit breaker that also feeds the regulator's Control terminal, but without a switch. On the 912iS/915iS engines, the regulators are exclusively controlled by the Rotax "Fuse Box" and the only regulator terminals accessible to the installer are the AC inputs. To provide pilot control, the module includes a latching PUSH ISOLATE switch, allowing it to be held in the off state (e.g. in the event of smoke/fire) or to be reset in the event of a nuisance trip. I'd love to hear feedback on this design from anyone who cares to offer it. As I've demonstrated repeatedly on this forum, I'm not an electrical engineer, so I may have overlooked something. Eric Read this topic online here: http://forums.matronics.com/viewtopic.php?p=510846#510846 Attachments: http://forums.matronics.com//files/ovp_module_oscilloscope_417.jpg http://forums.matronics.com//files/ovp_module_rev_j_177.pdf ________________________________ Message 3 _____________________________________ Time: 06:50:41 PM PST US Subject: AeroElectric-List: Re: Overvoltage Protection for Rotax 9-Series Engines From: "user9253" Eric, your schematic is way over my head. Are you sure that you aren't an electronic engineer. Good work. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=510847#510847 ------------------------------------------------------------------------------------- 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.