---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 03/11/17: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:12 AM - Re: Re: Hobbs wiring (Ron Burnett) 2. 05:30 AM - Re: Re: Hobbs wiring (Kelly McMullen) 3. 06:41 AM - Re: Hobbs wiring (user9253) 4. 07:33 AM - Re: Re: Hobbs wiring (Alec Myers) 5. 09:10 AM - Re: Re: Hobbs wiring (Robert L. Nuckolls, III) 6. 09:16 AM - Re: Re: Hobbs wiring (Robert L. Nuckolls, III) 7. 02:14 PM - Re: Re: Hobbs wiring (Ron Burnett) ________________________________ Message 1 _____________________________________ Time: 05:12:29 AM PST US Subject: Re: AeroElectric-List: Re: Hobbs wiring From: Ron Burnett Joe, Don't have picture so will try to describe. I have converted from a Subaru back to a Lycoming, so I have a keyed master switch and EFII ignition. The whole system comes alive with the key, but has a switch that bypasses all if necessary. Trying to tie in a Hobbs bought and in panel but never hooked up before. Now I have the oil pressure activated switch teed into the VDO oil pressure sender for the GRT EIS. Thanks, Ron Burnett May you have the Lord's blessings today! Sent from my iPad > On Mar 9, 2017, at 7:55 AM, user9253 wrote: > > > You are on the right track if my interpretation of your post is correct. But I can not say for sure until seeing a complete schematic of your proposed circuit including the master switch and battery contactor. A picture is worth a thousand words. > > -------- > Joe Gores > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=467106#467106 > > > > > > > > > ________________________________ Message 2 _____________________________________ Time: 05:30:40 AM PST US Subject: Re: AeroElectric-List: Re: Hobbs wiring From: Kelly McMullen What might be the advantage of a hobbs in a plane that cannot be used for hire? Just curious. Seems like tach would be more than sufficient. A hobbs will accelerate when maintenance is required, make the aircraft look higher time than it really is, etc. Not to mention the extra complexity and potential failure points. Certainly your choice to do if you want one. On 3/11/2017 6:09 AM, Ron Burnett wrote: > > Joe, > > Don't have picture so will try to describe. I have converted from a Subaru back to a Lycoming, so I have a keyed master switch and EFII ignition. The whole system comes alive with the key, but has a switch that bypasses all if necessary. > > Trying to tie in a Hobbs bought and in panel but never hooked up before. Now I have the oil pressure activated switch teed into the VDO oil pressure sender for the GRT EIS. > > Thanks, > > Ron Burnett ________________________________ Message 3 _____________________________________ Time: 06:41:36 AM PST US Subject: AeroElectric-List: Re: Hobbs wiring From: "user9253" Ron, It doesn't matter where the 12 volt supply comes from as long as it goes on and off with the battery contactor. Just connect 12 volts to the hobbs meter and to the indicator light as pictured in your original post. This advice is based on the assumption that the switch in your picture is an oil pressure switch. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=467166#467166 ________________________________ Message 4 _____________________________________ Time: 07:33:52 AM PST US From: Alec Myers Subject: Re: AeroElectric-List: Re: Hobbs wiring Most TC aircraft Hobbes meters don't get switched via the battery master. Too easy to hide time by flying with the master off. > On Mar 11, 2017, at 9:39 AM, user9253 wrote: > > > Ron, > It doesn't matter where the 12 volt supply comes from as long as it goes on and off with the battery contactor. Just connect 12 volts to the hobbs meter and to the indicator light as pictured in your original post. This advice is based on the assumption that the switch in your picture is an oil pressure switch. > > -------- > Joe Gores > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=467166#467166 > > > > > > > > > ________________________________ Message 5 _____________________________________ Time: 09:10:24 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Hobbs wiring At 09:31 AM 3/11/2017, you wrote: > >Most TC aircraft Hobbes meters don't get switched via the battery >master. Too easy to hide time by flying with the master off. Correct. Most folks are unaware of the fact that tens of thousands of Cessnas had an always hot battery bus right at the battery contactor. It feed two fuses . . . one for the Hobbs meter controlled through an oil pressure switch . . . the other for the electric clock. If one would like to add a low oil pressure warning light, then the hobbs feeder needs to drive from a controlled source. In OBAM aircraft a good alternative feed is the e-bus. Now the low oil pressure light (and perhaps warning buzzer) serves four functions. It monitors oil pressure, it controls the Hobbs meter to measure ENGINE RUN time, it gives warning at shut down that both the DC master and E-Bus alternate feed switches are open. See . . . http://tinyurl.com/zlpjzuc If you have an engine fitted with a PM alternator (a la Rotax or SD-8 standby) one COULD fabricate a circuit to watch for the existence of AC voltage on the alternator winding and use this signal to control the Hobbs and offer warnings for DC power shutdown . . . you just wouldn't have oil pressure warning. Bob . . . ________________________________ Message 6 _____________________________________ Time: 09:16:20 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Re: Hobbs wiring At 11:07 AM 3/11/2017, you wrote: >At 09:31 AM 3/11/2017, you wrote: >> >>Most TC aircraft Hobbes meters don't get switched via the battery >>master. Too easy to hide time by flying with the master off. > > Correct. Most folks are unaware of the fact that > tens of thousands of Cessnas had an always hot > battery bus right at the battery contactor. It > feed two fuses . . . one for the Hobbs meter controlled > through an oil pressure switch . . . the other for > the electric clock Hmmm . . . not always two fuses . . . seems the 1976 C-172 drove the Hobbs and clock from the same fuse Emacs! Bob . . . ________________________________ Message 7 _____________________________________ Time: 02:14:02 PM PST US Subject: Re: AeroElectric-List: Re: Hobbs wiring From: Ron Burnett My only tach is provided by the EIS. I do not have an engine tach. Thanks. Ron Burnett May you have the Lord's blessings today! Sent from my iPad > On Mar 11, 2017, at 7:28 AM, Kelly McMullen wrote: > > > What might be the advantage of a hobbs in a plane that cannot be used for hire? Just curious. > Seems like tach would be more than sufficient. > A hobbs will accelerate when maintenance is required, make the aircraft look higher time than it really is, etc. Not to mention the extra complexity and potential failure points. > Certainly your choice to do if you want one. > >> On 3/11/2017 6:09 AM, Ron Burnett wrote: >> >> Joe, >> >> Don't have picture so will try to describe. I have converted from a Subaru back to a Lycoming, so I have a keyed master switch and EFII ignition. The whole system comes alive with the key, but has a switch that bypasses all if necessary. >> >> Trying to tie in a Hobbs bought and in panel but never hooked up before. Now I have the oil pressure activated switch teed into the VDO oil pressure sender for the GRT EIS. >> >> Thanks, >> >> Ron Burnett > > > > ------------------------------------------------------------------------------------- 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.