---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 10/04/10: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:50 AM - Re: Apparent grounding problems (Sam Hoskins) 2. 07:06 AM - Re: Apparent grounding problems (user9253) 3. 08:35 AM - Re: Apparent grounding problems (Ken) 4. 01:31 PM - Re: Bob's take? (Robert L. Nuckolls, III) 5. 05:48 PM - Re: Diode type, size (jonlaury) 6. 06:10 PM - Re: Re: Diode type, size (Dan Billingsley) ________________________________ Message 1 _____________________________________ Time: 05:50:20 AM PST US Subject: Re: AeroElectric-List: Apparent grounding problems From: Sam Hoskins Simon, thank you for taking you time and your thoughtful explanation. I'll print it out and take it to the airport with me. Unfortunately, the Dynon temp sensor is a single wire system, that's why they suggested going to the two wire GRT sensor, and like I said, I have to pull the engine to install it. This means that I'll order the sensor now and see if I can remember to install it, the next time I have the engine pulled forward. You can see the problem with getting to the mags: http://picasaweb.google.com/Sam.Hoskins/MyQuickieQ200?authkey=Gv1sRgCPnWj4CVu-_ZSg#5355132824613895954 I'll look over the Dynon installation instructions a bit more and see what they call out for the grounds. I believe they specify a case ground to the instrument panel. I probably ran a ground wire from the case to the d-sub connector which I use a a common ground, per Bob's mini-bus method: http://aeroelectric.com/Pictures/Grounding/Minibus1.jpg In the meantime I'll look over the connections and pin insertions. Thanks again. Sam On Sun, Oct 3, 2010 at 8:21 PM, S. Ramirez wrote: > Sam, > > Ground problems are common on this forum, on other forums, and in the > engineering world, where they literally start. The best way to look at a > ground system from an engineering point of view is to model it using not > only the components involved but also the wires. Wires are what cause most > ground problems, especially if the design and/or construction is wrong. > > When Dynon says that you have a bad ground, they can be talking about > faulty construction or faulty design. You are the designer in this case, > not Dynon, and I believe they are telling you that you designed and > constructed a "bad ground." > > I studied your diagram, and it lacks wire lengths, which are crucial to a > good analysis. However, one can still study it, because there is anecdotal > data from this topology. There is strong evidence that your problem lies in > your sensors' grounding methods. In order to overkill the problem and have > high probability of success, you should run individual sensor grounds from > each sensor to the brass block located behind the instrument panel and on to > the D180. In other words, ground wires should exist from each sensor all > the way to the D180. Furthermore, you should twist each signal and its > dedicated ground wire. > > Most people do not know why wires should be twisted. They are twisted in > order to guarantee that the wires stay adjacent and as close to each other > as possible. Why is this important? One reason it is because when a signal > travels from the sensor to the D180, it actually travels in two directions. > One direction is current flowing from the sensor to the D180 on the signal > wire, and the other direction is the return current traveling back on the > ground wire (or vice-versa). When these currents travel down a wire, they > give off electrostatic and electromagnetic fields that potentially interfere > with signals on other wires. If the signal and return wires are adjacent, > their fields literally cancel each other out because of the two wires' > mutually exclusive inductance. Furthermore, since they cancel, they do not > interfere with other signals traveling down other wires. Of course, this is > the ideal situation. In real life, fields don't actually cancel 100%, but > the trick is to minimize interference as much as possible. Multistrips and > striplines on circuit boards are two well known methods to transmit high > frequency signals. In cables, twisted wires and shielded cables are two > well known methods. The theory behind all of the above methods is the same, > just different equations. > > In order to easily accomplish what I said above, I believe you should get > two wire sensors where practical and run individual twisted wires from the > sensors to the D180. If you cannot get two wire sensors, pick up the ground > where the sensor ground meets the engine block. I'm quite certain but not > totally sure that the D180 provides for individual sensor wires. If it > doesn't, then you will have to run the D180's ground to a ground bar, not a > connector, and connect all sensor grounds there. This will mean that all of > the sensors will have their return currents flowing on that one wire for a > short distance, which of course robs you of the mutually exclusive > inductance effect for that length of the wire. If the wire is short enough, > you will not see problems. If the Dynon D180 does provide for individual > sensor return currents, you will notice that each return is adjacent to its > respective signal. Now you know why it is so. > > It seems to me that since you already have your ground system designed and > built, the easiest way to solve your problem is to first prove what I say > above by running the twisted wires from the D180 to the sensors directly. > This should be fairly easy if you start at the D180 and then group all the > wires as a unit (taped or cable tied together) and run them back to the > engine through the easiest placement possible, even if it's through the > cabin. Then cut them to the correct length at the engine and connect them > to the sensors. Then fire up the airplane and see what happens. > > Good luck on whatever you decide to do. > > Simon Ramirez > Oviedo, FL USA > LEZ N-44LZ > > > On 10/3/2010 9:49 AM, Sam Hoskins wrote: > > I am experiencing a digital "flicker" in a couple of my electronic engine > indicators. I am using a Dynon D180 in my all composite Quickie Q-200. > > The problem is most apparent in the oil temp. It rapidly bounces from > 190, to 235, to 200, etc, many times a second. A couple of the other > instruments do the same, but the oil temp is the worst. > > I contacted Dynon and they said most likely it is a "bad ground". I am > attaching a crude sketch of my instrumentation ground system. (I don't have > the backside of the forest of tabs grounding block mounted directly to the > firewall, because is just so very hard to access, so I have an 8AWG wire > connecting the two.) > > The Dynon oil temp sensor is a single wire unit, with the ground path > completed through the engine. Dynon suggested I try a GRT two wire sensor. > I may do this, but I have to pull the engine to access the accessory case, > and besides, I want to get at the root cause. > > Any suggestions? > > Thanks. > > Sam Hoskins > Murphysboro, IL > www.samhoskins.blogspot.com > > ________________________________ Message 2 _____________________________________ Time: 07:06:02 AM PST US Subject: AeroElectric-List: Re: Apparent grounding problems From: "user9253" Page 2-2 of the FlightDEK-D180 Installation Guide deals with grounding. The manual says, "If your panel is not metal, or is otherwise isolated from engine ground, connect a 14 AWG or larger wire to the instrument case." The manual does not say where to connect the other end of the 14awg wire, but the engine case would be ideal. The Dynon EMS pins 3, 5, 13, 16, & 17 are for grounding. If EMS pins 5, 16 & 17 are connected directly to the brass forest of tabs, you could be assured that the Dynon is well grounded. Doing this might not fix the problem but it is worth a try and is easier than pulling the engine. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=314604#314604 ________________________________ Message 3 _____________________________________ Time: 08:35:47 AM PST US From: Ken Subject: Re: AeroElectric-List: Apparent grounding problems Many automobiles and aircraft use single wire sensors with no problems. Temperature and pressure sensors typically are simply resistors that flow a constant small DC current so there is often little advantage to using sensors with two wires. My GRT EIS has numerous single sensor wires bundled with ignition coil, injector coil, and alternator wires with no problems. But yes the those ignition and injector coil wires are twisted with their respective grounds since they are pulsed relatively high current circuits. I'd look for poor connections especially in the ground circuits since multiple sensors are having issues. But also make sure any push on connectors on the sensors themselves are also clean and tight. With sensors fed by a common 5 volt supply, an erratic connection there could also affect multiple sensors. Speaking of grounds, I have two independent ground straps running from my engine block to two bolts on the firewall forest of tabs. That is generally recommended for electrically dependent engines. Darned if one of them hadn't worked itself loose on the engine block (despite having strain relief) on my last annual inspection. Ken Sam Hoskins wrote: > Simon, thank you for taking you time and your thoughtful explanation. > I'll print it out and take it to the airport with me. > > Unfortunately, the Dynon temp sensor is a single wire system, that's why > they suggested going to the two wire GRT sensor, and like I said, I have > to pull the engine to install it. This means that I'll order the sensor > now and see if I can remember to install it, the next time I have the > engine pulled forward. You can see the problem with getting to the > mags: http://picasaweb.google.com/Sam.Hoskins/MyQuickieQ200?authkey=Gv1sRgCPnWj4CVu-_ZSg#5355132824613895954 > > I'll look over the Dynon installation instructions a bit more and see > what they call out for the grounds. I believe they specify a case > ground to the instrument panel. I probably ran a ground wire from the > case to the d-sub connector which I use a a common ground, per Bob's > mini-bus method: http://aeroelectric.com/Pictures/Grounding/Minibus1.jpg > > In the meantime I'll look over the connections and pin insertions. > > Thanks again. > > Sam > > > On Sun, Oct 3, 2010 at 8:21 PM, S. Ramirez > wrote: > > Sam, > > Ground problems are common on this forum, on other forums, and in > the engineering world, where they literally start. The best way to > look at a ground system from an engineering point of view is to > model it using not only the components involved but also the wires. > Wires are what cause most ground problems, especially if the design > and/or construction is wrong. > > When Dynon says that you have a bad ground, they can be talking > about faulty construction or faulty design. You are the designer in > this case, not Dynon, and I believe they are telling you that you > designed and constructed a "bad ground." > > I studied your diagram, and it lacks wire lengths, which are crucial > to a good analysis. However, one can still study it, because there > is anecdotal data from this topology. There is strong evidence that > your problem lies in your sensors' grounding methods. In order to > overkill the problem and have high probability of success, you > should run individual sensor grounds from each sensor to the brass > block located behind the instrument panel and on to the D180. In > other words, ground wires should exist from each sensor all the way > to the D180. Furthermore, you should twist each signal and its > dedicated ground wire. > > Most people do not know why wires should be twisted. They are > twisted in order to guarantee that the wires stay adjacent and as > close to each other as possible. Why is this important? One reason > it is because when a signal travels from the sensor to the D180, it > actually travels in two directions. One direction is current > flowing from the sensor to the D180 on the signal wire, and the > other direction is the return current traveling back on the ground > wire (or vice-versa). When these currents travel down a wire, they > give off electrostatic and electromagnetic fields that potentially > interfere with signals on other wires. If the signal and return > wires are adjacent, their fields literally cancel each other out > because of the two wires' mutually exclusive inductance. > Furthermore, since they cancel, they do not interfere with other > signals traveling down other wires. Of course, this is the ideal > situation. In real life, fields don't actually cancel 100%, but the > trick is to minimize interference as much as possible. Multistrips > and striplines on circuit boards are two well known methods to > transmit high frequency signals. In cables, twisted wires and > shielded cables are two well known methods. The theory behind all > of the above methods is the same, just different equations. > > In order to easily accomplish what I said above, I believe you > should get two wire sensors where practical and run individual > twisted wires from the sensors to the D180. If you cannot get two > wire sensors, pick up the ground where the sensor ground meets the > engine block. I'm quite certain but not totally sure that the D180 > provides for individual sensor wires. If it doesn't, then you will > have to run the D180's ground to a ground bar, not a connector, and > connect all sensor grounds there. This will mean that all of the > sensors will have their return currents flowing on that one wire for > a short distance, which of course robs you of the mutually exclusive > inductance effect for that length of the wire. If the wire is short > enough, you will not see problems. If the Dynon D180 does provide > for individual sensor return currents, you will notice that each > return is adjacent to its respective signal. Now you know why it is so. > > It seems to me that since you already have your ground system > designed and built, the easiest way to solve your problem is to > first prove what I say above by running the twisted wires from the > D180 to the sensors directly. This should be fairly easy if you > start at the D180 and then group all the wires as a unit (taped or > cable tied together) and run them back to the engine through the > easiest placement possible, even if it's through the cabin. Then > cut them to the correct length at the engine and connect them to the > sensors. Then fire up the airplane and see what happens. > > Good luck on whatever you decide to do. > > Simon Ramirez > Oviedo, FL USA > LEZ N-44LZ > > > > On 10/3/2010 9:49 AM, Sam Hoskins wrote: >> I am experiencing a digital "flicker" in a couple of my electronic >> engine indicators. I am using a Dynon D180 in my all composite >> Quickie Q-200. >> >> The problem is most apparent in the oil temp. It rapidly bounces >> from 190, to 235, to 200, etc, many times a second. A couple of >> the other instruments do the same, but the oil temp is the worst. >> >> I contacted Dynon and they said most likely it is a "bad ground". >> I am attaching a crude sketch of my instrumentation ground >> system. (I don't have the backside of the forest of tabs >> grounding block mounted directly to the firewall, because is just >> so very hard to access, so I have an 8AWG wire connecting the two.) >> >> The Dynon oil temp sensor is a single wire unit, with the ground >> path completed through the engine. Dynon suggested I try a GRT two >> wire sensor. I may do this, but I have to pull the engine to >> access the accessory case, and besides, I want to get at the root >> cause. >> >> Any suggestions? >> >> Thanks. >> >> Sam Hoskins >> Murphysboro, IL >> www.samhoskins.blogspot.com > > > * > ________________________________ Message 4 _____________________________________ Time: 01:31:06 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Bob's take? At 04:12 PM 10/3/2010, you wrote: > > >Bob, if you get a chance, take a look at the Rotax list as there is an >interestiing difference of opinion concerning Amps and wire sizes. I >would like >your take on it. I've capture it to a thumb drive but it needs a LOT more attention to it than I have right now. I'm headed back to M.L. in a few minutes and I'll see if I can get to it tonight or in the morning. Bob . . . //// (o o) ===========o00o=(_)=o00o======== < Go ahead, make my day . . . > < show me where I'm wrong. > ================================ ________________________________ Message 5 _____________________________________ Time: 05:48:24 PM PST US Subject: AeroElectric-List: Re: Diode type, size From: "jonlaury" Dan, Radio Shack IN 5400 type diodes are the ones that Bob has recommended for your purpose. I think mine were IN 5402's. If I remember correctly, the last number doesn't have much bearing on suitability for our purposes John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=314706#314706 ________________________________ Message 6 _____________________________________ Time: 06:10:17 PM PST US From: Dan Billingsley Subject: Re: AeroElectric-List: Re: Diode type, size Thanks John, I appreciate the reply. Dan ----- Original Message ---- From: jonlaury Sent: Mon, October 4, 2010 5:44:55 PM Subject: AeroElectric-List: Re: Diode type, size Dan, Radio Shack IN 5400 type diodes are the ones that Bob has recommended for your purpose. I think mine were IN 5402's. If I remember correctly, the last number doesn't have much bearing on suitability for our purposes John Read this topic online here: http://forums.matronics.com/viewtopic.php?p=314706#314706 ------------------------------------------------------------------------------------- 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.