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dr
cjs
charlesmc
jclark
Dad’s RV-10
RE: CAN bus pulse width and rise times
…N49ex
Moving from theory and datasheet to reality, I decided to actually look at the CAN bus in my plane. I have the typical 22 gauge Tefcel twisted shielded pair wiring, not the special CAN bus stuff, and darn close to the 66 foot limit. I hooked the scope up at the AHARS, which is somewhere in the middle of the bus. Here are some pictures of CAN HI, CAN Lo, and the difference in red. While there are some edge artifacts indicative of reflection components, they are minimal, and noise is really minor. Looks like rise times are in the 66 to 72 ish nS and fall times are 140 to 142 nS. Pulse times are 1 uS and Hi and Lo signals are 1V each. Looks easily clean enough to have no problems. Also measured the twisted pair and determined its impedance is about 67 ohms, and prop delay is 1.57nS/foot.
So, given these rise and fall times and the prop delay of this cable, you can see how Garmin says around 66 feet max, as with the worst case transmitter to receiver delay/distance, the the impedance mismatch reflections end up pretty much absorbed in the slow rise and fall times.
yahugh
dr
WDYDWYRTW? (11 / 2-3 / 2024)
...getting this weekend's started. Pretty BR and RA in N.TX this Saturday. v/r,dr Sunday update (yuck): KDFW 031553Z 13013G17KT 1 3/4SM -RA BR FEW010 BKN015 OVC031 23/22 A2982 RMK AO2 SLP090 T02280217 PNO $ KDFW 031450Z 0315/0418 16012KT P6SM VCSH BKN016 FM031600 16016G26KT P6SM VCSH BKN025...
vansairforce.net
cjs
Whirlwind 300 series composite prop issue on my RV14
Want to bring to light an issue I am having with the 300 series three-bladed Whirlwind composite prop on my RV14: Scoring of the hub from the rubber gaskets. Bottom line, so far its a Cluster F and I am not sure how it will resolve. Background Info: RV14 with IO-390 Thunderbolt - about 620...
vansairforce.net
charlesmc
3D Printed Drill Bit Organizer
To speed access to common RV drill bits, I created a drill bit organizer in F3D and then 3D printed it. I've found it to be very useful, so I thought I'd post the design. The slots to the right are unlabeled for misc. drill bits, but if there is a common size that I missed, let me know and I'll...
vansairforce.net
jclark
Canopy UHMW Block Failure (Disintegration) Applies to RV6, 7, 8, and 9
Yesterday, as I attempted to open the sliding canopy on my RV8, it got "stuck/hung up". Upon closer inspection, I realized that the UHNW block on the sliding rail was DISINTEGRATING!!! It crumbled into several pieces. I could then lift the canopy's rear end up without resistance! I have no idea...
vansairforce.net
Dad’s RV-10
F-716 Seat Rib - Adding a Hole
Is it acceptable to drill an additional penetration for a snap bushing in a F-716 seat rib? Is there written guidance about this somewhere? Thanks.
www.vansairforce.net
RE: CAN bus pulse width and rise times
…N49ex
Moving from theory and datasheet to reality, I decided to actually look at the CAN bus in my plane. I have the typical 22 gauge Tefcel twisted shielded pair wiring, not the special CAN bus stuff, and darn close to the 66 foot limit. I hooked the scope up at the AHARS, which is somewhere in the middle of the bus. Here are some pictures of CAN HI, CAN Lo, and the difference in red. While there are some edge artifacts indicative of reflection components, they are minimal, and noise is really minor. Looks like rise times are in the 66 to 72 ish nS and fall times are 140 to 142 nS. Pulse times are 1 uS and Hi and Lo signals are 1V each. Looks easily clean enough to have no problems. Also measured the twisted pair and determined its impedance is about 67 ohms, and prop delay is 1.57nS/foot.
So, given these rise and fall times and the prop delay of this cable, you can see how Garmin says around 66 feet max, as with the worst case transmitter to receiver delay/distance, the the impedance mismatch reflections end up pretty much absorbed in the slow rise and fall times.
CAN bus pulse width and rise times
Anybody out there used an oscilloscope to look at the Garmin CAN bus during normal operation? Looking for photos showing minimum pulse width and rise times. Thanks
vansairforce.net
yahugh
RV-7 #70155 N461RP
This plane, built by Robert Paisley, was previously in an airworthy condition and has about 500 hours on the airframe with a Subaru engine. The previous owner (a friend of Mr. Paisley) was in the process of converting it to an O-360 with an electronic fuel injection and ignition system produced...
vansairforce.net
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