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STR
May 12, 2006

I thought I was a nice jester


devicenull posted:

It appears my Mobius has forgotten what time it is again.

None of my dashcams have ever kept good time. My current one gains about 10-20 minutes a month, and corrupts the memory card at random (yes, using high endurance cards, and I've tried several cards).

I really need to email Anker about it; the battery in it has gotten to where it no longer runs for the full 60 seconds after I shut the car off (which is probably why the card is getting corrupted). It's less than a year old.

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Platystemon
Feb 13, 2012



STR posted:

None of my dashcams have ever kept good time. My current one gains about 10-20 minutes a month, and corrupts the memory card at random (yes, using high endurance cards, and I've tried several cards).

WTF

I didn’t know it was possible to make a quartz clock that bad.

Sagebrush
Feb 26, 2012





Gravy Boat 2k

Sure it is. (Nearly) all quartz clocks use a standardized 32.768 KHz timing crystal whose frequency is electronically divided in half 15 times to get a 1-second pulse. One way to cut costs in your mega bargain dashcam is to buy your timing crystals from the factory reject pile, because 32.783 KHz is close enough, right? Who's gonna notice anyway?

Platystemon
Feb 13, 2012



So worst crystals Digikey will sell me (hundred parts per million tolerance) work out to four and half minutes per month in tolerance, but when you factor in frequency stability, the arithmetic checks out.

That’s before accounting for the temperature swings automobiles experience.

I would like to note that we’re talking about parts that cost seven and a seventh cents apiece when you’re not buying from the reject pile.

Using the same crystal as the CPU clock would saves money and make the clock more accurate because higher frequency crystals have better precision and stability, at the expense of power consumption. That would require effort, though.

Or maybe they’re really saving money by not using a crystal for the CPU clock at all. The catch with that is that it can break things like USB because the timing becomes too inaccurate for the host to accept.

Platystemon fucked around with this message at 06:09 on Sep 18, 2018

Laserface
Dec 24, 2004

Sipping harsh elixir,
the ice above us melting fast


Is this why my head unit clock loses 2 minutes over the course of 8 months? I normally gotta add 2min whenever I switch DST On/off

Sagebrush
Feb 26, 2012





Gravy Boat 2k

Yes, probably. 2 minutes in 8 months is roughly 6 parts per million, which is right what you'd expect for a generic quartz timing crystal (most of those I've seen are specced +/- 20ppm or so).

Crystals also expand and contract slightly with temperature, which alters their frequency even more, so if you live in a particularly hot part of the world you might find that your marginally larger crystal beats just a little slower and your clock loses time a bit more rapidly.

In general the crystals are trimmed for the median temperature in the sort of places humans usually inhabit, though, so the annual weather changes will mostly average out.

Platystemon
Feb 13, 2012



Laserface posted:

Is this why my head unit clock loses 2 minutes over the course of 8 months? I normally gotta add 2min whenever I switch DST On/off

Fifteen seconds per month is respectable.

Many quartz wristwatches aim for that and they have the advantage of operating at a more controlled temperature.

Platystemon
Feb 13, 2012



Sagebrush posted:

In general the crystals are trimmed for the median temperature in the sort of places humans usually inhabit, though, so the annual weather changes will mostly average out.

This can be true for high‐frequency crystals:



32768 Hz crystals have the unfortunate property that elevated and depressed temperatures both make them run slow:

Sagebrush
Feb 26, 2012





Gravy Boat 2k

^^^^ neat, I did not know that. What's the reason? Do they cut high-frequency crystals into different shapes from low-frequency ones?

Anyway, point is that if you're buying your electronics from random mystery Chinese sellers on AliExpress or Amazon or eBay, I absolutely expect that they are using the cheapest possible components, including Z-bin timing crystals that won't hold 10 minutes in a month. Or they're just leaving the crystal out entirely and relying on an on-chip resonator or whatever that is even less accurate. Watch some of the EEVBlog or BigClive videos of cheapo AE/DealExtreme/Banggood product teardowns if you really want to blow your mind.

Platystemon
Feb 13, 2012



Sagebrush posted:

^^^^ neat, I did not know that. What's the reason? Do they cut high-frequency crystals into different shapes from low-frequency ones?

Yes.

If a 33 kHz crystal were just a scaled version of a 4 Mhz crystal, it would be impractically large.

Instead they’re cut in the shape of tuning forks, which allows them to resonate at a much lower frequency in a compact package. They’re also cut at a different angle to to crystalline structure.





This page has more.

e: Actually, Wikipedia’s page is absurdly detailed now.

Platystemon fucked around with this message at 01:34 on Sep 19, 2018

Godholio
Aug 28, 2002

Does a bear split in the woods near Zheleznogorsk?


Sagebrush posted:

Crystals also expand and contract slightly with temperature, which alters their frequency even more, so if you live in a particularly hot part of the world you might find that your marginally larger crystal beats just a little slower and your clock loses time a bit more rapidly.

I have noticed exactly this over the past couple of months (just moved to a hotter location). Hot drat.

Laserface
Dec 24, 2004

Sipping harsh elixir,
the ice above us melting fast


Sagebrush posted:

Yes, probably. 2 minutes in 8 months is roughly 6 parts per million, which is right what you'd expect for a generic quartz timing crystal (most of those I've seen are specced +/- 20ppm or so).

Crystals also expand and contract slightly with temperature, which alters their frequency even more, so if you live in a particularly hot part of the world you might find that your marginally larger crystal beats just a little slower and your clock loses time a bit more rapidly.

In general the crystals are trimmed for the median temperature in the sort of places humans usually inhabit, though, so the annual weather changes will mostly average out.

Yeah im in Sydney AUS and it goes from as low as 1C in winter nights to 45C+ in summer (and I can only imagine in-car temps in summer would be nearing 60C+)

that explains it! cool.

Craptacular
Jul 11, 2004



Most dashcams seem to have GPS capabilities for displaying the lat/long. Why would they not just grab the time from the GPS signal to update the clock?

Sagebrush
Feb 26, 2012





Gravy Boat 2k

If you're really into it, you can assume that your crystal is pretty average, get some datasheets from digi-key for generic timing crystals that have t/f graphs like those posted above, find their reference temperature, compare that to your average annual temperature, and see how well the graph lines up with your observations.

I am working on building a digital instrument cluster for my motorcycle, and in the current version I took some shortcuts with the timing system, and it's fairly cool to see how my speedometer accuracy changes quite dramatically with the outside air temperature (as the timing system that's measuring the wheel revolutions speeds up and slows down).

STR
May 12, 2006

I thought I was a nice jester


Sagebrush posted:

^^^^ neat, I did not know that. What's the reason? Do they cut high-frequency crystals into different shapes from low-frequency ones?

Anyway, point is that if you're buying your electronics from random mystery Chinese sellers on AliExpress or Amazon or eBay, I absolutely expect that they are using the cheapest possible components, including Z-bin timing crystals that won't hold 10 minutes in a month. Or they're just leaving the crystal out entirely and relying on an on-chip resonator or whatever that is even less accurate. Watch some of the EEVBlog or BigClive videos of cheapo AE/DealExtreme/Banggood product teardowns if you really want to blow your mind.

My dashcam is from Anker, which is typically a bit better quality than random AliExpress and eBay poo poo. It's still Chinese stuff, but with a good warranty behind it and generally good quality.

And the clock just recently started picking up time a lot quicker. Previously it was a minute here and there. But the internal battery is pretty much done on it, after less than a year. Emailed Anker last night, haven't heard anything back yet, but they've always been pretty easy to deal with.

chrisgt
Sep 6, 2011



Now I wonder how far out the time on my dashcam is... I don't think I've ever checked that. I used to have a car that gained 5 minutes PER DAY. It didn't always do that, though, and it didn't start gaining 5 minutes a day all at once. But at some point I started noticing I was a bit late when I got in my car, caught on that the clock was fast, all was well. Same thing happened again, and from there on out it just started messing with me. At some point I put tape over the clock because it was worse than useless, then I junked the car. Hey if the clock doesn't work, why keep the thing around...

EIDE Van Hagar
Dec 8, 2000

MVP
Most Valuable Poster Awarded 2002, 2005, 2007


Cybernetic Crumb

make all clocks with ring oscillators so the timing is just random by process variation

wolrah
May 8, 2006
what?


Craptacular posted:

Most dashcams seem to have GPS capabilities for displaying the lat/long. Why would they not just grab the time from the GPS signal to update the clock?
Those with GPS usually do exactly this. Many do not have GPS though, and some who own GPS-capable models choose not to install the antenna or enable the feature due to a variety of concerns (mostly that if a court gets involved there are more ways for the GPS info to hurt you than help you).

Does anyone here have the Aukey DR02 dual camera? Techmoan seems to like it, any first-hand experience from goons? Looking to finally replace my G1W.

wolrah fucked around with this message at 19:27 on Sep 19, 2018

TotalLossBrain
Oct 20, 2010

Hier graben!

Craptacular posted:

Most dashcams seem to have GPS capabilities for displaying the lat/long. Why would they not just grab the time from the GPS signal to update the clock?

Any GPS device that decodes position also inherently decodes time. The dashcam disciplines its local oscillator to the GPS-decoded time and gives it a correction whenever needed.

Cartoon
Jun 20, 2008

poop

Not as much smashing glass but...

https://www.youtube.com/watch?v=Okp8XYj3Uik

Those good ol'boys in their logging trucks politely moving over a couple of cms.

https://www.youtube.com/watch?v=tJFBxLWhR0o

Hello Mrs Logger! Forgot the rig I see.

https://www.youtube.com/watch?v=WVaudP9YCaU

Chicken Doodle
May 16, 2007



I'm hoping you guys can help as I'm looking for something particular in a dash cam. All the ones I could find recommended in this thread are attached by suction cups to the windshield, but my car is like teflon and nothing with suction cups sticks to it. My current camera has a kind of mount that is stuck with sticky backing to the windshield, and I can remove my camera from that dock when not in use. I'm looking for something similar.

Current camera for example: http://www.ojocam.com/

The quality isn't that great in the build of this camera which is why I'm looking for any alternatives. I appreciate any suggestions!

spog
Aug 7, 2004

It's your own bloody fault.


Chicken Doodle posted:

I'm hoping you guys can help as I'm looking for something particular in a dash cam. All the ones I could find recommended in this thread are attached by suction cups to the windshield, but my car is like teflon and nothing with suction cups sticks to it. My current camera has a kind of mount that is stuck with sticky backing to the windshield, and I can remove my camera from that dock when not in use. I'm looking for something similar.

Current camera for example: http://www.ojocam.com/

The quality isn't that great in the build of this camera which is why I'm looking for any alternatives. I appreciate any suggestions!

Any one that uses a screw-in tripod mount will happily work with a 'car windshield tape mount':



Like my mobius, for example

LongSack
Jan 17, 2003



Chicken Doodle posted:

I'm hoping you guys can help as I'm looking for something particular in a dash cam. All the ones I could find recommended in this thread are attached by suction cups to the windshield, but my car is like teflon and nothing with suction cups sticks to it. My current camera has a kind of mount that is stuck with sticky backing to the windshield, and I can remove my camera from that dock when not in use. I'm looking for something similar.

Current camera for example: http://www.ojocam.com/

The quality isn't that great in the build of this camera which is why I'm looking for any alternatives. I appreciate any suggestions!

I have the same problem with my windshield, and I ended up buying a mount that attaches to the rear view mirror support

STR
May 12, 2006

I thought I was a nice jester


Roav (by Anker) dashcams come with a permanent windshield mount with 3M's best tape. The mount was so good that I couldn't get it removed from my old car (they sent me a new suction cup mount that's good, but not as good, but it was free upon request).

.... currently fighting with them over a warranty replacement though. Never had an issue with any other Anker product, they're giving a lot of push back on this (battery is all but dead and less than a year old).

Nitrox
Jul 5, 2002

Slur, your fighting style is extremely problematic!

Who the gently caress would ever put a dashcam on a suction cup mount? Proper cams sit directly on base plate that is glued to the glass. The more pivot points away from chassis, the more flex and vibration you get in your footage. Don't do suction cups.

This is my go-to recommendation for dashcam, can't do better at this price point. And it's nearly invisible from outside
https://www.amazon.com/Blueskysea-B...g/dp/B0773FXVKL

PenisMonkey
Apr 30, 2004

Be gentally.

I use suction cup

Fo3
Feb 14, 2004

RAAAAARGH!!!! GIFT CARDS ARE FUCKING RETARDED!!!!

(I need a hug)


I use a suction cup. My footage comes out OK even though there's some play in the horizontal adjustment of the the mount (nothing to do with suction cup or not). It's the old favourite g1w and the quality looks better than many cameras people now use ~$100 instead these days, and it hasn't broke yet.
It's fallen off the windshield 3 times in the past 5 years or so. If only some old GPS and phone mounts could have made a suction cup mount this bloody good - they fell off or got out of shape in the sun all the time.

Fo3 fucked around with this message at 15:31 on Sep 26, 2018

Chunjee
Oct 27, 2004
I can't read or write

I'm looking at this one that goes over the existing rearview mirror because I want a backup cam without messing with adding a screen:
https://www.amazon.com/Pruveeo-D700...g/dp/B073WFJ7HV

Any experience on how shaky that might record? I only really care about the video in event of insurance claims.

Rev. Bleech_
Oct 19, 2004

We was comin' back from the island of Tinian to Leyte - just delivered the BUMB, the Hiroshima bumb. Eleven hundred men went into the water.


STR posted:

Roav (by Anker) dashcams come with a permanent windshield mount with 3M's best tape. The mount was so good that I couldn't get it removed from my old car (they sent me a new suction cup mount that's good, but not as good, but it was free upon request).

.... currently fighting with them over a warranty replacement though. Never had an issue with any other Anker product, they're giving a lot of push back on this (battery is all but dead and less than a year old).

Weird. I sent them an email a week and a half ago saying my battery had swelled and the screen would pop out. After requesting a photo, they said "fuckit, have a brand new unit and don't bother sending the old one back"

Krakkles
May 5, 2003

like and subscribe for more passive-aggressive roadway bullshit adventure in Chigcao

Chunjee posted:

I'm looking at this one that goes over the existing rearview mirror because I want a backup cam without messing with adding a screen:
https://www.amazon.com/Pruveeo-D700...g/dp/B073WFJ7HV

Any experience on how shaky that might record? I only really care about the video in event of insurance claims.
This isn't a perfect parallel, but:

https://www.youtube.com/watch?v=f6DyNFcRjA8

That's a Mobius attached to the stem holding the rearview, in a lifted Jeep on mud tires. There's some noticeable vibration/shake, but it's generally still clear enough to capture details. If your car shakes less than a lifted Jeep, I think you could probably count on it being reasonably steady. Because the camera is attached to the mirror, though, I'd make a point to make sure it's as securely attached as possible, which might take some doing.

Godholio
Aug 28, 2002

Does a bear split in the woods near Zheleznogorsk?


How well is it going to hold in an accident?

Krakkles
May 5, 2003

like and subscribe for more passive-aggressive roadway bullshit adventure in Chigcao

Godholio posted:

How well is it going to hold in an accident?
Yeah, it looks like it just clamps onto the mirror (four corners, from above and below), and if that's the case ... I mean, i'd be surprised if it stayed on during driving on anything but glass smooth roads in smooth cars. From that standpoint alone, I'd want to reinforce that.

Beyond that, you have a pretty good chance that the mirror itself (meaning, the part of your car mounted to the glass) comes off in an accident anyway - I've seen that happen, a lot. Part of me thinks that as long as it captures everything up until, it might not be a big deal, but a) it might be, and b) it's another projectile now.

If it could be secured well, I kind of dig the idea, because it lets you add a backup cam relatively easily as well. I'm kind of tempted to get one and see what I can do to mount it.

STR
May 12, 2006

I thought I was a nice jester


Rev. Bleech_ posted:

Weird. I sent them an email a week and a half ago saying my battery had swelled and the screen would pop out. After requesting a photo, they said "fuckit, have a brand new unit and don't bother sending the old one back"

Yeah, that's why I'm kinda surprised about all the back and forth - Anker's usually really easy to deal with.

To be fair, they did have me update the firmware, and that did fix most of my issues. Except for it powering down early. Which they keep insisting is the LCD timer being turned on, and I keep saying no, it's once the car is off, it's during the 60 second countdown, and I can't power it back up without power connected afterwards (and often have to format the card thanks to getting corrupted during the sudden shutdown).

cakesmith handyman
Jul 22, 2007

Pip-Pip old chap! Last one in is a rotten egg what what.



Krakkles posted:

Yeah, it looks like it just clamps onto the mirror (four corners, from above and below), and if that's the case ... I mean, i'd be surprised if it stayed on during driving on anything but glass smooth roads in smooth cars. From that standpoint alone, I'd want to reinforce that.

I use a wide-screen mirror replacement that clamps over my own mirror in exactly that way, it vibrates a little more than the stock one but is never in danger of falling off, even with spirited driving and speed bumps/potholes everywhere. I've used it for 18 months.

Enos Shenk
Nov 3, 2011




https://www.youtube.com/watch?v=AgdlrlT28WI

Two idiots in the same drive. The second one was a little old grandma and I could see her shouting at me as I honked at her. A shame the camera didn't pick that up.

PainterofCrap
Oct 17, 2002

Hey bebe





Enos Shenk posted:

https://www.youtube.com/watch?v=AgdlrlT28WI

Two idiots in the same drive. The second one was a little old grandma and I could see her shouting at me as I honked at her. A shame the camera didn't pick that up.

That second one is almost exactly how my (81-yo) mother got broadsided by an Odyssey. Mom first said no one was to her left, then later claimed the mom, with her three young kids in the car, was speeding.

Fortunately the mom & kids were OK. Mom broke her back & pelvis and degloved her left knee. She’s fine now. Saved by curtain & side airbags.

Chicken Doodle
May 16, 2007



Thanks for the answers! This has helped a lot. Think I'm going to order through Amazon cause it's relatively painless to return if it ends up sucking.

I like Anker for their charging products and cables so I'll probably try them first and see what's what.

Enos Shenk
Nov 3, 2011




Well, here's more. I guess my dad's been on a string of bad luck, Thursday night some drunk idiot blazed some synthetic marijuana and went for a drive, ended up taking out two cars my dads included.

https://www.youtube.com/watch?v=Xbpl_uVk8UI

He's fine, just a couple scrapes. His side airbags went off, car is almost certainly totalled. The OWI idiot is in jail and getting charged. Everyone in the SUV that got flipped was okay as well, thankfully.

Chunjee
Oct 27, 2004
I can't read or write

Enos Shenk posted:

Thursday night some drunk idiot blazed some synthetic marijuana and went for a drive, ended up taking out two cars my dads included.

Xbpl_uVk8UI

It just took a tap to flip that SUV; hot drat. This would have ended a lot more poorly if anyone had caught him head on. Don't be a hero.

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Hdip
Aug 21, 2002


That was nice of your dad to do a 180 spin maneuver so that his dash cam was basically a follow cam to get the accident behind him too.

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