Question for you 'Electronic Gurus' - whoever you may be

[niko]

Can you try it in your own car mounted at rear, using same power connection and playing same AM stations. This way can see if its car-related or unit ( or its power supply ) related issue.

 

[SawMaster]

I understand your frustration. Here's a primer for those who don't understand how switching power supplies (charger circuits) and voltage reducers (USB adapters) operate.

When the battery or super-cap is fully charged there are just a few random power pulses to keep things topped off, but when charging heavily the pulses which controls the charging is nearly continuous. The input voltage is steady and the output rises over time (milliseconds) until it reaches a cut-off point of maximum allowed charging voltage, the current flow is stopped, then the process starts again (switches on and off). In operation this creates a steady electrical vibration- in other words a low-grade radio frequency transmitter. These oscillations are inherent in this type of power supply/charger and are not easy to filter out (certainly not economically) so shielding or distance is the only viable 'cure'.* When located close to a receiving antenna this 'transmitter' can be strong enough to interfere with AM radio broadcast signals of lower power that are also reaching the antenna. The receiver simply plays what the antenna hears best- the stronger signal- or it plays the mixed signal from both sources.

The 12V to 5V USB power adapter operates a bit differently by altering the allowed voltage flow by continuously adjusting the bias on a transistor to control the output voltage- not in pulses. It's more like a water valve that is always on with the opening being the variable so there are no pulses and therefore no electrical vibrations, so if it is operating correctly there is very little oscillation occurring (a tiny amount will occur within the regulating transistor but it's so small you need a RF probe and scope to detect it). Since the regulation is steady (5V always up to full amperage) this is easily accimplished with component selection whereas with a charger circuit you must slow or stop the current flow when the batter is fully charged or it will be destroyed, which is why the simpler (and cleaner) circuit will work here but not in a charger. The normal failure mode of these is a dead output because the regulating transistor will not pass any current without the bias applied, so if a component in that circuit goes bad, the result is no output and still no offensive oscillations. That protects from over-voltage on the output and saves your 5V devices. Therefore I doubt it will be the problem, so alterations here will not be the 'cure' either. It is theoretically possible that if this unit's cabling parallels the antenna lead far enough that some interference can be transferred but this is unlikely.

*- Some high-end switching power supplies have a switchable frequency, so that while you can't eliminate the "transmitter effect' you can move it elsewhere in frequency range where hopefully it will not give interference where you want to operate. Not cheap to do, and this will never found in consumer-grade electronics because of that. Older transformer-type power supplies/chargers had different circuity that could go over-voltage in failure, destroying equipment. It was also larger, heavier, and more costly to build which is why almost everything uses switching-type power supplies these days.

Hope I didn't bore you with all this, but remember I'm a radio nut which I hope makes this post forgivable
Phil

 

[niko]

I understand your frustration. Here's a primer for those who don't understand how switching power supplies (charger circuits) and voltage reducers (USB adapters) operate.

When the battery or super-cap is fully charged there are just a few random power pulses to keep things topped off, but when charging heavily the pulses which controls the charging is nearly continuous. The input voltage is steady and the output rises over time (milliseconds) until it reaches a cut-off point of maximum allowed charging voltage, the current flow is stopped, then the process starts again (switches on and off). In operation this creates a steady electrical vibration- in other words a low-grade radio frequency transmitter. These oscillations are inherent in this type of power supply/charger and are not easy to filter out (certainly not economically) so shielding or distance is the only viable 'cure'.* When located close to a receiving antenna this 'transmitter' can be strong enough to interfere with AM radio broadcast signals of lower power that are also reaching the antenna. The receiver simply plays what the antenna hears best- the stronger signal- or it plays the mixed signal from both sources.

The 12V to 5V USB power adapter operates a bit differently by altering the allowed voltage flow by continuously adjusting the bias on a transistor to control the output voltage- not in pulses. It's more like a water valve that is always on with the opening being the variable so there are no pulses and therefore no electrical vibrations, so if it is operating correctly there is very little oscillation occurring (a tiny amount will occur within the regulating transistor but it's so small you need a RF probe and scope to detect it). Since the regulation is steady (5V always up to full amperage) this is easily accimplished with component selection whereas with a charger circuit you must slow or stop the current flow when the batter is fully charged or it will be destroyed, which is why the simpler (and cleaner) circuit will work here but not in a charger. The normal failure mode of these is a dead output because the regulating transistor will not pass any current without the bias applied, so if a component in that circuit goes bad, the result is no output and still no offensive oscillations. That protects from over-voltage on the output and saves your 5V devices. Therefore I doubt it will be the problem, so alterations here will not be the 'cure' either. It is theoretically possible that if this unit's cabling parallels the antenna lead far enough that some interference can be transferred but this is unlikely.

*- Some high-end switching power supplies have a switchable frequency, so that while you can't eliminate the "transmitter effect' you can move it elsewhere in frequency range where hopefully it will not give interference where you want to operate. Not cheap to do, and this will never found in consumer-grade electronics because of that. Older transformer-type power supplies/chargers had different circuity that could go over-voltage in failure, destroying equipment. It was also larger, heavier, and more costly to build which is why almost everything uses switching-type power supplies these days.

Hope I didn't bore you with all this, but remember I'm a radio nut which I hope makes this post forgivable
Phil

Man, you are electronics guru !
Many things that you wrote reminded me what we learned in high-school physics classes. But back then you don't realise how helpful can be this knowledge in the future. And actually if you don't use learned knowledge on daily basis, you keep forgetting it. Thanks for reminder-lesson !

 

[DT MI]

...
Hope I didn't bore you with all this,...

Not at all - it's quite the opposite.

Hopefully today I'll have sufficient time to play with multiple 12V-5V cables and different routing and get this mess sorted out.

I'm a chronic OCD perfectionist when it comes to stuff like this and won't let it stay unsolved, even though my wife keeps insisting that "it's OK as long as the interference goes away in a minute or two".

Who knows, I may end up spending more money on adapters/cables/etc. than I originally did on the camera. It's a serious disease...

 

[Module 79L]

Not at all - it's quite the opposite.

Hopefully today I'll have sufficient time to play with multiple 12V-5V cables and different routing and get this mess sorted out.

I'm a chronic OCD perfectionist when it comes to stuff like this and won't let it stay unsolved, even though my wife keeps insisting that "it's OK as long as the interference goes away in a minute or two".

Who knows, I may end up spending more money on adapters/cables/etc. than I originally did on the camera. It's a serious disease...

Let's hope the problem isn't your wife. Have you noticed that it only happens when she's around or driving the car?

 

[DT MI]

Problem solved - mostly.

Turns out it was the 12V-5V adapter, but with a twist. It only occurred when the engine was running - with the ignition in accessory (ACC) mode things were fine. Explains a lot as to why I was having trouble getting a handle on things. When I was rerouting cables, etc. I would check the results in ACC - but when my wife was running errands she actually had the engine running.

...Have you noticed that it only happens when she's around or driving the car?

Ha, you were pretty much right on the money.

I more or less got around the problem using a different adapter but the interference has moved to different frequencies on the AM band but only stations she doesn't listen to so it's good. What this actually tells me, however, is it's likely a combination of the 12V-5V adapter AND something in her car - the car is almost 14 years old so I'm sure some electronics are becoming marginal. I'm sure @SawMaster will have a lot more insight into this than I do.

The one thing that still has me a bit perplexed is why when I test drove it I couldn't replicate the issue. It could be I was not on the right frequencies when the engine was running versus when I was scanning stations in ACC mode. Unfortunately I just can't remember exactly what I did and in what order.

 

[SawMaster]

Just my hobby, same as dash-cams are for many here. Everyone has their 'specialty' and where we share our special knowledge, everyone gains something from it.

The difference between "ACC" and "IGN" is the car's computers and fuel pump, which are not powered in "ACC". These generate a lot of broadband noise ("hash" is the common term) which travels along the car's wires, and now that noise is closer to the antenna. Knowing the defroster grid was there, the manufacturer made sure that power line was filtered clean, then simply distanced the rest from the antenna as needed. Chokes (ferrites) operate only within a certain frequency range, so they didn't help because they were out of the range you're dealing with. There's also a mixing of all 'signals' happening which generates 'harmoinics' on a third (and 5th, 7th, 9th etc) frequency. Even numbered harmonics are 'in phase' and cancel themselves out. Parallel cables look nice but form an inductor so noise is more easily transferred between them. That's called "cross-talk" in USB cabling and is why it has length limits. Especially at the antenna run everything as perpendicular to it as you can for a few feet (1M). As space, wire length, and the situation permit, making a small loop (about 6in/150mm) every few feet in power wiring breaks up resonance much like a choke does and that can help. I'm not quite sure why the USB adapter change helped but if it works go with it.

Used to be that all you had to deal with was ignition noise 'popping' as spark plugs fired and some alternator whine. A very different world today. Next time you're driving next to a Prius, turn on your AM radio between stations and listen, then note how it fades as distance changes between you and the Prius. And note all the different loud noises you hear- clicks, several hinds of hums (some will vary in frequency or intensity), static. scratching, and more. Their radios are made to filter all that out but yours isn't. Several years of US Fords had electrically noisy fuel pumps. Every car has this problem to some degree today, but most are unaware of it because most don't listen to AM broadcasting anymore if their car even has an AM radio at all. And many cars now have the radio antenna integrated into the roof panel itself where you'd never expect to find one. Like my friend said, you can't always want what you get, but I'm glad you're making progress.

And listen to the wife- if you reach the best you can do and she's happy then all is well. It's entirely possible that you'll never get rid of all the noise but if she's happy that's good enough. Job well done!
Phil

 

[DT MI]

...And listen to the wife- if you reach the best you can do and she's happy then all is well. It's entirely possible that you'll never get rid of all the noise but if she's happy that's good enough. Job well done!
Phil

Yeah, I really need to get over this 'compulsive perfectionism' issue. Thanks for all the insight. Now to go out and throw a couple of 'loops' in the excess cable - they may be ovals versus 'perfect' loops though.

 

[Module 79L]

There's also a mixing of all 'signals' happening which generates 'harmoinics' on a third (and 5th, 7th, 9th etc) frequency. Even numbered harmonics are 'in phase' and cancel themselves out. Parallel cables look nice but form an inductor so noise is more easily transferred between them.

Next time you're driving next to a Prius, turn on your AM radio between stations and listen, then note how it fades as distance changes between you and the Prius. And note all the different loud noises you hear- clicks, several hinds of hums (some will vary in frequency or intensity), static. scratching, and more. Their radios are made to filter all that out but yours isn't.

Keeping the conversation on this note and being a professional aerial installer for 31 years now, I've come across some situations that could easily be classified as X-Files material, all of them related with interferences caused by "defective" home appliances' power supplies, like VCR's and Microwave ovens.

But then, in the old days of the analog TV broadcastings, there was always a way of finding out the source of the interference, even if it meant having to walk the streets with a TV set, an extension cord, the field strength meter and a antenna, asking people in the affected area if we could plug the extension somewhere inside the house so that we could have power for the TV because that way we could "see" the interference, among other crazy stuff, but we always managed to find and solve the problems.

When I thought I've seen it all, this happened to me recently: a defective switching power supply in a IF Sat/Terrestrial Combiner-Amplifier was generating signals in the 500-600kHz range that interfered with all the broadband-based IPTV client's signals in the building, to a point where no one could watch TV or use the internet!
At first I was very skeptical when the pay-tv operator's technician told me that he measured those frequencies with his meter and they were all over the building, so much that he brought a AM radio with him and he could clearly hear the noise from the interference in it.
I already knew that these switching power supplies could generate noise (sometimes I have to isolate the ground contacts on the plug of the band's laptop power supply, because when the CPU is running it can be heard on the audio system) but not in such low frequencies. We're talking about kHz, not MHz or GHz.
After running some tests and seeing with my own eyes that in fact it was the IF Amplifier that was causing the problem, I took it out and sent it to repair. The repairman confirmed it was generating noise in those frequencies and he was also surprised because he never saw a switching power supply do that before.
Anyway, I re-installed it 3 days ago and, so far, no complaints.

Knowing all of this, when someone has complaints like DT MI's I'm always suspicious of these low quality power supplies that come with the cameras, especially of those flimsy cables. Like I usually say "you can even feel the quality, just by touching the material", and these power supplies don't "feel" good.

 

[SawMaster]

I'm sure we could swap tales of interference found but we'd be a bit far from the topic here. Consumer-grade goods will always be made to minimal standards to keep manufacturing costs down- dashcams, cars, and computers all included. Here it was pretty simple with me knowing about switching PS's propensity to generate 'hash' on the lower frequencies because I've heard it as low as ~450 kHz myself. The video aspects of dashcams is new to me and a large part of what fired my own interest in them. I'll never reach the level of some of the experts here but I do want to learn more.

BTW, with the band's laptop perhaps a grounded isolation transformer might help? Then again I doubt there is much risk running it un-grounded as long as nobody chews on the power cord as part of the show! And as we know, if it works and everyone is happy then all is well.

Phil

 

[throrope]

I have the same interference with my spare GS9000 unit on the rear window with antenna. FM signals suffered especially weak stations. A ferrite core helped, but didn't solve the issue. In the end, I just removed the dash cam.

 

[Module 79L]

BTW, with the band's laptop perhaps a grounded isolation transformer might help? Then again I doubt there is much risk running it un-grounded as long as nobody chews on the power cord as part of the show! And as we know, if it works and everyone is happy then all is well.

Phil

That doesn't happen very often but I noticed that when it does I also have to switch the DI's ground lift on, so it must be a ground loop-related problem that some venues have and others don't.
It's no biggie, really, because the noise is only noticeable in silence and our music is anything but silent.

 

[Mandami]

... then the process starts again (switches on and off). In operation this creates a steady electrical vibration- in other words a low-grade radio frequency transmitter.

I don't think the EMI noise comes from the stoping-staring the charging process. Instead, as you wrote, the problem it's the charging circuit itself.

The 12V to 5V USB power adapter operates a bit differently by altering the allowed voltage flow by continuously adjusting the bias on a transistor to control the output voltage- not in pulses.

... only if the DC-DC is linear. If it's a switching converter then we will have the same problems as above. Moreover, the EMI noise from the car circuitry can be passed through the converter.

@DT MI have you tried the idea of @Nigel to use the camera without any power connection ? and then using an external battery to charge this camera ?

 

[DT MI]

...
@DT MI have you tried the idea of @Nigel to use the camera without any power connection ? and then using an external battery to charge this camera ?

I had no interference at all when the charging adapter was unplugged. I did not use an external battery pack but there was no detectable interference when the G1W-H was operating on it's internal battery - meaning there was no charging of any sort going on and the power adapter was removed from the environment.

That leaves me/us in the position where it could be either:
1) interference from the charging circuit in the G1W-H - or -
2) interference generated by the power adapter - or -
3) interference being generated from the car and picked up by the power adapter - or -
4) any combination of all the above.

This was when I was using the G1W-H. I've now changed that to a 2nd A118-C as a rear camera. The current installation (A118-C front and rear) is not causing any complaints from my wife and I've not had the time, or inclination, to go out and research it further. It would be nice, at least from an academic perspective, to determine what exactly the cause of the problem was but it's going to be a few days before I even have time for that exercise.

Note also that I've since replaced the 12V splitter that I was using with a different unit. A quick check right after I did that 'seemed' like the interference was lessened somewhat - but that was very subjective and may well have been just a matter of wishful thinking on my part, so maybe I shouldn't even mention it.

 

[Mandami]

That leaves me/us in the position where it could be either:

I will also add a 5th possibility where the cable plays the role of an antenna for the interference (due to dashcam or charger). It was already specified by @SawMaster the utility of shielded cables.

I did not use an external battery pack but there was no detectable interference when the G1W-H was operating on it's internal battery

An external battery and a short cable (and then a longer cable) will give a final answer whether the problem is the charging circuit or not.

The current installation (A118-C front and rear) is not causing any complaints

Probably you're using the charger+cable from the A118-C. What if you connect the G1W-H to this charger ?

 

[DT MI]

I will also add a 5th possibility where the cable plays the role of an antenna for the interference (due to dashcam or charger)....

I thought it was kind of implied with #3 but I'll go along with that.

...An external battery and a short cable (and then a longer cable) will give a final answer whether the problem is the charging circuit or not....

Agreed, but that will have to wait a few days.

...Probably you're using the charger+cable from the A118-C. What if you connect the G1W-H to this charger ?

No, I just replaced with G1W-H with the A118-C - same power source was used.

In my original trouble shooting of the problem I used multiple charger cable units so I know it's not isolated to a single one. Changing did cause the interference characteristics to change but did not eliminate them. (In addition to them being different 12V to 5V converters they were, in some cases, different cable lengths as well.)

I'm sure some of the interference is coming from the car itself and being picked up by the cables because it's there with the engine running but not with the switch in the accessory (ACC) position. @SawMaster alluded to this as well in one of his posts.

 

[Mandami]

The current installation (A118-C front and rear) is not causing any complaints from my wife

No interferences at all, or simply no complaints ("acceptable" interference) ?

same power source was used

Then it's the dashcam. On the other hand it's not clear if this problem appears only when the key is on 'ACC' or 'IGN' position.


My G90 is also affected by some strange EMI. I planned to open it again (but I never had time). During the cold period when I was starting the heat at maximum, the the first 1-2 min of video clips had some fluctuations: similar to those when the camera heats. I'm almost sure the problem it's not the heat itself (during hot weather I haven't seen any fluctuations) but a mixture of EMIs: lights on, radio on, FM transmitter on, GPS on, rear defrost on, both sets of wipers on, cooler at maximum.
In December when I couldn't use from the start the wipers, even though the cooler was set at maximum, there were no fluctuations. During the rain, when I used the wipers, once again, no fluctuations.

 

[DT MI]

No interferences at all, or simply no complaints ("acceptable" interference) ?

Then it's the dashcam. On the other hand it's not clear if this problem appears only when the key is on 'ACC' or 'IGN' position....

I don't think it is the camera, or at least not 'only' the camera. If you go through my original post(s) you'll see that I swapped the G1W-H and A118-C between the front and rear and there was always 'some' interference. It would change depending on which camera was where. It may be that the camera was contributing but was not the sole source. (To summarize I was able to get the interference to move to frequencies that my wife does not listen to.)

When I say 'no complaints' what I mean is replacing the G1W-C with the 2nd A118-C things did not change (or change enough) to cause me to notice with a quick check or my wife to notice while using the car normally. I installed the 2nd A118-C just yesterday so it has not been in the car that long. I have not had an opportunity to go through a systematic analysis of performance to see what is or is not happening since the change.

Some of the interference was always present. With the engine running there was additional interference - this I think I can safely assume is coming from the car and being picked up by the cable and/or camera and from there into the antenna.

The G1W-H that I was using as the rear cam had previously been used as the front cam in the same vehicle and there was no issue. The radio antenna is integrated in the rear window so being in closer proximity to the camera definitely has a bearing.

As I said, I'm not getting any complaints from my wife so I have less incentive to get involved in chasing down all the possible scenarios. One of these days when I'm bored and she's not using the car I may go out a play around with it again. In the meantime - "Happy Wife, Happy Life".

 

[SawMaster]

Both cameras could be producing similar interference with one simply making more of it than the other. They are both essentially doing the same thing in the same way with many similar components and similar circuits. The only certain way to eliminate RFI would be to re-engineer the cams and power supplies which ain't gonna happen, so all you can do is try the known approaches to the most common solutions and hope for the best.

Phil

 

[old4570]

Wow , power adapter ( Cigarette lighter as a source ) , I think the Cig lighter is bad idea and the cause of numerous issues ..
I would suggest hard wiring the cameras ..
Get on of those 12v or 12-24v to 5v power adapters with the USB plug at one end and + - wires at the other and just hard wire the camera .
I plan on running mine from the tail lights ( Parking light ) for the rear camera .. So if I want my rear camera to work , in need to turn on the parkers or Half lights or what ever you call them .
The front camera will be powered via my interior cabin light , the power to which will turn on when the ignition is turned on .
So the rear camera will require me to turn on the head lights .. ( Plan so far )
I dont know if there is enough room in the roof mounted interior light for two power adapters to be wired in ( interior lights run a 5A fuse ) Im sure one camera will be fine ...