Transient Voltage Suppression question

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
I was looking to see if anyone else had something similar. Found an article back from 2012 and to my dismay it was not resolved.

Here's what I'm thinking: I have a dash cam that used to work really well. Going to replace it in the coming week or two. The problem it experiences is that you start it and it will film for 30 seconds to 2 minutes then shut itself off without going through the shutdown routine. It has a small L-ion battery in it that is supposed to retain memory and assist writing the last file to the SD card when main power is shut off.

For some reason I've grown concerned that there may be some transient voltages causing problems. We all know automotive electronics can be very very noisy. So instead of just buying a new camera and plugging it in I want to plug it into a TVS protected circuit so that there are no transient voltages potentially damaging the new camera. I will be opening the camera later this afternoon to see if I can determine any issues, but I suspect that in the end I'm simply going to buy a new cam and let it go at that. I put a new camera in my wife's car and it will record some files and some files will record as corrupted data, leaving potentially crucial information unattainable. So if I can learn how to solve this transient voltage problem I'll probably put the same thing in my wife's car. Her camera still works. It's just that some files are corrupted.

So where can I learn more about TVS? Do you have any advice? Are they so stupidly simple that I'm overthinking the problem? Avelanche diode? Zener? Capacitor? MOV? I'm certain the power is quite low. The system runs on a 12 volt circuit but supplies typically the same power your cell phone charger produces. Anyone any thoughts? Comments? Suggestions? Directions?

Thanks.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
Check to see if the battery is fully charged.
I'm sure the battery is old and PROBABLY not holding a charge. However, the unit is powered from the cigarette lighter through an adaptor that powers the unit at some lower voltage, probably 5 volts. Could be 3.3 volts, I don't know and haven't tested it yet. Wife's unit has a super capacitor instead of a battery and can provide up to 30 seconds of run time, which made it a bad choice, especially because it has motion detection and record features. How are you going to record anything more than 30 seconds. Let someone walk past and eat up that charge, then someone comes along later and key's the paint (or something).

I have some chores to get to this morning. I'll be opening the case of the camera later today, and testing the adaptor to make sure it's functioning properly as well. Y'know, it could be a power supply problem. Maybe I should try a different supply just for kicks. Lord knows I have enough laying around.

[edit] I might add that the unit is sometimes in direct sunlight for hours on end. I'm confident the battery hasn't done well under those conditions.
 

bwilliams60

Joined Nov 18, 2012
1,156
I would look at your supply first and as you said, perhaps try a different source. You could also try a different access point other than cigar lighter as they are known to have a lot of noise on them as well. Do you have a scope that you could put on the lines to see what is happening on them?
A capacitor would make a better source because of its discharge curve in comparison to a battery.
 

crutschow

Joined Mar 14, 2008
23,149
It may just be hash on the line rather than any high voltage transients, so an added line filter may help.
A small resistor in series with a large capacitor to ground (say 1mF or more) should go a long way to minimize any noise.
The resistor can be selected to drop no more than a volt or so at the current drawn by the camera.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
@bwilliams60 I think I failed to clarify my needs. I suspect I'm having automotive noise on my 12 volt line that may be affecting my camera. So I was hoping to learn a little about noise suppression. Crutschow suggests a small resistor and a big cap. I'll give that a try tomorrow. Right now my power supply is the automotive 12 volt system. My alternator is good and my battery voltage (dash meter) says 14.4 after a start and 13.8 during normal operation, so I'm confident there's no issues with supply. There is a plug in adapter that powers the camera. It runs at the same voltage as a typical cell phone. There may be issues there instead of with the car electrical. There may be issues caused by the car electrical. The camera may just be old (from 2012). Could be a faulty battery backup inside the camera. Lots to look at, but filtering the supply can't hurt any.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
I think I'm starting to discover one of the problems: The battery looks rather swollen. Also, I suspect the power port connector on the camera may have a bad solder joint or two. If I wiggle it the camera will shut down and restart, depending on how I wiggle it.

image1.JPG
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
The next question is: How do I properly dispose of this battery?image1 2.JPG
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
Just ordered a replacement battery. Will take a month to arrive. Meanwhile I have a Lithium Ion battery that is slightly smaller and would require some wiring in, whereas the original Lithium Polymer battery - well, I'm sure there are different charging characteristics from LiPo to L-ion. Don't want to blow up a battery while driving. Any sound advice (other than don't do it)? If someone can recommend something. I HAVE the safe charging board from the old LiPo battery. Will it work on L-Ion? Or will the charging current be too high?
 

crutschow

Joined Mar 14, 2008
23,149
That battery looks like it was overcharged, so I would look into some method of reducing the charge cutoff voltage and perhaps the charge current.
Look up the specific characteristics of your battery to determine how it should be charged.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
The battery had a charge circuit built into it. I have no control over the charge current unless I start rebuilding the charge circuit. It was possibly heat from being in the sun. Not directly, but the camera mounted under the mirror would sit in the sun for hours, daily. I wonder if that was behind the demise of the battery. Oh, and the unit was built and inspected in 2013. The inspection sticker is dated 2013 so it can't be much older than that.

I've ordered a replacement LiPo battery and it should be here any time within the next six weeks. Slow. That's why I'm wondering about using a L-Ion battery in the meantime.
 
Hi

In case you are still curious about TVSes, they are extremely useful in automotive transient voltage situations. They have a response time much faster than a zener diode clamp and in general are designed to handle power surges better. Littelfuse has some excellent information about them.

Also I'd advise against the RC low pass filter suggested earlier in this thread as your camera would be drawing more than a few mA. You can get a similar filtering effect without the voltage drop using an LC low pass filter.

Put a suitable TVS after your LC low pass filter and you will have a MUCH safer 12V supply.
 

crutschow

Joined Mar 14, 2008
23,149
Also I'd advise against the RC low pass filter suggested earlier in this thread as your camera would be drawing more than a few mA.
That's why I recommended a resistor value that would drop no more than a volt with the current drawn by the camera.
I think the camera would operate fine with less than a volt below the battery voltage.

With an inductor you need to be concerned about resonance which can cause an overvoltage up to twice the input voltage upon application of power.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
3,470
Well, now I'm not getting any response from the system - with or without a battery, with or without the adapter. Maybe I killed it.

My L-Ion battery is resting at 3.66 volts and floating at present at 3.91 volts. Wiring is hooked up correctly, voltages are present at the battery and the PCB where the battery connects. I'll let it charge a little longer, but it should have fired off the moment I plugged in the adapter. Battery or no battery.

[edit] - - - and now it's working! I haven't a clue what I changed other than remove the battery and reinstall it.
 
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