Think I figured out why I couldn't power a camera - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 22, 2018, 11:20:24 pm
content: I have a AX500 (iirc) camera and it eats batteries. I tried to power it off a 12V 2A wallpack, that runs an LM317 adjustable regulator. So I feed it 3V, and it would only powerup for a moment, then shut off. I thought maybe door clip bridging the 2xAAs might have been hooked to something that needed 1.5V, so I tried that to no avail.Then I measured the current draw, and what happens it the SMPS in the cam, that charges up a bank of caps to 320V, was drawing over 1.5A, and the LM317 is only rated for 1.5A. I didn't notice before that it was getting super hot in the few seconds the cam tried to start. So it's hitting it's thermal limit or current limit and shutting down.So I will have to make a better 3V source and try again. I'll also charge some AAs, and measure the current on them. To me thats a crazy amount to draw from batteries, but it would explain why they die so quick.I really want to look at its PCB. So far I took the case apart, but thats hard to do. I don't want break it tho just to map out the PCB for fun.

author: Brumby
author_rank: Unknown
timestamp: September 23, 2018, 12:52:12 am
content: If your camera only draws 1.5A, then that won't be the limiting factor. The LM317 datasheet specifies 1.5A as the minimum, with a typical maximum current of 2.2A (for Vin<15V).At 12V in, 3V out, the LM317 will have to drop 9V. At 1.5A that works out at 13.5W. While that is under the Pmaxof 20W, you have another problem.With a junction to case thermal resistance of 5ºC/W, you are going to have to have quite a decent heatsink to keep the junction temperature below the 180º limit where it will shut down. For an ambient of 25ºC, this means a figure of 6ºC/W or better for the heatsink and thermal paste. That 6ºC/W is a maximum and it still has the regulator running way too hot for my liking.A better approach, IMHO, is to reduce the voltage drop across the LM317 by powering it with a 9V - or even better still, a 6V - supply. This will reduce the power dissipation to 9W or 4.5W respectively. You will still need a heatsink, but not as beefy as you would for 12V.

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 23, 2018, 01:35:21 am
content: I don't remember the number, maybe 1.6A, but it's enough to shut it down, yeah it's not heatsinked. I'll check again, this was July/August .IDK what the voltage did, I'll check more, I have an LED the goes out under short-circuit, it stays on so I didn't suspect heat/current problem. But I also didn't remember that its a major boost -converter of some type in the camera, 3V to 320V, thats huge.

author: ArthurDent
author_rank: Super Contributor
timestamp: September 23, 2018, 01:36:33 am
content: Watch this video.

author: MK14
author_rank: Super Contributor
timestamp: September 23, 2018, 01:47:04 am
content: Terrible video.You have to use the right battery type for a camera (and set the battery type in the menus if applicable and make sure the battery is not too run down, else it won't supply enough current). Some don't supply enough current, so the camera can't work properly.This is a somewhat known problem, and why some sources recommend rechargeable battery types. As these usually have no problem supplying the necessary current.It seems, the LM317 is (as you suspect), is just being overwhelmed by excessive current requirements, at times, and hence is not working properly.You could try a higher current version of the LM317, such as the LM350T, with around a 3amp max output current limit.

author: drussell
author_rank: Super Contributor
timestamp: September 23, 2018, 02:04:09 am
content: Quote from: lordvader88 on September 23, 2018, 01:35:21 amYou shouldn't be surprised that trying to run an un-heatsinked LM317 at 1.5 A with a 9 volt drop across it doesn't work, even for a very brief time. You will hit the thermal shutdown limiting almost instantly.

author: MK14
author_rank: Super Contributor
timestamp: September 23, 2018, 02:07:01 am
content: Quote from: drussell on September 23, 2018, 02:04:09 amGood point. I'd mainly read the OP's opening post, and had not noticed the no-heatsink bit, which seems to have appeared later in the thread.1.6Amps is too much (or too close to the limits) really for a LM317 without an external pass transistor (circuit in app notes), to handle more current.

author: ArthurDent
author_rank: Super Contributor
timestamp: September 23, 2018, 02:42:22 am
content: It is true that batteries make a difference but here is an shot of the AX500 setup screen that shows the default battery type is alkaline and in the video the person said they used both the batteries that came with the camera plus tried another pair of fresh batteries that they show measuring on a DMM then they show that the batteries died in mere seconds. I can see them dying sooner than rechargables (like I use) but with different sources suspecting a drain problem and the video showing it actually happening, I'd be willing to think camera problems.

author: MK14
author_rank: Super Contributor
timestamp: September 23, 2018, 02:57:54 am
content: Quote from: ArthurDent on September 23, 2018, 02:42:22 amAs regards,YOURcomments and thoughts. I think they are good and sound, and I agree with them. Except perhaps with the video recommendation, but even that could well be correct.But, there is a (known to me and others) situation, whereby a number of digital cameras, over the years, do use rather large amounts of current. Making most non-rechargeable batteries unsuitable in practice for powering them.If you try, you perhaps get only 10 (very approximately) shots done, before the camera shuts down due to too low battery voltage.So, really you need to use rechargeable batteries, with their somewhat low internal resistance (impedance). So they can readily supply the current and take lots of shots, before running down.The thing is that, calling this aFAULT, is somewhat a matter of opinion. I don't think it is a fault, but some other people do. Since it is more of an opinion (in my opinion), than a technical thing, I'm happy for others to call it a fault.Camera manufacturers. Haven't always done themselves justice, because for marketing reasons (I believe), they tend to keep quiet about things like that.E.g. My Panasonic Camera (can't remember the model number), came with supposedly good batteries (possibly used by another customer, because although brand new, the battery pack was not sealed), but they did not last long at all. But Nickel Hydride batteries lasts for ages and take many shots (perhaps 100), before running down.tl;drI'd blame poor marketing and keeping too quiet, about how badly alkaline (and similar) batteries do, with many of the digital cameras, that have been for sale, over the years. Rather than saying they are faulty as such (my opinion).But if you want to say they are "faulty" that is fine by me, as it is only a differing opinion. I can see why they can be classed as faulty, since they should really work well with standard (Alkaline) AA batteries.

author: ArthurDent
author_rank: Super Contributor
timestamp: September 23, 2018, 03:45:45 am
content: MK14 - "E.g. My Panasonic Camera ..."I do love my Panasonic Lumix DMC-FZ300 for all around use and its fantastic features. It does use a specific Lumix lithium battery so that just means I have to carry spares when I go way off road. Using 4K video can really eat up batteries and the fast memory cards that the camera requires but, as with anything, there are trade-offs. For something really specific I use my DSLR but for quick shots in the field, especially where I can't get that close, it works great. Here is a shot of a wood stork I got from a distance.

author: amyk
author_rank: Super Contributor
timestamp: September 23, 2018, 04:00:27 am
content: A buck converter would be far better than a linear regulator at those currents and voltage differences.

author: MK14
author_rank: Super Contributor
timestamp: September 23, 2018, 04:01:57 am
content: Quote from: ArthurDent on September 23, 2018, 03:45:45 amYour picture looks really nice!Very relaxing, I would not mind being there now.Lithium batteries, have exceeded my expectations. I originally had lots of reservations. But they seem to keep on working for many, many years, and just keep on charging and charging. So they have turned out to be a worthwhile replacement on Nickel Hydride AA's.A while back, I use to want to get a high end Panasonic FZ100 (and similar) camera, and it (but latest models now) would still be on my short list. if/when I next need to buy a camera.I think a lot of Panasonic as a make. One of the better Japanese brands.