Quick weatherproof camera box. - page 4 - Hotwire! Hardware Mods, Accessories and Insights - CHDK Forum

Quick weatherproof camera box.

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #30 on: 12 / August / 2013, 12:33:04 »
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The external triggers tend to be pulses. I need some sort of signal to keep the power on, until the camera has completed its task. I don't want the lights going out while we are in mid shot.
So you want to turn off the power supply as well as the camera then?  As mentioned above,  a CHDK script can turn the camera off on its own when its done shooting.

I appreciate that, however I want the camera to both keep the power on, and turn the power off. Only once it has performed its task, do I want it to turn the power off.

In other words, an external wakeup event turns on power (and therefore camera). The camera maintains power after the external event has finished. Camera does its stuff. Camera shuts down, power goes off.

The reasoning is this.. a  digital watch, PIR or pressure switch uses zero power (or more exactly, very little in the case of the PIR and watch, and none at all in the case of a pressure switch) and therefore if we only wake up the camera (by turning on its PSU, with the power switch on the camera held in with an elastic band) we only use main battery power for the limited time needed to complete our shooting sequence.
 
The camera must decide when to switch the PSU back off, otherwise this is not retriggerable, since it is the action of switching on the power that turns the camera back on. Only having CHDK shutting down wont work in this case, it actually has to power off, otherwise it wont automagically switch back on next time the wakeup event takes place. With the PSU switched off, we use zero battery power (except for the self discharge of the battery).

Using this method, we should be able to shoot very long timelapses, or use CHDK for wildlife shooting, without the need for a huge battery.
« Last Edit: 12 / August / 2013, 15:35:19 by ahull »

Re: Quick weatherproof camera box.
« Reply #31 on: 12 / August / 2013, 14:08:35 »
Just in passing, I was testing an SX20is powered from an external source (6V battery, buck/boost converter).

I turned the camera off.

Fifteen seconds later it turned itself on !!!

Hmmm ............


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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #32 on: 12 / August / 2013, 15:20:17 »
Just in passing, I was testing an SX20is powered from an external source (6V battery, buck/boost converter).

I turned the camera off.

Fifteen seconds later it turned itself on !!!

Hmmm ............

Does the SX20 IS turn on automatically when the buck converter is attached? It could be that there was a short brownout of the output of the buck converter, just enough to have the effect of powering off the camera and power it back on.

If the SX20 IS does not turn on automatically when power is applied, then this could be a similar scenario to "boosting" arcade games by briefly interrupting the mains power to them, and crashing them in interesting ways in order to try to get extra credits or engineer mode, not of course that I ever tried that sort of thing my youth ;).

Do not try this with modern arcade games folks, they probably have alarms fitted. Furthermore this is also a very neat way of buggering up the PSU or blowing the mains fuse  :blink:.
« Last Edit: 12 / August / 2013, 15:32:39 by ahull »

Re: Quick weatherproof camera box.
« Reply #33 on: 12 / August / 2013, 15:36:48 »

Does the SX20 IS turn on automatically when the buck converter is attached?

No.

The behaviour only happened when dial was in movie mode and I had been running some test code that read DIGIC registers.

I will try to reproduce the effect when I have time.


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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #34 on: 13 / August / 2013, 16:58:27 »
I uploaded some pictures of the buck regulator USB +5V to 3.7V converter attached to an Ixus 850 IS  here.
Not sure how useful they are,  but someone might be keen to copy the idea.

I took them back in May meaning to upload them then, and forgot. Fortunately I just found them again now while going through the rest of the contents of the memory card.




I used a cheap Chinese knockoff DC-30 power supply as the source of the dummy battery. I would treat these mains PSUs with some suspicion. The dummy battery is fine however. 

I didn't have the correct connector in my junk box, but I had lots of multipurpose adapter tips, so I simply soldered a couple of wires to one of those and added a bit of heat-shrink tubing and a ballpoint pen cap to turn it into a fairly convincing right angle connector. I could of course have snipped the lead from the PSU, since I am not very likely to actually use it, but it wasn't right angled, so it would have taken up more space in the weatherproof box.   

The buck regulators as you can see arrived from China in non antistatic bubble wrap, but seemed to be none the worse for that.
« Last Edit: 13 / August / 2013, 17:05:24 by ahull »

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #35 on: 19 / August / 2013, 08:21:09 »
I've not had any time to work on this, but just for the record I decided to use the extending and retraction of the lens for my feedback. To this end I ordered a bunch of reflective photosensors.

The idea is to position them next to the lens, and when it extends, use the photo transitsor output to hold the battery output on.

The method would be something like..

PIR or whetver decides to switch on camera, this is done by switching on MOSFET 1, this energises the camera and the photosensor.

When the photosensor detects the lens has extended it energises MOSFET 2 in parallel with MOSFET 1

PIR or other trigger stops triggering, and switches off MOSFET 1 (but the camera and photosensor are still powered by MOSFET 2)

Camera decides it has done its job and shuts down. Photosensor switches off when lens retracts and powers off MOSFET 2.

Hopefully this will result in zero power use when the camera is not needed.  Time and experimentation will tell.

One advantage of this is that I dont need to complicate my scripts by flashing a particular LED, and furthermore it should allow me to use pretty much any camera in this rig which has a retractable lens.
« Last Edit: 19 / August / 2013, 15:48:46 by ahull »

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #36 on: 21 / August / 2013, 12:13:55 »
The solar chargeable USB batteries I talked about here just arrived. Naturally the first thing I did was tear one of them apart to see what made it tick. This is easy to do, just remove two small screws (one hidden beneath a QC sticker) and prise gently apart.

First impressions are that it is quite well constructed (which is more than I can say for the mains charger that comes with it, which I also tore down for your amusement). The solar panel itself is a pretty robust bit of glass, and the charger PCB is well soldered. The LiPo is not physically particularly large, so there is a fair amount of spare room under the solar panel for a small control PCB of my own.  The LiPo is suspiciously label free, so we have no idea of its source or capacity. It also has some small dents in it suggesting it may be either a "recovered" device from some other source, or perhaps a cosmetic factory reject. What the heck though it seems to hold a charge, and if necessary is easy to swap.





The circuitry looks familiar (the usual DW01 Plus and 8205A dual mosfet to protect the lipo), some sort of 3.7 to 5V boost  regulator and a charge circuit from the solar panel and mini USB input.

For full gory details of the teardown are here.
« Last Edit: 22 / August / 2013, 08:10:54 by ahull »

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Offline bwh13

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Re: Quick weatherproof camera box.
« Reply #37 on: 21 / August / 2013, 20:58:53 »
awesome teardowns.
So what's the plan with the solar / lipo rig?  Are you going to tap in to the 3.7v and bypass the the 5v?  Tapping straight in to the battery would likely bypass some circuit protection I imagine.  Judging by your post on the photo-resistors, it sounds like you can read a PCB well enough to know where to catch the 3.7 before its boosted to 5.

I've been working on a (ultra!) low dropout regulator for my timelapse rig.  I've finally taught myself how to read circuit diagrams well enough to produce this.  It's a TI regulator with 5 leads that weren't really breadboard friendly. The leads are pretty tolerant to reshaping, but not bombproof.  It is a good thing I bought 2.

I'm a couple of days out from soldering this together.  I have a different regulator that I would like to try out and see if there are any gains to be had with it.
« Last Edit: 21 / August / 2013, 21:13:30 by bwh13 »


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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #38 on: 22 / August / 2013, 04:55:11 »
@bwh13 You are quite correct when you say that connecting directly to the battery is a bad idea. I intend to connect to the output from the battery protection circuit.

If you look at the "typical Application circuit"  on page 3 of the DW01 Plus data sheet you can see that you  will need to connect to +BATT and -BATT, rather than to to the battery itself, that way you keep the battery protection circuitry in place. +BATT is easy to find as it is actually connected to the + wire or tab of the battery (the red wire if your version has a wired battery). -BATT needs to be located on the PCB, and is the point where the Source pin of M2 and the 1K resistor meet.



In this particular charger, it looks like the pad from U3 to R11 is where we need to connect for -BATT and I have marked the points for +BATT and -BATT in the picture above. There is probably an easier place to solder to -BATT, as it is presumably the 0V or ground line for the rest of the circuit. That obvious round silver pad between the mini USB connector and the LED looks a likely candidate.  I would need to dig out my multi-meter and  verify this though. 

The usual caveats about copying these instructions apply, especially since there are several different variants of this particular solar charger about, each of which has a different circuit board layout. You try this entirely at your own risk, LiPo batteries are particularly unforgiving, even relatively small "2600mAh" cheap Chinese ones. If you short things out or wire them back to front, you WILL start a fire.  I would also recommend an in line fuse to your external device, as although there is some short circuit protection build in to the DW01 plus, fuses are cheaper and easier to replace. I would say a 2A slow blow automotive (car fuse) or even a 20mm 250V 2A would be fine. Remember with fuses, the 2A is the important value here.

Bear in mind that this circuit is always energised, albeit with relatively low voltages, both from the battery, and also the solar panel, and is in an aluminium enclosure, so if you are soldering on an earthed metal work surface, and your soldering iron is also earthed, you run the risk of shorting things unintentionally. Stick a bit of card or plastic under the thing before you start prodding about with the soldering iron.

I would be interested to hear how you get on with your low drop out regulator. and see any timelapses you make with it. I have used a couple of the buck regulator modules I mentioned earlier in this thread, and they work well. I haven't actually attempted to measure current while in use, nor have I tried to see how efficient they are, but they certainly do the job. 
« Last Edit: 22 / August / 2013, 11:14:05 by ahull »

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Offline ahull

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Re: Quick weatherproof camera box.
« Reply #39 on: 22 / August / 2013, 08:35:23 »
Here is a quick sketch diagram of what I am aiming for with all of the charge circuitry omitted for clarity.



I'll add in the trigger circuits (and all of the missing pin numbers and names) once I have refined the design a bit (in other words once the remaining parts of the puzzle have arrived, and I have done a lot of head scratching).

The PIR or external trigger would be powered from +3.6V and the un-switched 0V
The camera (and the opto-isolator) would rely on the +3.6V and switched 0V

Pulling either of the two control pins high would switch the battery through to the camera, and keeping either high would maintain the output.

Ignore the capacity of the battery in the diagram, that is probably just as random a number as the actual capacity of the battery.  :D

EDIT: On the subject of capacity, I just fired up the Battery Intervalometer script from here (with shooting disabled, it only does a half shoot. 'cos its running on an old 128Mb SD card I use for testing). I am going to see how long it takes to drain the battery. The test setup is my 850 IS with a buck regulator module connected to the solar charger, in a well lit room. It will be interesting to compare the life of this battery with the Canon NB-5L, this should give me a better figure for the capacity then the stated value on the charger (2600mAh).

I don't expect the solar panel to increase the life by much in this setup, as we are constantly switched on. Where the solar panel should help is in the situation where it can top up the battery between shots, when I have made the necessary modifications.   

I am also not factoring in any losses due to using the buck regulator.

EDIT: Well it seems I forgot to actually charge this particular beast  ::)  and the charged one is in the office, so in about 8 hours I will fire up the script. One interesting thing is that when it dies, the device appears to be completely dead, even the charge light stops working (I thought I'd killed it). The charge light comes back on after a minute or so of charging. I expect the Chinese manual may explain this, but since I don't speak Chinese....  :P
« Last Edit: 22 / August / 2013, 12:07:00 by ahull »

 

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