120v to 3.7v circuit

[joshzstuff]

Hello, I have been out of town for the extended weekend, so I finally got back and had some time to work on my project.

Battery Replacement​

This is now successful!
I changed a few things and I have finally replaced the stock battery with a much larger 18650 and so far it works perfectly.
(I changed the telephone connectors out for 1/8" phono- style jacks, perhaps this was atleast part of my problem)
No damage to the camera's I previously tested!

AC power​

With that hurdle cleared I did a quick & dirty AC trial with a zener modified USB charger.

I found that with most of these chargers, the voltage can only be measured while under load.

Power Supply "C" (and "A") that use opto-couplers appear to keep a ~5.25 voltage Pre-load.
The "B" supply started at ~7.92 - 8.28v and I assume will fall to ~5v when under load.

Even the "A" supply started with this behavior though once I started replacing the zeners. (perhaps it required a slight adjustment of the reference resistor?)

Video Test​

I could probably rename this thread because of what I've learned since starting it, one reason is the 3.7volts.

I found that a fully charged lithium battery is closer to 4.1-4.2 volts, so I expect to find performance optimal closer to that voltage.

Results​

I got the camera to function correctly with a load voltage of ~3.7 volts.
The motion activation worked, however - there was a "popping, and crinkling noise, and the audio was very muffled.
Also, there was some streaks and flashes in the video.

Next . . .​

My next step is to use a regulator to better condition the power.

However there are a plethora of low-dropout regulators which can regulate to voltages much closer to the input voltage. You might consider using one of them. I will mention a couple (based on nothing more than they are some I happen to have) MC33269DT-ADJ, and LM1086CSX-ADJ.

Thanks Steve,
I only found 1 supplier for the "LM1086CSX-ADJ/NOPB"

http://www.newark.com/jsp/search/productdetail.jsp?SKU=41K3388&CMP=AFC-GB100000001

I couldn't find anything for the "MC33269DT-ADJ"

Where do you buy these at?

Note that these are not a panacea -- they typically have much more stringent constraints on input and output capacitors.

Understood.
Can you give me any more detail about what kind of supporting components I will want to have on hand for these regulators?

Or, if you can point me to where I might be able to find a viable diagram it would give me an idea.

I might want to look into the small value capacitors if power quality continues to be an issue.

Thank You.

 

[(*steve*)]

Thanks Steve,
I only found 1 supplier for the "LM1086CSX-ADJ/NOPB"

I couldn't find anything for the "MC33269DT-ADJ"

Where do you buy these at?

As I suggested, I was not recommending those parts particularly. Go to your normal supplier and look up "low dropout regulators". For example, if you use digikey, they list a plethora of them. Search for several that seem to suit your requirements and then read the datasheet to determine which of them is the best. The datasheet will tell you all you need to know.

Can you give me any more detail about what kind of supporting components I will want to have on hand for these regulators?

That's what the datasheet is for.

Or, if you can point me to where I might be able to find a viable diagram it would give me an idea.

The datasheet...

 

[joshzstuff]

Sorry for the month sabbatical. I've been struggling to find time to advance my project, and I didn't want to post until I had something meaningful to report.

I've made some progress, and run into some walls.
Here's where I'm at:

Regulator selection​

I did a search for a low dropout regulator @ Digikey
I couldn't see or atleast figure out how to narrow the product listings to some of the more important criteria you described, so I asked their support.
The following is my request:

I am looking for a "low dropout linear Regulator IC (DC to DC)
I tried to find what I'm looking for in the section "PMIC - Voltage Regulators - Linear (31,986 items)"
Am I inputting the wrong information?

Here are the specs I'm looking for:

-3 prong IC
- low dropout (less than 1volt will be fine)
- variable output
- Input~5volts (can be a range 5-10v)
- Output ~3-5volts​

Here is there reply:

Unfortunately we can not offer you anything with your specifications. For future reference when searching for an item in our website find a broad link first like you did perfect with PMIC - Voltage Regulators - Linear and then add your specs into the drop boxes one at a time and click "Apply Filters" after every selection. It will usually help you end up with the desired product or something close. Sorry for the inconvenience.

So undeterred I experimented with the LM337 by replacing the stock zener diode with a larger value to allow for the head room of the regulator.

Results:​

-I modified the diagram above flipping the +/- for the LM337

-I had success powering the cam with a few different modified zener USB chargers.
Problem:
The resulting video was pretty noisy, and their was some flickering of the video.
Some units were better than others but I came up with an even better candidate for 'unregulated power supply':
Solution:

Nokia charger​

As you can see, this is a MUCH more complicated circuit and provides perfectly clean power @ ~7 volts which means I don't have to modify it at all (which is probably a good thing considering my current understanding )

Next Hurdle:
Battery/ Capacitor replacement​

The power supply for the camera will be turned on and off with a switch.
A problem occurs when the power is switched off while video is still recording, the result is that the video file is not saved and lost.

I fiddled with Capacitors, then switched to Batteries for a while then back to Super Capacitors.

Batt/ Cap Results:​

-The battery charge, discharge cycle proved problematic.
- Super Caps seemed promising, but even after adding 5F+ with 5.5v 1F Caps in parallel, the voltage dropped too quickly to allow the cam to save the vid file and shut down safely.
- Finally, (probably out of desperation) I used a 4.7F 2.5v Cap and it worked!!
I don't understand why the 2.5v Cap gave such a better discharge rate than the bank with >F??? (any ideas?) (internal resistance etc?)

Cap voltage concerns:​

I was leery of the long term effects of seemingly over-driving the voltage for this capacitor so I tested it over night.
After hours of use powering the camera in the circuit I could detect no adverse effects.
-The Cap rating is 2.5 volts
-I'm currently using ~4 volts to drive the camera ( and charge the cap)
-the data sheet lists a + 80% tolerance = 4.5v

Problems with Camera + Cap Circuit:​

'zombie mode effect'
The camera requires that the minimum voltage be reached fairly rapidly to start the camera.
If not then it just goes into 'zombie mode' and will do nothing but flash it's led until it is reset by removing power completely.
From my experience so far it seems that this requirement means the voltage must reach ~ 3.5v within 2-3 seconds to satisfy the camera.

This 'zombie' effect is problematic when charging the capacitor/batt and starting the cam simultaneously. (the voltage rise is slowed by the capacitor)

Solution #1:
diode/resistor solution
I used a diode & resistor to 'choke' the charge rate of the cap enough to allow the cam to start ok.
The diode allows the full voltage to be delivered back to the cam when the power is cut, but forces a slower charge to the capacitor.

'Choke' Problem:
The problem with slowing the charge of the Cap is that it takes longer to build a sufficient current to bring the camera down safely.
This problem surfaces when power is turned on and off too quickly. Thus the cap cannot fully charge in time and the video file is lost, also a possible zombie effect ensues.

Solution #2:
Timer delayed start
I am currently attempting to delay the start of the camera, giving the capacitor time to sufficiently charge.

I used this diagram with a 555 timer to envoke it's Monostable 'one shot' function to delay the start of the camera.

555 Problem:
The circuit works, and I did not use the 2 diodes adjacent to the relay coil (does anyone know what thier function is?)
EDIT: I found it in my electronics book, it protects the timer from surges caused by the relay opperation

The problem is that the camera will not accept voltage from the timer, when I try to power the camera from the 555 output it simple will not power on.
The voltage reads 4v @ the camera, but no dice.

- might I utilize transistors to switch the camera instead of directly from the timer?

Other Problems:
I still have not worked out how I am going to:
-charge the cap while isolating the camera

I must do this in a way that will allow the capacitor to completely discharge into the camera when the supply voltage is removed
(i.e. power off)

Sorry for the long absence and subsequent long post.
future posts will be shorter.

Thanks again for everyone's help!!

 

[joshzstuff]

Ok, I have an Idea about what type of circuit would work, but I need some help designing it.

I drew a rough diagram:

"T" = timer
"R" = a component to conduct power when activated by the timer only. (transistor?)
"X" = Needs to conduct all the time EXCEPT when "R" or "T" have power.

So basically:
1) when the power turns "on" it will remove "X" from the circuit and start the timer.
2) The timer will delay the camera until the Capacitor charges enough to safely shut down.
3) When power is cut, "T" & "R" will drop out leaving "X" to supply power to the Camera from the capacitor until it shuts down safely.

Possible problems:

The Capacitor cannot be allowed to power the Timer when power is "off". Does this look like it's a problem in this diagram?
If so, can I use a type of transistor to remove power when it's lower than what the "on" condition would provide?

I appreciate any pointers on alternate design, identifying the needed components, or pointing out any flaws.
Thanks!