Converting 3V Battery Device to DC: Choosing the Right 3.3V Converter

What would be the best way to convert a 3V battery device to DC?
I would like specifically to use a door sensor without a battery. Obviously, there are some 3.3V converters, but I am not sure if they are actually suitable. I think that in cheap converters they probably don't bother to smooth out the phase peaks, and I am not sure how/if this affects the sensor functions.
I am sure somebody has done this before.

I understand that you want to build a 3V to 3.3V DC converter?
What current (mA) efficiency should it have?

max-bit wrote:

I understand that you want to build a 3V to 3.3V DC converter?
What current (mA) efficiency should it have?

He wants to power a battery-powered device from a DC power supply.

The best way is to modify the power supply from an old Nokia phone. You have to modify the feedback loop.
Usually it comes down to replacing the zener diode. However, it depends on what kind of power supply you have.
If you have one, take it apart and post some pictures.

Personally I would get a wall wart/old phone charger that has 800mA or more and a module like this one:
https://www.aliexpress.us/item/22558004492321...651!ppc!!!&gatewayAdapt=glo2usa4itemAdapt

This module can deliver 800mA and that should be more than enough for this, it also has the minimum number of capacitors onboard.
It is an LDO, that means it can be used with low voltage drop applications like this.

Have fun!

I'm currently planning to do something similar for some Zigbee temperature/humidity sensors and I got these for the experiment: https://www.aliexpress.us/item/3256805591743309.html They may be what you are looking for.

>>21397936
Well, I wait for the results. I have seen those and many others. Problem with all of those is unknown quality. Also, I don't have really anything to test it.
Battery has a real DC linear graph. Worst "DC" converters just cut off one side of the AC graph. Even when sometimes there are some smoothing capacitors, the result mostly is still horrible. Only real information about DC wave quality gives an oscilloscope. Most people obviously don't have that.

How your door sensor looks like? Does it run directly from battery? If it's using a WiFi module that's run from 3.3V, then 3.3V voltage should be good. You can just go for 5V along with 3.3V LDO. Just make sure to check the datasheet of chosen LDO first and do not exceed its maximum ratings, Vin, etc.

minusync wrote:

The only real information about the quality of a DC wave is given by an oscilloscope. Most people don't have one, of course.

.
But the battery is discharging which means its voltage is not constant and if the device can tolerate the voltage drop and is working it will tolerate a non-linear DC waveform and if it doesn't then you have an oscilloscope and you can add Low Esr smoothing capacitors ferrite filters etc.

The modules mentioned by minusync are pretty good, even using a scope, but use these for designs that they are meant for.

The main problem is that you need a place to put it so it will be safe, what if the housing breaks?, what if you have a fire and the insurance see your self-built device?
A doorsensor doesn't have a lot of room, and it isn't really feasible to have a mains line entering that device.

That is why I told you about this one: https://www.aliexpress.us/item/3256805591743309.html
It is within spec, of the regulator that is being used in that design, if it is genuine of course.
There are better LDO regulators out there, but this should be fine.
Stay away from the regulator modules that use a pot for voltage trimming, these tend to cause problems in the long run.

You can put it in the housing with a DC barrel jack or a USB connector and it will look like factory.
A simple wall wart or a cheap/old 5v phone charger can supply the 5v power
And because the wall wart/charger is a device that is already been (CE) approved and tested, it will not be a problem later on.
Your device is then running on 5v, so that is safest way.

If you are worried about the 3.3V vs the 3v battery voltage you can simply add a schottky diode (1N581x) between the positive lead of the LDO and the positive lead of the sensor.

Maximilian0017 wrote:

The main problem is that you need a place to put it so it will be safe, what if the housing breaks?, what if you have a fire and the insurance see your self-built device? A door sensor doesn't have a lot of room, and it isn't really feasible to have a mains line entering that device.

I have some renovation planned and based on that, it would be a good time to set it up a little better. Whatever the power source is, it goes to the electrical box. Fire is always a problem. Part of that is why there is a little concern with Chinese goods.

Maximilian0017 wrote:

cheap/old 5v phone charger can supply the 5v power

I thought about that too. My esp modules all work similarly, but to get to 3.3V you have to add additional complexity. Eventually maybe I should go for that.

p.kaczmarek2 wrote:

How does your door sensor look like? Does it run directly from battery?

I have a regular cheap sensor with 2xAAA power source. Bcs I have some renovation on the way I probably put it directly in door frame and never touch it again. That's why power from AC/DC is necessary.

Do you have hollow walls or a lowered ceiling?
PSU's have a tendency to die after a few years, so it is better to make sure that you can reach it somehow to change the device, I have seen this a couple of times with automatic door locks and transformers for halogen and led lights.

In many buildings with lowered ceilings you see WCD's on the ceiling to connect lamps and other devices, this is done to make sure that the building is up to code for their electrics.
It is better to have a WCD between the net and your device.

Sorry, but is this topic not sticking at all? It is not really clear what the questioner is asking.
Sorry what is this topic about?
The questions and answers are unclear. It is not clear what the purpose of this post is?

max-bit wrote:

In principle, it is not clear what the questioner is asking.

.
Something can be understood there though. He wants a power supply but is concerned about voltage instability.

To the author:
Maybe I'll suggest another option. Place the sensor where you want, permanently, run the wires out of it and finally install a battery basket. Place it in a good place so that you can change them. For example, behind a suspended ceiling if you have one.

It's a simple matter (knowledge of the type I have regips redundant)
So the specifics:
Power supply :
What output voltage / what current capacity.
Battery supply, other voltages ? (backup)

So the specifics:
Power supply:
What output voltage (one, multiple) / what current efficiency.
Battery power supply, other voltages? (backup)

Maximilian0017 wrote:

It is better to have a WCD between the net and your device.

(WCD is a normal power outlet)

I probably will try this time with phone charger and try to lower its output to 3,3V.
When someone has some actual practical experience with 220 to 3,3V power sources it would be great to know. Maybe there is actually better option for next time.