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136  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 21, 2012, 11:54:59 am
Jack Christensen explained me that batteries have long shelf life when not used, so this should go for years.

An other idea would be to always measure the batteries voltage via analogue input (and voltage divider) and if this is under a threshold, have some alarm or so. However, I think, measuring the voltage will also have some, but small, current drawn and thus decrease their life...
137  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 21, 2012, 11:34:01 am
Great! Now I know, how a UPS works!

And now, to create it, I have the following idea:

Everything in a junction box, and using these 2.1mm Power female jack Connector Adapter. To have everything in a box.

138  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 21, 2012, 11:17:38 am
The UPS
139  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 21, 2012, 09:43:16 am
Ok, thank you retrolefty, and especially Jack Christensen!
@Jack Christensen: I didn't know that 5V pin can be used as input, so when I buy the boost converter and a use my universal wall wart, I can do this ,aswell.
After having looked more detailed on your schematics, I noticed that you put the boost converter after the 5V wall wart. Why do you do that? The wall wart gives you exactly 5VDC, doesn't it? Or just as a  matter of safety?

I will post my schematics, too, then.
140  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 21, 2012, 08:04:21 am
Could I also use a voltage divider if I  use a 12V wall wart instead of the boost converter . And then this circuit


That is 12V*220Ω/(1000Ω+220Ω)=2.16V, which is 2.16V/5V*1023=442 analogRead(A0) value, if the wallwart supplies 12V.
If it does not supply any voltage, 220Ω works as pull down resistor and current flows only GND-220R-A0, so analogRead(A0) returns zero (like connected to GND directly), right?

An additional question:
Is it right that Arduino does not even reboot if the mains fail because if they fail, immediately the power from the battery is taken? So, the temporary data won't be lost
141  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 21, 2012, 03:38:13 am
To know whether the mains fail. Then, for example, a signal can be sent... Actually, to be honest, I don't know yet what I want to use the measurement for. But I want to use it, maybe just because of an experimental use.

And, I have yet to understand how you can bypass the built-in linear regulator. So VIN  cannot be supplied with something else than 5V and via the power jack can be supplied with 7V~12V. (?)
142  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 20, 2012, 04:21:15 pm
this should measure the voltage, with a voltage divider the voltage gets 0.18*Voltage.
Alternatively it could be mounted between each powersupply and the correspooding diode. Then this goes to A0 respectively A1 to know what the battery supplies and what the power adaptor supplies.
143  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 20, 2012, 02:26:02 pm
And to understand you correctly, to use this infamous boost converter, the only thing is to add it and to change the ACtoDC-12V-converter's input to Vin_ACtoDC≤5V input and the batteries Vin_batteries <Vin even if they are completely full.

Is it a difference to use the V_IN pin or to use the power-jack at the top?

Next Idea:
144  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 20, 2012, 12:58:07 pm
Hello,
I think, the boost converter isn't necessary. This could also work with the 6*1.5V=9V battery pack and a 12V wall wart (I have a universal wall wart supporting selectable 5,9,12,... V)
And yes I already also  heard that batteries can supply more power than what they are sometimes said to supply (I measured 1.6V instead of 1.5 right now, a "Aerocell 1.5V" even if it was used for some weeks)

145  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 20, 2012, 10:19:49 am
When the mains are supplying power, the voltage at J1 is greater than the battery voltage at TB1. This causes D2 to be reverse-biased and prevents current from flowing out of the battery.
This is not clear for me, that means, always the higher power supply is taken?
I think, that would result that the sum of each voltage is supplied then, that might be too much.
And what is the sense of the diodes, then?

Some diodes like this,

I am thinking of something like this now
146  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 20, 2012, 06:51:13 am
Hello.
In my circuit, no current is drawn from the AA cells unless the mains power fails. Normally all power is provided by a 5V wall wart. AA alkaline cells are advertised as having seven year shelf life, so while I would replace them after a significant power outage, otherwise I plan on just changing them maybe every 2-3 years, just to be conservative.
Ok, that is very good - especially the first sentence. I think, if I put them in dry area, this will decrease the self-drain (self-discharge).

However, I have to admit that your circuit is very complex for me.

I am thinking of something like this (red=9VDC, blue=GND)



I have heard, relatively long ago, something with diodes so that electricity can only flow in one direction...

I am really clueless  now... And I really want to do it the way you told: "no current is drawn from the AA cells unless the mains power fails"
147  Using Arduino / Project Guidance / Re: Control all 3.3V devices with 5V Arduino ? on: October 19, 2012, 05:51:40 pm
Ok, that is fine!
And thank you very much for the help. This is a very easy way to work with 3.3V modules smiley
148  Using Arduino / Project Guidance / Re: Control all 3.3V devices with 5V Arduino ? on: October 19, 2012, 05:45:27 pm
Ok, Could I also use 10K resistors? That would minimize the current drawn.
And, thank you very much for the explanation.
149  Using Arduino / Project Guidance / Re: Control all 3.3V devices with 5V Arduino ? on: October 19, 2012, 05:35:12 pm
You should always read the data sheet for these modules, some will take 5v because the chips is able to or the module has an inbuilt voltage divider.

The modules 3.3v high outputs can go direct to the arduino as the digital inputs see anything over 3v as high.

Yeah, I knew that already smiley-wink

The question is using those 3.3V modules not having an intern voltage divider and as output.
150  Using Arduino / Project Guidance / Re: rechargable batteries for uninterruptible power supply on: October 19, 2012, 05:28:23 pm
For me it is very important to charging the batteries. There are also AA /AAA rechargable ones?
Or do you think it is a problem when they get empty while power is supplies from the wall wart?
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