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31  Using Arduino / General Electronics / Re: Powering 45M of LED light strips safely on: April 21, 2014, 12:19:20 pm
Please note that power supplies come in a wide variety of qualities.
A "480w" Logisys brand PSU will die (likely to due to a switching transistor exploding) at around 180w load.
A "450w" Corsair brand PSU will shut down at around 500w of load, and restart happily.

"Watts" is also a bad measure of power supplies. You have to look at how it's distributed between 5V and 12V. Some cheap supplies put a lot of amps on the 5V rail to boost the overall wattage rating. You need 12V for these strips so that's the number you should look at, not "watts"

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32  Using Arduino / General Electronics / Re: 3.3V modules, battery power, and voltage divider level shifting on: April 21, 2014, 10:02:07 am
I want to run a battery powered bread board Arduino on 3xAA batteries (so about 4.5V to 4.0V).  I understand the concept of using a voltage divider to do level shifting between the ~4.5V MOSI pin on the Arduino to the radio module.  But if your input voltage dips a bit, you won't get a consistent output voltage.  I expect the battery voltage to drop over time, to from 4.5V to 4.0V before needing to change the batteries out.

It will actually drop a lot lower then 4.0V. AA batteries go from 1.6V (new) down to 1.0V (almost dead) so your voltage range from 3xAA is going to be 4.8V to 3.0V over the life of the battery.

Is the voltage drop a big deal for radio modules like the RFM69?

Yes.

The simplest answer is to use a 5V voltage booster: http://www.ebay.com/sch/i.html?_nkw=5v+dc+boost+pfm

Glue one of those to your 3xAA battery pack and connect your device to it with an old USB cable.
33  Using Arduino / General Electronics / Re: power problem !!! please help on: April 21, 2014, 09:36:35 am
okay if i try to replace it !! do i have to use the same regulator/reference  or just any 5V regulator ?

The one on the board is this:

http://unihedron.com/projects/sqm-le/PDFspecs/NCP1117-D.PDF

But it's nothing special. In theory anything with more or less those characteristics will work.

Another option is to get a LM7805 regulator. Cut a USB cable in half and connect the output of the regulator to the red/black wires of the cable. Connect that to the Arduino USB connector.
34  Using Arduino / General Electronics / Re: power problem !!! please help on: April 21, 2014, 08:19:32 am
Sounds like the 5V regulator is broken.

35  Using Arduino / General Electronics / Re: USB2 motherboard power on: April 21, 2014, 06:35:39 am
So I have a project where I intend to power the arduino board from the internal motherboard USB2 connection. I'm just wondering if anyone here can tell me if it's always powered even when the PC is turned off?

That depends on the PC...some do, some don't.

36  Using Arduino / General Electronics / Re: Using multiple capacitive sensors accurately on: April 21, 2014, 05:24:55 am
Any ideas?

The standard capsense library is rubbish.

You know what values are OK, makeyour code to reject values which are massively outside of range.
37  Using Arduino / General Electronics / Re: Sharing a power supply between arduino and led strip? on: April 21, 2014, 05:17:17 am
My question is, why can't they both share the external psu?

They can both use the same PSU, no problem. If it's a 5V PSU then simply connect the 5V from the PSU to the Arduino 5V pin.

nb. Make sure it's a regulated (switching) supply with exactly 5V. Don't try to connect the USB cable at the same time or anything like that. Connecting two PSUs together is bad, mmmmkay...
38  Using Arduino / General Electronics / Re: cannot measure current for some reason? on: April 19, 2014, 03:35:11 pm
I have checked my fuse and I realised it's non existent!!!! Hahahahaha!!! But what's confusing now is why does it show 0.75mA without a fuse at all?

Some multimeters do that

(no, I don't know why...)

39  Using Arduino / General Electronics / Re: cannot measure current for some reason? on: April 19, 2014, 01:46:46 pm
Check your multimeter fuse.
40  Using Arduino / General Electronics / Re: Is capacitive sensing possible with batteries? on: April 19, 2014, 08:49:37 am
...by that I mean there's definitely a measurable effect with the piece of foil on a wire for "ballast". The only challenge is to measure it.

41  Using Arduino / General Electronics / Re: Is capacitive sensing possible with batteries? on: April 19, 2014, 06:18:11 am
Any new progress?

It's pretty much working.

This is for a workshop where people bring their own jars to decorate so I don't have any fine control over it. I think it will work with a piece of foil and 8MHz CPU clock. I can always increase the size of the resistor if it starts failing on the day.

42  Using Arduino / General Electronics / Re: Interesting post from another board related to this topic on: April 19, 2014, 06:15:37 am
From this exchange it appears that the lights will not draw close to maximum watts/amps even while full on. This has helped ease my mind with regards to the maximum amount of power I could possibly see.

Complete rubbish.

He didn't get the full current draw because he was connecting them up with crappy wires and the strip wasn't getting enough volts.

45 meters of LEDs at 60 LEDs/meter is 2700 LEDs.

At 60mA per LED (they're RGB color) that's 162 amps if you set them all to white.

Luckily for you they're connected in groups of 3 so the current is a third of that, 54 amps.

You shouldn't run a power supply at 100% rating if you expect it to last so you need a 75A, 12V power supply.

Next you need to think carefully about how to wire it.

You can't just connect 12V to one end of a 45m strip and expect 54 amps to go down it. It simply won't work. You need to connect it in sections and make sure you're not getting much voltage drop anywhere along the strip. If you see voltage drop ("droop") you need to chop it up more and run more power cables. This is how you figure out how to wire it - measuring the voltage along the strip and make sure it stays at 12V. If you see (eg.) 11V anywhere then you need to chop it up more and run more power cables.

Once it's wired up with little power losses you need one of those "amplifier" boxes for each section of LEDs, all hooked up to a central controller.

43  Using Arduino / General Electronics / Re: Wireless sound on: April 18, 2014, 01:29:10 pm
I'm not quite sure about 8 and 10 bit, wouldn't be this a problem?

That depends on the microphone.

You might need an op-amp to amplify it and get the full range on the ADC.


44  Using Arduino / General Electronics / Re: High Voltage Regulation on: April 18, 2014, 11:45:40 am
I am setting up  project, in which I use Arduino to control the wall outlets in my room, after closer examination of digital potentiometers, they cant handle anything near to my MAX voltage (240v), and looking at voltage regulators, I can only find the TL783, I hoped I could find a regulator that is tolerant to higher voltages, and if I found one, how would I go about automating it?

I am just looking for suggestions to control higher voltages (using analog).

Seriously: If you're asking these questions, you shouldn't be doing it. Houses burn down.

What devices do you want to control? Maybe there's replacement devices with built in PWM controllers that could connect directly to an Arduino, etc.
45  Using Arduino / General Electronics / Re: Wireless sound on: April 18, 2014, 11:06:16 am
I understand your suggestion but that way i wouldn't be learning smiley-sad

Well.... start without the "wireless" part.

Hook up a microphone and DAC to a single Arduino, see what happens.

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