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1  Using Arduino / General Electronics / EL wire current rating and Opto-triac to drive it on: Today at 03:27:58 pm
For my project I am planning to drive 7*1 meter EL wires with the following inverter, which claims driving 15m of EL wire;

http://www.ebay.com/itm/12V-DC-To-AC-Inverter-for-EL-Lamp-Wire-With-Switch15M-Meters-LJN-/161209107330?pt=US_String_Lights_Fairy_Lights&hash=item2588cfc382

First of all, for in total 7 meters EL wire (2.3mm diameter) how much current would I need ? I searched a bit and read that 100mA what it needs (well, I am not certain of that, sounds a bit too much for EL wire) And do I need to power the inverter for 15 meters or it will be only drawing for 7 meters, not sure though.

Once I power the EL wires, I need to control them with arduino. To do so I need opto-isolators. Not familiar with those components but as far as I researched I need to couple each opto-isolators with a triac since they are not designed to drive the load but another triac instead.

However, heard that opto-triacs replaces the need of a optoisolator and triac couple and are capable of driving the load. Since I don't know how much current I will be handling for each 1 meter EL wire, I couldn't pick a proper opto-triac.
Appreciate if you give me advices. Thank you.

Oh by the way, the opto-triac I found and thought would be useful is that;
http://www.ti.com/lit/ds/symlink/moc3023.pdf

What do you think ?

2  Using Arduino / General Electronics / Re: LED strip question on: July 10, 2014, 02:29:18 pm
For Dumb LED strips: Every 3 LEDs will have its own current limit resistor; power & gnd are passed along in parallel to the next group of 3. Each group of 3 will draw ~20mA from 12V supply. A shorter length will thus draw less current.  PWM/transistor can be used to control brightness.

For Smart LED strips, a control chip will control each LED/group of LEDs. Current draw will be similar. Software controls the brightness.

No external resistor is needed either way.

As an example, here is 74HC595 controlling AOI518 N-channel MOSFETs to fade strips with 9 LEDs (3 groups of 3) up & down.
http://www.crossroadsfencing.com/BobuinoRev17/
http://youtu.be/hAVf1D1L-7c


One more question if you don't mind;

To drive one of these LED strips, I need to use a NPN transistor. However, I am not sure which transistor to choose and the resistor to connect its base.

I reckon the resistor should be something like that for 5 Meters;

5* Hfe / (1.3 * 2)

where 5 is the switching voltage from digitalOutput and 2 is the load current drawn by LED strip
3  Using Arduino / General Electronics / Re: LED strip question on: July 10, 2014, 02:10:11 pm
For Dumb LED strips: Every 3 LEDs will have its own current limit resistor; power & gnd are passed along in parallel to the next group of 3. Each group of 3 will draw ~20mA from 12V supply. A shorter length will thus draw less current.  PWM/transistor can be used to control brightness.

For Smart LED strips, a control chip will control each LED/group of LEDs. Current draw will be similar. Software controls the brightness.

No external resistor is needed either way.

As an example, here is 74HC595 controlling AOI518 N-channel MOSFETs to fade strips with 9 LEDs (3 groups of 3) up & down.
http://www.crossroadsfencing.com/BobuinoRev17/
http://youtu.be/hAVf1D1L-7c


Okay, so regardless of the brand and length of the LED strip, I will power it with 12 VDC without any resistors.
Thank you (:
4  Using Arduino / General Electronics / LED strip question on: July 10, 2014, 12:51:30 pm
I have some questions regarding LED strips

Consider the one below;
http://www.ebay.com/itm/Cool-White-Non-Waterproof-5M-3528-Led-SMD-600-Lights-Flexible-Strip-Light-DC-12V-/131135597329?pt=US_Car_Lighting&hash=item1e884a6b11

Length: 5 meter
Working voltage is 12 VDC
Working Current/meter: 0.35 - 0.4 A

First of all, do all those LED strips on the market have their own resistor ? So, do I need to add a current limiting resistor ?

If I decide to use 1 meter, then I will still be applying 12 VDC. However, this time I need to limit the current to 0.35 - 0.4 A with a resistor, am I correct ? Or can I drop the voltage and do not use any resistor ?

I am kinda confused. Appreciate if you clarify it.

Thank you.

5  Using Arduino / General Electronics / Power jack for arduino prototyping on: July 09, 2014, 05:34:36 pm
I found this tutorial for building your own arduino on a breadboard.

http://arduino.cc/en/Main/Standalone

I'm planning to do that on a PCB and also  power the the processor with 12V DC.
The thing is, where should I connect the power jack ?

I would connect it to either pin 7 or 20 but not sure what the difference is between Vcc and AVcc

And also how can I reach to 5V output ? Is it also introduced through voltage divider on the arduino board ?

6  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 09, 2014, 12:23:01 pm
Quote
Are you sure that's the reason or is this just a guess ?
I am sure that the capactor you have used is useless for the task you have give it so it needs changing in any case. if you have anything else wrong it is hard to say at this stage. You must always correct the things that are wrong when ever you see them. As itcouldexplain everything and needs changing anyway then you loose nothing by changing it.

Okay. Thank you so much. I'll try to find a ceramic one and replace it.

So, changed the capacitor but problen insisted. Then check the code once again and realised I used the same output twice. Now it is working with even plastic capacitors (FYI). Also noise of LEDs are gone.

7  Using Arduino / Audio / Re: MSGEQ7 Noise problem on: July 09, 2014, 12:19:41 pm
Why have you started a new thread on this?

My bad !
Confused this forum with another. So, thought I started the other one on another forum.
Sorry about that.
8  Using Arduino / Audio / MSGEQ7 Noise problem on: July 08, 2014, 09:58:54 am
I'm trying to use MSGEQ7 IC for spectrum analysing purpose.
When I hook up an LED there is a little noise sound on the speaker. One more LED increases the magnitude of the noise. Also I realised that if I change the ground connection for LEDs from one GND input to another GND input on arduino, noise also increases or decreases. Kinda weird and no idea why this is there.

Any idea ?
9  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 06, 2014, 03:13:58 pm
Quote
Are you sure that's the reason or is this just a guess ?
I am sure that the capactor you have used is useless for the task you have give it so it needs changing in any case. if you have anything else wrong it is hard to say at this stage. You must always correct the things that are wrong when ever you see them. As itcouldexplain everything and needs changing anyway then you loose nothing by changing it.

Okay. Thank you so much. I'll try to find a ceramic one and replace it.
10  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 06, 2014, 05:53:26 am
The capacitor between pins 1 & 2 is for supply decoupling. This should be a ceramic type capacitor, not the type that you have used. It could be that the chip is oscillating as a result.

Are you sure that's the reason or is this just a guess ?

Also I do wonder why I read "0" from the audio signal input ?
11  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 05, 2014, 06:25:30 am
A new, more clear setup.

12  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 05, 2014, 05:58:23 am
Quote
when the end of the cable connected to the A0 input is floating, there is some random noise and when I touch the cable it changes prominently.
That is exactly what I would expect.

Quote
but when it comes to reading it through an Analog input,
What do you mean by that?
Can you post a schematic of what you have actually done. I can't marry up those photos with the schematic on that link.

I simply get the left channel of the audio signal through a 3.5mm Jack and connected it to A0 (analog input 0)

Datasheet below;
https://www.sparkfun.com/datasheets/Prototyping/Audio-3.5mm.pdf

pin 2 and 3 are the same pins for left channel. So, audio signal is coming from computer and going to the arduino. However, I read "0"
13  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 04, 2014, 05:12:38 pm
Okay, I did some debugging and concluded that when I read the left or right channel of the audio signal through A0 input of arduino, I read "0" all the time. However, when the end of the cable connected to the A0 input is floating, there is some random noise and when I touch the cable it changes prominently.

The thing is, I get the audio signal from laptop's audio output and channel it to the speaker over breadboard, meaning the signal is there on the breadboard and going to the speaker without any problem, but when it comes to reading it through an Analog input, there is nothing.
14  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 04, 2014, 02:56:04 pm
Quote
Why is it so ? I always used LEDs directly. I really don't know the potential problems ?
The problems that you are destroying either your LED or the thing that drives it.
Read this:-
http://www.thebox.myzen.co.uk/Tutorial/LEDs.html

Thanks for the link. So now you need to post what you are doing. A good quality photograph, less that 1000 pixels wide woul be a good start.

Ooh I didn't know it is that serious. Thank you!

Below the photos of the setup and thank you for your interest

15  Using Arduino / Project Guidance / Re: Beep sound problem with MSGEQ7 on: July 04, 2014, 01:33:50 pm
Quote
Directly connected.
BAD BAD BAD

Even if it did not solve your immediate problem it will cause others.

Quote
There are a lot of tutorials and also guidance on the datasheet.
So which one are you trying to follow? Link please.

Why is it so ? I always used LEDs directly. I really don't know the potential problems ?

This is one of the tutorials I've found;
http://nuewire.com/info-archive/msgeq7-by-j-skoba/

And this is the Data sheet contains the extra component connection schemes;

https://www.sparkfun.com/datasheets/Components/General/MSGEQ7.pdf

Thank you.
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