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16  Using Arduino / Audio / Re: How MIDI changed the world on: December 03, 2012, 04:43:04 am
Good read!
Thank you for sharing...
17  Using Arduino / Audio / Audio noise caused by a micro servo on: December 03, 2012, 03:14:12 am
I have built a wireless pedal board. I can now control my amp and my effects from switch panels taped on my guitars.
Effects are located in a box and connected to my amp by short patch cables (mono 1/4 jack).

So I tried to add a new function, kind of programmable volume control by using a micro servo. 
I have chosen this el-mechanical solution because I didn't want to modify my amplifier.
I was afraid that two sided tape wouldn't be strong enough to hold servo in position and worried about hundred other things.
See video clip:
Both mechanical transmition and arduino sketch turned out to work perfectly but micro servo caused another problem:
Audio noise, a lot of audio noise, booming, buzzing and popping noise.
Not only from my amp but it affected PA and few other amps in the room.
(You can't hear the noise because I don't have a speaker cabinet at home so amp was off while I was recording video)

I wonder is there any way to prevent this noise... Maybe micro servo and audio equipment just don't work together.

18  Using Arduino / General Electronics / Re: Looking for a connector on: November 09, 2012, 10:03:11 am
Thanks for the info!
I can live with that! Fortunately I never used them outside so once I get
inside, they soften up after a while and I can unfold them.
Still, I would like them more if they were more flexible.

19  Using Arduino / General Electronics / Re: Looking for a connector on: November 09, 2012, 06:52:28 am
I'm not sure I understand exactly what you are asking for, but if you are wanting to connect 6 wires, one thing you might think of is a RJ-45 connector that is used for ethernet cables.  You can buy the female plugs that you can attach wires to at places like Radio Shack or Home Depot.  For example here is Radio Shack's version:
I use network adaptors and cables for my project. They are almost perfect but I do have a little problem.
They are often very stiff and if I take them out in cold winters day they just stay folded for a long time.
I found a flat type of network cable on the internet but nobody can tell me if they are stiff or not.

Is there anyone who's tried one of those?
20  Using Arduino / General Electronics / Re: Power step down on: October 30, 2012, 03:34:54 pm
This is exactly what I had in my mind! Only thing I am worried about is
how to isolate those two 9V outputs.
But, I'll try it first with no isolation and see if
it gets noisy. I can always use separate 9V adaptor like I do
at the moment but it would really be great if I could use
only one power supply cable.

Thank you!
21  Using Arduino / General Electronics / Re: Power step down on: October 30, 2012, 11:39:24 am
Do I need an extra heating tank for it? Or maybe
there is no need for it if the current is less than 1A???
22  Using Arduino / General Electronics / Re: Power step down on: October 30, 2012, 06:18:35 am
Thank you for your help guys.
I'm going to order one linear and one fixed converter and see how they behave in my circuit.
I'll monitor heating and audio noise and decide later which one is most suitable for my application.
(I guess, the cheapest one is gonna lose, but we'll see)
Anyway, the price is not really issue here since it costs nothing comparing to what I paid for my guitars and the amplifier.

23  Using Arduino / General Electronics / Re: Power step down on: October 29, 2012, 09:22:55 am
You have two main choices for DC step-down:

    Linear Regulator:  Inexpensive. Throws away excess voltage as heat.

    DC to DC Converter:  More expensive.  More efficient.

You didn't say what the input voltage is (your 5A supply).  You didn't say what the power requirement on the three output lines (4.5V, 6V and 9V) are.  You did say 1.6A but is that one EACH or all combined?

Input (primar) voltage to my adaptor is 240V AC,
I need total current of 1,6 A.
4,5V output  200 mA
6V output, 350 mA
2 pcs 9V Outputs 400 mA each.  (total 0,8A)
I hope I could still use 12V output where I need 250 mA.

Would it be posible to isolate those two 9V outputs?

I am running two guitar effects on each output (today I use two seperate 9V adaptors )
One pair of pedals is connected to front of guitar amplifier, the other pair is connected in amplifiers LOOP (ie in between preamp and power amp).
It get noisy when I run everything on the same power supply.


24  Using Arduino / General Electronics / Power step down on: October 29, 2012, 03:25:24 am
I intend to use only one power supply for my project. It can supply 5A of current (though, my max load would need 1,6 so I am good whith the amount of current)

The question is what step down units are recommended so I could make 4,5 , 6, and 9V outputs.

I have no expiriance with voltage divaders so before I purchased some parts I would like to know downsides of different devices :



All epoxy sealed containers with Waterproof Housing;
Light compact, convenient to use and transport;
High efficiency:>96%;
Reliable, low heat dissipation max. 40 ℃;
With overload / over-current / over / low voltage protection, stable performance.
Auto recovery

Input range: 8~23v
Output voltage:9V
Output current/power:3A
Efficiency: >96%
Weight: 30g
Size(LxWxH): 26×36×21(mm)
Cable length: 100mm


Dimensions: length (45mm) wide (31mm) high (22mm)
Input: DC 10-15V
Ouput: DC 0.9-12V
Ouput Current:  5A
Output Power (MAX): 25W
Efficiency: 93% (12V to 5V/5A)

Testing numbers:
12V to 5V/2A:
Efficiency = (5.00 * 2.000) / (12.00 * 0.894) * 100% = 93.2%

2V to 5V/4A:
Efficiency = (5.00 * 4.000) / (12.00 * 1.782) * 100% = 93.5%

12V to 5V/6A:
Efficiency = (5.00 * 6.000) / (12.00 * 2.705) * 100% = 92.4%

12V to 5V/8A: ( A serious decline in the efficiency, Severe fever)
Efficiency = (5.00 * 8.000) / (12.00 * 3.680) * 100% = 90.6%


Input voltage: DC 7-20V
Output voltage: DC 5V
Output Current: 1A  (can work at 1A for long time)
Rated continuous current: 1A
Output power: 5W rated continuous

What about this? (I guess it woun't do a job alone)


Product Name    Positive Voltage Regulator
Model   L7812CV
VRRM   12V
IR(AV)   1.5A
Pin Length   13mm / 0.511"
Pin Spacing Pitch   2.5mm / 0.098"
Body Size   16 x 10 x 5mm / 0.6" x 0.4" x 0.2"(L * W* T)
Hole Diameter   3.6mm / 0.14"
Color   As Picture Show
Weight   4.7g


Three-terminal positive regulator are  available  in the TO-220 package and
with several fixed output voltages,  making them useful in a wide range of applications.
Output Current up to 1.5A.
Thermal Overload Protection  .                                 
Short Circuit Protection.
Output transition SOA protection.

I am sure there are plenty of other options.

I guess it's all about resistors ( pull down) which means they will use some current all the time.
That means heat too but I guess I can live with it. I use my device once a week and it's on just for a 4 hours.

25  Using Arduino / Programming Questions / Re: Blinking LEd controlled by servo state on: September 22, 2012, 06:04:12 am
Just a little update:
Aurdino arrivef
tested connection with my DOD digital delay pedal and it worked fine.
This pedal gave only 1.6V from the spot marked on my diagram above.
I used another spot to soldier my signal wire which reads 3.3 V.
I'll test my DS-1 pedal tonight.

Still waiting for my servo to arrive but I don't have
any doubts about that. Nothing unknown on that part.

Thank you guys a lot!
26  Using Arduino / Microcontrollers / Re: Arduino Uno Rev3 pinouts photo on: September 22, 2012, 03:47:46 am
Thank you Lefty, you are Righty actually.
I didn't dare to power it externally before I was sure.
Been waiting 2 weks for it and didn't want to take any chances.
What Rev is my board?
27  Using Arduino / Microcontrollers / Re: Arduino Uno Rev3 pinouts photo on: September 21, 2012, 01:43:37 pm
Where are "jumper" pins on this card. I tested the card and it works fine using USB as supply.

Now I want to connect it to external power supply and ...

Uploaded with

What is polarity for external power supply socket?
Is GND around and + in the middle?

28  Using Arduino / Programming Questions / Re: Blinking LEd controlled by servo state on: September 18, 2012, 01:42:09 am
Thank you guys!
I think all my questions have been answered and while I'm waiting for components to arrive I can draw my detail diagram,
mechanical drawings and do some reading. I'll let you know how it went.
I'll probably struggle to get my finale sketch to work perfectly but it's a part of the game.

29  Using Arduino / Programming Questions / Re: Blinking LEd controlled by servo state on: September 17, 2012, 02:10:00 am
Are you using ordinary small low power LEDs? They don't draw much current at all so they will cause very little voltage drop. Unless you're trying to run wires over hundreds of yards I wouldn't have thought you would have any problems. And if you do run the lines so far that voltage loss is a problem, given that the resistance of the lines is known and constant, you can just subtract that resistance from your current limiting resistors for the LEDs.

Thank you!
It makes perfect sense. I am using 4 ordinary 5mm LEDs.
We just discussed my first LED, which will tell me about Servo's actions.

My second LED will tell me when the effect pedal is ON.
I intend to connect it according to diagram below.
I will use same power supply both for the pedal and Arduino ( 9V DC)

IS THIS SAFE. Will it work?

Uploaded with

30  Using Arduino / Programming Questions / Re: Blinking LEd controlled by servo state on: September 16, 2012, 02:31:28 pm
If I want to place my LED in another room, I need long leads.
It will probably give me a trouble.
So I need separate power supply for the LED. I'm going to use a transistor as a switch.
Probably some resistors too and again connect ground with
Is this correct?
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