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16  Using Arduino / Project Guidance / Re: need help understanding code on: March 04, 2013, 04:15:01 am
Hey dude you need to chill, not sure why you so upset.

I didn't directly link the code because I want whoever looking to help me understand the project and what the owner of the code intended it for, I wouldn't think the code by it self would be much useful.

So if anyone want to help me that would be much appreciated, please message me and I will try to give you as much information I currently have and what I already done.

thanks
17  Using Arduino / Project Guidance / Re: need help understanding code on: March 03, 2013, 07:51:44 pm
I assume the code the owner used in the video, everything is in the link.

if you are seriously about helping me please say so, the problem is that the owner did not make any comments and my programming is not good enough to understand what is happening.
18  Using Arduino / Project Guidance / need help understanding code on: March 03, 2013, 07:30:55 pm
Any good coders willing to help me with my project, I have some code but I don't understand how it works. The owner is not responding.

http://codinglab.blogspot.co.uk/2010/09/diy-laser-projector.html

Please say if you can help.
19  Using Arduino / Motors, Mechanics, and Power / Re: Motor current draw from 5V pin MADNESS! on: January 22, 2013, 02:28:07 pm
Quote
That is probably a minimum specification so manufacturers of

No, 500mA is the maximum for USB according to the USB specification (versions 1 and 2, anyway, not sure about USB3).

USB spec says a device can have 100mA for "free", and can negotiate with the host for up to 500mA.  In practice, many hosts will supply 500mA without negotiation.  There are also other deviations from that spec, such as the Macs that provide 1A or more for charging iPads.

Powering a motor directly from an output on the arduino will kill the processor - maybe one output pin, maybe the whole IC.  The maximum for a single pin is 40mA (that's on the original ATmega8, newer may be a bit higher but similar).

Keep trying to drive a motor from an output pin and you will kill your arduino, if you haven't already.

-j


If you read the post it says the motor was powered fro the 5V power pin on the arduino.
Quote
I partially stopped the motor and saw the current draw rise to 1A.

Placing drag on the motor causes the current to rise toward the stall level.  Thus if the motor coil has 5ohm resistance, a 1amp current is quite possible.

USB standard requires 500 milliamp supply.  An externally powered hub can provide more.  I hope you are not directly powering with your laptop usb. You do not want to conduct a 'smoke test' on your pc  smiley-sad

What is wrong with powering it via a laptop usb? please explain.

The arduino was powered using a desktop computer, not the motherboard but the case.
20  General Category / General Discussion / I was logged in as someone else WTF? on: January 21, 2013, 09:42:57 am
Strangely I was logged in as this guy named: Ruffsta for like 5 mins.

Could see messages, email and all that stuff.

This website is messed up lol.
21  Using Arduino / Programming Questions / Re: Help with RPM code on: November 29, 2012, 02:57:58 pm
Any clues?
22  Using Arduino / Programming Questions / Re: Help with RPM code on: November 29, 2012, 06:51:08 am
Let me ask you this: Does your fan have 3 wires? A lot of computer muffin fans have 3 wires... power, ground and a TACH OUTPUT! (open collector).

Check it out.

Yes I did get one of the 3 wire fans yesterday to test the code and it worked fine, got about 2400rpm.  I also built a new IR rpm sensor instead of using the photo-interrupter, It still gave me wrong numbers.

Here is the circuit I used:


I have seen other people make these circuits so why is not working for me. What is wrong?
23  Using Arduino / Programming Questions / Re: Help with RPM code on: November 28, 2012, 05:31:20 pm
Ok I figured that my photo-interrupter might be faulty. So I build my own IR transmitter receiver circuit. I am getting the same problem, the output is too high. I tested to see the rpm with the hall effect output from the fan and it gave me about 2400 rpm. 

What is the problem with using IR sensor and source for speed monitoring?

24  Using Arduino / Programming Questions / Re: Help with RPM code on: November 28, 2012, 09:46:54 am
Found this:
Properties of Pins Configured as INPUT
Arduino (Atmega) pins default to inputs, so they don't need to be explicitly declared as inputs with pinMode(). Pins configured as inputs are said to be in a high-impedance state. One way of explaining this is that input pins make extremely small demands on the circuit that they are sampling, say equivalent to a series resistor of 100 megohm in front of the pin. This means that it takes very little current to move the input pin from one state to another, and can make the pins useful for such tasks as implementing a capacitive touch sensor, reading an LED as a photodiode, or reading an analog sensor with a scheme such as RCTime.

on the Arduino site under Learning/Foundations/Microcontrollers/Digital Pins.

- Scotty

Yes I read this but what value is very little current?
25  Using Arduino / Programming Questions / Re: Help with RPM code on: November 28, 2012, 08:39:53 am
The photo transistor outputs about 7mA without the 10kohm resitor. I assume with the resistor connected in series it would output even less.

I remember testing it like so but the arduino did not detect a change on the pin.  


What current is required for the arduino digital inputs? Can't seem to find that on the site.
26  Using Arduino / Programming Questions / Re: Help with RPM code on: November 28, 2012, 03:12:21 am
Sounds like the opto coupler is either broken or wired the wrong way round - you're giving it a good 30mA or so of drive - have you checked that each side of the opto coupler is connected the right way round?

And those values aren't very meaningful without _all_ the code - or some idea of what you are expecting (whats generating the pulses?  how many per revolution?)

it says it all in the post, 12V dc motor from pc fan running at 9V set up to block the photo-interrupter every revolution. Not sure how fast it is suppose to spin but the values am getting are way too random. I am sure the photo-interrupter works because the arduino detects when it is blocked.  The code am using is from the readingRPM page from arduino playground.

27  Using Arduino / Programming Questions / Re: Help with RPM code on: November 27, 2012, 08:11:00 pm
tiny mistake on picture fixed


The reason I did not get the output from the photo-transistor directly is because the output voltage and current are too low to register as high logic and could not even light a red led.  If the current coming into the base of the 2n2222a is that low I hardly doubt it would wreck the transistor.

28  Using Arduino / Programming Questions / Help with RPM code on: November 27, 2012, 06:55:08 pm
Hi Arduino Forum members,

looking for some help with this code for rpm http://arduino.cc/playground/Main/ReadingRPM

Instead of using an hall effect sensor, I have in place a photo-interrupter that gives a high logic when blocked.
Since I am only gettings 1 pulse per revolution I have changed the line:
Code:
rpm = 30*1000/(millis() - timeold)*rpmcount;
  to
Code:
rpm = 60*1000/(millis() - timeold)*rpmcount;

The arduino uno  I'm using is R3 and have the output from the photo-interrupter connected to pin2.
photo-interrupter name: KTIR0611S

connected as in picture below.


Motor am using is a 80mm 12V pc fan, running on 9Vdc. Not sure about how fast such a motor should go.

Here is some of the kind of values am getting.
Quote
31984
59580
59580
31984
31984
53212
25876
4448
53212
15072
53212
42508
5096
28400
54312
29584
32592
32592
21068
36900
53212
15072
15072
9724
36900
25876
15072
21068
9724
36900
15072
25876
29584
9724
53212
4448
21068
27856
59568
48144
25876
25876
64136
25876
48144
48144
29584
29584
56300
29584
29584
56300
1460
29584
2908
41848
17520
21068
21068
48144
32592
48144
48144
48144
44336
56300
17520
32592
59568
21068
59568
32592
59568
36900
64136
64136
64136
64136
9724
9724
25876
25876
64136
9724
36900
9724
59568
59568
48144
44336



Hope some one can help me.

Thanks.


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