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31  Using Arduino / General Electronics / Re: USB power jack needed on: August 25, 2014, 09:08:34 am
Search for "USB socket" on eBay.

32  Using Arduino / LEDs and Multiplexing / Re: what are the limits of leds in series? and are their any hazards to be aware of? on: August 25, 2014, 08:07:41 am
I would like to set in series 4 LEDS to blink when called upon, and hope I can get away with a single resistor..Can I?

Yes.

Is that youtuber full of crap

I don't know exactly what he said ... but putting LEDs in series is no problem.

(Although they might be very dim if you only have 5 Volts available)

33  Using Arduino / General Electronics / Re: NRF24L01 2.4ghz wireless on arduino on: August 25, 2014, 08:06:15 am
hello fungus thank you yes i  found many topics on the NRF24L01  module and tut but what i can't find if it be able to run 2 or more transmitting  to a single receiving  nrf24l01 module or only a single NRF24L01  for transmitting and NRF24L01  receiving NRF24L01 module?

An NRF24L01  can listen to six transmitters simultaneously. See the "MultiCeiver" section of the datasheet.


34  Using Arduino / General Electronics / Re: NRF24L01 2.4ghz wireless on arduino on: August 25, 2014, 06:04:46 am
my question is if anyone has NRF24L01 module on each transmitting side and a single one on the receive side with the leds can it tell in sketch which one comes from where? can someone help me out please sorry new to this and trying to get more information about the NRF24L01 module?

The NRF24L01+ is very commonly used with Arduinos. A quick google search will give you thousands of pages.

There's even a playground page for them: http://playground.arduino.cc/InterfacingWithHardware/Nrf24L01
35  Using Arduino / General Electronics / Re: Piezoelectric Accelerometer on: August 22, 2014, 11:54:03 am
I will have a go with an op amp maybe, the accelerometer I am using is for industrial applications so they ebay one would be no good.

eBay is just an example, you can search for the chip at more expensive suppliers if you want to. I'm sure Adafruit will have one and Adafruit products are made in New York in the US of A.

It's really just an chip on a PCB though, there's not much they can do wrong even in China.


PS: Yep, they do

PPS: The one you're using right now doesn't look any more "industrial" to me

36  Using Arduino / General Electronics / Re: Piezoelectric Accelerometer on: August 22, 2014, 10:52:27 am
The smallest signal an Arduino can measure is about 5mV. This will work on paper but in practice trying to measure down to a single bit doesn't work because of electronic noise (especially when you add a breadboard to the mix).

Similarly the 16-bit ADC.. The breadboard, wires, etc. is most likely drowning the signal.

You can try amplifying the signals with an op-amp but really it's much better to get an accelerometer with an SPI/I2C interface. These chips do all the measurements internally and you just read the results over the data bus.

eg.

http://www.analog.com/static/imported-files/data_sheets/ADXL345.pdf

http://www.ebay.com/sch/i.html?_nkw=arduino+accelerometer+adxl345

37  Using Arduino / General Electronics / Re: Using encoders off board without an interrupt on: August 22, 2014, 10:15:14 am
according to the attachInterrupt page another ISR that is supposed to be called would be ignored.

Where does it say that?

When I read it it said:

Quote
"...other interrupts will be ignored (turned off) until the current one is finished"



38  Using Arduino / General Electronics / Re: Using encoders off board without an interrupt on: August 22, 2014, 09:54:09 am
if another interrupt was called, it would interrupt the interrupt, stopping playback, which defeats the purpose entirely.

Why would it stop playback?

That quadrature decoder looks promising and I've seen it before, but I'm having difficulty figuring out from the datasheet alone how to hook it up and what exactly the output is. Is there a resource with examples on these?

They're very simple devices. There's billions and billions of examples on the web.

Quote from: Paul_B
Misunderstanding of how interrupts work goes hand-in-hand with misunderstanding of why and whether it might be desirable or in fact undesirable to use interrupts at all.

Interrupts and mechanical switches are rarely a good combination. Switches bounce and cause dozens of interrupts when they're switching, causing as many problems as they solve.

(...and "Hardware debouncing" belongs in the same category as using interrupts with switches - sounds good on paper, terrible idea in practice)

39  Using Arduino / General Electronics / Re: Using encoders off board without an interrupt on: August 22, 2014, 08:07:53 am
The reason an interrupt should be used is because every pulse needs to be counted and added to a counter.

That's not a reason to use an interrupt.

If there's any delay in the main code it will miss a pulse and the count will be off.

So ... the trick is to make sure there's no delays in the main code.

40  Using Arduino / General Electronics / Re: One potentiometer for gain control of two LM 386 amplifiers on: August 22, 2014, 07:51:29 am
Sure, just use a stereo potentiometer.

41  Using Arduino / General Electronics / Re: Potentiometer vs Absolute Rotary Encoder on: August 22, 2014, 07:16:43 am
Oh, wait, I found some: http://www.farnell.com/datasheets/1822666.pdf

42  Using Arduino / General Electronics / Re: Potentiometer vs Absolute Rotary Encoder on: August 22, 2014, 07:09:06 am
Never seen those chips before.

This one is 16-bit: http://uk.farnell.com/avago-technologies/aeat-6600-t16/encoder-magnetic-ic-16-bit-program/dp/2213639


Can you get then in prebuilt potentiometer-shaped modules with magnet, shaft, etc?

It seems an obvious next step but I can't find any.

43  Using Arduino / General Electronics / Re: Potentiometer vs Absolute Rotary Encoder on: August 22, 2014, 03:49:08 am
What is wrong with an incremental encoder?

What is wrong with calibrating each control when you switch on?  It only requires moving each control in turn from stop to stop until the dashboard says "OK".

I could be wrong, but I thought that was actually part of aviation protocol anyway.


You could maybe combine one with a pot. Read the pot at startup to get a rough idea of where the wheel is then use the  incremental encoder from then on.
44  Using Arduino / General Electronics / Re: The right parts to make my project smaller.... on: August 21, 2014, 10:54:36 am
Quite frankly the question is simple, What if anything would be a suitable smaller  substitute for a TIP120 Darlington Transistor when only using 5VDC?

No it isn't. "5VDC" could mean many different things.

I understand that amps play a role

Yep.

I also said that I am using and ATMega328P which to the best of my knowledges keeps the amp limited to an extremely low number.

You're shorting a Mega328P pin to ground with a transistor? Is the pin set to output? If so, stop doing that.

45  Using Arduino / General Electronics / Re: Potentiometer vs Absolute Rotary Encoder on: August 21, 2014, 09:39:22 am
Something like this?  http://www.ebay.com/itm/281346507599

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