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46  Using Arduino / Project Guidance / Re: Is 5.5volts from external regulator to Vin pin enough?? on: July 26, 2014, 08:00:47 am
There is also the problem that if Vin is lower then spec then the FET that isolates USB +5vdc from the board will not be turned off so you end up with a low Vcc being wired to your PC's USB +5vdc, which can cause problems when you try to upload a sketch or use the serial monitor.

47  Using Arduino / Installation & Troubleshooting / Re: I killed the USB serial connection on: July 25, 2014, 01:10:08 pm
Perform the loop back sketch test, that will determine if it's a serial USB problem or a bad 328 problem.

48  Using Arduino / Installation & Troubleshooting / Re: how can I program a pro mini arduino on: July 25, 2014, 12:33:11 pm
Do I need a ttl to usb converter or can I connect the vcc, gnd, tx and rx pins of the mini such as this one

to the UNO pins vcc, gnd  digital 0 and digital 1 after removing the atmeg chip and just program as if it was the chip on the board?

 Also wire a reset to reset connection as that should allow the IDE auto-reset to function when you proceed to upload, otherwise you will have to master the 'well timed manual reset switch' dance.

49  Topics / Robotics / Re: Encoder Quadrature confusion from a newbie on: July 22, 2014, 08:52:10 pm
Specifically what can I do with having the encoder quadrature lines connected that I would not be able to do without them?

 The encoder supplies two measurement values useful in closed loop control of the DC motor, speed and direction of rotation. Without the encoder providing your program this information you have to fall back to open loop control (no feedback measurements). Sometimes a given application doesn't require full feedback control, some do. That is what learning is all about and directly relates to robotic controls.
50  Using Arduino / Project Guidance / Re: Interfacing with rope leak detector cable? on: July 22, 2014, 08:33:14 pm
Cool. A noob question for you - what all does the change in capacitance mean in this instance versus if it was just changing resistance?

 Most simple sensors work by either changing it's resistance, or capacitance, or induction in presence of a change of the thing being sensed. That in turn determines what kind of circuit it has to interface with.

51  Using Arduino / Project Guidance / Re: Interfacing with rope leak detector cable? on: July 22, 2014, 07:30:32 pm
Well it may have nothing to do with it's resistance, but rather it's change of capacitance in the presence of moisture. The capacitance would then be used to measure a R/C time constant and alarm at a certain value.
52  Using Arduino / LEDs and Multiplexing / Re: starting point for 5x5 RGB LED matrix on: July 22, 2014, 07:25:44 pm

Crossroads' advice will allow you to drive the matrix, you just need 5 npn transistors,  but only with 7 colours. So the next thing to figure out is how to mix more colours using pwm. But you have only 6 pwm outputs. I seem to remember there is a library that emulates more pwm outputs in software...


I am not understanding why I would only get 7 colors.

 Well if you want to count off as a color you have 8 possible combinations, that's all you get with a 3 bit digital selection.
53  Using Arduino / General Electronics / Re: Help understanding transistors on: July 22, 2014, 03:55:39 pm
But what about the 5 volt bit? Surely it would be different spec for one that had minimal resistance at 10 volts.

That will best be handled by using a 'logic level' N-channel MOSFET. They can reach their best Ron spec with just +5vdc gate voltage applied.

54  Using Arduino / Motors, Mechanics, and Power / Re: Minimizing power consumption of an Uno? on: July 22, 2014, 11:47:50 am
What is the base power draw with nothing attached with an empty sketch?

Oh around 40mA or so is a good guess. As others have said it's not a good board for trying for minimum current consumption what with the power on led, usb serial convertor chip, voltage regulator consumption, etc. 
55  Using Arduino / Project Guidance / Re: Interfacing with rope leak detector cable? on: July 21, 2014, 12:30:25 pm
Well if you unit announces a leak by turning on a buzzer alarm you could tape a microphone sensor module to it and use it's output signal as the trigger to an arduino.

56  Using Arduino / Programming Questions / Re: Playing with watchdog and sleep mode - can't upload sketches anymore on: July 20, 2014, 05:45:03 pm
Use Nic Gammon's bootloader program and wiring, it's proven and works fine for the 2560.
57  Using Arduino / Microcontrollers / Re: How to bootload ATmega 328 with arduino UNO as ISP on: July 20, 2014, 01:49:52 pm
Wow, Crossroads, that looks seriously complex! I've always used the method described by ScienceKid with my uno, and never had any problems. This post says it works on uno, you just have to change the delay in the ISP code if you are using Arduino >= 1.0:

Use Nic Gammons sketch and target device wiring as CR posted. It's the simplest fool proof validated method to burn bootloaders to target boards. It also is interactive as you have to open the serial monitor and the sketch tells you what it's doing, when it's doing it and gives other information and of course asks you when to perform the burn.

58  Using Arduino / General Electronics / Re: confusion about Uno schematic and reset-en on: July 20, 2014, 01:36:16 pm
And to further explain the auto-reset 'feature' of the arduino I will add some context. The arduino IDE uses the serial com DTR signal to generate a short pulse that is routed by the signal trace to cause the 328P to reset and start the bootloader which then waits a short time to see if the IDE wants to upload a new sketch, and if not then just runs the sketch that was last loaded into the flash memory. However a side effect of this function is that on most operating systems the opening of a com port (which is what happens when you open the serial monitor) also cause the same board reset that you are seeing, the IDE can't do anything to prevent this behaviour. However as you see the trace art work allows you to 'cut' the signal going to the 328P to stop auto-reset function but then you would not be able to load a sketch unless you either use the reset switch at the correct time when needing to upload a sketch, or install a jumper clip across the cut trace and add the shorting jumper when you wish to upload using auto-reset or remove the jumper when wishing to prevent auto-resets.

59  Using Arduino / LEDs and Multiplexing / Re: starting point for 5x5 RGB LED matrix on: July 20, 2014, 01:18:50 pm
You can control a 5x5 matrix using just 10 output pins. You don't require pwm output pins, your sketch just needs to handle the timing to scan the whole matrix at a rate that prevents 'blinking' display. Generally if you can drive the matrix at a say 20 millisec rate or faster you won't see any indication of scanning, just steady lights.

60  Using Arduino / Programming Questions / Re: How to use TX and RX pins on Arduino Duemilanove on: July 19, 2014, 07:44:47 pm
You DO realize that you can't use the Rx & Tx pins on the UNO as a HOST because they are tied to the USB  via the FTDI chip.
I think you need a second serial port, like Software Serial.

One can use the Rx and Tx pins to send and receive to an external serial device (like another arduino) as long as there is no application on the PC responding to anything sent to it and sending anything back to the arduino. It just gets problematic when one needs to upload a new sketch where usually you have to disconnect the external wiring on the Rx and Tx pins.

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