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16  Using Arduino / Project Guidance / Re: Information for a rover on: November 02, 2012, 03:07:45 pm
Webcam and Arduino don't sit well in the same sentence.

Even if they did, ultra sonic or infrared sensors would probably be just as effective, if not more so, for obstacle avoidance.  A webcam could be better for things like object recognition.
17  Using Arduino / Project Guidance / Re: Weather Station and Solar tracker on: November 02, 2012, 02:16:25 pm
The first issue I run into is how I am going to power it (the tracker and the weather station).  Not being familiar with weather station sensors and servo motors, will I need two separate power supply sources (e.g. 2 separate solar panels/batteries)?  I don't want to have it plugged in, so that way I can place it wherever I want.  I was thinking a solar panel might be good - I live in Houston, TX and it's pretty sunny here.  That coupled with a rechargeable LiPo battery might do the trick?  I have a nice 9V@1W solar panel from Parallax, and about 5 or 6 of those little garden light solar pannels that, if wired in series, might be able to get me up to 9V in peak day light (maybe 4 or 5V indoors) total.

LiPo batteries are a possibility, but they aren't as temperature tolerant (scroll down to "Temperature Effects" section), as some other battery chemistries. If the battery is going to be outdoors it should be an at least somewhat sheltered place, but still with at least some potential air flow (e.g. under a building's eave or deck).  So it isn't exposed to the worst extremes of heat and cold.  Of course if your system has the batteries inside a temperature controlled room, that would be even better.

On the other hand, while there are still limits on operational temperatures a sealed "gel" lead-acid battery would better tolerate exposure to both higher and lower temperatures, and would have significantly less risk of fire, etc... if it severely overheats.  An appropriate SLA would be both heavier and bulkier than a LiPo battery pack, but reasonably sized (1 to 2 lbs and ~96 in3) 6 V and 12 V batteries are available in most hardware stores and some department or hobby stores.  I'd recommend something like that for a "remote" weather station, even if "remote" really means a couple of yards from the nearest heated building in an unshaded case.

In any event, you'll probably need to regulate the power coming from the battery / solar panel so to a predetermined and known level before it gets to your electronics.  The linear regulator most Arduinos would work with voltages that are ~7 VDC to 12 VDC, but it wouldn't work at all with a nominally 3.7 VDC LiPo pack and it wouldn't work well with a nominally 6 VDC SLA.  Depending on the exact levels involved you might need to either step-up or step-down the voltage.  To go from a range of lower voltages to a higher one (step-up) you'd need what's called a boost converter.  To go from a range of higher voltages to a lower one (step-down) you'd need a buck converter, buck converters are also more efficient and generate less heat than linear regulators.  There are boost-buck converters (a boost and a buck converter, and possibly some control circuitry, in the same module) that can do both, but they are generally more expensive and usually avoidable through proper planning and design.   
18  Using Arduino / Microcontrollers / Re: hows the due? on: November 02, 2012, 12:43:04 pm
"pro" ($2.6K, but uncrippled) version of Atollic?

Unless that's for some sort of 10+ multi-seat license I don't understand how they can (ethically) justify that price! smiley-eek  
19  Using Arduino / Project Guidance / Re: Variable resistance to control MEAN WELL HLG-120H-42B on: November 02, 2012, 11:51:08 am
Can you post an example of an amplifier similar to what might work to give me a better idea?
The gain for an op-amp is usually set using two or more resistors, there exact configuration is based on what type of amplification circuit you use.  In a non-inverting amplifier you'd normally have two resistors (R1 & R2) configured similar to a voltage divider between the output and ground, with point between R1 and R2 going to the inverting input ("-" or "V-" on schematics) of the op-amp.  The ratio between them determines the gain, for many op-amp "families" the formula for voltage gain will be AV ≈ (R1/R2)+1 but check the datasheets for the exact performance of a specific part.  The other connections are straight-forward the non-inverting input is connected to the input voltage, and the positive power supply pin needs to be at least as high as your desired output voltage level (it doesn't matter if it's higher) and your negative power supply pin will be grounded (Aside: most op-amps can have negative voltages but in this case you don't want to do that).  

Here's an example of a non-inverting amplifier using a LM358N op-amp.  If you were to use that op-amp and wanted to output exactly 10 VDC from exactly 3.3 VDC, the voltage gain would need to be 3.0303... (i.e. AV = VOUT / VIN = 10/3)   Therefore, the ratio of resistor values should be 2.03... (i.e. R1/R2 = AV - 1 = 3.03... - 1).  The exact resistance values you use are less important than achieving the necessary ratio of resistance values.

Edit: Here's a on using op amps...
20  Using Arduino / Project Guidance / Re: Variable resistance to control MEAN WELL HLG-120H-42B on: November 02, 2012, 09:13:39 am
That is good enough, it doesn't need to be very close.  From the early description of the DAC I thought this might only output a wave, for example, a smooth wave between 0 and 1.2345 V at a specific frequency.
A DAC takes an integer value (specifically a number between 0 and 2n-1, where n is the resolution in bits) each cycle and outputs a voltage level between the minimum and the maximum output voltage.  For example, on the Due 0 would be 0 VDC and 4,095 would be 3.3 VDC; but many DACs have a much wider output voltage range, including negative voltages on some.  If you want a constant output, just keep feeding the DAC the same integer value.  If you want some sort of waveform vary the integer value so you get the frequency and wave shape you want.

Can you tell me more about this?  I am a software guy.  I see some very cheap op-amps online, but they all have much larger voltage gains.  Also, why 3.85?  3.3V (or 5V) + 3.85V is less than 10V
Amplification is generally expressed as a factor (AV) that's either the ratio of output over input , AV = VOUT / VIN , or multiplied with the input to get the desired output,  AV * VIN = VOUT.  Regarding the value of 3.85, for some reason I thought the desired voltage was 12 VDC not 10 VDC.  3.85 * 3.3 VDC = 12.705 VDC  So you'd have enough for 12 VDC plus the forward voltage drop of a standard diode to prevent any back EMF.
21  Using Arduino / Motors, Mechanics, and Power / Re: Battery Source for Arduino Uno & 1 12v dc motor? on: November 01, 2012, 01:06:46 pm
And I don't have a multimeter.. unfortunately even if I had one I wouldn't know how to use it
Well that's easily fixed...  Here's a simple tutorial on using the main functions of a digital multimeter.  It doesn't cover everything you can use a multimeter for, of course, but it will show you how to take all the basic measurements.

Now you have no excuse! smiley-razz

Edit: Adafruit has a slightly more extensive tutorial as well, if the one from Sparkfun glossed over things a bit too much.
22  Using Arduino / Project Guidance / Re: Variable resistance to control MEAN WELL HLG-120H-42B on: November 01, 2012, 12:59:52 pm
Any suggestions as to how to amplify the signal?
You could use a transistor (either BJTs or MOSFETs would work) and some resistors for a simple level converting circuit (as in this schematic). 

Or you could use an op-amp based non-inverting amplifier with a voltage gain of about 3.85, but since a PWM signal is digital there's no innate advantage to use this method.

By ADC, are you referring to the DAC on the Duo?  Does this mean the Duo can't output a constant 1.2345 V signal, for example?  Anyone, I think the correct road to go down is using a capacitor as a low-pass filter for the standard PWM.  I could get this working first with PWM only, then try to add the filter.

No, I'm referring to analog-to-digital conversion and this capability exists in some form on all official (and probably all non-official) Arduino boards, not just the Due.  DAC, or digital-to-analog conversion is basically the opposite process and the Due is currently the only official Arduino board to have real DAC outputs.  In some circumstances PWM (which again all Arduinos have) can be used to effectively simulate ADC, but that really only works with some types of parts.

I don't know if the Due can output exactly 1.2345 VDC.  However, since it's DAC has 12-bit resolution that means there are 4,096 distinct voltage levels it can output between 0 and 3.3 VDC.  So even if it cant output that specific value it can get very close.  By the way, if you wanted to amplify an analog voltage like this than you would need something like the op-amp based amplifier I mentioned before, rather than just a logic level shifter.   
23  Using Arduino / General Electronics / Re: What size fuses do IEC sockets require? on: November 01, 2012, 08:51:19 am
You're quite welcome.
24  Using Arduino / Project Guidance / Re: suggestions for a suit project on: October 31, 2012, 04:24:18 pm
I think im going to have to sit down one night with a bottle of wine and just go through this forum for hours reading abou different things with these circuits.

Just as a little Public Service Announcement, drink that bottle slowly...  Drunk posting is never a good idea! smiley
25  Using Arduino / Project Guidance / Re: Variable resistance to control MEAN WELL HLG-120H-42B on: October 31, 2012, 04:21:35 pm
How does the PWM output work?  Is there an input that corresponds to the output?  For example, can I just hook 10V somewhere and output a 0-10V PWM signal?  Or I am forced to output at 5V and someone how need to turn this into 10V?

If you are using PWM from an Arduino it will be the same voltage level as what is powering the microprocessor IC (usually 5 VDC but sometimes 3.3 VDC.  You will need some type of amplifying or level shifting circuitry to increase the signal to a higher voltage level.

As far as correlating input all the following assumes your inputs are configured for the same voltage level as the PWM signal... 

PWM is a square wave, so a digital input would read it either LOW or HIGH depending upon what part of the waveform the signal is on the pin at any given time.  If you have the proper logic, either software or hardware-based), you could determine things like frequency and duty cycle.  ADC is intended for true analog signals, not digital pulses, but most of the time would read close to the extremes of the range of numbers used for the conversion (e.g. around 0 for when the signal is LOW and for HIGH around 2n - 1, where "n" is the number of bits of resolution).  The only time you'd see a number toward the middle is if the ADC managed to catch some part of the near instantaneous transition between the two extremes.  So generally nothing is gained by using ADC on a PWM signal, unless it is coupled with some sort of buffer or record of past values (like in a digital oscilloscope).   
26  Using Arduino / General Electronics / Re: What size fuses do IEC sockets require? on: October 31, 2012, 03:36:31 pm
Well at least there's a picture... it looks like a C16 on this table.  So I'd suppose a 10 A fuse of some type.    

I can't read it from the image, but it looks like there are some letters on the fuse panel door just below what appears to be a drawing of a fuse.  What do they say?

Edit: This looks like the same, or very similar, part.  That would accept 5 x 20 mm fuses.  Also that's a C16 not a C15...
27  Using Arduino / General Electronics / Re: What size fuses do IEC sockets require? on: October 31, 2012, 03:01:34 pm
Do you have the part number for the socket?
28  Using Arduino / General Electronics / Re: About the article "10 Ways to Destroy an Arduino" on: October 31, 2012, 01:18:56 pm
You need a separate power supply / driver that is controlled by the arduino. Could be as simple as a logic-level MOSFET for each LED.

Can I use shift registers (e.g. 74HC595) instead to solve the same problem?

For many shift registers you'd only be able to fully power one 0.3 to 0.5 mm LED per output pin of the device.  That's because they will have a maximum continuous output current of only 20 to 40 mA.  In the case you are asking about that might be sufficient; but a transistor used as a switch could power arrays of multiple LEDs, or other much higher current loads.

Edit: And some of them, like the 74HC595, have a maximum input current of around ~75 mA.  So you wouldn't be able to use the 74HC595 if you needed more than two LEDs lit at the same time.
29  Using Arduino / Project Guidance / Re: suggestions for a suit project on: October 31, 2012, 12:47:33 pm
Anyway, the electrician got a call from one of his other clients, and mentioned something about a military grade RJ-45 setup (RJ-45 is the cat 5/6 cables used for ethernet cables).  I asked him what was a military grade RJ-45, and he said you could pick up your whole computer while it was dangling on the RJ-45 cable.  I would imagine that is secure.

Of course, I meant the type of RJ series connectors you could pick-up at your local store (Radio Shack, hardware store, etc...). smiley-razz  I can believe that the military-grade connectors of any type are more robust and physically secure, but I doubt they'd be as hobbyist budget-friendly as other connectors I mentioned.  Unless you happen to be lucky enough to find some at a surplus store...

Edit: I don't think this is quite what your electrician was referring to, but here's the datasheet for Amphenol's "Ethernet Connection System for Harsh Environment".  It's a set of accessories to harden the ends of an existing standard RJ-45 cable, but you could easily get a couple hundred sets of normal RJ-45 connectors for the price of a mated pair of the most inexpensive options in this product line. smiley 
30  Using Arduino / Project Guidance / Re: suggestions for a suit project on: October 31, 2012, 12:17:32 pm
You want to make sure all connections are secure, since costumes can endure a lot of movement.

As far as secure connections, you can sometimes get away with using modular connectors, i.e. the connectors used for telephone and network cabling.  They are cheap and widely available, but can still be pulled loose under some circumstances.  Free hanging JST type connectors normally hold better and can be found various pin counts.  In-line banana plugs and jacks are also possible, but can be rather bulky.  The most secure option (and usually water resistant as well) would be to use circular connectors with an interlocking threaded shroud like this, but not only is it more expensive once you get above a few pins per connector they become awkward to use on most garments/costumes.  Finally, if you are using conductive thread in a larger section of fabric it's possible to use clothing snaps as a secure connector.
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