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Member Since 30 Nov 2010
Offline Last Active Aug 03 2014 04:12 PM

#20978 Measure high current and voltage

Posted by JonnyBoats on 25 November 2011 - 08:15 PM

A power sub-station with voltages measured in kilovolts and 1000s of Amps is really a special case where safety is paramount. As suggested in another response only properly designed industrial equipment tested and certified for such an environment should be used.

For others who might be considering measuring voltages in a residential location such as 120V or 240V (still lethal) there is a good "general" model to follow.

A Netduino (or any other micro-controller) is generally designed to operate on 5V or less (3.3V in the case of a Netduino). It is not designed to survive the application of high voltages (think of it this way, if it would kill you, it will kill a Netduino).

The best approach is to keep the high voltage (or current) on a separate board from the Netduino,

There are many Digital Multi-Meters (DMMs) out there which will output their readings on a serial port. The DMMs are designed and tested to be safe and reliable for measuring voltages and currents within their design specification. You can connect such a DMM to a Netduino via the serial interface (you may or may not need a level shifter such as a MAX232 but that is another issue).

Here is a post where someone used a DMM from Radio Shack in conjunction with a computer: The price they paid for the DMM seems high (old post perhaps?), I know I bought one on sale (different model) for about $30.

#20659 simple put to localhost confusing

Posted by JonnyBoats on 15 November 2011 - 07:28 PM

Perhaps there is some confusion about "localhost". It refers to the current computer, so if you use localhost on your PC, it refers to the PC. If however you use localhost in your Netduino program it would refer to the Netduino, not the PC. If you want to have the Netduino talk to the PC use the ip address of the PC, not localhost.

#19408 GPS, GRPS and Google Latitude Tracking

Posted by JonnyBoats on 19 October 2011 - 02:05 PM

First off, let me say how glad we all are that your son is safely home again. Also welcome to the Netduino community.

Before proceeding it is extremely important to remember the difference between a hobby project and a safety critical device involving life or death. The "gold standard" for being found in an emergency is a EPIRB (and it's little brother, the Personal EPIRB, or PLB that fits in your pocket). These are extremely rugged, waterproof, tested to the highest standards and have long life batteries. Unfortunately one needs to press a button to activate them, so this is probably a "show stopper" for your application.

Another common device with a built in GPS and communication capability is a cellphone or smart phone. In an emergency authorities can easily locate a cellphone provided it is turned on and within range of a tower. It is highly unlikely that you can engineer a solution with similar capabilities at a lower cost than a used cellphone.

As far as a hobby project is concerned, you might want to consider fox hunting, where you simply attach a small transmitter to your son that sends a radio tone for a couple of seconds every minute or two. To locate the transmitter one only needs a simple receiver and a directional antenna. This is how biologists track animals in the wild. See http://www.predatorc...diotracking.htm for details. Newer versions often include a GPS as well. Here is a link where someone did it on the cheap to find model rockets.

Finally there are commercially available pet tracking devices such as the Garmin Astro.

#18782 What's in the magical, mysterious, box of crappy surplus?

Posted by JonnyBoats on 04 October 2011 - 03:14 PM

The BOCS arrived in Maine! The box arrived here in Phillips, Maine yesterday. Is anyone interested in having a box opening party? I know Phillips is rather remote, so I am open to traveling to Portland, Bangor or Augusta ME to meetup with anyone who would like to share in the fun. I am even open to traveling to Portsmouth, NH if that is better for people. Please respond if you are interested. I do not want to hold the BOCS up too long, so we need to do thus soon if you are interested. Today is Tuesday, 4-OCT-2011. If nobody responds by tomorrow night, I will simply open it by myself and then send it along on Thursday.

#17173 Netduino+ WeatherStation / Environment Monitor / Webserver

Posted by JonnyBoats on 28 August 2011 - 01:37 AM

I too find this sort of project fascinating. Thanks in advance for whatever details you choose to share with us.

#15657 Measuring Angle of Attack

Posted by JonnyBoats on 18 July 2011 - 10:22 PM

Have you considered measuring magnetic field?

#12239 C# Coding standards

Posted by JonnyBoats on 19 April 2011 - 01:52 PM

I'm not arguing. or trying to open the can anymore, however I will put in my two cents. One statement in the standards, I do Disagree with but only partially. It says DO NOT use Hungarian Notation! I will say if you give me a code snippet to help you out with something. and there are variables declared out of the current context. Hungarian Notation is very helpful. I don't know everything about your code so I have to make a guess as to the type. and My guess could be wrong making it take 3-4 Times as long to help you out. I come from a background where Hungarian Notation was used well strictly. However I have since grown lazy since I moved to c# from VB and VBScript. Intelisense takes care of most of that question for you. but a snippet well is just that. it is a small snapshot of a great meaning. So it just helps.

As an old 16 bit Windows C programmer, I used to be a big user of Hungarian Notation. You may wish to read http://www.joelonsof...cles/Wrong.html where Joel Spolsky talks about the difference between Apps Hungarian and Systems Hungarian. (Scroll to to the bottom of the post to find it).

I believe Apps Hungarian is extremely useful, but quite frankly today with managed code Systems Hungarian has lost much of its usefulness.

#11545 Best Hobby Oscilloscope

Posted by JonnyBoats on 31 March 2011 - 10:57 PM

You are getting lots of good advise, but unfortunately you didn't really say what you wanted to do with an Oscilloscope. beyond perhaps "Gee, wouldn't it be fun to have...".

There is a reason that a top end Agilent scope costs $10,000; it will do certain things that a cheaper scope will not.

To learn more about oscilloscopes I recommend you check out the EEV blog: http://www.eevblog.c...g/oscilloscope/

There was also an interesting short video on checking out the clock oscillator on an Arduino at http://www.adafruit....with-fet-probe/

On the low end, I have one of these I rate it good value for the money, but it would never do what a Agilent would.

Also a key factor is do you want to look at analog, digital or both? For analog only go buy a good used analog only scope from a top manufacturer, you can easily get one for low dollars (way less that $100). For digital what you may want is something more than just an oscilloscope. You may want a logic analyzer (which better digital scopes will have built in or available as an option) or perhaps a protocol analyzer. The reason for this is if you are hooking something up to the SPI or I2C bus for example your are probably more concerned with "Is the proper data being sent and received at the correct time?" than "What does the trailing edge of the waveform look like?" or "is there ringing on the line?" which are also important and the kind of thing that a scope would show but a logic analyzer would not.

Hope this helps ;-)

#11412 Garbage collection in the .Net MF

Posted by JonnyBoats on 29 March 2011 - 01:38 AM

A key issue for time critical routines (think RTOS) on a Netduino is that application code may be preempted by the .Net MF for Garbage Collection ( see http://msdn.microsof...y/0xy59wtx.aspx for an explanation on how this works on a PC).

Since garbage collection takes time and impacts performance, one does not want it to get out of hand. Basically on the full framework it is so efficient that one hardly ever needs to worry about it for "normal" programs.

As a .Net programmer, I sort of assumed that garbage collection on the MF would be basically the same as on the full framework. Apparently this is not the case!

In watching this video ( http://skillsmatter....-the-path-of-go ) on porting a DLL from the full framework to the X-Box (which uses the compact framework), garbage collection turned out to be a major factor. David Stern spends a good part of the video explaining the differences in how garbage collection works on both the full and compact framework.

Unfortunately he does not address GC in the micro framework, and I have yet to find a good resource that does.

I highly recommend this video to anyone wanting to learn more about how garbage collection works.

#11268 Sweet deal to add DSP

Posted by JonnyBoats on 25 March 2011 - 01:10 AM

I tried to order one today, but the promotional code had expired. It does look like it was a sweet deal, though!

There are actually a couple of different codes out there, try:




#11254 NETMF 4.2 Alpha Available

Posted by JonnyBoats on 24 March 2011 - 06:47 PM

There is an alpha version of .Net Micro Framework available for download. For details of what is in it see the link above.

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