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151  Using Arduino / Sensors / Re: What kind of sensure pressure for extreme environment? on: October 25, 2012, 10:55:09 am
It seems that when I have looked for inexpensive pressure sensors with good performance they employed MEMs and were all surface mount, although many of the surface mount sensors from Freescale are very easy to solder by hand.  Just because the sensor says MST in the catalog do not discount it immediately look at it and then Google surface mount hand soldering or something similar.
152  Using Arduino / Project Guidance / Re: Multiple Gyro Sensors on: October 25, 2012, 10:48:16 am
You will also need pullup resistors on the SDA and SCL lines, usually somewhere between 4.7k and 10k Ohms.
153  Using Arduino / Project Guidance / Re: PID Heating Control on: October 22, 2012, 11:09:48 am
In the far past I used low wattage light bulbs to heat up small boxes, I made a couple of incubators as projects in grade school.

Put the bulb in the middles of the box for even heating but also to keep bulb away from the walls for fire safety reasons.
154  Using Arduino / Networking, Protocols, and Devices / Re: IMU RS232 communication on: October 21, 2012, 10:18:41 am
The serial monitor speed is 9600 by default so if you do not change the baudrate of the serial monitor or the Arduino you will get nonsense characters.  This is a pretty common mistake.
155  Using Arduino / Project Guidance / Re: Obtaining Magnetic Declination on: October 21, 2012, 09:47:26 am
Maybe the easiest thing to do is to get g different GPS that outputs the declination.
156  Development / Other Hardware Development / Re: Found a place for cheap pcb manufacturing on: October 20, 2012, 11:08:18 pm
I have usually gotten my boards back from Itead in a month
157  Development / Other Hardware Development / Re: Found a place for cheap pcb manufacturing on: October 17, 2012, 10:02:30 am
One debugging step I have learned the hard way is to view only layer 19 the unrouted layer.  In a complex board you may not be able to see short unrouted air traces, by only showing the unrouted layer you of course can see them clearly if they are there.

Unrouted traces can occur if you route by hand or auto so I think this is a good debugging step.

wade
158  Using Arduino / Networking, Protocols, and Devices / Re: gps trouble shooting on: October 17, 2012, 09:52:09 am
The GPS is transmitting data to the Arduino and it is being received, the 3rd to last column on the output is the cumulative number of characters received from the GPS, the 2nd to last is the cumulative number of sentences received.

The strings of asterisks are hat symbol that routine uses for invalid data, meaning the GPS has no fix possible reasons for the lack of fix
- no clear view of the sky
- the GPS has not been on long enough for the almanac to be loaded, the almanac gives it an idea what sats in that geographic area and time should be visible
- bad antenna connection
- bad GPS unit

Focus on the first and give it up to 30 minutes for it to get its cold fix.

wade
159  Using Arduino / Networking, Protocols, and Devices / Re: Maestro GPS on: October 16, 2012, 10:46:17 am
One drawback of the Maestro products is the technical support as the manual is incomplete and emailing Larry for help is time consuming as it takes one day to get a question answered, so it is probably one of those you gets what you pays for.  One example of the technical support I got was when I asked about the PPS signal Larry told me they did not recommend the PPS for timing.  I got concerned about the PPS signal after hearing their recommendation, so I emailed him and asked what the problem was, he told me the signals were only accurate to 330 nanoseconds in the worst case.  Maestro's timing errors on the PPS signals is on par with everyone else.  My timing requirements are on the order on milliseconds so the standard PPS errors are fine for my app.

I recently ordered a couple of the newer models the 2035 http://www.mouser.com/ProductDetail/Maestro-Wireless-Solutions/A2035-H/?qs=sGAEpiMZZMsjLMBIknjmkuVhKqprv9GpN3Jf4M%2fyBeA%3d as it is a little more sensitive, will track more sats, and is about $2 cheaper.  The soldering pads footprint of the 2035 are the same as the 1035 so the breakout card will only need minor tweaks.

Long story short:  I would buy one of the better known GPS modules if I was only going to use one or two, as the learning curve does not make it worth it for the Maestro.  As stated earlier I wian yo using many of them so it makes sense for me.

wade
160  Using Arduino / Networking, Protocols, and Devices / Re: Maestro GPS on: October 14, 2012, 10:59:32 am
I agree that your suggested GPS would be better for me if I only needed a few of them, but I am using them in sensor nodes and there will be more than a few so the cost savings is significant as I can have some PCBs fabbed and skillet reflow for a few bucks and I probably save $15 per unit.

I mainly posted the results because I asked the question about the maestro units and figured since I had some data I would share my results in case someone else looks at the Maestro units.

wade
161  Using Arduino / General Electronics / Re: Auto shutoff for LiPo battery on: October 14, 2012, 09:50:24 am
I think you should be monitoring the voltage of each pack.  In your description you seem to be assuming that all three packs are balanced and if they remain balanced through the discharge cycle it will work fine.  When I worked with large LiPo packs I always checked the voltage of each cell to know when to turn off the draw.

wade
162  Using Arduino / Networking, Protocols, and Devices / Re: Maestro GPS on: October 13, 2012, 10:35:09 am
Thought I would give an update to this post now that I have gotten the boards back and populated them.  The Maestro GPS unit works great no problems just drove the TX from the GPS to a softserial RX on UNO and it was reporting the correct location and time after the almanac was loaded.

Given the price of this GPS unit it may be useful for others.

wade
163  Using Arduino / Project Guidance / Re: Agriculture Equipment, Ultra Sonic based auto height control on: October 13, 2012, 10:16:16 am
There are filtering methods that are designed to ignore some data points that are much different than the previous datapoints that would get around  the tall weed (a simple low pass to the more advanced Kalman) and to keep the boom from going above a certain level a simple heightmax can be set in the code so the boom does not exceed heightmax.
164  Using Arduino / Project Guidance / Re: Help with DS18B20 sensors running relay and logging data on: October 13, 2012, 09:53:39 am
I to what was stated re: contactors, they can be found on ebay for about the same cost as comparable SSR's
165  Using Arduino / Project Guidance / Re: Data syncing on: October 10, 2012, 09:14:35 am
When you say "nearly the same time" how close do you need the arrival time to be?  I ask as I was trying to set up a similar setup using XBee's and the synching was not good enough, it was off by +/- 1-5 ms and I needed about .1 ms resolution.  The timing difference adds up from things like the serial interface lag on both sides among other things. 

I am now redesigning the system with GPS modules at each units that output a pulse per second that each GPS will receive at very close to the same time, I think the differences are on the order of nanoseconds.  The PPS will trigger an interrupt and the MCU will reset the system timer and record a time stamp, then when an event happens the remote units will send back the number of timer counts and the last time stamp.

Not all GPS modules output a PPS so if yo are going this route make sure the GPS modules you buy do output a PPS.

wade
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