Dynamic Testing of Hardware.

Postby Sparkicidal » Tue Sep 04, 2012 10:05 pm

I have briefly mentioned this to Nathan, but to push the project on, I'm going to start researching components to try to finalise the hardware schematic and then create a working circuit diagram.

As part of this, to start the testing, I want to get the GPS receiver and anemometer sorted out first. The plan is to attach my RPi, the GPS receiver and the compass to my Hyper 7 and send it around the field autonomously. Once I can get it going around the field correctly, then I will add the anemometer and get it "tacking" up and down the field as well. The point of this testing is to get a decent navigation procedure designed around a PID loop to mitigate any hunting effects when it's traveling, getting it to react to the different conditions quickly and accurately.

The compass has already been identified as ST Microelectronics LSM303DLM.

The GPS receiver that Nathan looked into was the GlobalSat Em-411 for around £30 that connects via standard serial comms. I have looked into a couple of options, and have seen the Maplin A73KF with is a USB dongle for £25 that I know there is RPi Python code out there for. I will continue looking for other options for the GPS dongle. I am being lazy and seeing what code is out there for specific GPS modules to save us having to re-write it.

Okay, I'll have a look around for it all. If anyone in the forum has other ideas, shout and we can add them in. The quicker we can sort this out, the better our testing will be.
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Re: Dynamic Testing of Hardware.

Postby nathan » Wed Sep 05, 2012 9:03 am

Not a bad idea, i can't afford to buy anything just yet as i'm off to LA at the end of the month but we can certainly identify the sensors etc.

As i'm sure you know only two things have been confirmed;

Tilt compensated compass
Satellite communications (http://rockblock.rock7mobile.com)

We need to be careful on the amount of USB devices we using (Pi only has 2), the sat comms will use one and we may need a USB stick for storage.

Once we've identified the hardware components, we'll know what sort of energy budget we have and what sort of batteries we'll need. I'm itching to trial reversed propellor on the keel leg to try and harvest power.
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Re: Dynamic Testing of Hardware.

Postby nathan » Wed Sep 05, 2012 4:37 pm

i bought 2 1-wire waterproof thermometers awhile back, Unsure if we can use 1-wire stuff with the Pi. Would like to get a air and water temp reading.

Parts i bought: http://www.ebay.co.uk/itm/251065651624? ... 26_rdc%3D1

Could have sticking through the bottom of the hull (towards the rear) and one sticking out the top of the hull for the air temp.
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Re: Dynamic Testing of Hardware.

Postby Sparkicidal » Wed Sep 05, 2012 8:02 pm

nathan wrote:Not a bad idea, i can't afford to buy anything just yet as i'm off to LA at the end of the month but we can certainly identify the sensors etc.

As i'm sure you know only two things have been confirmed;

Tilt compensated compass
Satellite communications (http://rockblock.rock7mobile.com)

We need to be careful on the amount of USB devices we using (Pi only has 2), the sat comms will use one and we may need a USB stick for storage.

Once we've identified the hardware components, we'll know what sort of energy budget we have and what sort of batteries we'll need. I'm itching to trial reversed propellor on the keel leg to try and harvest power.


You are correct, RPi only has 2 physical USB ports, but I believe it has multiple virtual ports. i.e. can we connect more USB devices through a USB hub? I haven't looked into it yet, I just assumed we could as each device would be set up as a seperate port.
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Re: Dynamic Testing of Hardware.

Postby nathan » Wed Sep 05, 2012 9:03 pm

Sparkicidal wrote:
nathan wrote:Not a bad idea, i can't afford to buy anything just yet as i'm off to LA at the end of the month but we can certainly identify the sensors etc.

As i'm sure you know only two things have been confirmed;

Tilt compensated compass
Satellite communications (http://rockblock.rock7mobile.com)

We need to be careful on the amount of USB devices we using (Pi only has 2), the sat comms will use one and we may need a USB stick for storage.

Once we've identified the hardware components, we'll know what sort of energy budget we have and what sort of batteries we'll need. I'm itching to trial reversed propellor on the keel leg to try and harvest power.


You are correct, RPi only has 2 physical USB ports, but I believe it has multiple virtual ports. i.e. can we connect more USB devices through a USB hub? I haven't looked into it yet, I just assumed we could as each device would be set up as a seperate port.


Hubs tend to be a bit unreliable, or that's what i've found in the day job. Even had issues with powered ones.
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Re: Dynamic Testing of Hardware.

Postby Sparkicidal » Thu Sep 06, 2012 10:09 pm

(a) I'm approx 3 weeks away from my RPi.
(b) If we can decide on the GPS module we wish to use, I can start testing whilst you're in LA as I'll buy the parts req.
(c) The sensors look good, but for the water one, instead of going through the hull, could we create a "dogs leg" to hold it?
(d) ...erm...nope, forgotten. :)
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Re: Dynamic Testing of Hardware.

Postby Sparkicidal » Thu Sep 06, 2012 10:11 pm

Oh yes:

(d) USB hubs! On the RPi forums there are lists of reliable hubs with the RPi so if we need one, it shouldn't be too hard to get a one.
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Re: Dynamic Testing of Hardware.

Postby nathan » Fri Sep 07, 2012 12:16 pm

Ah cool, that's a possibility then!

Looking at some options for GPS then;

    The one you listed from Maplin
    http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=1777460&MER=baynote-1777460-pr

I'll put them into a nice table when i get home including power/price/connection etc. Some of those contain a battery so you only have to warm start them each time meaning a faster fix so it wouldnt need to be powered as long.
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Re: Dynamic Testing of Hardware.

Postby Sparkicidal » Fri Sep 14, 2012 8:04 pm

Just so that you all know that I haven't abandoned this, I have started a comparison of the GPS receivers, I just haven't had time to finish it yet. If our weekend visitors leave early enough on Sunday, I'll aim to get it done then.
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Re: Dynamic Testing of Hardware.

Postby Sparkicidal » Sun Sep 23, 2012 4:58 pm

I have finally got around to finishing off the GPS selection from what we have. It lines up as shown:

GPS Selection2.jpg
GPS Selection2.jpg (142.84 KiB) Viewed 21966 times


I was expecting to do an in-depth analysis of them all, but there is no need as I think we have a clear winner in the shape of the UBlox receiver due to it's stupidly low current consumption when it's tracking. Any other opinions?

P.S. I should be about 1 week away from my RPi. Excited! :D
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