cheaper large instrument displays - mast mount

andyxs said:
I am happy to go with the consensus and put some money in to buy a few screens.
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Before buying more than one display of any type, the following needs confirming...

Speed of screen update.
Backlight performance.
Readability from complete dark to bright sunlight.
Contrast performance in required temperature range.

I guess a temperature range of 0c to 40c would be adeqaute. Not sure how to test the display at the hot end short of going on holiday to Bahrain. Anyone any ideas?
 
that all makes sense to me.

For the backlight, i think an LED backilight in place of CCFL will be easier to implement and use less power to run.

0-40 in would have thought a little tight, although mostof the specs i have seen seem to go to -20 (where the LCD freezes) As for testing at 40C, i reckon we could jsut sit in the office today as the heating seems to think its -40 outside
 
ShaunG said:
that all makes sense to me.

For the backlight, i think an LED backilight in place of CCFL will be easier to implement and use less power to run.

0-40 in would have thought a little tight, although mostof the specs i have seen seem to go to -20 (where the LCD freezes) As for testing at 40C, i reckon we could jsut sit in the office today as the heating seems to think its -40 outside
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For LCD contrast, it's not just what the manufacturer's temperature range specification says, it's the required voltage you need to drive the contrast control with at low temperature that matters. Some displays will work at -20c to 60c, but will only show anything if you drive the contrast control voltage deeply one way or the other. Although the RS display has a negative voltage generator on the panel, controlling it from software over the hot to cold range required may not be easy. That's why it's a good idea to put a test display in the fridge/toaster and see what happens.

LED backlighting is the way to go as its level can be controlled with a PWM output from the processor through a FET costing a few pence.
 
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ShaunG said:
that all makes sense to me.

For the backlight, i think an LED backilight in place of CCFL will be easier to implement and use less power to run.

0-40 in would have thought a little tight, although mostof the specs i have seen seem to go to -20 (where the LCD freezes) As for testing at 40C, i reckon we could jsut sit in the office today as the heating seems to think its -40 outside
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Just FYI, most equipment with an LCD screen is specced down to 0 degrees, and the display becomes very sluggish below that. The advice for LCD screens in Antarctica was to either keep them inside your clothing and only bring them out when needed, or use them in the tent. If they were useful at -20, we wouldn't have had any problems; for other reasons, BAS people tend to stop working when the temperature goes too low (your heat-loss gets high, and you start burning calories like no-one's business; you can't handle metals, you can't work on things requiring a sensitive touch and so on).

They might well survive down to the freezing point of the LCD, but they are not useful in the lower part of that range.

Of course, an LCD that freezes will be destroyed.
 
The scene at YAPP HQ...

SDC11512.jpg


That green board in the foreground is a NMEA simulator as I don't have a NMEA system.

Now working are both Seatalk (coming in on the right) and NMEA (coming in on the left), both handled simultaneously...

SDC11513.jpg


Seatalk can display about a dozen different types of boat data, NMEA so far only 3, but the framework is there and just needs filling in for the other types.

The user interface is complete for settings, choosing channels etc. I'm going to add an NMEA raw display.

Backlight intensity control is working from software using PWM, but because this screen has no backlight control it just varies an LED. It's pretty non-linear at the moment, but that can be fixed when a real screen is available.



The following drivers need doing -

LCD for 240x128 RS screen, but I have some code for an old project that just needs porting.

Contrast, but this needs a real screen to experiment. I'm not entirely sure how to do this yet from software as a negative voltage needs controlling. Perhaps an electronics engineer could suggest something.

NMEA input is currently reading from RS-232 not RS-422, but that is just a 50p chip change.

The current screen is 128x64 pixels, but the software is written to be able to cope with screen size changes easily.

Is anyone else doing anything, or is this turning into a YAPP?
 
I am still going, as you can probably tell I am a long long long way behind you..would I be better focused on housings/PCb/assembly etc..I am really enjoying learning to code these things, at the same time I am finding out just how different embedded is...

How would I be best able to help at this stage...am trying to work on some cad housing designs at the same time for some prototype housings to be made...
 
Jabamusic said:
I'm just in awe of what is being achieved thus far...trouble is I don't know how to contribute !!
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I am on a learning curve too...a massive one, although it is very very slowly starting to make sense,,,I really hope I can be more helpful on the housing and manafacture side...I really am lagging hugely in the software side but trying hard...I have the spent the weekend learning more an more and reckon. Could at the very least now contribute to adding more to the nmea side..as a general dogsbody anyway :)
 
ShaunG said:
Finally....it looks like an lt1617 is a dc-dc inverting voltage thingy...



http://uk.rs-online.com/web/p/dc-dc...24552267573743D4C74313631372677633D424F544826
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The RS LCD has a negative voltage generator on it. This is needs to be varied to feed in to the contrast control pin on the LCD. They suggest, and I have used before, a 10k pot. This works, but is no good for us as we need software control. Digital pots can't be used here, as they won't work with negative voltage.
 
AngusMcDoon said:
Is anyone else doing anything, or is this turning into a YAPP?
Click to expand...

I think that the point is that this project, because of its wide applicability, is building a community. It is also prompting people to learn new things, in the hope of contributing.

There is little I can contribute at this point; it is over 20 years since I last did embedded programming (on a Z80 based system with no operating system, using a CP/M micro (an Osborne 1!) as a development system!). If it gets to the point of needing ways of handling map data, then I can contribute - that's been my primary field for over 30 years.
 
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