cheaper large instrument displays - mast mount

ShaunG said:
I will try the LCD in the sunlight tomorrow and try to post some pics taken with a decent camera..and eventually with the backlight...reading through your code it looks like Pwm for the backlight?
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LEDs cannot be brightness controlled by varying their voltage. Instead you switch them off part of the time, just very quickly, i.e. thousands of times a seconds. The less on compared to off means less light output on average. The PWM output line from the processor can drive a small single LED, but not the backlight for this display as it takes too much current. Instead use the PWM output to feed into the gate of a power MOSFET transistor. This will switch the current to the LED backlight. I haven't chosen a suitable one yet. I have tried it, but with a MOSFET that switches amps that I happened to have. We need one that can switch about 250mA, which will be cheaper than the one I use. Have a search on RS for a 250mA MOSFET. Should be about 20p in small numbers.
 
ShaunG said:
the contrast range adjustment is very slim, not a lot either way between black and nothing...
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That's normal. When software contrast control is working it can all be offset to make a nice range of contrast. Need to freeze/cook the display some time and measure the voltage into Vo when the contrast is mid-range.
 
ShaunG said:
Data sheet is 0-50, storage -10-60 and wide storage -30-80


Look like 0-50 to replicate and test the voltage at

I will do that as soon as possible....as for mosfets...sounds like a job for tomorrow night
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You will probably find it gets increasingly sluggish in operation at the low end of the scale. Whatever you do, don't go low enough to freeze the liquid; that will destroy the display.
 
thanks antartic...it looks like 0 is the bottom of the range and 50 is the upper...


although to make sure that we are aware of what the limits are i guess i should destroy a couple by going to the upper and lower limits to find out where they are
 
ShaunG said:
thanks antartic...it looks like 0 is the bottom of the range and 50 is the upper...


although to make sure that we are aware of what the limits are i guess i should destroy a couple by going to the upper and lower limits to find out where they are
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I'd guess that the numbers you have say the 0 is the lowest operating temperature - and it will probably be slow responding at that temperature. Below that, it can be stored (but not usefully used) down to -20. Not sure what the "wide temperature range is"!

I'm reporting what people taking LCD devices to Antarctica have said; as you might guess, that sort of thing is of interest to people working in temperatures down to -20 :) The general wisdom is that you shouldn't expect a device to operate normally much below 0; if you need to use such a device, keep it inside your jacket and only bring it out briefly as required!
 
thank you...all makes perfect sense..I was looking through the manafacturers site and it seems the offer a 'heated' display option that works down to -20.

I question if it is worth it? we do of course have temperatures below 0 in the UK during the winter (for the last few years anyway) has anyone heard of any problems with their exisiting LCD's or instruments that are left outside

I cant say i have had any 'broken' displays although they are mounted outside, is the temp range used by the commercial boys better
 
Here in Finland the boats are winterized and mostly stored outside. The temperature drops below -20C every winter for a few days at least. LCD displays do survive this semi-arctic treatment. My B&G displays have several missing lines after 10 years of use, but that may be also due to moisture.
 
I would love to become involved with this project but have no idea where to start. My background is that of electrician but some 30 years ago I was teaching microprocessor appreciation using Intel's SDK 8085 system development kit. The stuff Angus and Shaun doing is a mystery to me.

Just a thought about touch screens. A few months ago I checked into my doctors surgery using their interactive screen. It had been raining and I had to dry my hands before the screen would work - so perhaps membrane switches would be better in the marine environment.

Paul
 
paul.norton said:
Just a thought about touch screens. A few months ago I checked into my doctors surgery using their interactive screen. It had been raining and I had to dry my hands before the screen would work - so perhaps membrane switches would be better in the marine environment.
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The display isn't touch. The buttons on the screen you see are intended to line up with some real off-screen buttons.
 
paul.norton said:
I would love to become involved with this project but have no idea where to start. My background is that of electrician but some 30 years ago I was teaching microprocessor appreciation using Intel's SDK 8085 system development kit. The stuff Angus and Shaun doing is a mystery to me.

Paul
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Well, my last involvement with this kind of stuff was using a Z80 s100 bus based machine - the development system was an Osborne 1 using asm and link, with WordStar as the editor! I reckon you're more up to date than I am :)
 
I know very little...learning as I go..I have a small amount of software development and am involved in a managerial level as a day job..I know a little but nothing in relation to the language that we are using ( I am learning a lot every day :))

We have plenty of distance to go and need to resolve a number of things

4 way membrane switch
Waterproof housing that looks commercial and quality
Pcb design and manafacture
Testing
5-30v stabiliser with a solid 5v output to the board
LCD temperature testing and results
Electronic backlight and contrast control from the processor
Etc etc


Feel free to jump in, grab an area, research and contribute....google, rs components and their data sheets really have been my friend then last month or so :)
 
ShaunG said:
4 way membrane switch
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I would suggest that it would be better to have PCB mounted low-profile buttons with a flexible membrane over the top, rather than true membrane switches. It will be cheaper and more reliable.
Waterproof housing that looks commercial and quality
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still work in progress, I guess.
Pcb design and manafacture
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I could help with this, if you like
Testing
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ditto
5-30v stabiliser with a solid 5v output to the board
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Chances are you also need 3.3V for the processor - but easy enoug to design in
LCD temperature testing and results
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I'll leave that to you, Shaun, as I can tell you're looking forward to it!
Electronic backlight and contrast control from the processor
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Angus has already suggested the way forward for backlight control, and I think we have a solution for contrast too - just waiting for Angus to test it.
 
Hi mike

I was trying to think of anything that we don't have fully completed yet.

I seem to be making a reasonable amount of progress with housings and I am off to see a company in amersham next week, although as you said previously costs range hugely..the nearer we can get to a standar pd housing the better

I thought the same abut switches, although I was not so sure on the waterproofing element, never thought of waterproof membrane over the top

Freezing lcd's, I guess as I have one I will get on freezing and cooking it, I need to run in to town tomorrow and get an accurate thermometer, I am fairly happy with the cooking (leave for 10 minutes or so at 50c and then test, I have not quite worked out how to ensure I test at 0c yet, my freezer is -18 according to the readout, I have to work out how to enure the display is at 0 to test..I was thinking i may just leave it in the freezer and run some fly leads out

Stabilised voltage...your right of course..will follow your lead on that one

Contrast and backlight :)

Pcb - if you want to take this on it would be great..I downloaded some software but it looks like Greek to me at the moment..I had a try and it ended up about an acre in size :( I guess the overall pcb could/should be the same size as the LCD pcb for ease of assembly..I guess it depends if we stick with sil connectors and through hole or sm and ribbon...I have no idea on what is best although I guess ribbon and sm makes an smaller package overall

I think we need to include the seatalk and nmea interface on the board as well

Testing..I will be at the boat Sunday or next weekend so should be able to grab some nmea data and wire the unit in to see how it goes and start some testing..I will try and write some test packs to go with the data set

As you can all tell....I am learning (making it up) as I go..what we are achieving here is pretty amazing..YAPP marine instruments plc are but a sale away ;)
 
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For the temerature range checking, assuming you don't have access to an environmental chamber, you might have to settle for setting your fridge to it's lowest setting - should get you down to 2 or 3 degrees above freezing, maybe lower.
 
mikefleetwood said:
For the temerature range checking, assuming you don't have access to an environmental chamber, you might have to settle for setting your fridge to it's lowest setting - should get you down to 2 or 3 degrees above freezing, maybe lower.
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That sounds like a plan...environmental chamber ( the house.??? Cold for me and boiling hot for the swmbo? So all I need to do is move from every room in the house which is at 50c to the study where it is nice and cool :D:D:D)
 
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