Solid State Ananlogue Displays

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cpedw

Senior Member
Not explicitly a Picaxe question, though if it runs off 5 volts then a picaxe wil be involved eventually ...
Can anyone suggest a display that looks like a needle on a moving coil meter but has no moving parts? I expect it will be an LCD or LED device I think. I realise that an LED bargaph is nearly what I'm looking for but if it could display circularly instead of linearly, that would be perfect.
If it costs less than £10 I'm particularly interested.
Thanks,
Derek
 
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cpedw

Senior Member
That's approximately what I want but ideally - larger range of angles (240 degrees?); higher resolution (that has 9 steps; about 20 would be good); and of course cheaper!
Thanks,
Derek
 
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BeanieBots

Moderator
If you can get access to one of those laser cutters then it would be quite simple to make your own display panel.
Those bargraph chips can be cascaded to give up to about 40 segments.
 
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Dippy

Moderator
Aha. Good luck :)

I have seen bigger displays with more steps, but under a tenner?? Sorry.
Might be time to look at GLCDs... nothing on that bay place?
 
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womai

Senior Member
You should be able to get a decent 128x64 pixel GLCD display for about $15 is you look around a little bit. Of course you'll need to write a good amount of driver code for it.

I'm actually looking into those displays for a very different Picaxe project (no, not a handheld oscilloscope :) and a "side benefit" should be a driver chip for such a display; it's actually quite simple since I use a compiler that comes with libraries for such displays. I could probably hack together a simple driver chip + firmware (for Samsung KS0107/KS0108 compatible GLCDs) in less than a day, based on a Microchip 16F886 or similar (same as the Picaxe 28X1). It would let you draw pixels, lines, squares, circles, and write text, you'd control it through a serial (RS-232) connection.

Wolfgang
 
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kevrus

New Member
I could probably hack together a simple driver chip + firmware (for Samsung KS0107/KS0108 compatible GLCDs) in less than a day, based on a Microchip 16F886 or similar
Click to expand...
I'm impressed...now something similiar to drive a T6963c GLCD with a resolution of 240x128 at the right price would be amazing as most products that I can find are a little costly
 
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cpedw

Senior Member
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cpedw

Senior Member
Jeremy Leach said:
Just curious ... what is it about a real analogue meter that you don't like?
Click to expand...
Perhaps a bit finicky but it's the reliability - the application I have in mind is on a sailing boat that can bounce about a lot at times. (Waterproofing is another issue altogether.)
Derek
 
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BeanieBots

Moderator
Like everything, relaibility comes with cost, or more to the point, those cheap things from eBay are NOT reliable.
Analogue displays are good enough for cars and aircraft, I'm sure a decent one would be reliable in a boat. (water proofing would be the same issue for any technology).
 
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womai

Senior Member
kevrus said:
I'm impressed...now something similiar to drive a T6963c GLCD with a resolution of 240x128 at the right price would be amazing as most products that I can find are a little costly
Click to expand...
Not much to be impressed about; as I said, my compiler comes with library functions for this GLCD controller, so my work would basically consist of reading commands and parameters from the serial port and calling the appropriate function. Now ... any other controller or display would be a lot of work because I'd have to write all the low-level access code and high-level drawing function myself.

Wolfgang
 
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papaof2

Senior Member
Thebay has lots of marine gauges - volt, rpm, fuel, etc. MerCruiser is one name that I recognize as being designed for marine use.

Search for
marine gauge

John
 
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gengis

New Member
National's LM3914 is easy to apply and can be daisy chained to increase the number of LEDs
http://www.national.com/mpf/LM/LM3914.html

I built a tachometer for my motorcycle using two stages (20 LEDs) with an auto-ranging circuit that gave me 4 X 20 leds of resolution.

I drilled holes in a 1/8" black anodized aluminum plate then epoxied the leds in from the back. For waterproofing the whole is mounted in a piece of 4" pvc pipe. I cut a ring of pvc and slotted it and fit that down into another piece. The ring forms a mounting lip for the LED board and window and is fastened in with silicone. It is 100% water proof. I did encounter condensation on the inside when the weather turned cold, so I broke the seal then put the whole display into a can with desiccant overnight - quickly assembled it the next day and its been working, and condensate free, for 10 years now.
 
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Dippy

Moderator
GLIC can put 2 pointers on a GLCD simultaneously. But that's over a tenner.

I could write you a T6963 driver for a 240x128 GLCD if you want me to, but that will cost a helluva lot more than a tenner. I've never seen that size display for under a tenner - and I'm not interested in a link to Ebay or Alibaba.

Keep Googling.

Alternatives?
Make your own out of LEDs (see you in 6 weeks ;) )
Give up and think of something else.

Remember, if there isn't a big market then it ain't going to be cheap.
 
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boriz

Senior Member
Make your own ‘analogue’ meter with a servo. Dead simple. Dead cheap. Dead robust.

You can drive two servos with one 08M using two ADC inputs.

Cheap servo’s HERE and HERE
 
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Dippy

Moderator
Umm... first post:-
"Can anyone suggest a display that looks like a needle on a moving coil meter but has no moving parts?"

I think the clue is in the question boriz... :)
 
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cpedw

Senior Member
Dippy said:
Remember, if there isn't a big market then it ain't going to be cheap.
Click to expand...
That's the bit that surprises me. I would have thought there was a substantial enough market to make it worth someone's while. But I suppose it's thinking like that (wrong) is why I haven't made a fortune!
Derek
 
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Dippy

Moderator
Well, I don't know, I was just suggesting a possibility.

Who would want one?
Most fancy devices use GLCD or TFT or OLED and so thats 95% of the market.
Others use LED bargraphs and similar, so that's 4.9%.
Others (quaint types with beards, retro fanatics or cheapskates) use analogue mechanical.

So that only leaves you :)

I have seen combined analogue LCD and digital LCD displays but they are a lot more than a tenner.
The trouble is that we are spoilt by cheap electronic devices and therefore assume that everything is (or should be) cheap, regardless of numbers made and regardless of quality etc.

I think that unless you are:-
1) Lucky
2) Prepared to flash the cash
3) Spend 3 years looking

.. then you will have to resort to Plan B
 
hippy

hippy

Ex-Staff (retired)
While linear not circular, a standard text LCD can display a single line bar on any character pixel position and you can also generate bar graphs. The gaps between characters aren't normally problematic and you can use every other pixel position for more consistency if it is.
 
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papaof2

Senior Member
hippy said:
While linear not circular, a standard text LCD can display a single line bar on any character pixel position and you can also generate bar graphs. The gaps between characters aren't normally problematic and you can use every other pixel position for more consistency if it is.
Click to expand...
And a multi-line LCD can have a data caption on one line (PSI 20 30 40, etc) and the bargraph on the next line.

Code: 
10 20 30 40 50 PSI
######
John
 
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Jeremy Leach

Senior Member
If a rough level indicator is required, I even think a single LED could be used with a flash duty representing the percentage level. Flash at 1Hz and duty 0 to 100%. I think it 'might' be easy to guess the level to at least the nearest 25% - not tried it though ! Just an idea. A bit quirky too :)
 
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Dippy

Moderator
Blimey! Deffo a bit quirky....;)

So, when it induces epilepsy that means 90% Full scale? Sounds good to me.
Whatever will they think of next?

I guess you could get an LCD, warm it up and bend it into a semi-circle.
 
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boriz

Senior Member
@Dippy.

"...it's the reliability - the application I have in mind is on a sailing boat that can bounce about a lot at times..."

Servo ticks the boxes. You could drop it on the floor and the 'needle' wouldn't move. Two servo's, an 08M, some glue. Two gauges for about £10. And dead reliable too. Can't think of anything else nearly as robust for that sort of money.
 
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BeanieBots

Moderator
Have to agree Boriz.
The verbal spec. might have been "no moving parts" but the reason is reliability. Servo fits the bill.
 
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Dippy

Moderator
You could drop a GLCD on the floor and the needle wouldn't move.

Look, I've just thrown my watch against the wall and it still tells the time. But, oops, the shaft on your servo has just bent. Oh heck my needle has just dropped off.

My LCD meter is small and light and uses b-all power, your servo...?

Just kidding of course, I'm sure servos are far better for making an analogue display. I'll just phone NASA :)
 
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