EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: cowboy303 on March 15, 2012, 05:16:37 pm
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Hi guys.
I'm trying to put to gether a Power supply kind of like Dave's (A little simpler) And was working on a display I plan on using a Atmega328p-pu and program it with the Arduino uno rev3 (like Dave). I would like a display for Volts and Amps I was thinking on using a 2x__ character display but don't know witch one to get.
I'd like something easy to work with but is not restricting for me later.
If any body knows of one that would be grate.
And if any body can show me what to look out for when buying one that would also be nice.
Thank you every one if you have any questions please ask.
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Look for HD44780 compatible displays, if you only want voltage and current then 2x8 would probably be enough. Or a 2x16 if you want more flexibility.
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The easiest ones to to work with are the ones that accept parallel input or i2c (but i2c may not be available in some controllers or you may reach the device limit with other components)
I'm currently working with a Midas made LCD sold by Farnell, a 4 x 16 one:
http://uk.farnell.com/midas/mc41605b6w-sptly/lcd-4x16-stn-ylw-green-b-l-5mm/dp/2063248 (http://uk.farnell.com/midas/mc41605b6w-sptly/lcd-4x16-stn-ylw-green-b-l-5mm/dp/2063248)
but there's plenty of 2x16 or 1x16 there which are also parallel input.
Here's the full page with all the lcds: http://uk.farnell.com/displays-lcd_alphanumeric (http://uk.farnell.com/displays-lcd_alphanumeric)
And here's some examples of 2x16 screens that would work:
http://uk.farnell.com/midas/mc21605a6w-fptlw/lcd-2x16-fstn-white-led-b-l-5v/dp/2063170?in_merch=New%20Products (http://uk.farnell.com/midas/mc21605a6w-fptlw/lcd-2x16-fstn-white-led-b-l-5v/dp/2063170?in_merch=New%20Products)
http://uk.farnell.com/midas/mc21605a6wd-bnmlw/lcd-2x16-neg-stn-white-led-b-l/dp/2063158?in_merch=New%20Products (http://uk.farnell.com/midas/mc21605a6wd-bnmlw/lcd-2x16-neg-stn-white-led-b-l/dp/2063158?in_merch=New%20Products)
http://uk.farnell.com/midas/mc21605b6w-fptlw/lcd-2x16-fstn-white-led-b-l-5v/dp/2063169 (http://uk.farnell.com/midas/mc21605b6w-fptlw/lcd-2x16-fstn-white-led-b-l-5v/dp/2063169)
http://uk.farnell.com/midas/mc21605b6wd-sptly/lcd-2x16-stn-ylw-green-b-l-5mm/dp/2063240 (http://uk.farnell.com/midas/mc21605b6wd-sptly/lcd-2x16-stn-ylw-green-b-l-5mm/dp/2063240)
The last two are with the pins arranged in an 2x8 set on the left of the screen. This is better if you want to use cheap existing cables to connect it to your pcb (where you solder a 2x8 0.1" pin header) but the lcds in the first links with all the pins in a row are better suited for breadboards as you can solder a row of header pins and then just plug the lcd in the breadboard like in the videos below.
The one I bought has a Sunplus controller, which is basically a clone of HD44780 chip, so it works just the same.
You need a minimum of 7 pins to talk to it, 3 for control commands and 4 pins to send half a byte, two times. If you want, you can use the full 8 pins of data to send a byte at a time.
But basically, with the 7 wires it's very convenient to tie it directly to the controller or if you want to save some pins you can use a .5$ serial to parallel chip which will receive 8 bits in a row from your controller through 2-3 pins and send 7 bits out of those 8 to each lcd pin.
Here's a very good tutorial about using such LCD with the controller :
Microcontrollers - AVR Atmega32 - Intro to LCD... Meet Mr. LCD and check out his crib. (https://www.youtube.com/watch?v=7-DK8kNHvlA#ws)
Microcontrollers - AVR Atmega32 - Writing our First LCD Program (https://www.youtube.com/watch?v=uCKShSBdDG8#ws)
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Thanks guys
Those are good videos really informative.
I think I'll get that one off Deal Extreme. But does any body know how long it will take for me to receive it.
Thanks again.
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I got this one (https://www.adafruit.com/products/181) from AdaFruit to experiment with, it took about 3 weeks to get to Africa, should be much quicker for you in America. Not sure how it compares price wise, to getting it from China, but $10 was far cheaper than any source I found locally (I spread shipping over several other items) and the support is great.
p.s. I also wanted it it play with Dave inspired PSU projects and find that 2x16 is just enough to handle a 2 Chanel PSU.
for the difference in price I think I would go with 20x4 next time.
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+1 for the HD44780 display. Using the LiquidCrystal Library in the Arduino IDE makes this easy. You'll need 6 pins to drive it though.
http://arduino.cc/en/Tutorial/LiquidCrystal (http://arduino.cc/en/Tutorial/LiquidCrystal)
Cheers,
Troy
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About 3 weeks , due to HK Post's system .
But adafruit's LCD is much cheaper anyway ...
Adafruit it is. I was looking what else they had to combine shipping and they also got a Atmega328p with a Arduino bootladder http://www.adafruit.com/products/123 (http://www.adafruit.com/products/123) thought that was pretty cool.
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Yeah definitely go for a HD44780 display. They are very easy to use and there are plenty of examples/libraries you can use.
You can also get them in quite a variety of colours :) Perhaps a different colour for Volts and Amps?
http://www.goodluckbuy.com/character-lcd-module-lcm-jhd-16x2-jhd659-16x2-10-color-aviliable.html (http://www.goodluckbuy.com/character-lcd-module-lcm-jhd-16x2-jhd659-16x2-10-color-aviliable.html)
(http://i.imgur.com/sYJUal.jpg) (http://imgur.com/sYJUa)
Adafruit sell ones with RGB backlights so you can make basically any colour, and you'll probably receive them faster, but at a higher cost.
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dave sales the 2x16 at aud2.5 each x10 unit here... http://www.eevblog.com/shop/ (http://www.eevblog.com/shop/)
(http://eevblog.com/shop/images/uploads/LCD-Green-Text-Backlight50.jpg)
(http://eevblog.com/shop/images/uploads/LCDblueEEVblog.jpg)
if you want save for combine shipping, you may get as well this, one or two ;)...
(http://eevblog.com/shop/images/uploads/uCurrent2side25.jpg)
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But australians only :(
duh! he already in my "suppliers list" >:(
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Thank you guys I think I'll get the 4x20 LCD but I just want to make sure of some stuff.
I still only need 6 I/O on the arduino.
and it said that the whole screen is 2x7cm that's means that the digits are 5mm is that right or did I read it wrong.
Thanks Again. :D
P.S. It looks like Dave's sold out on all his stuff in his store(just saying).
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Thank you guys I think I'll get the 4x20 LCD but I just want to make sure of some stuff.
I still only need 6 I/O on the arduino.
and it said that the whole screen is 2x7cm that's means that the digits are 5mm is that right or did I read it wrong.
That is the way I read it and WAY too small for a power supply display, in my opinion.
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I have a solution to our LCD problems :
http://www.dealextreme.com/p/16-x-2-character-lcd-display-module-with-blue-backlight-121356 (http://www.dealextreme.com/p/16-x-2-character-lcd-display-module-with-blue-backlight-121356)
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I have a solution to our LCD problems :
http://www.dealextreme.com/p/16-x-2-character-lcd-display-module-with-blue-backlight-121356 (http://www.dealextreme.com/p/16-x-2-character-lcd-display-module-with-blue-backlight-121356)
First Wow that was fast.
I like the looks of it. But It does not say it is a HD44780 display. But it does have 16 connectors which I think is a tell tale sign that it is.
Thank You
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It's a HD44780-driven display :D
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It's a HD44780-driven display :D
Thank you very much!
I will plan on buying it tomorrow that way I can see if any body can see any problems with it.
Thank you All especially Dave.S for always being there to help.
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The 4x20 displays have the same (physical) size characters as the 2x16, 2x20 etc. So 2x7cm is definitely wrong.
The 4x20 displays are a bit funny as well, because of the way the controller works, the lines aren't in order. It still acts like a "2 line 40 character" display but is arranged like this:
Line1:Chars1-20
Line2:Chars1-20
Line1:Chars21-40
Line2:Chars21-40
So if you just bang in data with the auto-character increment turned on, everything goes from Line 1 onto Line 3, to Line 2 and finally Line 4 :o
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Just think of it the same way you would having two 595s connected. The HD44780 only supports 2*20 max, so to get 4*20 there are two of them tied together.
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That is the way I read it and WAY too small for a power supply display, in my opinion.
takes a bit more code...
(http://opengauge.org/diympggauge/bignum.JPG)
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The LCD controllers have a number of characters hard coded and a bunch of positions where you can "upload" characters.
For example, the LCD I linked in one of my previous post has 48 places where you can define custom characters ... each one is basically 5 bytes (5x8 pixels)
With a bit of programming to manage the 48 slots for characters, you can basically use every one to treat the 16x2
display as a 80x16 dot matrix screen as in the picture above...
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surplus Nokia 3110, 5110, etc lcds are cheap and easy. Nokia 5110 with breakout (http://iteadstudio.com/store/index.php?main_page=product_info&cPath=57_60&products_id=155)
Maxim MAX7219 & MAX7221 are easy to drive if you're trying to light 7 or 14 segment led displays. its a expensive chip retail, but can be had on the cheap via china.
anyone know of a source for affordable HD44780 OLEDs?
-sj
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Just think of it the same way you would having two 595s connected. The HD44780 only supports 2*20 max, so to get 4*20 there are two of them tied together.
A single HD44780 can actually address 80 characters, as 2 lines of 40 chars. It is the 4x40 char lcds that need two controllers and an expansion chip.
It's just odd that they split the first 40 bytes of the character address ram across lines 1 and 3, instead of just 1 and 2. There must be a technical reason for it, but it makes no sense from a programming point of view.
This probably explains what I mean better:
"The lines on the screen can be a little misleading; both lines 1 and 3, and both lines 2 and 4 are treated as though they are one line each and that the display were really 2 lines of 40 characters each. As a result, after 20 characters have been written on each line the display wraps unexpectedly. The first character after line 1 will end up on line 3 instead of line 2, and the first character after line 2 will end up on line 4 instead of line 3. If a character is written after the end of line 3 it will end up at the beginning of line 2. The next write after line 4, though, writes to line 1 as anticipated. Luckily, this is accounted for in software as the microcontroller keeps track of the current position of the cursor."
A 4x20 character display is logically arranged as two lines, although physically it appears as four lines. The mapping is like this
Physical line 1: logical line 1, part 1
Physical line 2: logical line 2, part 1
Physical line 3: logical line 1, part 2
Physical line 4: logical line 2, part 2