Title: PAW15 - Twittorama
Post by: matseng on July 08, 2013, 06:42:44 am
Post by: matseng on July 08, 2013, 06:42:44 am
Some of my project ideas come up when I surf the interwebs looking at items in shopping sites. I found some really cheap dual alphanumeric (14-segment) diplays at Taobao and bought 4 kilos of them to make wall-mounted display that show my twitter feed.
Displaying tweets isn't anything new, but most I've seen have a small display and scrolls the tweets. I want the full 140 characters to be visible simultaneously. So I put 10 of the displays (20 characters) on a pcb with a heap of shift registers, resistor arrays and some n-fets.
Then I just daisychain 7 of the modules to get up to the 140 characters. Adding one more unit, placed on top of the 7, will give space to display the name of the sender as well.
I did the pcbs at Smart-Prototyping on a 30x10 cm board on 0.8mm to allow me to cut up the panel myself into 5 pieces. By having 10 displays on each board I got a little extra space at the end to put a separate USB-to-SPI board that can be used as a control board for each group of displays-.
My plan is to start out with populating eight boards to get a full tweet, and if I'm bored some days in the future solder up more, but my four kilos of displays is only enough for 6 tweets. :-(
A 0.8mm pcb at this size warps easily, they are a bit bent, but after bolting them down to some kind of aluminum structure I think they will be ok anyways. If I order more of them I'll go for the 1.6mm pcb and pay the fab to v-score them, probably I'll get a solder paste stencil as well, there's a *lot* of manual soldering to be done otherwise.
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Displaying tweets isn't anything new, but most I've seen have a small display and scrolls the tweets. I want the full 140 characters to be visible simultaneously. So I put 10 of the displays (20 characters) on a pcb with a heap of shift registers, resistor arrays and some n-fets.
Then I just daisychain 7 of the modules to get up to the 140 characters. Adding one more unit, placed on top of the 7, will give space to display the name of the sender as well.
I did the pcbs at Smart-Prototyping on a 30x10 cm board on 0.8mm to allow me to cut up the panel myself into 5 pieces. By having 10 displays on each board I got a little extra space at the end to put a separate USB-to-SPI board that can be used as a control board for each group of displays-.
My plan is to start out with populating eight boards to get a full tweet, and if I'm bored some days in the future solder up more, but my four kilos of displays is only enough for 6 tweets. :-(
A 0.8mm pcb at this size warps easily, they are a bit bent, but after bolting them down to some kind of aluminum structure I think they will be ok anyways. If I order more of them I'll go for the 1.6mm pcb and pay the fab to v-score them, probably I'll get a solder paste stencil as well, there's a *lot* of manual soldering to be done otherwise.
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Title: Re: PAW15 - Twittorama
Post by: ian on July 08, 2013, 08:50:17 am
Post by: ian on July 08, 2013, 08:50:17 am
This is so cool!
Title: Re: PAW15 - Twittorama
Post by: Bertho on July 08, 2013, 11:21:31 am
Post by: Bertho on July 08, 2013, 11:21:31 am
[quote author="matseng"]My plan is to start out with populating eight boards to get a full tweet, and if I'm bored some days in the future solder up more, but my four kilos of displays is only enough for 6 tweets. :-([/quote]
Better save on the number of tweets you send, or, alternatively, make a stronger wall to hold more than 4 kilos of display (you may need a power-generator plant too).
[quote author="matseng"]I want the full 140 characters to be visible simultaneously.[/quote]
But seriously, 14-segment displays are nice, but can only display numbers and simple alpha-characters (and some punctuation). How are you mapping the complete UCS space down? There must be a lot of mappings that will fail to render any intelligible form of information.
Better save on the number of tweets you send, or, alternatively, make a stronger wall to hold more than 4 kilos of display (you may need a power-generator plant too).
[quote author="matseng"]I want the full 140 characters to be visible simultaneously.[/quote]
But seriously, 14-segment displays are nice, but can only display numbers and simple alpha-characters (and some punctuation). How are you mapping the complete UCS space down? There must be a lot of mappings that will fail to render any intelligible form of information.
Title: Re: PAW15 - Twittorama
Post by: matseng on July 08, 2013, 11:41:03 am
Post by: matseng on July 08, 2013, 11:41:03 am
As lazy as I am I'll stick with 0x20 to 0x7E in ISO-8859-1. :-) I'm not even sure if I'll keep the lowercase, it might look better with uppercase only. Then I'll just manually map some common umlauts like the Swedish åäö to aao.
A lot of power will be used for a full 1.8x1.8 meter grid. :-) I measured an average of 320 mA @ 5 volt on a small 10-character test board I did previously. So one full tweet with 160 characters will be like 5 Amps. The full grid with ~30 tweets is 150 Amp so I'll need three PC PSU's for that.
A lot of power will be used for a full 1.8x1.8 meter grid. :-) I measured an average of 320 mA @ 5 volt on a small 10-character test board I did previously. So one full tweet with 160 characters will be like 5 Amps. The full grid with ~30 tweets is 150 Amp so I'll need three PC PSU's for that.
Title: Re: PAW15 - Twittorama
Post by: matseng on July 08, 2013, 01:19:44 pm
Post by: matseng on July 08, 2013, 01:19:44 pm
My lazyness strikes back at me again!
It took me about an hour to realize why my control board with a PIC18F25J50 wouldn't run at all unless I was starting it in debugging mode from the IDE.
I realized that it doesn't have internal pullup on the /MCLR and I didn't add a discrete external pullup. Easy to fix though - just a 22K resistor between the MCLR & VCC pins on the bottom of the ICSP connector and the cpu started up just fine.
[attachment=0]
It took me about an hour to realize why my control board with a PIC18F25J50 wouldn't run at all unless I was starting it in debugging mode from the IDE.
I realized that it doesn't have internal pullup on the /MCLR and I didn't add a discrete external pullup. Easy to fix though - just a 22K resistor between the MCLR & VCC pins on the bottom of the ICSP connector and the cpu started up just fine.
[attachment=0]
Title: Re: PAW15 - Twittorama
Post by: Sjaak on July 08, 2013, 01:38:53 pm
Post by: Sjaak on July 08, 2013, 01:38:53 pm
[quote author="matseng"]
I realized that it doesn't have internal pullup on the /MCLR and I didn't add a discrete external pullup. Easy to fix though - just a 22K resistor between the MCLR & VCC pins on the bottom of the ICSP connector and the cpu started up just fine.
[attachment=0][/quote]
Classic :) and sooo familiar :)
I realized that it doesn't have internal pullup on the /MCLR and I didn't add a discrete external pullup. Easy to fix though - just a 22K resistor between the MCLR & VCC pins on the bottom of the ICSP connector and the cpu started up just fine.
[attachment=0][/quote]
Classic :) and sooo familiar :)
Title: Re: PAW15 - Twittorama
Post by: Bertho on July 08, 2013, 02:32:43 pm
Post by: Bertho on July 08, 2013, 02:32:43 pm
[quote author="matseng"]As lazy as I am I'll stick with 0x20 to 0x7E in ISO-8859-1. :-) I'm not even sure if I'll keep the lowercase, it might look better with uppercase only. Then I'll just manually map some common umlauts like the Swedish åäö to aao.[/quote]
I don't think 14-segments can display both lower and upper case. So that is quite easy. I guess you are getting the input stream from a "real" computer with a "real" OS. Then iconv can probably help you map it down before you stream it.
[quote author="matseng"]A lot of power will be used for a full 1.8x1.8 meter grid. :-) I measured an average of 320 mA @ 5 volt on a small 10-character test board I did previously. So one full tweet with 160 characters will be like 5 Amps. The full grid with ~30 tweets is 150 Amp so I'll need three PC PSU's for that.[/quote]
That is 25W at full wham for a tweet. Man, you are gonna see a power-bill at the end of the twmonth 8-) But I know how it is. I'm working on a project with 72 7-segment displays, which takes 21W at full intensity.
At ~30 tweets, you will need an additional AC in your house. With the temperatures in KL, it is gonna be one sweaty affair. That is, unless, you are going to sell the wall to your friendly neighbor :-)
I don't think 14-segments can display both lower and upper case. So that is quite easy. I guess you are getting the input stream from a "real" computer with a "real" OS. Then iconv can probably help you map it down before you stream it.
[quote author="matseng"]A lot of power will be used for a full 1.8x1.8 meter grid. :-) I measured an average of 320 mA @ 5 volt on a small 10-character test board I did previously. So one full tweet with 160 characters will be like 5 Amps. The full grid with ~30 tweets is 150 Amp so I'll need three PC PSU's for that.[/quote]
That is 25W at full wham for a tweet. Man, you are gonna see a power-bill at the end of the twmonth 8-) But I know how it is. I'm working on a project with 72 7-segment displays, which takes 21W at full intensity.
At ~30 tweets, you will need an additional AC in your house. With the temperatures in KL, it is gonna be one sweaty affair. That is, unless, you are going to sell the wall to your friendly neighbor :-)