| ??? 11/10/09 23:55 Read: times |
#170663 - Tiny budget for tiny clock Responding to: ???'s previous message |
Richard said:
Not every student has the sort of budget that would be demanded by one 8x8 array as you, Erik, have suggested, for every character. Are you really reading the same text that I thought I was reading? I'm pretty convinced that Erik suggested one LED (not one 8x8 array) for each character. Since one array is a bit too small for a 10x11 character clock, you would need four arrays in total. Not 110 arrays. 256 LED in total (and 10*11 + 4 used) and not 7040 LED. Erik said:
I guess 4 $3 8*8 LED matrices and some nice lettering on semitransparent media could do the 'demo'. Note: 4 matrices. Erik said:
READ - NOT INTREPRET TO YOUR SATISFACTION - THE POST!! NOTHING moving, one LED behind each letter as in the display shown by the OP Note again: "one LED behind each letter" - not "one array behind each letter". Per said:
If using 2x2 LED for each character, you would need 20*22 LED, i.e. 3*3 = 9 LED modules. If each 8x8 LED module costs $4, the cost would be $36. Note: Suggested solution for a bit larger clock. 2x2 LED - not 2x2 LED arrays - for each character. In total 9 LED modules - not 110. Per said:
It must be up to the student to select if they can afford 1x1, 2x2, 3x3 or whatever for each character. Should be obvious that 1x1, 2x2 and 3x3 is one, four or nine diodes/character, and not one, four or nine arrays/character. Especially since nine arrays/character would be 9*10*11*64=63360 diodes. That would be more than one tenth of the diodes in this - previously linked - sign: http://www.rapidonline.com/latestnew...ED+display Per said:
Using four 8x8 modules would require a maximum of 16+16 signals if accepting a bad 16-to-1 multiplexing. [...] But a 16x16 backlight is bigger than needed so it will be enough to worry about the 11x10 part. Note: four 8x8 modules in total. Not four 8x8 modules/character. Only 16x16 diodes in total. A bit more than the 11x10 characters. Erik said:
I never did, I stated you would need four to get 1 LED per etched letter. Note: The goal was to get 1 LED (not one array) per etched letter. Per said:
The only issue then is if one character should have one LED. Or a 2x2 LED rectangle. Or a 3x3 LED rectangle. Doesn't leave much open for the imagination. Richard said:
These particular arrays (The ones initially suggested by Erik) are about 3 cm wide and high. How large a panel would the student have to prepare in order to use them? What impact would that have on cost? Obviously a very, very small panel. Four LED arrays would then need 6x6cm + border. So the material cost for the panel shouldn't be high unless the border is very, very, very wide. Per said:
If I put one LED behind each character (and the total display has 10x11 characters), then I will need 4 modules (total cost) $1.90*4 = $7.60. Definitely not a high cost. Many years since I could go out and get a lunch for that amount of money. Per said:
Each LED is 3x3mm. CC distance is 4mm.
The total area for the text would then be 10*4mm x 11*4mm = 40mm x 44mm. The size should make it obvious that we are talking about a small clock, with few diodes and obviously few LED arrays. Erik said:
to make such a sign you need a LED (or other controlled illumination) behind each character. Using the matrices I suggested you get 64 LEDs for #3 and the techniques for multiplesing LEDs are well known. "a LED" = one LED. Erik said:
multiple LED's per character (e.g. 2*2) was mentioned as a possible solution for larger/brigheter characters. Think small. 2x2 LED is 1/16 of one LED array. Andy said:
Purely a matter of size: if 1 LED is too small for 1 character, then use a group of LEDs for each character. Still 1 LED - not 1 array - for each character. No problem with costs. |
