Need ideas on LED Message Display

[L.E.D]

Good morning mga boss... Gusto ko pong mag construct ng LED Message Display. Magsisimula palang po ako kaya medyo marami po akong mga katanungan:

1. Ang nabili ko pong 8x8 LED Dot Matrix ay common anode (positive ROW, negative COLUMN). Ibig sabihin ba nito, ROW scanning ang magiging style in driving the Matrix?

2. Meron po akong PIC16F628A. Ok lang po ba eto gagamitin ko in controlling the Display?

3. Ano po ang gagamitin ko sa pag control ng 8 ROWS? yung CD4022B na may 8 decoded outputs po ba ay sapat na para madrive ang mga rows?

4. Sa column naman po, ayos lang po ba kung LS595 serial-parallel shift register gagamitin ko?

5. Kelangan ko pa po bang gumamit ng mga resistors at transistors?

6. Safe po bang gamitin ang lumang AT power supply ng computer para sa project na ito? meron naman pong stable 5 volts DC output eh.

Yan na po muna sa ngayon ang mga katanungan ko.. Sana po gabayan nyo ako.


 

[DigitalMind]

before anything else. anong programming language ang alam mo na regarding displaying a dot matrix?
i think ok naman yung circuit as planned mo.. atx ps is ok.

[labgruppen]

...
1. Ang nabili ko pong 8x8 LED Dot Matrix ay common anode (positive ROW, negative COLUMN). Ibig sabihin ba nito, ROW scanning ang magiging style in driving the Matrix?

pwedeng Row scanning, pwede rin namang Column scanning. It depends on your Row/Col drivers at programming. But IMHO, scanning by Row will give better results with respect to brightness and flicker lalo na pag mahaba yung gagawin mong matrix.

2. Meron po akong PIC16F628A. Ok lang po ba eto gagamitin ko in controlling the Display?

ok na rin sya. 2kb sya, so i think ok. gumawa ako dati napagkasya ko sa 1k (z86e04) so 16f628 will be more than enough.

3. Ano po ang gagamitin ko sa pag control ng 8 ROWS? yung CD4022B na may 8 decoded outputs po ba ay sapat na para madrive ang mga rows?
4. Sa column naman po, ayos lang po ba kung LS595 serial-parallel shift register gagamitin ko?
5. Kelangan ko pa po bang gumamit ng mga resistors at transistors?

pwede ring gumamit ng 595 for both row and column drivers. lets say may 6 kang 8x8 matrix, so you will need 6 595's for the columns. in addition to those 6, add 1 for the row so in total 7 na 595's ang gagamitin mo. you could connect them all in cascade, and use the first or the last 595 for the row.
you will definitely need transistors for the row and current limiting resistors on the columns if you choose to scan by row.

[L.E.D]

before anything else. anong programming language ang alam mo na regarding displaying a dot matrix?

assembly po tsaka C alam ko..pero mas prefered ko assembly. medyo hindi ko pa nagegets kung papaano yung scrolling ng text. hanggang static lang po alam ko. ano po technique in scrolling of display from left to right v/v?

atx ps is ok

you mean, ok lang direkta ko e.connect yung 5volts output ng AT power supply to the VDD pin ng PIC? wala ng extra components needed like resistors? eh yun pong USB port ng PC, 5volts DC rin pwede po ba e.supply ko sa PIC?

But IMHO, scanning by Row will give better results with respect to brightness and flicker lalo na pag mahaba yung gagawin mong matrix.

ok po. row scanning gagawin ko

pwede ring gumamit ng 595 for both row and column drivers.

CD4017 nalang po siguro gagamitin in driving the rows. Mas mahal po kasi LS595. Pero sa columns i'll used 595.

you will definitely need transistors for the row and current limiting resistors on the columns if you choose to scan by row.

anong klaseng transistor ang gagamitin ko? NPN o PNP? positive po yung rows ko.. ok na po ba 330 ohms para sa columns?

pasensya na po andami kung tanong.. 

[L.E.D]

request ko po sa mga moderators dito, pakilipat po ng thread kung ito sa PIC Microcontroller section.. TIA

[labgruppen]

CD4017 nalang po siguro gagamitin in driving the rows. Mas mahal po kasi LS595. Pero sa columns i'll used 595.
anong klaseng transistor ang gagamitin ko? NPN o PNP? positive po yung rows ko.. ok na po ba 330 ohms para sa columns?

since cd4017 ang gagamitin mo, mas straightforward kung NPN trannies ang gamitin mo configured as emitter follower. choose your current limiting resistors on your columns to suit your preferred brightness, but don't exceed the minimum value. your column current limiting resistors' minimum value will depend on the maximum allowable sinked current of the 595 or on your led matrix's maximum allowable current, whichever is lower.

[L.E.D]

salamat sir labgruppen.. syanga pala, ano po technique in scrolling the displays? hanggang static display lang kasi napagana ko. Simulation muna ginagawa ko ngayon using PROTEUS

[labgruppen]

salamat sir labgruppen.. syanga pala, ano po technique in scrolling the displays? hanggang static display lang kasi napagana ko. Simulation muna ginagawa ko ngayon using PROTEUS

overshift or undershift your column shift registers with increasing number of steps after certain time delay to scroll.. the time delay will determine how fast the scrolling will be. the delay should be a multiple number of full display refresh to prevent column position differences between the rows preventing font skewing.
example
1. display your message as usual by shifting your column data normally. repeat n times. (n display refreshes)
2. display your message by shifting your column data then shift one more time. repeat n times.
3. display your message by shifting your column data then shift two more times. repeat n times.
and so on..
varying n while shifting will accelerate/deccelerate the scrolling.


you can also "italize" your font by overshifting/undershifting the columns with increasing amounts according to the row. say first row, display as usual. second row, after shifting the all the columns, shift one more time (1 additional clock pulse). third row, after shifting the all the columns, shift two more times (2 additional clock pulses). and so on.. this will skew your font 45 degrees.

[L.E.D]

wow.. salamat sa idea sir. try ko to pag kompleto na ako sa components. puro simulation palang kasi ako. syanga pala, mas maganda po ba gamitin ang 74HC595 kesa 74LS595 sa project na ito?

[labgruppen]

wow.. salamat sa idea sir. try ko to pag kompleto na ako sa components. puro simulation palang kasi ako. syanga pala, mas maganda po ba gamitin ang 74HC595 kesa 74LS595 sa project na ito?

simulate mo na rin para maprep mo na yung firmware habang wala pa yung hardware. regarding HC vs LS, you can choose whichever is cheaper. LS is fast enough for this application, so you can use LS if it is cheaper. you can also compare their current sink capabilities, and choose the higher one.

[keyholder]

Boss labgruppen, possible rin ho bang mapagana ito sa 16f84a or kukulangin ang mga ports? Balak ho kasi namin this finals na bumuo ng LED display/signboard for our final project. Kaso nagkataon na nagkasakit ang prof namin. Lumalapit na po ang deadline (actually 2 weeks nalang) and its up to us para i-self study ito kasi tuloy pa rin daw ang project.

Ang condition ho kasi for our project is to use 16f84a or 16f877. Mas suitable ho bang gamitin ang 16f877? At, ayon, wala po talaga akong alam sa components kaya pasensya na kung wala pa kong mapapakitang schematic. *maghahanap muna sa net, muhahahaha...*
For programming, assembly po ang naituro samin mula prelim kaya balak ko pong i-code sa .asm.

[L.E.D]

simulate mo na rin para maprep mo na yung firmware habang wala pa yung hardware. regarding HC vs LS, you can choose whichever is cheaper. LS is fast enough for this application, so you can use LS if it is cheaper. you can also compare their current sink capabilities, and choose the higher one.

thanks po sir. i'm doing simulations in proteus right now. tanong ko lang po, paano po ma configure ang protues para hindi mag loloop in simulations? kasi po kahit walang loop sa program eh paulit2x parin.. saan po ma aadjust ang settings nito?

[labgruppen]

Boss labgruppen, possible rin ho bang mapagana ito sa 16f84a or kukulangin ang mga ports? Balak ho kasi namin this finals na bumuo ng LED display/signboard for our final project. Kaso nagkataon na nagkasakit ang prof namin. Lumalapit na po ang deadline (actually 2 weeks nalang) and its up to us para i-self study ito kasi tuloy pa rin daw ang project.

Ang condition ho kasi for our project is to use 16f84a or 16f877. Mas suitable ho bang gamitin ang 16f877? At, ayon, wala po talaga akong alam sa components kaya pasensya na kung wala pa kong mapapakitang schematic. *maghahanap muna sa net, muhahahaha...*
For programming, assembly po ang naituro samin mula prelim kaya balak ko pong i-code sa .asm.

kung tutuusin kaya ng 84A, pero just go for 877 na lang, mas bago, mas flexible with more peripherals such as UART, ADC etc.. you could ask/collaborate with L.E.D. about the hardware. you can use the same ports as what he is using, just follow the pinouts of 877.

[L.E.D]

meron po akong tanong about row scanning.. may pagkakaiba po kaya sa brightness ng display kung yung ROWS ko ay cathodes? kasi po in my case, di gaanong maliwanag kung lahat ng leds sa isang 8x8 matrix ang inactivate ko.. although hindi pa ako gumagamit ng transistors, sa tingin ko mukhang malabo parin kasi i'll be cascading 10-15 matrices..

sa tingin nyo po, kung cathode po ang rows instead of anode may pagkakaiba kaya?

[labgruppen]

meron po akong tanong about row scanning.. may pagkakaiba po kaya sa brightness ng display kung yung ROWS ko ay cathodes? kasi po in my case, di gaanong maliwanag kung lahat ng leds sa isang 8x8 matrix ang inactivate ko.. although hindi pa ako gumagamit ng transistors, sa tingin ko mukhang malabo parin kasi i'll be cascading 10-15 matrices..

sa tingin nyo po, kung cathode po ang rows instead of anode may pagkakaiba kaya?

gamit  ka ng transistor. baka masira pa yung row driver mo dahil malamang exceeded mo na yung maximum current sourcing ability nya. note that for row scanning, your row driver must be able to source (common anode) or sink (common cathode) current amounting to LED current times the number of columns.  So kung 10mA yung LED current mo (a bit low for scanned led displays, but check the datasheet to be sure) tapos may 5 kang 8x8 ang maximum row current mo @10mA led current will be 400mA. So kung 15 matrices mga 1.2Amperes na ang maximum row current mo.

[L.E.D]

sir labgruppen, paano ko po malalaman ang LED current ng matrix? ala po kasing datasheet para sa nabili kong dot matrix from e.gizmo... siguro naman may approx. value yun like ordinary LEDs..

tsaka about transistors po, i'll be using NPN trannies configured as emitter follower gaya ng sabi nyo.. ano pong e.coconsider ko in choosing the right trannies? i mean, ano po ang titingnan ko sa datasheet?

sensya na po, im noob when it comes to transistors...

[labgruppen]

sir labgruppen, paano ko po malalaman ang LED current ng matrix? ala po kasing datasheet para sa nabili kong dot matrix from e.gizmo... siguro naman may approx. value yun like ordinary LEDs..

tsaka about transistors po, i'll be using NPN trannies configured as emitter follower gaya ng sabi nyo.. ano pong e.coconsider ko in choosing the right trannies? i mean, ano po ang titingnan ko sa datasheet?

sensya na po, im noob when it comes to transistors...

walang part number na naka print sa body ng matrix mo? kung meron, search mo sa net malamang may datasheet yan. in case na wala, 10mA of LED current is imho safe enough.
regarding the transistors, check the max collector current. it must be higher (above 1.5 times) than the maximum total row current. also check the current gain, the higher the better. to check if the current gain is enough, divide the maximum row current by the minimum current gain of the transistor. the resulting current should be lower than the maximum current sourcing ability of your row driver ic.

[L.E.D]

wala po akong mahanap na datasheet for 2388ASR matrix..pero may mga nakita akong identical matrix ganito nakalagay sa datasheet:

Code:

Peak Forward Current per Dot: 100mA
Continuous Forward Current per Dot: 13mA

13mA po susundin ko? so bale kung may 5 matrices ako, 13 x 5( = 520mA ang max total row current ko. tama po ba?

yung ULN2803 po ang balak kung gamitin in amplifying row current kaso 500mA lang collector current nya, pero 1000mA ang min. current gain. Ok na kaya to?

[labgruppen]

wala po akong mahanap na datasheet for 2388ASR matrix..pero may mga nakita akong identical matrix ganito nakalagay sa datasheet:

Code:

Peak Forward Current per Dot: 100mA
Continuous Forward Current per Dot: 13mA

13mA po susundin ko? so bale kung may 5 matrices ako, 13 x 5( = 520mA ang max total row current ko. tama po ba?

yung ULN2803 po ang balak kung gamitin in amplifying row current kaso 500mA lang collector current nya, pero 1000mA ang min. current gain. Ok na kaya to?

you can safely use 13mA. total, as long as di mag hang yung row scanning mo, yung duty cycle ng LED mo ay 1/8 or 12.5%..
i see some issues if you are to use uln2803 for row drivers.. your row is positive and you need emitter follower config. unfortunately uln2803 have all emitters tied to a common pin, so it is a no go.. kung negative sana ang rows mo, ok lang.. you could rotate your 8x8 matrix by 90 degrees so that your rows will be negative.. nasa sides na nga lang yung mga pins, but if you have not done your PCB yet, then it is still possible. kung yung row current mo ay ma-eexceed yung 500mA, you can parallel two of the uln2803 to have more current capacity.

[L.E.D]

ganun po ba. so hindi pala pwede yung uln2803. cguro individual NPN transistors nalang cguro gagamitin ko sa rows.. pero mas ok sana yung isang package lang gaya ng uln2803. ano pong suggestion nyo sir?