leds and relay board


hello all,

i need project implies running 64m of leds. have materials 12v 16a power supplies, ebay 8 channel relayboard , arduino mega. switch leds strips, not need dimming. maybe relay board not best device it, should go mosfet instead. on other hand finish project have.

first of have question way can hook relay board arduino. it's active low relay board. plan use separate power supplies, 1 relay , 1 mega regulated 5v output driving relay. according joined schematic of relay board there resistor on path of optocoupler , status led, value not indicated. when directly on board can see 2 resistors labelled respectively 511 , 102 (closest status led).

the optocoupler 817c. according datasheet forward voltage 1.4v.
http://www.keepjump.com.tw/datasheet/others/dpc-817c.pdf
if right resistor value 102, 1k
(5v-1.4v)/1000ohm ~= 4ma

so should have 4ma on path arduino pin. right ?
now if don't need relays on board, example if need 5 of them, 20ma 5. because equal max 20ma per pin, can hook them same arduino pin ?

then second question calculation of max power can expect relay coil. on relay marking can read :
10a 250vac 10a 125vac
10a 30vdc 10a 28vdc
so it's maximum rating. if want use 12v instead ? how current can expect ? can calculate following :
30vdc*10a = 300w
then know max current under 12v :
300w/12vdc = 25a
is right way calculate ?

thanks in advance !

hi,

is relay board like one??

see schematic there.  102 1000 ohms  " 1  0  (2 zeros) " , 1 in series optocoupler internal led.   the 511 is  "5 1 (1 zero)" or 510 ohms base resistor transistor activating relay.

disclaimer: mentioned stuff own shop... (where have info!)

so: calculate 2ma current arduino.

make sure use separate 5v supply relay board , isolate it.  see:

http://arduino-info.wikispaces.com/arduinopower


and specfically:

http://arduino-info.wikispaces.com/arduinopower#oi

power can control:

the relays limited 10a, right?  power 'per relay' 12v * 10a = 120w calculation not right.

let know how works out...



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