8*8 matrix keypad and relay connection

hello , i am using a- 8*8 matrix keypad
mcu at89s52
8*8 relay matrix
my problem is that i have no idea regarding the current flow in this kind of circuits, so please give me sufficient information on this. i have attached circuit diagram of 8*8 relay matrix which i got from you.please reply me quickly i am in the middle of my project.thank you waiting for your replies

normally current through output port due to low imopedence

The 2803 can handle around 400-500 mA. 500 is listed as the absolute MAX.

The datasheet uses 100, 250, 300, and 350mA in its parameter tests, so those should be safe values to use for that chip.

What are you driving with it? inputs to other active devices seldom need such extreme currents, but things like LEDS and relays do.

Edit: never mind, I found the title on the drawing says relay matrix.

pleae tell me the difference between uln 2803 and udn 2982 in a descriptive way.

pleae tell me the difference between uln 2803 and udn 2982 in a descriptive way.

Click to expand...

Use the device numbers to search for data sheets.

i have gone through th datasheets but can't understand the functionality of udn2982.please reply so i can start my programing

UDN2982 is the high side controller. This device will control the columns of your matrix while ULN2803 is the low side controller and is responsabile to control the raws.

To control the matrix you will need two bytes, one byte for the colums and one byte for the raws. Give to these two bytes the value of one and you will activate relay #1, give the two bytes the value of 128 and you will activate the last relay.
Any other number from 1 to 255 will activate a combination of the 64 relays. (I leave to you the pleasure to discover the coding)

Cheers

Alberto