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1  Using Arduino / General Electronics / Arduino max shift register on: December 11, 2012, 02:43:58 pm
Hi all,

Can an Arduino Uno R3 drive 15 Shift Registers (74HC595) ? Arduino provides output enable, latch, clock and clear pins for all 15 SRs and data pin of first SR through its output pins. Also it provides VCC and ground for all SRs from its +5v and ground pins.

Thank you...
2  Using Arduino / General Electronics / Re: ULN2803 Question on: September 28, 2012, 04:15:44 pm
Thanks for the nice explanation, as you told when I removed the COM port everything worked smoothly.
3  Using Arduino / General Electronics / Re: ULN2803 Question on: September 28, 2012, 01:22:38 pm
Hi again,

Thanks all as you said when I switched places the led blinked. When I connect the +5v from arduino the led blinks properly there are 500ms between blinks.

Now I have another problem, when I connect a 12V, 1000ma ac/dc adapter with a 1K resistor as shown in the picture, the led is always on (no blink), even when arduino is detached from the computer. Another thing is even if I plug off the adapter the led is still on, it slowly fades away. Please bare with if this is too trivial smiley

Thank you..
4  Using Arduino / General Electronics / ULN2803 Question on: September 27, 2012, 05:36:02 pm
Hi all,

I am trying to use an ULN2803, but I can't get output (the led doesn't blink). Attached is my schema. I connected a shift register to my Arduino Uno and I connected the outputs of the shift register to ULN2803. I know that shift register works because when I connect the green wire going to the led to the output of the shift register (from orange dot to the green dot) the led blinks.

I connected the ground of ULN2803 to the breadboard ground and Vcc of ULN2803 to +5v of Arduino Uno. Am I doing something wrong?

Also if I will be able to make this work next step is to connect a 12v DC adapter to ULN2803 (and a resistor to the led). Is it ok if I connect + wire of DC adapter to Vcc of ULN2803 and - wire of DC adapter to breadboard ground? How can I understand + and - wires of the DC adapter (I just cut the cable of a 12v DC adapter)?

Thank you...
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