ULN2003, LED strip 12V, arduino nano problem

Hi,
I am really curious (not nervous, still) about my problem. I connected my components like this (attachment photo).
Later on, I unplugged two inputs and leave one for testing. The problem is:
I get little red light, and little green light although green input is not connected.
When I tried to touch other outputs with led I saw that 4 pins or more are working. One of the output pins (which is not turned on with his input) is working the best and others are much weaker.
Basicly, how can I get 0v on outputs (PIN 15,16,17,…) if I put only 5v (from arduino) on PIN 1 ?

uln2003-test.jpg

When I tried to touch other outputs with led I saw that 4 pins or more are working.

You have a floating input when an input is connected to nothing. You touch it and it injects interference and it looks like you are putting in a logic signal. Read Inputs

Basicly, how can I get 0v on outputs (PIN 15,16,17,...) if I put only 5v (from arduino) on PIN 1 ?

Is that right?
Basically you can't, but you don't want to anyway do you?

I connect it again from start, and everything works fine now :o.

Grumpy_Mike:
You have a floating input when an input is connected to nothing. You touch it and it injects interference and it looks like you are putting in a logic signal. Read Inputs

I am not sure if you understood me, by "touch with led" I meant connect LED with other output pins for testing. And thats when other outputs on ULN were "turned on" even only 1 input was connected.

Is that right?
Basically you can't, but you don't want to anyway do you?

Thats what was bothering me, no I don't. Thank you for response.

Sorry there is a lack of communication here.
The word touch means that you physically touch it. You should say connect.

Also a 5V signal on the inputs will turn on the Darlington pair in the buffer so you will get about 1.4V on the output not zero volts.

Grumpy_Mike:
Sorry there is a lack of communication here.
The word touch means that you physically touch it. You should say connect.

Sorry for that, my bad. I was under pressure. :slight_smile:

Also a 5V signal on the inputs will turn on the Darlington pair in the buffer so you will get about 1.4V on the output not zero volts.

Thanks, good to know!