Ok, here's the schematic I'm trying to use to test if my uln2003a chip is working. While checking the pinout with my multimeter, I couldn't find that pin out1 was connected in some ways to the com pin. When I short the input with 1.5v the led doesn't light up and the led never light up.
The led works when connected to the battery directly.
Is there a better way to test if my uln2003a chip actually works. I'm worried I might have damaged it while soldering it (it's a SMD part). Looking at the schematic if I check for resistance between any of the output and com, there should be no or little resistance but in my case my multimeter always shows 1 (infinite).
Ok since leds are a bit worrying I decided to move a bit further on this without leds.
I uploaded a stepper program on an arduino board. I connected the pinout to a digital analyser and can confirm that the arduino program is fine.
I connected my inputs to the uln2003 and checked with my analyzer the output. The uln2003 is powered with a 5v power supply.
When I check the output pin with the digital analyzer, I can see that I have spikes of less than 1ms from times to times but not similar to the input.
Now things get weird when I connect only one input, then I can see the 10ms up and down of the stepper motor on all four output but only 1 input is connected.
When I measure the resistance between all input pins, I can sense around 18kohm. That said, the digital analyser will raise up even if it sense really little amount of energy passing through.
Then I tried it without actually pluggin the power supply and if only one input is connected I can still see some output on all four connected output.
Then I configured the program on the arduino to make really long step so I could measure the voltage on output pins when they're up. But it looks like it's sinking only a few mv.
I measured the resistance between inputs on a chip I didn't solder yet and can still sense around 18k ohm between inputs.