Hi, i finished my project of automatic staircase with 4 sonic sensors. To control 16 leds with 2 shift register outputs.
Project works perfect with using leds as outputs. Today I tried to replace leds with the relay module.. But it's not working. I know module gets triggered when LOW so even I did change that in code..still relays isn't working.. I mean it's not getting triggered.and same time if I try with led it works.
This is the module I'm trying to use
And this is the schematic
Can you measure the output voltage of the IC? That the voltage that triggers the relay.
@er_name_not_found yeah.... I tried to check the voltage from shift register outputs to led using resister and it shows 2.7v
When I try that with relay it shows 0.07.. Less than a volt and I know the module needs minimum of 1v.
Not sure why that's happening. Also arduino is powered separately and relay is powered separately.
Not sure what's going wrong here.
Eveytime I think when my project works.. Their is always some issue.
There's your issue. You need 5V presumably for the relay signal.
Your power supply is 5V?
Yeah... I'm using separate 5v supply for arduino and separate 5v supply for relays and their gnd are connected together.
And the module I have can trigger with 1v to 5v.
Is that relay high triggered or low triggered?
LOW triggered
And this is the relay I'm using
Start here:
Thanks... But it's almost same as my schematic... Still not sure why it's not working only for me 
You read the entire article in 3 minutes?
I read that article long before during my initial project ideas... Even I have the same article bookmarked.
Ah, very good.
What's different between the two schematics?
Well... their isnt changes though. in the article , this is what works for me
There are one type of 8 channel relay boards has 10 pins (8 + 5v + GND) to directly connect with 74HC595.
this is the module im using .
One more chnage I would say is.. In article they used digital pins for shift register. But I have used analogue pins... Apart from this i don't see any changes.
may be i should gnd the relay with the gnd of shift register..
Measure the voltage between the 5V pin on the Nano and the IC.
Did you write that?
Where are these schematics?
Where are the bypass capacitors for the '595?
the 74hc595 may not have enough current to drive the relay. it may only be able to source 6 ma.
an arduino output pin can source 40 ma
thanks for everyone. its fixed and works now.
I rate this topic 1 out of 20. That 1 was for @anon57585045 's question.
