Power supply

I have a weird power problem with my ardunio circuit , I am using Arduino Uno to power a 5 v relay , this works perfectly fine as long as Arduino is connected to my laptop via USB , when I remove it and power it via 12V regulator , signal strength of relay goes down and its unable to trigger interfacing devices , why is this ? Thru voltmeter I had confirmed 12 V supply , what can be done to resolve it

Where is this 12v regulator being plugged into?

What is the current rating of the 12V supply? 12VDC, 1A?

Power source is directly from 240 V power socket , regulator output is 12 v , 4.5 A max

Shammy:
I am using Arduino Uno to power a 5 v relay , this works perfectly fine as long as Arduino is connected to my laptop via USB , when I remove it and power it via 12V regulator , signal strength of relay goes down and its unable to trigger interfacing devices , why is this ? Thru voltmeter I had confirmed 12 V supply , what can be done to resolve it

Need to be much more clear about your system, since 'powering' a relay means equipping that relay with a source of power or energy to do some work. But ...... then there is also 'control'..... as in - what are you doing to switch the relay on and off? A push-button connected to something? Arduino control signal? Some other control device?

This goes the same for the external regulated power supply. You power the relay, but what's the circuit you use to control the switching? This means ...... is the control circuitry correctly connected up? As in - ground connection of external supply is connected to ground point of control circuit?

Ardunio is connected to a 12 V solenoid valve thru the relay , and this circuit fails to take off when ardunio is externally powered from 12 v source but works perfectly fine with power coming from laptop

Please show us a schematic of your circuit.

This is the circuit I am following , instead of 5 v supply if I power from laptop it works , but when I use a 12V regulator o/ p signal is week

Before you power up your circuit again, please post a drawing of it as is - if you are getting
things wrong you may be risking frying the Arduino, so rather than tinker till it breaks,
show up exactly what circuit you have.

Hi,
When you use the laptop as the power supply, the 5V for the relay coil is supplied by the laptop power supply through the Arduino.

When you use a 12V power supply, the 5V for the relay is supplied from the on-board 5V regulator on the Arduino.
It sounds like the Arduino regulator cannot supply the current needed for the relay.

Do you have a DMM?
If so measure the 5V out on the Arduino when the fault is occurring.

Yes a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png would be appreciated.

Thanks.. Tom.. :slight_smile:

Scroll down 2/3 down the page here to THE REGULATOR’S LIMITS.

Perhaps you could try:

  • 7.5VDC at Vin
  • Regulated 12VDC at Vin, 12VDC relay coil
  • Regulated 12VDC at Vin, 12VDC with 1N5342B zener connected in series to 5V relay coil

Thank you , problem is fixed by supplying 12V directly to Vin pin and negative to the ground. I am able to power the relay as well as the valves connected to the circuit