5V relay almost switching, despite sufficient power

I plan to make a very simple arduino (Funduino Uno) controlled relay circuit.

I am using a 2 relay module pretty much identical with this: http://modtronix.com/mod-rly2-5v.html

I power my arduino with either a 9V battery or a 5V phone charger (same problem no matter which):
I have connected the VCC to the 5V pin on the arduino. And also GND to GND on the arduino.

The relay is inverted, so the IN1 (I'm only using one of the relays) triggers when I connect it to ground.
But to actually controll it I connect the IN1 to pin 13 and run the blink example. And sure enough the relay is triggered, an indicator led turns on (when pin 13 turns off) and I hear a click. However the click is very quite, and the circuit is never broken. (I have the relay connected to a lamp over NC). The lamp doesn't even flicker.

This feels like a problem with power to me, but the board requires 20mA according to a website I found and I checked with a multimeter; 23mA of current was flowing through it.

Summary:
My relay had enough power, and clicks silently when activated. But the actual circuit of 220V running through it remains unchanged.

What might be the reason, and how do I fix this?

Bad idea trying to supply a relay through an arduino. 23mA is about one third of the initial current surge through the relays which I use while switching. Supposing that yours are smaller and rated to work within the datasheet capability of the arduino. It is still a bad idea to run anything bigger than 'signalling' currents through the arduino because its digital outputs are all on the same silicon die and all heating it up a little bit. A ten-pack of 'bog standard npn transistor' (you do still have to read the datasheet) will cost about £2 or less, and then you can protect the digital outputs of your arduino by having a couple of kOhm down to transistor base.

Let us know how many Volts and mA you had to supply above the relay to get it to switch on while an npn below it is driven at the gate. It is probably better to go direct from one of your supplies than through the '5V' of the arduino. BTW, I think that 'uninverts' for you.

Your summary is doubly self-contradictory.

A better description of your hookup is needed, a pic or drawing would be good, but with your simple circuit you could also do something like this;

RELAY BOARD
Vcc >> ard 5V
Gnd >> ard GND
IN1 >>
Jumper >>
LOAD >> NC/COM ??

ARD

ad2049q:
Bad idea trying to supply a relay through an arduino. 23mA is about one third of the initial current surge through the relays which I use while switching. Supposing that yours are smaller and rated to work within the datasheet capability of the arduino. It is still a bad idea to run anything bigger than 'signalling' currents through the arduino because its digital outputs are all on the same silicon die and all heating it up a little bit. A ten-pack of 'bog standard npn transistor' (you do still have to read the datasheet) will cost about £2 or less, and then you can protect the digital outputs of your arduino by having a couple of kOhm down to transistor base.

Let us know how many Volts and mA you had to supply above the relay to get it to switch on while an npn below it is driven at the gate. It is probably better to go direct from one of your supplies than through the '5V' of the arduino. BTW, I think that 'uninverts' for you.

Your summary is doubly self-contradictory.

But the internet is overflowed with people hooking up relays this way, and it is a relay board that is commonly used the way I am.

The contradiction in the summary (assuming you're talking about -enough power but nothing happening-) is the very reason for my confusion.

tinman13kup:
A better description of your hookup is needed, a pic or drawing would be good, but with your simple circuit you could also do something like this;

RELAY BOARD
Vcc >> ard 5V
Gnd >> ard GND
IN1 >>
Jumper >>
LOAD >> NC/COM ??

ARD

RELAY BOARD
Vcc >> ard 5V
Gnd >> ard GND
IN1 >> ard pin 13 (also tried connecting straight to ground)
Jumper >> JD-VCC >> VCC
LOAD >> NC/COM!

The IN pins only control the opto couplers, not the relay coils themselves. 23mA is what it takes to drive the leds. The power to drive the coils comes from the JDVcc/ Vcc jumper, which when the jumper is in, uses power from the Vcc pin to drive the coils. As I understand it, Vcc is connected to the 5V pin on the arduino.

If you want to see how much current the coils take, hook the probes to the Vcc/JDVcc jumper pins and cycle the run the sketch

Make sure that:

  • The load isn't using the outer 2 terminals
  • The relay part number is SRD-05VDC-SL-C
  • A separate supply is used - remove jumper and connect it to RY-VCC or JD-VCC and GND

IMPORTANT:

When switching an AC load, use contact arc suppression (MOV or other) or the contacts could weld closed or have reduced life expectancy. Also, without arc suppression, there would be excessive EMI/RFI that could cause problems with your electronics (reset, lock-up or other).

Here's some MOVs rated for 300VAC

Removing the jumper and using a separate power-supply (broken 5V phone charger) fixed the problem. The click is now way louder and the circuit is broken. Thank you (and y'all) very much for your help.

The current between JDVCC and VCC was about 25 mA

That relay specs 71.4mA @ 5vdc with a max voltage of 120% of 5v.

Hi dlloyd,

That's a great photo/caption of the 2-relay board..

May I use that on http://ArduinoInfo.Info ?? I get asked that question once+ a week.

Thanks! Terry

Hi terryking228, You sure can!