Problem switching relays (wrong activations..). EMI problem?

Other Hardware Motors, Mechanics, Power and CNC
1

Hi, first of all, I want to introduce myself..

I'm Lucas Viñals and I'm a devotee reader of Arduino forum but I've never join you as a member until today :slight_smile:

Also, before I post this, I have searched a lot of information in the web..codes, special circuits, triggers, protections, isolation..etc,etc and, after all, I continue with this headache..

I want to tell you that I've been working in a domotic proyect to automate my home, but I'm having some problems with the power section.. I have been studing electronics for almost 10 years, but this kind of issues puzzled me :sweat_smile:

The problem comes when I want to activate any charge between output pins of a relay shield (COM and the NO of 2 relays) :

When I activate one relay, the other also activates! Or the same relay, turns ON and OFF quickly.

I said that, because when I test it without charge, everything works like a charm. (Two buttons send some comands, the Arduino decodes them, and turn on/off the target relay). So I assume the code is good..

First, I tried to put a Snubber circuit (RC low pass protection circuit) with a 100nF capacitor and a 100? resistor. Nothing happened.. Then I put a ferrite core with the cable rolled like a inductance (high impedance for high frequency trascient pulses and low impedance for signal). I thought that worked, but after some test, the relays started to fail again..

I also tried to put a external power supply between JD-VCC and GND in the relay shield (to polarize the output transistor in the optocoupler) , the Arduino power supply to the LED input signal, and shield (with a connector to GND) the 8-wired cable that send the signal...Also failed..

I thing that can be an EMI issue (because I have all together, the controller and the relay shield in a plastic case) but some users here said that they switch heavy loads of current(> 6A) or voltage(> 250v), without any problem.. So I tried to separate the Arduino from the relays..Same result...

BTW, the Arduino does not hang when that happens. It continues doing whatever it has to do with other things.

In any case, I'm thankful in advance to you.

PD: Sorry if I wrote wrong words or sentences, my english is not flawless. :sweat_smile:

2

The problem comes when I want to activate any charge between output pins of a relay shield (COM and the NO of 2 relays) :

Can you rephrase this ? I don't follow what you are saying.
Second, as by now you must be aware, posting on the forum involves more that just describing the problem. What you have done in your post thus far qualifies as nothing more than an introduction. The standard protocol here on the forum is as follows.
1 Introduction (describe the problem) [CHECK] you did this already
2 Post a schematic in one of the following formats:
A. JPEG image file
B PDF file
C Photo of hand drawn schematic taken with a cell phone
3 List Equipment /Parts used (only things that would require research, like arduino shields ,lcds, breakout boards ,sensors,motors
motor drivers, RELAYS, POWER TRANSISTORS or MOSFETS
4 Post datasheets or manuals for items that might require research , like power transistors, mosfets, motors , motor drivers, sensors , breakout boards, etc...
5. Post the code you are using with the "#" (CODE TAGS) button (above, just to the left of QUOTE button)
6. Last but not least, if a special circumstance applies, it may become necessary to post a photo of your equipment. A special circumstance is something like a one of a kind piece of custom equipment that cannot be researched on the net.

I want to tell you that I've been working in a domotic proyect to automate my home, but I'm having some problems with the power section.. I have been studing electronics for almost 10 years, but this kind of issues puzzled me smiley-sweat

Please confirm that this

domotic proyect

is a TYPOGRAPHICAL ERROR and actually should be this: DOMESTIC PROJECT. (I believe this is a language translation error) If you have 10 years experience with electronics then you realize that telling us you are automating your home doesn't tell us anything useful. There are many ways this could be done and you haven't described any of them. You have not posted a schematic. You have not posted any code. You have not given us a single part number to research. Basically, we know nothing about your circuit. You describe something you suspect is EMI. (I seriously doubt this, because the relays are the most reliable mechanical electrical device you can find. ) You have not mentioned what method of automation you are using. So, in short, until you complete items #1 through #5, there is little we can do for you. We'll wait.

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I think I have a similiar problem. Once I connect the relays to my arduino uno, the relays start turning on and off very rapidly. But when ever i Touch the Arduino's USB port, or the ground pin of my power supply,this does not happen.

I have used pins 2 to 9 as output pins.

My program is,when I give an input to pin 11, all 8 relays have to turn on.