Arduino resets when solenoid shuts off

You may also want to use some ferrite beads on your power feed

Trying to find the root cause first.

In nearly every conversation we've had on this forum that involved a stepper, relay or other inductive load, adding a large (10,000uF) cap fixes it.

Most people are not using a decent supply with suitable capacitance to handle the spike, and therfore when it is energised it causes a brownout on the supply which resets the Arduino.

Mark

Didn't I already suggest that as a possible cause by saying - "You also need enough power budget on the driving voltage as not cause it to sag and stop correct operation."

It doesn't immediately explain why the lack of connection of an HDMI monitor to the Rpi is causing the arduino to misbehave.

From what I understand thus far;

• The arduino and Rpi work fine when the Rpi is connected or not connected to an HDMI monitor if the RPi and arduino are not connected together but can be in close proximity to each other.

• The arduino becomes intermittently unstable when its relay is controlling the Rpi power only when no HDMI monitor is connected to the Rpi.

However I don't know the behaviour when the Rpi Power is not controlled by the arduino but with only one Rpi power lead connected to the relay (with or without the HDMI monitor attached to the RPi).

Hi COMPACT

Yes, you did say "You also need enough power budget on the driving voltage as not cause it to sag and stop correct operation." My battery can provide 2.1A@5V for the RPi and I thought that should be fine. I also tried to power the Arduino from an external power supply 2.25A @7-12V.

If I understand your last question correctly, I think I already answered what happens when one of the RPi power lead is connected to the relay (in the three points I mentioned before). The Arduino doesn't reset. I tried both power leads one by one and it didn't affect.

So is the problem only evident when the Rpi power is switched on/off by the arduino relay?

So is the problem only evident when the Rpi power is switched on/off by the arduino relay?

Yes, that is the situation.

Is it only at the time the Rpi is turned on?

The relay unlatches after few seconds (~3-4 sec)

The schematic for the relay board is here

http://shop.emscdn.com/catalog/emskits/relayshield/kitv1/G5LA_E.pdf

The 100uF is not adequate for powering via the USB ...

BUT you made the statement that you have tried powering the Arduino from an external 7-12v supply.

The Arduino will switch between USB and external power to whatever has the greater value.

The external socket goes through a regulator so it needs 7v minimum and the regulator is 500mA on proper Arduino's.

Some copies may not be supplying 500mA, and if the input voltage is not greater than the regulator dropout (2v) then weird stuff can happen.

The relay specs are 72mA for the 5v version BUT this is after it has pulled in and is operating.

It is very likely to draw 2-4 times than amount as it pulls in. ie 288mA

An Arduino draws 46mA when running.

So you could experiment by putting a large (more than 1000uF) cap across the Vcc and GND pins of the shield.

This should help eliminate any voltage sag causing a reset.

Also just to be sure can you attach the Arduino code (paste it, highlight/select it and use the >> Syntax highlight and C++)

Eventually we'll sort out the issue.

Mark

Hi Mark

I will replace the 100uF. I will rather solder a socket for plugging different capacitor values. Here is my code..

// define pin for the relay output 
#define RELAY 4

//define pin for the PIR sensor input
#define PIR 8

//define pin for reading status of raspberry pi
#define RPi 9

void setup() {
  // put your setup code here, to run once:
  pinMode(RELAY, OUTPUT);
  pinMode(PIR, INPUT);
  pinMode(RPi, INPUT);
  digitalWrite(RELAY, LOW);
  digitalWrite(RELAY, LOW);  
  delay(1000);
}

void loop() {
  
  if(digitalRead(PIR) == HIGH){
    digitalWrite(RELAY, HIGH);   
    }   

}

Thanks

I presume the RPi detection aspects haven't yet been implemented ...

You will need to tie the RPi GND and the Arduino GND together if you intend to detect it's state.

Because the GPIO on the RPi is 3v3 the Arduino can handle it and it will be detected.

You can simply put the cap onto the pins of the relay shield in the meantime.

It will be enough to sort out the issue.

Mark

Hi Mark

Thanks.

At the moment, I just want to power up the RPi when PIR sensor is active. If this issue is resolved, I will read the state of the RPi so that I can switch-off the relay when the RPi completed shutdown. I got this working when the display is connected.

I got now 1F. I will replace the 100uF and see if the problem goes away. I hope I don't get electric shock with the 1F

Hello maranatha, can you use the arduino led (digital pin 13) to debug the problem? Turn on the led the same time you want to activate relay then click in the button that you replace by the PIR sensor and see what happen.

Hi Mark

Thank you!!!

I have to confess that I had been ignoring some basic principles.  I almost went to cry when the 1F didn't resolve the issue. Desperately, I just connected the grounds of the raspberry pi and the arduino...and it worked. I said desperately, because I had the GNDs of both Arduino and RPi connected when I started the project. It was working. But then, somewhere on the internet I read that connecting the GNDs of two separate circuits can be dangerous. So, I removed it. Removing that common GND didn't affect the operation until I decided to run the RPi headless. I removed the HDMI display and I start to have this ugly problem for more than a month. I should have tested removing the HDMI display in my original setup where both GNDs are connected.

I hope this fixes the problem permanently! I will just keep this 1F capacitor for decoupling. I have also soldered ferrite beads for extra protection.

I would be more than happy if somebody could explain me about the relevance of connecting the GNDs of both

Your diagram of your set up is incorrect. The most vital bit of information was missing - the input feed to the Arduino from the Rpi.

If you want to keep both boards electrically isolated you'll need to use an optocoupler or a relay set in in reverse to drive the Arduino input pin to it's own gnd.

You've got plenty of relays so it should be an issue.