Relay always on when its load is connected to power supply

[knowledgeseeker]

Hello everyone,

I have 8 channel 5vd relay (songle srd-05vdc-sl-c 8) with active low and its first and second relay are connected to a solenoid valve (airtac solenoid valve 4v230c-08 , 24vdc 4.8W, and it has two solenoid). I have used an external PSU with 24vdc 12,5A and step down XI405 (to convert to 5vdc). the first solenoid is connected to first relay and so on. I have coded the program for only turn on the first solenoid and next turn on second solenoid, turn off first solenoid, like a running blinking LED. The problem is that when the lod isnt connected to the PSU, everything is fine, the first relay but when they are connected to the PSU then the relay won't switch off, for example after the first solenoid turn on, then delay 2 sec and then turn off, but the relay won't turn off and my second relay won't turn on. Are the relays faulty? or am i missing something?

Any help or advice you could provide would be much appreciated.

[knowledgeseeker]

Here is the schematic and code

const int relaysolv1 = 2;
const int relaysolv2 = 3;
void setup() 
{
 Serial.begin(9600);

  pinMode(relaysolv1,OUTPUT);
  pinMode(relaysolv2,OUTPUT);
  digitalWrite(relaysolv1,HIGH);
  digitalWrite(relaysolv2,HIGH); 
}
void loop() 
{ 
  digitalWrite(relaysolv1,LOW);
  delay(2000);
  digitalWrite(relaysolv1,HIGH);
  digitalWrite(relaysolv2,LOW)
  delay(2000);
  digitalWrite(relaysolv2,LOW)
  delay(2000);
}

[LarryD]

• Appears the 24v power supply powers everything ?

• If so, the solenoid should have its own power supply.

• Ideally, the 5v relay board should have its own supply different from the Arduino.

• What voltage goes into the Arduino Vin pin ? Should be 7 to 9v.

---

If this was a 4 channel relay board, it should be wired similar as below.

[Paul_KD7HB]

@knowledgeseeker

Any help or advice you could provide would be much appreciated.

Please confirm that you have measured the various voltages while your code is running and the voltages are correct and change very little wile operating.

[knowledgeseeker]

I have separated the power like you schematic (4 channel relay board), one from usb (from my laptop) for arduino and one for the relay board from psu. As in my schematic, the solenoid have their own power supply that is 24vdc. When i try to run my code the solenoid work for a while just as intenden in the code, but then the first relay keep turning on while the second relay turn on and off very fast.

[knowledgeseeker]

i have measured the voltage, everything is fined except the voltage output from the arduino pin. It shows 1.8-2.8v eventhough the pin is active. I have read that the output voltage from pin when the arduino is connected to usb is 5v. Am i missing something?

[Paul_KD7HB]

That shows the pin is actively changing from low to high because your program is doing something with that pin. Perhaps your program should not be changing that pin quite so rapidly.

[ledsyn]

And if the pins (2, 3) are not connected - what does your meter show

[knowledgeseeker]

its zero and i have measured the voltage from vcc board that is connected to 5v arduino (when arduino plug into usb laptop), it shows zero too, eventhoung the arduino led is on

[TomGeorge]

Hi, @knowledgeseeker
I hope this is an error on paper only?

PLEASE get out pen(cil) and paper......
Reverse engineer your project.

Draw a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.

Tom..

[ledsyn]

So with the sketch running there should be activity from those two pins. Somewhere to start.

[knowledgeseeker]

Hi, @TomGeorge
the error is only on the paper.
The hardware are:

1. Arduino Uno R3 with chip CH341
2. 8 relay module SONGLE SRD-05VDC-SL-C
   SRD-05VDC-SL-C-Datasheet.pdf (circuitbasics.com)
3. Airtac 4V230C-08
   Airtac 4V230C-08: Solenoid Air Valve - 4V230C08BG-W (airtacs.com)
4. light box power supply (from local electronic shop) 300W 24V
   Input: 200-240V-50-60Hz
   Output: 24V 12,5 A
5. Step down 5A XL4015 Module
   Voltage and Current Input= 4-38V & 4A
   Volt and Current Output = 1.25-36V & max. 5A
   Power Output: max. 75W
   Consumtion: 18mA without load
6. terminal block
   Here is the hand drawn circuit and the photos:
   
   
   
   
   
   
   
   
   
   
   
   
   
   

[ledsyn]

How do you plan to power that relay module, if you connect +5 V but not GND? And as already being said, depending on the power need (both continuous and peak), it might be better to power the relay module from a dedicated 5 V source and not the Arduino.

Edit:
From the datasheet, and notice the marked numbers

[TomGeorge]

Hi,
Include in your code the "Blink without delay" example.
This will make the on board LED flash when your code is running.
Its termed a "heartbeat LED".

If when you problem occurs and the LED ceases to flash, then it means your code has locked up.
Probably due to noise spikes on your power supplies form the valve solenoids.

If it continues to flash then a wiring or software problem.

Tom...

[TomGeorge]

@knowledgeseeker

light box power supply (from local electronic shop) 300W 24V
Input: 200-240V-50-60Hz
Output: 24V 12,5 A

They are usually designed just for that, "lights", not loads with high instantaneous loads like valve solenoids.

Do you have a 1000uF or 2200uF 35V electrolytic capacitor that you can connect to the 24V output of your 24V power supply?

Also use the DMM to monitor the 24V output when you activate the valves.

Tom....

[knowledgeseeker]

Hi,
I have found the problem and it just as you said, its the noise spikes from my solenoids. I have put the a diode accros the solenoid and now it works fine

Thank you for your advice

[ledsyn]

Please mark the post that helped you, as the Solution.