Relay help (opto mos)

[Rajinder]

Hi all,
I have attached a schematic of an issue. I have a relay AQY212S, which is fed from a car supply of 12V. This is then switched by a relay. The relay is breaking down, I think it is due to voltage. The relay is rated at max load voltage of 60V.
I am thinking of using a diode suppression on this line, reverse stand off of 60V. Can anyone see any issues? It's a bi direction type.
Thanks in advance.

 

[Harald Kapp]

A 60 V SSR should have no issues when operated on 12 V, even accounting for the voltage spikes due to load dump.
What is the load the relay is driving? I suspect a high inrush current to be the cause of failure.

The relay is breaking down

Does it fail open circuit or short circuit?

 

[bertus]

Hello,

What is the led current?
What is the load of the opto-relay?
When it is inductive, you should use a Bemf diode.

Bertus

 

[Rajinder]

It fails open circuit. it's a photo relay, MOSFET type. The load is power to a couple of circuits, one is a voltage regulator 7805, then this is used to power a opamp (non-inverting), single sided to 5V.

 

[Rajinder]

Hello,

What is the led current?
What is the load of the opto-relay?
When it is inductive, you should use a Bemf diode.

Bertus

The current of the LED

Hello,

What is the led current?
What is the load of the opto-relay?
When it is inductive, you should use a Bemf diode.

Bertus

Led current is 900uA
Load is 7805 + opamp circuit configured as non inverting amplifier. I do not think it is inductive, the current through the load is not substantial, about 50-100mA. Hence I think it is a voltage spike issue.

 

[Rajinder]

The current of the LED

Led current is 900uA
Load is 7805 + opamp circuit configured as non inverting amplifier. I do not think it is inductive, the current through the load is not substantial, about 50-100mA. Hence I think it is a voltage spike issue.

Not sure but it may because of the noisy voltage from the car battery. Also does the position of the diode look correct?

 

[bertus]

Hello,

The led current of 900 uA might be marginal.
It is on the border between on and off.
Raise the led current to 3 mA for correct operation.


Bertus

 

[Rajinder]

Hello,

The led current of 900 uA might be marginal.
It is on the border between on and off.
Raise the led current to 3 mA for correct operation.
View attachment 51250

Bertus

Thanks.

 

[Rajinder]

Hi all,
Is the placement of the diode in my schematic correct? Or should it go across the output pins of the relay?
Thanks in advance