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Relay help (opto mos)

Rajinder

Jan 30, 2016
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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.
 

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Harald Kapp

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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

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Nov 8, 2019
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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
 

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Rajinder

Jan 30, 2016
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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

Jan 30, 2016
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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

Jan 30, 2016
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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

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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.
aqy21_characteristics.png

Bertus
 

Rajinder

Jan 30, 2016
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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
 
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