Why Does My Relay Fail?
Printed From: the12volt.comForum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=146029
Printed Date: April 29, 2024 at 9:03 PM
Topic: Why Does My Relay Fail?
Posted By: danger dave
Subject: Why Does My Relay Fail?
Date Posted: February 17, 2020 at 10:16 AM
Hi I am more of a programming guy and new with hardware so please take it easy on me. I am helping my son to build a customize car horn for his toy car which operates on 24V with BLDC motors.
I removed the outer body and traced the wires to check how the in-built horn works. It was powered directly from one of the 12V battery through a switch (horn switch) which when pressed turned on the horn. So from this, I concluded that horn operates on 12V, so I replaced the switch with a 5V relay that is triggered by Arduino. The NO and C of the relay are used to complete the connection of horn with 12V battery. I have the tone function on Arduino which switches the relay to output a music. Everything working fine but relay gets very hot and then stops working after like 10-12 times usage. I have changed the relay a couple of times by failure appears again.
To find the problem I opened the relay (broke the outer blue casing) and found coils were good but the contact was burnt (in both the failed relays). Sorry I cant take pictures but the i took a picture from internet which looks exactly similar, the burnt area is circled blue.
Everything I know about relay including this image comes from this relay article https://circuitdigest.com/article/relay-working-types-operation-applications
I have tried the following
1. suspected that current is the problem so measured the current using multimeter found it to be 550mA well within limits
2. Thought I am switching relay very fast so slowed down the tone but still not help
So what is causing the failure? is there a special type of relay that I should use?
I removed the outer body and traced the wires to check how the in-built horn works. It was powered directly from one of the 12V battery through a switch (horn switch) which when pressed turned on the horn. So from this, I concluded that horn operates on 12V, so I replaced the switch with a 5V relay that is triggered by Arduino. The NO and C of the relay are used to complete the connection of horn with 12V battery. I have the tone function on Arduino which switches the relay to output a music. Everything working fine but relay gets very hot and then stops working after like 10-12 times usage. I have changed the relay a couple of times by failure appears again.
To find the problem I opened the relay (broke the outer blue casing) and found coils were good but the contact was burnt (in both the failed relays). Sorry I cant take pictures but the i took a picture from internet which looks exactly similar, the burnt area is circled blue.
Everything I know about relay including this image comes from this relay article https://circuitdigest.com/article/relay-working-types-operation-applications
I have tried the following
1. suspected that current is the problem so measured the current using multimeter found it to be 550mA well within limits
2. Thought I am switching relay very fast so slowed down the tone but still not help
So what is causing the failure? is there a special type of relay that I should use?
Replies:
Posted By: eguru
Date Posted: February 17, 2020 at 10:50 AM