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relay buzzes while energizing


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the_rusty_gear 
Member - Posts: 5
Member spacespace
Joined: March 02, 2011
Location: Alberta, Canada
Posted: March 03, 2011 at 1:57 PM / IP Logged  

I followed the wonderful directions on this site to change the polarity of my door switch from a negarive to positive output in order to install an overhead DVD player (with lights) using the wiring to the dome light.

The installation went great and the lights on the DVD player now function properly, however the relay seems to be misbehaving.

I'm using a 30A, 5 prong automotive style relay and when I open the door, the relay takes a second to activate and it does so with an buzz which increases in tone and volume until the switch is activated.  When the key is in the ignition and the relay deactivates, it does so much more quickly, but is also quite noisy with what can only be described as a short BZZRT. (very descriptive and helpful I'm sure . . .relay buzzes while energizing -- posted image. )

I tried swapping other automotive relays into the socket and all of them exhibited this behaviour.

What could be causing this behaviour in the relay? Where do I start troubleshooting? Is it likely a voltage problem? not enough current? Not enough lode (couple of LED lights on the DVD player)  

Thanks in advance!

KPierson 
Platinum - Posts: 3,527
Platinum spaceThis member consistently provides reliable informationspace
Joined: April 14, 2005
Location: Ohio, United States
Posted: March 03, 2011 at 2:35 PM / IP Logged  

Does your dome light fade on and fade off with the door?  It sounds like your voltage is slowly ramping up down which will cause some chatter.

The easiest solution would probably be to replace the relay with a reed relay - they are silent.  I'm sure there are other ways to fix it as well.

Kevin Pierson
the_rusty_gear 
Member - Posts: 5
Member spacespace
Joined: March 02, 2011
Location: Alberta, Canada
Posted: March 03, 2011 at 3:29 PM / IP Logged  

I haven't observed the lights that closely but It certainly sounds worthwhile trying a reed switch.

I never considered a reed because I was not familiar with them (I thought they were only used on circuit boards, and I thought soldering directly on to their tabs can overheat them?)

Is it safe to solder directly of the pins, or is there some sort of socket I can solder the wires to which will fit on the pins of a Reed relay?

Thanks for helping out an ignorant newbie such as myself!

KPierson 
Platinum - Posts: 3,527
Platinum spaceThis member consistently provides reliable informationspace
Joined: April 14, 2005
Location: Ohio, United States
Posted: March 03, 2011 at 3:54 PM / IP Logged  
I always get a prototype circuit board and solder them to that - that gives you a little more meet to solder. They should have proto boards where you buy the reed relay. I have never seen one in a socket, but that doesn't meant they don't exist.
Kevin Pierson
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: March 04, 2011 at 4:32 AM / IP Logged  
Have you dioded across the coil of the relay?
the_rusty_gear 
Member - Posts: 5
Member spacespace
Joined: March 02, 2011
Location: Alberta, Canada
Posted: March 04, 2011 at 4:28 PM / IP Logged  

howie ll wrote:
Have you dioded across the coil of the relay?

No I haven't - Should I have? How would a diode affect the relay? I thought a diode only helped for deenergizing the coil?

howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: March 04, 2011 at 4:45 PM / IP Logged  
Please humour me, try it and let me know. 1N4004, band side to either 85 or 86 whichever is at the voltage rather than ground.
the_rusty_gear 
Member - Posts: 5
Member spacespace
Joined: March 02, 2011
Location: Alberta, Canada
Posted: March 04, 2011 at 5:16 PM / IP Logged  

Thanks and will do! I should have some time to try this over the weekend. I'll report back Monday!

<5 posts vs >6000 means "humour" the expert! relay buzzes while energizing -- posted image. 

the_rusty_gear 
Member - Posts: 5
Member spacespace
Joined: March 02, 2011
Location: Alberta, Canada
Posted: March 05, 2011 at 11:27 PM / IP Logged  

Well, here are the results!

The place where I bought the relay was out of 1N4004 Diodes, so I went with the 1N4007 ones (I assumed a higher voltage rating could only be better?) I ran the diode across the coil, and it did not cure everything, but it somewhat improved the noise, especially on denergizing. It still took a while to activate and had quite an audible (from outside the vehicle too) buzz.  Pulling magical nubers out of the air, I'd say the energizing noise / delay was improved by 30% whereas the de-engergizing was probaly 50% quieter and faster. (still a quick buzz and not the "click" you would expect)

So, with that part of the experiment out of the way, I proceeded to cut up a prototpye PCB, solder a Reed Relay to it, and attached the appropriate wires. Worked like a charm! Now I have practically silent switching. Thanks for the advice howie II and KPierson. If you ever find yourselves in Edmonton, I owe you a drink!

howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: March 06, 2011 at 2:52 AM / IP Logged  
Glad you got a good result.
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