relay problem

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hello friends,

I am doing a project for automatic light control.i am using mechanical relays to switching the 230v ac bulb,i used 8 relays to switch 8 bulbs...the relays are operated using ULN2803 relay driver..my problem is that, when i switch any one bulb to off the other bulbs also going for a slight blinking..other bulbs also go for off for a slight time...just a small blink.. how can i avoid this? please help me friends.. i hope your replays.thank you very much

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Are you using the internal diodes for the relay coil suppression without separate diodes on the relays? If so, that could be the issue. Same thing happened to me in the 70's. My relays were far from my driver and I saw this issue. (Far being around 3 inches.) Try separate diodes on the relays in addition to the internal diodes.

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jaydhall wrote:

Are you using the internal diodes for the relay coil suppression without separate diodes on the relays? If so, that could be the issue. Same thing happened to me in the 70's. My relays were far from my driver and I saw this issue. (Far being around 3 inches.) Try separate diodes on the relays in addition to the internal diodes.

 

ohh yes yes .. you mean the diode connected to the coil to avoid back emf..i forgot to give it.... i will add it and test it again.. thanks for your support my friend

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There is a COM pin on the ULN2803 that should be connected to the V+ rail of your relays.  THat works as the back EMF diode for your outputs.

 

Post a schematic of your circuit, and a picture too if possible.

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

Last Edited: Tue. Jun 7, 2016 - 12:04 PM
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hello friends,

 i did the above thing now the blinking is not here its fine but here generated another issue that the logic is going wrong when switching relay..when switch of first bulb may be other bulbs too going to off..give me a suggestion to over come this ... please... thank you very much

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Can the power supply provide enough current for the load?

Imagecraft compiler user

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thank you my all friends for your helping mentality.. thanks for your help.. now its working....i gace com to vcc as mentioned above and now its working fine.. thank you very much

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What on earth is ".i gace com to vcc" supposed to mean?

Ross McKenzie ValuSoft Melbourne Australia

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I think he means " I connected COM to Vcc"  If he is using a 'smart phone" or tablet the Auto correct has a nasty habit of changing things it thinks looks correct....with often poor results.  It happens to me a lot on my android when I reply to emails in tech terms.

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Ahhh... I think he wanted to type "I gave com to vcc".... but the "v" is next door to the "c"... a simple typo that auto correct is not responsible for.

Ross McKenzie ValuSoft Melbourne Australia

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valusoft wrote:
a simple typo that auto correct is not responsible for.

I think you need to go work on that tree some more wink

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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valusoft wrote:

What on earth is ".i gace com to vcc" supposed to mean?

ohh sorry sir..sorry for the mistake and sorry for th late reply..I meant i gave com( common pin of uln 2803) to vcc .

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Buy relays, or relay sockets that have the diode build in, then the diode is placed close to the coil. 

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sparrow2 wrote:

Buy relays, or relay sockets that have the diode build in, then the diode is placed close to the coil. 

thank you sir.. thanks for your valuable suggestion