[SOLVED] my 6vdc Relay not giving output voltage.

[omkardespande]

In my project, I have connected 6vdc relay to to pic16f877a through uln2003. I am driving 5v smps fan according to some condition. Now when that particular condition is met, a mechanical sound (of pole switching) comes, but there is no voltage at relay output. Means fan does not get on. When that condition becomes false, again mechanical sound comes.

I have attached the schematic. i wanted to know whether my connection is wrong or relay itself is malfunctioning. Please help.

 

[barry]

do you have anything connected to terminals X1-1,2, etc? I don't see anything on your schematic that would indicate that you do.

 

[omkardespande]

do you have anything connected to terminals X1-1,2, etc? I don't see anything on your schematic that would indicate that you do.

x2, x1-1 => NC of relay
x2, X1-2 => Pole of relay
x2, X1-3 => NO of relay

but after schematic i realized NC connection should be left open. So I have connected my fan to only x1-2 & x1-3. I am attaching eagle schematic file for your reference in case pdf is not clear.View attachment schm.zip

 

[barry]

So, if all you've got connected to x1-2 and x1-3 is the fan, then all you are doing is shorting and unshorting a contact across the fan!!!!

 

[omkardespande]

So, if all you've got connected to x1-2 and x1-3 is the fan, then all you are doing is shorting and unshorting a contact across the fan!!!!

Yes exactly. pole of x1-2 gets connected to x1-3 when the condition is true(coil is energized). If it is false, pole again gets detached from x1-3. Is it right connection ? If not, what should be right connection ?

 

[betwixt]

The connection you want to make is between 'P' and 'O'. It is more usual to call these 'common' and 'NO' (Normally Open). These are the pins that short together when the relay energizes so they should be in series with your fan.

Brian.

 

[barry]

Don't you think you might need some power for your fan? Connect X1-2 to your voltage (VDD, if that's appropriate for your fan), X1-3 to one side the fan, and the other side of the fan to common.

 

[omkardespande]

Don't you think you might need some power for your fan? Connect X1-2 to your voltage (VDD, if that's appropriate for your fan), X1-3 to one side the fan, and the other side of the fan to common.

Oh shit...how foolish I am.

Anyways.. after i corrected my connections, still I am not get my fan switched on/off. The voltage I measured across fan (after relay activation ) was just 2V to 2.5V. It should be 5V. Is m relay ok? Or need to change it?

 

[barry]

it's pretty unlikely that you are dropping 3 volts across your relay contacts. Maybe your power supply can't handle the fan; or the fan is wired backwards.

 

[nick703]

if relay is trigger then relay is OK .