Relay ttl 5vdc coil problem

Hi, I use wc32 board for a specific project. There are 4 x 5vdc relay attached to the wc32. The problem is that 2 relays stay activated when i hit ''turn off'' on the webpage. This is not the wc32 since when I hit turn off, the led on the relay turn off then I know that the output pin is low.
 
So I replace 2 relays for brand new but it's still the same. Each relay's contacts can support 10A @ 125vac. I only use 3.5 A @ 122vac. What should I do? Is it wise to replace those 5vdc relay to 12vdc or stronger? 
 
 
When a relay is locked to ''activate'' I need to hit the coil with a screwdriver to unlock it. :wacko:
 
 
Thank you for your suggestion.

Interesting problem. It could be a physical problem with the relay or a digital threshold problem with the relay board/WC.
 
What I would do when you have a stuck relay ist to disconnect that output from the WC but leave everything else connected.
 
1) If the relay drops out the board does not like the WC outputs. In that case an easy fix is to use a transistor or gate (like a 7407) between the WC and board.
 
2) If the relay does not drop out the load is probably too high for the relay. Assuming this is a cheap Chinese relay board I take power ratings with a grain of salt.
 
/tom

Since you have to hit the relay to get it to deactivate, it sounds like the contacts are welding shut.  Despite the 10A rating on the contacts, it appears that they can't handle the load.

RAL said:

Since you have to hit the relay to get it to deactivate, it sounds like the contacts are welding shut.  Despite the 10A rating on the contacts, it appears that they can't handle the load.

Click to expand...

 
 
This is the first thing I though. But how to solved the problem? Bigger coil, 12vdc 24vdc ... Something stronger than micro welding on the contacts
 
 
 
The load :
 
 5 x 80w fluo tube light. So it equal to 400W. Maybe there is a spike that make pins weld together.

Tschmidt said:

Interesting problem. It could be a physical problem with the relay or a digital threshold problem with the relay board/WC.
 
What I would do when you have a stuck relay ist to disconnect that output from the WC but leave everything else connected.
 
1) If the relay drops out the board does not like the WC outputs. In that case an easy fix is to use a transistor or gate (like a 7407) between the WC and board.
 
2) If the relay does not drop out the load is probably too high for the relay. Assuming this is a cheap Chinese relay board I take power ratings with a grain of salt.
 
/tom

Click to expand...

 
 
I already replaced the board!

Three things can cause this.
- residual current leaking from the drivers holding the coil on once energised.

- burnt contacts which should be visible. We always found new relays seemed to have an oily coating on the contacts which burns with the first few current breaks and then turns into a gummy substance sticking the contacts together. Your contacts sound rated sufficiently for your load and AC is being used. DC tends to weld contacts more and contacts are typically rated a lot less voltage and current for DC usage..

- pole struck relay armature. This can happen using AC coil relay construction with DC voltage. DC relays typically have a copper or soft non-ferrous metal plate where the laminations meet between the moving armature and the laminations with the coil on it. If it doesn't the release can be a problem where the laminations get permanently magnetised slightly and/or the magnetic loop has no weak link and just won't collapse.

The softer armature metal can also get formed to stick in between the lamination ends and will not let go without some physical abuse.

This usually just indicates poor quality relays, or possibly labelled incorrectly for sales purposes.

BTCAD said:

I already replaced the board!

Click to expand...

That really does not prove very much. You still need to determine if root case is drive problem between relay board and WC or a stuck relay. It takes less energy to keep a relay energized then to hold it in state.  However given you have swapped out the board it points to a stuck relay. But if it were my project I’d do more testing.
 
As I’ve mentioned some of these cheap imports get creative with specs and regulatory approvals. If it is the relay you need to use a better relay. For electronic control projects I generally like to use SSR (solid state relays) rather than EMR (electro mechanical relays).
 
/tom

okay, i opened a ''broken'' relay and it sounds like contacts weld togheter. I can see 2 littles spot of welding.
 
Can you suggest me better relay. 10A for this application is enough but i'm looking to drain more power such as 12a @ 125vac. So 20A or 15A should prefered. 
 
 
Let me know guys, and thank you for your support!

BTCAD said:

This is the first thing I though. But how to solved the problem? Bigger coil, 12vdc 24vdc ... Something stronger than micro welding on the contacts
 
 
 
The load :
 
 5 x 80w fluo tube light. So it equal to 400W. Maybe there is a spike that make pins weld together.

Click to expand...

 
 
Fluorescent light fixtures can draw significant current during initial start up, depending on the type of fixture and the ballast it uses.  So it's possible that you are exceeding the 10A rating of the relay contacts for a short period when they switch on.
 
Are you using the WC32 output to drive the relay coil directly?  Or are you using the WC32 to drive a control input to a relay board that has a separate power input?

I use wc32 output to drive relay coil.

In general, I don't like to drive relay coils directly from a TTL output.  The back EMF generated by the relay when the TTL output shuts off can damage the output.  At the very least, you should put a diode across the relay coil, with the cathode connected to +V,  to protect the TTL output. 
 
Depending on the situation, my preference is to use a SSR or a relay board with a TTL control input.
 
In this case, I agree with LarryILix's suggestion... go with a SSR rather than a mechanical relay.  Get one with at least a 240V/20A rating and you should have enough margin.   Something like this one looks like it would do just fine.

In this case, I agree with LarryILix's suggestion... go with a SSR rather than a mechanical relay.

Click to expand...

It was Tom that suggested the SSR.

People using ISY HA systems are happy with this one. Just use your WEBSET commands and no wiring required.


http://www.digital-loggers.com/din.html


FINALLY! Quoting and pasting here is finally working!!!!!

LarrylLix said:

FINALLY! Quoting and pasting here is finally working!!!!!

Click to expand...

 
But your link doesn't seem to work... it goes to cocoontech.com/din.html  

Maybe this one: http://www.digital-loggers.com/din.html

If the relay can be driven by TTL output, it must be a tiny one, since TTL output from WC board is only 10mA, larger current could cause TTL output gate IC overheat. 
 
Small relay has a few different kinds, one kind can turn on by one direction current, then requiring reverse voltage to turn it off. Hope the relay being used is not that kind.
 
There is a discussion thread about relay in this sub forum. Those relay boards have transistor drivers, and they are very reliable.  You maybe also consider those relay boards.