Relay delay circuit?

Something simple like this should work. R1 C1 would be your time constant. A current limit resistor in series with D1 should be added depending upon the drive. |--------->

12vdc>--+--|R1|-----+--|R2|---|

Needs a resistor in parallel with C1 to insure discharge. Without the resistor, the circuit depends on discharge through D1 and the supply - but the +12 may be connected to the circuit via a switch. Open the switch and +12 is disconnected, along with the discharge path through the supply.

Ed

If the input goes to an open circuit, D1 won't do anything at all. For a more robust circuit, I would add a driver transistor to the input. This will invert the polarity; so, you need a pull-up resistor from its base to +12 (or +5) , and supply ground to the input to operate the relay. Also, the threshold is not well controlled. I would put a 6V Zener in series with the source of the FET, and use the drain current to operate a PNP transistor to actually switch the relay. The PNP should have about a 330 Ohm resistor from base to emitter to ensure the FET and Zener are drawing current before operating the relay.

Tam

You will be better off using a delay-on-make solid state relay (DOM SSR) to do the timing and switching, a sealed unit with push-on connectors. Just fit it into your existing set-up like so: View in a fixed-width font such as Courier.

. . . . . . . . .-------------------------. . | | . | .----------------. | . | | | | . | | | | . | | +----------+ | | . +----------+--|----|--|+ ~|--+------o o----mains . | | | | | | | / . +-----+ - o | | | - o----->

. |solar| DOM|\| |< | | | 240|\| . |panel| SSR|\| | | | inverter | VAC|\| LOAD . |+batt| |\| o-- | | RLY|\| . +-----+ - | | - o----->

. | | | | | \ . +----------+----------|- ~|------+--o o-----mains . +----------+ . .

switch off immediately the 12VDC goes off. What's the best way to do this? If you need to know why I want this, see the paragraph below:

output and the mains supply. Currently I have a relay with a 240VAC coil which does the switching based on the output of the invertor. It doesn't work too good - the invertor output falls a bit as the battery gets low, and the relay starts jumping back and forth. What I would prefer is to use the 12V signal from the solar regulator (which is on whenever the battery is ok (and is what switches the invertor on). However I need to wait at least 1 second before moving the load to the invertor, as the invertor takes a while to start up.

--
Is the 12V signal from the regulator a separate signal which is used
to turn the inverter on or off depending on the state of the
batteries, or is it the 12VDC which feeds the inverter?

--
Unfortunately, that won't solve the 240 volt relay chatter problem.

This should:
                                                    
                                                      
.                                                  
.                            +----------+          
.      +----------+----------|+        ~|---------o  o----mains
.      |          |          |          |           /
.   +-----+       -          |          |          o----->
.   |solar|   DOM|\|         |          |          
.   |panel|   SSR|\|         | inverter |              LOAD
.   |+batt|      |\|         |          |        
.   +-----+       -          |          |          o----->
.      |          |          |          |           \
.      +----------+----------|-        ~|---------o  o-----mains
.                            +----------+
.

There is some question as to whether he's turning the inverter on
and off with the 12V source or whether there's a separate 12V signal
being used to do that, which could also impact the scheme.

switch off immediately the 12VDC goes off. What's the best way to do this? If you need to know why I want this, see the paragraph below:

output and the mains supply. Currently I have a relay with a 240VAC coil which does the switching based on the output of the invertor. It doesn't work too good - the invertor output falls a bit as the battery gets low, and the relay starts jumping back and forth. What I would prefer is to use the 12V signal from the solar regulator (which is on whenever the battery is ok (and is what switches the invertor on). However I need to wait at least 1 second before moving the load to the invertor, as the invertor takes a while to start up.

It's some kind of UVP signal for the inverter from the battery monitor. I suspect his problem is that his load runs the battery down, causing the 240VAC to drop out, then the inverter gets off-loaded, causing the battery output to come back up to run the inverter unloaded, causing the

240VAC relay to pull back in - then battery output falls, everything drops out- ad nauseum repeat. As usual, the OP doesn't know what he needs...the signal he has in mind will not work for him.

The problem is not relay chatter- the AC relays especially have huge hysteresis. His problem is the highly non-linear output impedance increase of the battery as it is discharged under heavy load. The off-loaded battery voltage turns the inverter back on. He needs a fuel gauge type battery monitor that accounts for re-charge through the solar panel, and that is way over his head. Take a shot at if you want:-)

switch off immediately the 12VDC goes off. What's the best way to do this? If you need to know why I want this, see the paragraph below:

output and the mains supply. Currently I have a relay with a 240VAC coil which does the switching based on the output of the invertor. It doesn't work too good - the invertor output falls a bit as the battery gets low, and the relay starts jumping back and forth. What I would prefer is to use the 12V signal from the solar regulator (which is on whenever the battery is ok (and is what switches the invertor on). However I need to wait at least 1 second before moving the load to the invertor, as the invertor takes a while to start up.

If I knew what I needed I wouldn't be asking would I?? Not sure what you mean by "as usual" either - I've only been in here twice in the last year.

The problem is the relay I currently have takes the 240V from the invertor output to trigger it, but this tends to fall slightly as the battery gets low, so the relay stutters. If I had a relay driven off the 12V signal instead there wouldn't be this problem.

--
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A farmer drives his tractor away from the homestead when half a mile later his
brake cable snaps.
He sees his wife on the porch and manages to catch her attention but is unable
to make her hear what he is shouting.
However, he thinks she should understand what he wants if he uses sign language.
So he raises his hand above his head and starts to operate an imaginary pair of
pliers, then opens and shuts an imaginary cupboard door and then puts the tips
of his fingers together to indicate a shed roof.
His wife waves to him and then grasps both her breasts, then grabs her crotch
and lastly lifts both her buttocks.
"Stupid woman", he mutters to himself. "Hasn't understood a thing".  So he
repeats his signals, but gets the same response.
Exasperated, he walks back to the homestead ready to berate his wife.  "Didn't
you understand  a damn thing?' he asks.
"Yes", she says, "you wanted a pair of pliers from the cupboard in the shed. But
what I was telling you was that there is a pair in the toolbox under the seat."

switch off immediately the 12VDC goes off. What's the best way to do this? If you need to know why I want this, see the paragraph below:

output and the mains supply. Currently I have a relay with a 240VAC coil which does the switching based on the output of the invertor. It doesn't work too good - the invertor output falls a bit as the battery gets low, and the relay starts jumping back and forth. What I would prefer is to use the 12V signal from the solar regulator (which is on whenever the battery is ok (and is what switches the invertor on). However I need to wait at least 1 second before moving the load to the invertor, as the invertor takes a while to start up.

It's a signal from the regulator which switches on the invertor.

--
http://www.petersparrots.com    http://www.insanevideoclips.com   
http://www.petersphotos.com

An infantry brigade was training in the summer heat, learning
methods to counter Soviet offensive tactics.  That summer, the
area had experienced an infestation of rattlesnakes.  Officers
and NCOs were given one magazine of live ammunition to counter
this danger, as several men had already been bitten.

So much ammunition was expended shooting, supposedly, at
snakes that the post commander demanded that  every officer
and NCO who had shot at a snake present the dead snake as
proof that the expenditure of rounds was justifiable.

The next day, the post commander entered his office and spotted
a shoe box on his desk.  He opened it, revealing a sleepy and
sluggish, but very live, rattlesnake.  Inside the box were twenty
expended cartridges, and a short note.  The note said, "I missed!"

Peter Hucker wrote: > On Sun, 06 May 2007 15:25:25 +0100, Fred Bloggs > wrote: >

Don't take it personally, I am only referring to you as a generic entity.

I don't think so. Almost any AC relay pulls in at 70% and holds until

10% before dropout, so your assumptions are baseless unless you have the specifications sheet for the relay that says otherwise. The relay drops out because that 12V battery control signal to the inverter drops out and shuts it off entirely, this is my guess.

That's what I said, essentially. But it doesn't matter what D1 does, the problem is that C1 can't discharge through either D1 or R1 when the input circuit is opened. Also, discharging through the supply is not the best idea.

Ed

I think that sounds better....

The invertor is running properly and continuing to power the load. The invertor does start bleeping around that point to indicate a low battery, but is supposed to cut out if it's too low. My guess is the "240V" output is nothing like what it's supposed to be at that point.

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http://www.petersphotos.com

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