Capacitive Coupling ???...

[SG-1]

Form A contacts are NO.
Form B contacts are NC.

You can effect a SPDT by using one of each and making one terminal from each common. Typical such arrangement would be, but not always, "beak before make"?which would be ideal.

Is the "operator" two contact capable?

If I have enough spares I can build a form "c". The contacts are all open together for less than 3 cycles.
Also there are two MOC switches from two breakers controlling the timer. I think you are suggesting grounding the wire when the contact changes. Through a resistor ?

Why not just place a pulldown resistor on the input of the timer ? I like what you are suggesting it is just a little more complicated to wire in at this point.

 

[Smart $]

...

If I suddenly turned the voltage down. It would stay latched right down to zero. It takes a very specific rate of decay, but I found it after a few tries. It is very repeatable. I am using a 3 volt bell to detect the change in contacts.

It's an off delay relay. :roll::roll::roll:

What delay is it set at? From your pic' it has a range of 0.1 to 10 sec. If it don't time out (contacts change state) per setting, the relay is bad.

 

[Smart $]

If I have enough spares I can build a form "c". The contacts are all open together for less than 3 cycles.
Also there are two MOC switches from two breakers controlling the timer. I think you are suggesting grounding the wire when the contact changes. Through a resistor ?

Why not just place a pulldown resistor on the input of the timer ? I like what you are suggesting it is just a little more complicated to wire in at this point.

Well, it was a suggestion more when I thought the relay had a trigger input, but it should also suffice for the "power removal" type. The main reason for suggesting it is snubber (R or RC) has to sink full power, also. If sinking is done with contact switching, the snubbing circuit (direct, R or RC) only has to handle "floating" power. Yes, complexity may very well be the deciding factor...

 

[SG-1]

I have it set to minimum .1 second.

It will not change if I drop the voltage at a specific rate I am waiting plenty long.

Could be bad.

I have a second one. It will do the same. Just tried it.

I have one with a 1 to 60 sec. delay which I cannot make malfunction.

 

[SG-1]

Here is a picture of part of the circuit. 6ST is the timers name. Wire TA is the 120VAC signal.

 

[Smart $]

I have it set to minimum .1 second.

It will not change if I drop the voltage at a specific rate I am waiting plenty long.

Could be bad.

I have a second one. It will do the same. Just tried it.

I have one with a 1 to 60 sec. delay which I cannot make malfunction.

Well the whole idea I imagine is to have it work in the circuit as designed... and I can't see you adding a "voltage ramper" to the circuit. If the relay don't function properly on instant power removal (as in contact switching time) on the bench, without the wiring reactive voltage, then it's no good to you. Look into using a different (make/)model relay. There may well be a reason the 388 series has been discontinued

 

[SG-1]

Well the whole idea I imagine is to have it work in the circuit as designed... and I can't see you adding a "voltage ramper" to the circuit. If the relay don't function properly on instant power removal (as in contact switching time) on the bench, without the wiring reactive voltage, then it's no good to you. Look into using a different (make/)model relay. There may well be a reason the 388 series has been discontinued

What do you mean discontinued :grin: :grin: :grin:

The customer specified these. We have used them for other circuits in the past for them, but not on the grand-daddy of all their schemes.

 

[gar]

100314-1747 EST

SG:

This model time delay relay apparently uses a magnetically held bi-stable relay. Could be two coils, a set and a reset, or one coil with reverse polarity to change state. Thus, after AC power is removed the relay will remain in its last state even though no power exists to keep it closed.

Combined with this bi-stable relay is electronic circuitry with energy storage, a capacitor or maybe a battery, timing circuitry, and a device triggered at the end of the time delay to dump energy into an reset coil (maybe polarity into one coil) to return the latched relay to its normal residual state.

This means this relay can provide off delay even when no power is available. This is equivalent to the old pneumatic time delay relays.

If a capacitor is used as the energy storage device, then slowly lowering the input voltage may lower this voltage to the point that when power is removed from A and B that there is not enough energy to reset the latched relay.

Smart $:

SG's time delay relay can be found at the bottom of the page 4-17. This printed copy catalog just copied and put on-line is very confusing. Maybe it would be in paper format as well.

.

 

[Smart $]

Smart $:

SG's time delay relay can be found at the bottom of the page 4-17. This printed copy catalog just copied and put on-line is very confusing. Maybe it would be in paper format as well.

.

gar:

Yeh I found it. Note the picture of the relay on that page that I attached above. But the catalogue you linked to above is from the library archives. It is an older catalog and it appears they no longer manufacture any 388 series relays.

Just go to their website and try to find info of any type for any [current] 388 series relay if you don't believe me: http://magnecraft.com/time_delay_sensor_relays.php to start...

I'm not saying you can't buy one new. There may well be a whole shi-i-i-i-bang load stockpiled somewhere.

 

[SG-1]

gar:

Yeh I found it. Note the picture of the relay on that page that I attached above. But the catalogue you linked to above is from the library archives. It is an older catalog and it appears they no longer manufacture any 388 series relays.

Just go to their website and try to find info of any type for any [current] 388 series relay if you don't believe me: http://magnecraft.com/time_delay_sensor_relays.php to start...

I'm not saying you can't buy one new. There may well be a whole shi-i-i-i-bang load stockpiled somewhere.

I have a suggestion for the stockpile, but I would be banned from the forum.

I will run this by engineering. No replacements in the near future.

 

[SG-1]

100314-1747 EST

This means this relay can provide off delay even when no power is available. This is equivalent to the old pneumatic time delay relays.
.

Yep, that is what they are trying to replace. Try,try again ?

 

[SG-1]

Just so you can get a feel for the complexity of this application here is a picture of the main AC controls. For some reason the exciter circuit is in another unit on another barrier, guess they could not pack it on this one.

 

[gar]

100314-1933 EST

SG:

What kind of delay and what accuracy do you require?

.

 

[ELA]

100314-1628 EST

ELA:

I think I see where my confusion was. I do not see the full picture on the screen as I would on a piece of paper.

If you look at SG's part number W388ACPSRX-30 and I originally found this on page 4-17. If you go to this page it is classified as a true off-delay timer, and has only one circuit drawing on p 4-17. This unit has no control input. So I am back to my original analysis that energy is stored to use to unlatch the magnetically latched relay.

This relay should drop out after its time delay following the trailing edge of the AC applied to terminals A and B. Probably this needs to be a somewhat abrupt turn off. But there seems to be a problem from what SG said about abrupt reduction of input voltage.

.

Gar,
This is a very confusing data sheet indeed. The wiring diagram in the picture of the actual device on 4-17 does not agree with the separate wiring diagram?

Since SG-1 indicates there is no terminal #8 then I am unsure what to think. Looks like it was my miss understanding? , sorry.

 

[SG-1]

100314-1933 EST

SG:

What kind of delay and what accuracy do you require?

.

Good question, I think this is a case of a bean counter trying to cut cost. They have been using Agastat ( finally spelled it right ) for nearly 30 years that I know of. You can buy 4 of the Magnacraft for the price of one Agastat.

1-15min TDPU
.6-60 sec TDDO
.1-10sec TDDO
1-180sec TDPU

I would think the published accuracy of the Agastat pneumatic.

 

[gar]

100315-0721 EST

SG-1:

If you require the long timing ranges indicated, then it is hard to consider a unit that does not use a mechanically bistable relay.

Other than this problem from leakage current is the Magnacraft relay satisfactory?

If so, then just use one of the two means discussed above to solve the problem. These are a continuous shunt impedance, or a SPDT contact that forces a low impedance to the time delay relay input when the control signal is logically 0.

.

 

[Smart $]

changed my mind ???

 

[Smart $]

100315-0721 EST

SG-1:

If you require the long timing ranges indicated, then it is hard to consider a unit that does not use a mechanically bistable relay.

Other than this problem from leakage current is the Magnacraft relay satisfactory?

If so, then just use one of the two means discussed above to solve the problem. These are a continuous shunt impedance, or a SPDT contact that forces a low impedance to the time delay relay input when the control signal is logically 0.

.

I agree with you with the exception his bench tests seemed to prove the Magnecraft relay specified is unreliable for the design criteria.

 

[gar]

100315-0807 EST

Smart $:

I am not clear on what was his bench test.

Without doing any calculations I believe I could use a GE RR series relay, a several thousand mfd capacitor at 30 V DC, some electronics, and be able to work to a limit of 15 minutes.

GE RR relays are a mechanical snap blade bi-stable relay.

.

 

[ELA]

SG-1
Any reason you cannot use the non-"true" off delay model that I was thinking you might be using earlier?
Applying a constant voltage to terminals A & B and your control switch between A & 8?
Of course I am not sure if it would work any better until you tried it.

Your bench test results confused me a little bit. Do you no longer feel that either yours or Gar's suggested shunt drain resistor would work?

It sounds like the induced voltage causes the internal energy storage circuit to retain enough charge such that the timer circuit never times out?