Reliable board with described functions?

Discussion in 'The Projects Forum' started by steward, Jan 21, 2011.

  1. steward

    Thread Starter Active Member

    Jan 21, 2011
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    I have a need to build a reliable Printed Circuit Board that can do the following:

    It would be powered by 24 VAC & have 12 latched on 24 VAC outputs that are turned on & off with 13 momentary switches. 13 synchronized outputs for LEDs are also needed. The 13th LED would show its off position --- & would be the default position --- if the PCB was only powered on & not made switchables with the following input.

    The momentary switches other than off would only work if there was continuity created by an external 24 VAC timer that was acting as a continuous timed 24 VAC input to the proposed PCB. This would not be the power supply for the PCB. It would be from the same 24 VAC source though.

    What triacs to handle the 24 VAC switching would someone more experienced recommend? Also any fresh approaches for the best way to come up with the 13 synchronized LED outputs within the circuit?

    Mike
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    You are asking a lot and not giving sufficient detail.

    Post a schematic or pictures of the circuit you are trying to describe.

    Are you sure you want to use triacs for 24VAC switching. A relay set would do everything you are asking, and need very little switching logic.

    We need more info to give you any advice that would be worth having.
     
  3. wayneh

    Expert

    Sep 9, 2010
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    You'll need to also specify how much current each "channel" needs to supply, and whether they are all drawing power from the same supply.
     
  4. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Thanks Kermit2 for responding,

    Hopefully, down the road I will be able to post a schematic, actual physical layout & pictures of the work in progress. At this point hopefully, the description of the fairly simple circuit will be good enough to put together a starting point of components before I commit to the schematic. At this point I am stating what needs to be accomplished by the circuit --- if you will.

    It seems like 13 of the below IDEC Latching relays mounted on an 8 Inch din rail (or 2 rows of din) mounted could make the proposed distribution board work with 13 momentary switches. Because they are double pole - double throw (DPDT) I could use the second pole to switch lower volts & milliamps to LEDs to show a specific "on-latched" position. The problem is that we would still need some way to get a 24VAC pulse to the on relay's coil to shut it off simultaneously as another momentary switch is pushed. I guess the end user could accidently push a button twice real quick & that could also be an issue too. You mention switching logic --- does anyone have a suggestion to keep it as simple as possible to accomplish what we need to do? It would require some maintaining of logic in such a way only one relay would be latched at a time & that would be the last one latched & not the pulse that switched it in reverse. Below would be the described relay.

    http://www.precisionelectronics.net/productdetails.asp?ID=4254

    Wayneh,

    Also thanks for weighing in a bit.

    On my initial post, I did try to explain that the latching switches would be 24 VAC latched on & off & that the common power supply 24 VAC would be for everything. There is a source that I could come up with the DC voltage that might be the cheapest for the possible $1.99 Radio Shack 12 volt LED complete with its holders etc. as an alternative to more conventional lower voltage LEDs. That DC source would be as follows:

    http://www.directron.com/dvcpc24vc.html?gsear=1

    So you see --- I am trying to avoid as much printed circuit board circuitry as possible but it appears that some logic on a PCB with the best fit connectors & color coded wire leads like Kermit2 suggests will be necessary.

    If nothing else --- hopefully this post will lead to a discussion of when & why a more sophisticated solid state circuit than what I describe would be wise. Long term reliability could tip the scale for --- everything except for the momentary switches to be on a PCB --- addressing the switching & LED need that I described. So any & all input suggestions at this earliest stage of development --- even though might seem worthless will be appreciated. It would be nice to see some real pros in action.

    Thanks again for the patience!

    Mike
     
  5. Kermit2

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    Feb 5, 2010
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    http://stevenengineering.com/pdf/24rlyry2ks.PDF


    According to the data sheet it has TWO coils; a set and reset coil.

    This will make it easier to perform the 'one active relay at a time' req. you stated.

    Have you tried to make any diagrams of how you want it layed out?
     
  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    The pushbutton switching function you described is often referred to a "radio buttons". Outside of ganged mechanical switches or microcontrollers, I've never seen a "simple" way to do this. The two-coil relays might be the key though.

    Does anyone know: if both coils are powered simultaneously and the power is removed from the Reset coil first, then removed from the Set coil, will the relay always go to the Set state?

    Ken
     
    Last edited: Jan 22, 2011
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    What exactly does this 'external' 24VAC timer do for your circuit? What function does it perform in the operation, or what does it prevent from happening?

    Could the external signal be something other than an AC voltage?
     
  8. wayneh

    Expert

    Sep 9, 2010
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    That's fine but you still haven't specified the CURRENT that you will be switching. Voltage is just one piece of the puzzle, current is another. You're not just turning on an LED are you? What load are you turning on and off?
     
  9. KMoffett

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    OK, I'm going to take a shot...using my previous assumption about activating both coils at once and deactivating one at a time. Also, that the DPDT push buttons will handle the coil current. And, that you have 12DCV for the control circuit. The second set of relay contacts are used to switch whatever 24VAC circuit is attached.

    Somewhat simple:

    DX, RX, CX, DRX, RLYX and SWX form monostable multivibrators. When SWOff is pressed, it activates the PMOSFET that pulls all of the capacitors, CX, to +12V through DX. Because they're discharged, the RLYX's Reset coils are activated. When the capacitors charge, the coils loose their voltage and all of the relays are left in a reset state. When SWoff's button is lifted the capacitors discaharge through RX and DRX. DRX keeps the Reset coils from being activated by the discharge current. If any switch, SW1 through SW12, is pushed all the relays are reset. But, the selected switch also activates the Set coil on it's relay. Because the relays' Resets have quickly come and gone, the Set state on that relay will be left when the switch button is lifted.

    If my assumption is wrong.....ignore all of the above. ;)

    Ken
     
  10. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Ken & others,

    I am putting together a schematic that will hopefully help. If I could find some smaller double coil latching 24 VAC relays it would be nice --- I have not had a chance to check yet. The 24 VAC output would just power small 11 watt solenoids & I motor starter coils etc which I believe tend to be about 11 watts also. I suppose it would be wise to make sure the relays are the best approach though. The circuit will be on 24/7 but I believe during the latching there is no energy consumption --- I am not sure. It would be great to compare the considerations of the various approaches.

    Thanks --- the responses have been great so far!

    Mike
     
  11. KMoffett

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    Mike,

    There are lots of small, 2-coil latching relays that will handle your spec'd 24VAC loads. Where are you? It helps in locating an acceptable vendor.

    Ken
     
  12. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Ken & others,

    I apologize for not having a schematic at this point in time ---- you may have to allow extra time & until I get caught up on some other unrelated work that I need to get done. I did study Ken's schematic using the capacitors to take care of the logic. I live in North Dakota so I do have one day shipping from DigiKey & 2 days from Minneapolis & 3 days from Mouser. The schematic I am working on ---- I am adding a small diode branching out from each LED so one dedicated relay will reset the rest of the relays but still allow the most recently pushed MOM SWT to be the only specific relay that can stay on. There is still over 10 VDC of voltage after the diode that I tested & that should be enough to not create a problem with the proposed dedicated standalone 12 VDC dual coil latching DPDT relay. On my schematic the rest of the relay coils are 24 VAC.

    Ken, can you specify the other specific relays besides the IDECs that would be suitable for the project --- I could set up & test a condensed or simplified version of the circuit to verify if the coils will reset in the order that you are concerned about. Maybe talking to the right person at IDEC could put the speculation to rest also. I have an industrial lab grade soldering station & can get a temporary breadboard from Radio Shack locally. I am not sure of every single specific part number of all the components you specified ---- but like I said --- Digikey is just one day ground shipping.

    Mike
     
  13. KMoffett

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  14. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Ken,

    Do you have a straightforward way to put your schematic in dwg format? If so, I could tweak that & share on the forum. Hopefully, the final schematic will be good enough for a experimental board to be made. Do you know of anyone in our region who might be willing to give me a quote on creating one fairly simple test board that we came up with. After looking at the less cost of your components --- I am kind of leaning towards not continuing with my schematic in which I was going to every length to avoid any printed circuit items at all & just putting 12 diodes inline via heat shrink encapsulation --- it seems like i might still need something that creates a delay --- plus by having the coils 12 VDC it makes it so we aren't just locked into the IDEC choice. Does your schematic thoroughly address the fact that only one 24 VAC output & one LED can be on at one time? I suppose the Radio Shack's LEDs with their built in milliamp current limiter are still the best choice without going to 5 VDC coils which might be less common than the 12 VDC coils. It seems like the relays could be socketed for quick replacement --- if ever needed.

    Mike
     
  15. KMoffett

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    Sorry, can't convert it to an editable DWG. If you go to ExpressPCB.com you can download a free copy of the schematic editor that I used. Their PCB editor will let you create (manually, not automatically) a board layout from a schematic. PM me your email address and I'll send you a copy of the schematic file that you can edit.
    Since I haven't tried this specific design I offer no guarantees. In my head it works. The big "if" is: if you power the SET coil and pulse the RESET coil will it maintain SET when the button is released. If I had the relays, I'd try it for you.

    Ken
     
  16. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Ken & others,

    It appears like I have not been on the forum long enough to be allowed PMs. Another way to send me an editable version of the schematic that you suggested would be through my business's website <snip>--- Some of my long term goals is to be able to actually animate the paths, actions & reactions within circuitry to make it less likely something is overlooked. With a pdf vector, dxf, or dwg file that would be easier it seems. Even in 2D that could be of value for certain mission critical projects.

    Since I am gradually getting more acquainted with the finer points of electronics vs expecting too much from just relays & PLCs ---- hopefully I will eventually become a senior member & contributing more as time goes by.

    Considering the low cost of the components --- hopefully, within a week or so I will have some test components either drop shipped to someone or to ourselves etc. to eliminate the big "if" you mentioned. It should work unless there is some timing technicality between the latching mechanism & both coils on at once for a moment that could work against us.

    It does not look like those specific relays can be socketed occording to their data sheet if I am reading it right ---- but socketing is usually another potential point of failure anyway so that should not make us fret too much. 15 x 7.5 mm is really tiny!

    Thanks --- the more I browse this website & its guidelines etc --- the more I am growing to appreciate the potential good from it.

    Mike
     
    Last edited by a moderator: Jan 27, 2011
  17. KMoffett

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    Dec 19, 2007
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    Mike,

    I sent it. Go back and edit your last post to remove the email address. Spy bots find these and spam recipients.

    If you would like I would be happy to breadboard the circuit.

    Ken
     
  18. KMoffett

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    Dec 19, 2007
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    Mike,

    I just wondered, did you turn on your PM access? Go to: User CP>Edit Options>Messaging & Notification>Private Messaging>[check] Enable Private Messaging.

    Ken
     
  19. steward

    Thread Starter Active Member

    Jan 21, 2011
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    Ken,

    On my specific nested screen --- this is what the hierarchy shows:
    User CP>Edit Options>Messaging & Notification>Messaging & Notification>Receive Email from Other Members> is now checked & saved. Hopefully that is the same as enable private messaging.

    On my specific nested screen ---- User CP>Edit Options>Messaging & Notification>Private Messaging>[check] Enable Private Messaging ---- does not show at all on the form.

    Thanks

    Mike
     
  20. KMoffett

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    Dec 19, 2007
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    3AM epiphany...good news and bad.

    The good news...Since the reset coils are always activated simultaneously, there is no need for 13 separate monostable circuits (DX, CX, RX). I was just sticking existing circuits together. All of the RESET coils can be paralleled. DR1-DR12 can be replaced with one diode. The PMOSFET (could be an NMOSFET arrangement) can be configured as a monostable, to trigger all the RESET coils.

    The bad news...If one button is pressed and released, only its relay will be activated. If two or more buttons are held down and released...all their associated relays will be activated.

    Back to the drawing board. (That's the downside of low bid, part-time, contract labor ;) )

    Ken
     
    Last edited: Jan 28, 2011
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