Design Interlock for two operations (Manual Switch and Automatic Switch)

Thread Starter

maitrey

Joined Sep 4, 2014
61
Hello,

I am in the process of designing an interlock for two operations.

1. Operated by Manual Switch
2. Remotely through an Automatic Switch (Can't be controlled Manually)

If user turns manual switch then operation should start. (In this case, if someone activates automatic switch it should do nothing!) May be add an Normally close block here?
And if automatic switch is active then this case manual switch interlock should be actived to avoid any malfunction in the overall circuit.

I tried to add some NO and NC blocks in the circuit but can not justify the overall design as the two wires (+2) and (+3) will be activated at some point. Can anyone please help me with this? Can I use specific relays or NO/NC contact blocks to design this?

Please see attached picture for circuit diagram. Unfortunately, I can not change the most of the wiring diagram as it's fixed at this point. Please advise.

Thank you in advance,
Maitrey Pandya
 

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crutschow

Joined Mar 14, 2008
25,451
How about just having the manual and automatic inputs each operate a DPDT relay.
The signals would then go through the opposite relay NC contacts.
Thus either circuit active will open the NC contacts and block the signals from the other.
 

Thread Starter

maitrey

Joined Sep 4, 2014
61
How about just having the manual and automatic inputs each operate a DPDT relay.
The signals would then go through the opposite relay NC contacts.
Thus either circuit active will open the NC contacts and block the signals from the other.
It may work. Let me see how can I implement this with current wiring. I will let you know the results. Thanks
 

Thread Starter

maitrey

Joined Sep 4, 2014
61
I have tried using DPDT relay but got confused in the second part. How do I connect signals through the opposite NC relay? I think I did it for 1st relay but if I do it for second relay then I get an error.
Please note that I only have 3 light bulbs in total. So, when both switches are active then it should avoid any malfunction. Please advise.

Please see attached..

Thanks,
Maitrey
 

Attachments

Reloadron

Joined Jan 15, 2015
5,646
Using two relays it would look a little like this:
Auto Man Off.png

Not the best rendition as the control switch would normally be an Auto - OFF - Manual with a center Off position. The idea is if I select Auto RY1 is energized through the NC (Normally Closed) contacts of RY 2 and with RY1 Energized RY 2 can't be energized because RY 1 NC contacts are now Open. RY1 and RY2 can be for example DPDT or 3PDT relays and the remaining contacts for whatever you wish to control.the coil voltages are whatever you wish. This is merely a rough drawing.

Ron
 

Thread Starter

maitrey

Joined Sep 4, 2014
61
Hi Ron,

Thanks for a response. The problem here is that Auto and Manual switches are different. Please see attached.

I have tried everything here, may be not! The manual switch is actually a 3-way switch COLD-OFF-HOT operation in the current design. Right now I am only designing remote cold start.

If I want to add remote start/stop for both COLD/HOT operation then I will need to provide 24 VDC to the (+2) and (+3) wires on the left side. Now what if someone turns the switch into cold position when the remote cold start is also active? I want to avoid this situation here.

Thanks,
Maitrey
 

Attachments

Thread Starter

maitrey

Joined Sep 4, 2014
61
Using two relays it would look a little like this:
View attachment 203141

Not the best rendition as the control switch would normally be an Auto - OFF - Manual with a center Off position. The idea is if I select Auto RY1 is energized through the NC (Normally Closed) contacts of RY 2 and with RY1 Energized RY 2 can't be energized because RY 1 NC contacts are now Open. RY1 and RY2 can be for example DPDT or 3PDT relays and the remaining contacts for whatever you wish to control.the coil voltages are whatever you wish. This is merely a rough drawing.

Ron
Also Manual and Auto/Remote Switch has different supplies.
 

Reloadron

Joined Jan 15, 2015
5,646
It doesn't matter if one relay is active the other can't be active. Even if I use individual switches for RY1 and RY2. Anytime one relay is active regardless of coil voltage the other relay can't energize. Using two auto man switches would yield the same results. If one is active the other can't be active. You can have one or the other but never both at the same time.

Ron
 

Thread Starter

maitrey

Joined Sep 4, 2014
61
It doesn't matter if one relay is active the other can't be active. Even if I use individual switches for RY1 and RY2. Anytime one relay is active regardless of coil voltage the other relay can't energize. Using two auto man switches would yield the same results. If one is active the other can't be active. You can have one or the other but never both at the same time.

Ron
Will it still work if I have two different power supplies? Here is the circuit I am working on with DPDT relays.
1585762464230.png
 

Reloadron

Joined Jan 15, 2015
5,646
Yes, SW1 & SW2 need only be SPST switches. There is no need to switch both sides of RY1 and RY2 coils. With each switch you place a NC set of contacts of the opposite relay.

Ron
 

Tonyr1084

Joined Sep 24, 2015
5,091
Does this work for you? Two DPDT relays, when one is activated the other is blocked out.
1585763750275.pngWhen the remote switch is activated the manual switch can not change the status of the relays. When the manual switch is activated then the remote switch can not change the status of the relays. The other set of contacts can control whatever you're switching.
 

Thread Starter

maitrey

Joined Sep 4, 2014
61
Yes, SW1 & SW2 need only be SPST switches. There is no need to switch both sides of RY1 and RY2 coils. With each switch you place a NC set of contacts of the opposite relay.

Ron
Hi Ron,

I connected a set of NC contacts to the RY2. But, when I do the same for RY1 it doesn't work. Not sure why!
1585764198678.png
 

Thread Starter

maitrey

Joined Sep 4, 2014
61
Does this work for you? Two DPDT relays, when one is activated the other is blocked out.
View attachment 203157When the remote switch is activated the manual switch can not change the status of the relays. When the manual switch is activated then the remote switch can not change the status of the relays. The other set of contacts can control whatever you're switching.
That's what I have been working on right now. But the power supplies for both switch Manual and Auto/Remote are different that's where I am confused with the connections.
 

Tonyr1084

Joined Sep 24, 2015
5,091
You don't have to use a common source for the remote and manual switches. When one source switches in the other source is blocked out. Just remove the jumper that goes over the top of the manual switch and you have separate sources. Note that when one relay is active it removes ground from the other - so it isolates control to whichever was first to switch in. If you flip the manual switch, the first relay clicks in and removes ground from the second relay. The remote switch can not activate the second relay unless the manual switch has been switched off. Vice versa is true if remote is activated first.

The second set of contacts can be wired to control whatever you're controlling. And it doesn't have to be the same voltage as the relay.
 

Tonyr1084

Joined Sep 24, 2015
5,091
Just recently considered something sort of along the lines of what you might be attempting. I am planning a second floor on my garage for a wood shop. There's a single heater. I want to be able to control it from one thermostat in the shop - OR - from one in the garage. Easy enough. But what if I want to control it from both thermostats at once?

SW1A chooses between the shop or garage. SW1B lights the appropriate LED to visually indicate which ThermoStat (TC) is in control. SW2A jumps both TS's together so that when either of them calls for heat - both shop and garage receives heat. I'd LIKE to add control to the damper so that when the garage calls for heat only the garage receives it. Like SW1B, SW2B ties both LED's together and indicates that the system is being controlled from two locations. As for the swing gate - trial and error will help control how much heat goes which direction. But in the end I'd like to add a control to the gate so that when one TC calls for heat that zone and that zone alone gets heat. If both zones call for heat then the swing gate goes to some preset position to divide the heat proportionally.

Here's my drawing: Perhaps it might spark an idea for you.
1585764985099.png
 

Tonyr1084

Joined Sep 24, 2015
5,091
In post #12 you had no connections to RL1. Wondering why that was. Was it on purpose? I see now that you are using RL1 to isolate RL2 - the way I drew it.

All in all, I'm hoping this is leading you to the solution you want.

[edit] from what you've drawn it looks like you want all three lamps to be on at the same time. This seems to indicate that you want the second relay (V2) to either allow lighting or to block it. You're only adding the ground circuit. I guess if I had a better picture of what you're attempting to do maybe I could come up with a more specific approach.
 

Thread Starter

maitrey

Joined Sep 4, 2014
61
No, actually I was following simple replay connections topology in the begining but got confused as all that circuit did was to turn on/off three lamps.

Yes, this is definitely helping me a lot. Thank you.
 

Tonyr1084

Joined Sep 24, 2015
5,091
Approach it this way:

Condition - - - - - - - - - - - - - - - - - - - Results
1) manual switch is on. Remote off - - 1) Lights are on
2) manual switch is off. Remote on - - 2) Lights are on
3) manual switch is off. Remote - off - 3) Lights are off.
4) manual switch is on. Remote - is on 4) Lights are off.
 
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