Help determining which switch is open

SteveD

I am trying to find a way to interface an SX28 or BS2 with the following schematic.· The purpose is for the SX to let me know which switch is open.· I know I could accomplish this by redesigning the control circuit but I am trying to find a way around that.· I would like to be able to keep the wiring the way it is and add components that would isolate the high voltage from the necessary inputs to the micro.· Everything I come up with (such as opto22 110v input 5v output wired in parallel with each switch) could affect all the switches that follow the one that opens.

Thanks
Steve

Bruce Bates

SteveD -

It's a bit difficult to determine what you're trying to do just from that schematic. Is this some sort of START-STOP set-up for controlling some device?

If so, you want to put all of the STOP stations in SERIES, and all of the START stations in PARALLEL. That will solve that sort of problem.

Lastly, I trust you realize your blown fuse indicator is inherently UNSAFE! If there is current flow in a circuit where an overload or a short circuit has occurred, you HAVE NOT cleared the fault, and that's the purpose of an overcurrent device (fuse, breaker, etc). It's even possible that a fire and/or a shock hazard may be the outcome. Forwarned is forearmed.

Regards,

Bruce Bates

Post Edited (Bruce Bates) : 11/3/2006 2:26:40 PM GMT

Bean

I don't see why opto's across each switch would affect the others ? As long as they are closed.

I don't know if this is an option, but can you just use double-pole switches ?

P.S. I totally agree with Bruce about your "blown fuse indicator" very unsafe.

Bean.

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Cheap used 4-digit LED display with driver IC·www.hc4led.com

Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com

"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·

DaveG

Steve,

What is R1 and R2? How much current do they draw?
Why is there a "+" symbol next to them when it appears that they are powered by AC?

DaveG

SteveD

Bruce,
Thanks for your reply and I appreciate you taking the time to caution me on my blown fuse indicator. The drawing is not completely accurate to my circuit in use I simply used it to express the only method that comes to my mind in order to accomplish what I need to. Without going into detail about that circuit, unless you would like for me to, if the things you mention should happen to occur the lamp will also act a fuse if more than 2ma passes through it. The other circuit with the switches in series is a control circuit for an old machine should one of these switches become open for any reason the machine will stop. I have not included the whole start and stop circuit I am only interested in knowing which switch has caused the machine to stop. The way it is now if the machine stops you have to look all over the machine looking for a paper jam or has someone accidentally hit a stop button or worse has switch simply gone bad. Again if I were to rewire the whole stop and start control circuit this would not be a problem I would make the control circuit a low voltage one and incorporate the micro into it.

Bean,
Yes double pole switches would be great unfortunately this is not an option many switches not easy to get to however the terminal that connect everything is very accessible.
I guess that is what I am asking I have never used this type of opto22 and the very thing you guys are cautioning about happening with the blown fuse indicator could happen here, correct? Even if the switch opens would the current passing though the opto keep the coil energized if not destroy it should the current that the relay is using be too much. Which I believe is what Dave G is getting at.

Dave,
I apologize for the confusing symbol please don’t pay attention to it. I was just trying to figure out a way to monitor which switch was open on this 110 vac circuit.

Sorry for the length
Thanks
Steve

Bean

Steve,
How about connecting a neon bulb (with resistor) after each switch and to the neutral. When the machine is operating ALL the bulbs will be on. When a swich opens the bulb for it, and all that follow will turn off. So if the first 4 bulbs are lit and the rest are off, then the 5th swich must be open. If all the bulbs are off, then the 1st switch must be open. Etc..

Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Cheap used 4-digit LED display with driver IC·www.hc4led.com

Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com

"People who are willing to trade their freedom for·security deserve neither and will lose both." Benjamin Franklin
·

Unsoundcode

Hi Steve, I see what you want in fact its·similar to a situation I occasionally face. If it is possible to indicate to a machine operator which button,switch,safety gate etc. has been activated then they can usually deal with it quickly saving production down time. The same if the switch is faulty maintenance are able to locate the problem faster. If you have room in your electrical panel you could mount a DIN rail with 20 120v slimline relays, connect one coil connection off each·relay to·the downstream connector of each safety switch and the other coil connection off each relay to neutral. Pass 5v through a set of each of the relays contacts·back to a BS2p40 as inputs. When the circuit is healthy all relays are energised, when a switch is open then its respective relay is the first de-energised relay in the circuit. If more than one switch were open then the logic would be to indicate the first in circuit that was open. The status of an open switch or healthy circuit could be displayed to the operator via a serial LCD. I would guess the initial cost would be something to balance against predicted downtime cost. Also if the switch is not open but has high resistance it can give odd results especially on lower voltage systems.

Jeff T.

EDIT Bean posted as I was typing , same principal not as slick but much more cost effective and·probably what I would do.

Post Edited (Unsoundcode) : 11/5/2006 12:30:43 AM GMT

SteveD

That is the other idea that I had and what I meant in my original post about the following switches being affected. There may not be an easy way to use the micro. The ideas you all suggested will work and would probably be the most cost effective and would certainly achieve the goal.
Yes Jeff that is exactly the reasoning for the project.

Thanks guys,
Steve