Need some help building a circuit involving switchs and relays

[Shaydzmi]

I need some help and suggestions to build this circuit:

It has 4 sections, and a board with relays, which lacks components needed to operate the relays.

How it works :

Section1 : When one of the 84 switches closes, Relay1 should operate.

Section2 : When one of the 84 switches closes, Relay2 should operate.

Section3 : When one of the 3 switches closes, Relay3 should operate.

Section1 : When one of the 3 switches opens, Relay4 should operate.

Power supply : 6Amps max
Lamps: 24v 1.2w

https://i.ibb.co/QD7zR60/cats-vert2.jpg

[Benta]

"Section 4" seems to be a short circuit???

[themadhippy]

Hope you dont intend all the lamps being on at once coz 6A aint gonna be enough,as to a solution any one make a 84 input OR gate?

[Ian.M]

Full wave rectify the supply to all the lamps and switches so they are running on unsmoothed DC so you can use diodes to implement the two 84 input, and single three input OR gates required.  Use 24V DC coil relays, and if they chatter, add just enough capacitance across each coil to hold up the coil voltage through the zero crossings.  Don't use too much capacitance, as in the limit, it will increase the average coil voltage by a factor of  up to 1.4 and cook the relays!

As Benta has pointed out, section 4 wont work as drawn.  Either swap the thee NC switches in series to three NO switches in parallel, with the whole switch group in series with the relay 4 coil, or put the coil in series with the NC switches, and wire the contacts based on its normal state being energised and releasing on any button press, or use an extra relay to energise relay 4 when it releases, or (assumiong DC supply) use a transistor, a couple of resistors and a diode to implement an inverting driver for the relay 4 coil controlled by the three NC switches.

N.B this all assumes you've either got access to *BOTH* ends of the transformer secondary supplying the 24V AC, or can rewire the ground side of all the lamps to the negative terminal of the bridge rectifier.  If not, so all you've got is ground-referenced AC, it gets a *LOT* harder . . .

[Shaydzmi]

In some cases, they will bi lit all of them, maybe I need some thing that can cut the power when it reaches the maximum current, but in the same time keeps the relay energized.

[Shaydzmi]

Thank you for your valuable answer, I didn't quite understand it though, can you please demonstrate it in a circuit diagram?
Section4 is easy: I can put the relay in series with the switches. the big trouble is in other sections.

[Ian.M]

Here's the circuit for three switches/lamps.  Extend it with more diodes for extra switches/lamps.   C1 is optional - to be fitted if the relay chatters when on and increased in value till it stops chattering.   All the sections can share the same bridge rectifier.

N.B. it still doesn't solve the problem with overloading the AC supply if too many lamps are on.
 

[Shaydzmi]

Thank you for your efforts, very appreciated..
First of all, the lamps and switches are a standalone device, And I don't have access to the ground, because it is conned to the machine's chassis, so I can't put any thing between the device and the ground/ chassis, or inside the device.

[Ian.M]

That makes it a *LOT* harder.   If all you've got access to is the 24V AC feed to each lamp/switch pair with a common ground, your only option would be to add a sensitive current sensor in the feed to detect the lamp current.   That wont work if the 24V AC is used for other functions in the device.   It *MAY* be possible to use one current sensor for multiple devices, but it may be difficult to get enough sensitivity (in a potentially high EMI   environment) to reliably discriminate between the 50mA of one lamp on, and no current when all switches are off, and still be able to handle the high current when lots of lamps are on.  Also it will miserably fail to detect the switch position if the lamp fails.

[Shaydzmi]

The part of the lamp failing, is not a problem, because inside the device, there is a resistor across every lamp.

Cant I use a power transistor or a similar  device to monitor the switches before going to relays?

[Ian.M]

Transistors don't work on AC so any simple current monitor using one is not going to work. 

To avoid further confusion, take a hilighter and on your schematic, hilight the sections of it that are purely internal in the device(s) and you have no access to, then re-post it.

[Shaydzmi]

I've edited the picture above.

[Renate]

Huh? I'm not soldering in 171 diodes in a machine with moving parts.

Just make sure you have the 24 VAC feed that is only going to the bulbs.
Put in this circuit (and the rest, an op amp to amplify and rectify and detect the 1.4 V P-P signal).
The diodes are beefy enough for any number of amperes.
The resistor is the right size that the diodes are still conducting when just a bulb bypass resistor is conducting.
The cap cleans up potential noise.

[Shaydzmi]

Thank you, I didn't fully understand this circuit, can you explain to me how does it work, and the purpose of each component?
Tank you.

[Renate]

Well, it's basically a shunt for measuring current.
You have to be able to measure 25 mA or so, but it has to be able to tolerate amperes going through it.

You could just use a single resistor, but then if 22 bulbs went on it would drop too much voltage, heat up too much and burn out.
So we have the two big diodes across it so that no matter what happens we only drop 0.7 V in either direction.
We just want to know if any bulb is on, not how many.
(If we wanted to count bulbs, we would use a very small value resistor and a much more sensitive/precise measuring circuit.)

What is the value of the bypass resistors across the light bulb?
Some rough numbers here:
If the bypass were 1k then the normal current would be 24 mA (RMS)
If the sense resistor was 30 ohms the voltage across it would be 0.7V (RMS without the diodes in place).
The diodes would flatten the peak to 0.7V instead of the 1.0V peak.
That's enough of a nice "to the wall" signal"

Why did they put in those bypass resistors?
Did they have their own measurement system for any of the bulbs going on?

If you wanted to make things easier and you could tolerate a bit more drop on the voltage to the bulbs:
You could use two (or 3?) diodes in series (and two (or 3?) diodes in series the other direction).
With that you could get enough voltage to run an LED on an optoisolator.
That simplies the whole problem of using an op amp with a separate floating supply.

[Ian.M]

Hmmmm . . .  I don't like the voltage drop for the optoisolator solution.
I'd experiment with using a common mode choke as a saturating 1:1 current transformer.   Once you've got an isolated and limited signal, you've got a lot more options.  Core saturation lets you use a fairly large burden resistor for a decent amplitude at 24mA RMS without the high voltage drop issues when passing several amps.

[Shaydzmi]

Why did they put in those bypass resistors?
Did they have their own measurement system for any of the bulbs going on?

They put them to ensure continuity if the bulb burns.

If you wanted to make things easier and you could tolerate a bit more drop on the voltage to the bulbs:

It doesn't matter, as long as I have enough voltage to glow the bulbs, it's OK.

[Shaydzmi]

Hmmmm . . .  I don't like the voltage drop for the optoisolator solution.
I'd experiment with using a common mode choke as a saturating 1:1 current transformer.   Once you've got an isolated and limited signal, you've got a lot more options.  Core saturation lets you use a fairly large burden resistor for a decent amplitude at 24mA RMS without the high voltage drop issues when passing several amps.

A little schematic diagram would be better for me to understand as a beginner.

[Benta]

Much simpler: let each 24 VAC line run through a current transformer. Detecting current/no current on the secondary side is a simple exercise, and you even get isolation for free. I'd suggest a 1:50...1:200 turns ratio, but it's uncritical.
https://www.quora.com/How-is-a-current-transformer-connected

[Renate]

Why did they put in those bypass resistors?
Did they have their own measurement system for any of the bulbs going on?

They put them to ensure continuity if the bulb burns.

Yes, but that presumes that they have interest in continuity.
I can't believe that this loom? has 168 "thread out" indicators and no common indicator.
Was that an option that wasn't installed or got broken?

[Shaydzmi]

What do you mean by "common indicator"?

[Renate]

What do you mean by "common indicator"?

The same thing as what you are trying to build. A light bulb/relay/siren that goes on when any bulb goes on.

[Shaydzmi]

Oh, OK, there is one not working as it should, but I'm trying to build my own for the purpose of learning, and to replace the old one if I succeed in this building.

Sorry for the bad English, I learned it by myself no teachers, no schools involved.

[Benta]

Sorry for the bad English, I learned it by myself no teachers, no schools involved.

In that case, you're doing extremely well. There's absolutely nothing "bad" about your English

[Shaydzmi]

Quote from: Renate on Today at 06:57:28 pm

>.. this loom?

This is a circular knitting machine:
https://www.xdknitmachinery.com/circular-knitting-machines-an-ultimate-guide/