Author Topic: Need some help building a circuit involving switchs and relays  (Read 7499 times)

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Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #25 on: May 26, 2020, 10:42:52 pm »
Well, could you take a photo of the original detector circuit board?
I'm sure we'd all be interested in how they did it.

The current transformer idea would work fine.
I just like my own idea.  ^-^
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #26 on: May 27, 2020, 08:57:19 am »
Ok





 
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Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #27 on: May 27, 2020, 03:30:24 pm »
That's interesting.
First, the stacked power resistors are bypassed with a big solder blob.

I'm still confused.
Looking at those three bridge rectifiers/capacitor/top resistor/bottom resistor/optocouplers:
I can see that they are designed to detect a 24VAC signal.
Those half watt 3.3k (top) resistors make sense at 24 VAC = 7mA
Still, that 470 ohm on the bottom seems to steal too much of that 7 mA.
(I can't really tell because I don't know what the LED forward voltage is.)

It looks to me that there must be three external current transformers?
Something's going on here that I don't understand.
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #28 on: May 27, 2020, 03:49:46 pm »
You can look at only one section: Bridge, cap, 3.3k, 470, optocoupler

I think that 470 ohm is to reduce the voltage going to optocoupler.

The optocoupler gets 1volt, when the switch is closed.
 

Offline Benta

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Re: Need some help building a circuit involving switchs and relays
« Reply #29 on: May 27, 2020, 03:53:20 pm »
The stacked resistors are 330 ohms, not 3.3 k.

Current transformers may very well be external and mounted directly on the power leads, that would be the natural place.

 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #30 on: May 27, 2020, 04:12:31 pm »
There is nothing else other than this board. This is how I see it :
 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #31 on: May 27, 2020, 04:27:33 pm »
I agree with @Shaydzmi on the interpretation.
(I had mentioned the "sandbox" power resistors only in passing, the ones I care about were the 1/2W 3.3k)

So, we went looking for a current sensor and we found something that is a 24 VAC voltage sensor.

So, being more exact, 24VAC * sqrt(2) = 34 VDC - 1V (led drop) = 33 VDC  / 3.3k = 10 mA - (1V / 470 ohm) = 8 mA

This seems peculiarly designed for a voltage source, not a current transformer.
It would have to be a very small ratio transformer to get 10 mA out of a 50 mA main current, or?
 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #32 on: May 27, 2020, 04:54:23 pm »
Are you quite sure that the thread-out switches are not actually double pole, DPST?

I say that they are double pole.
The cable that runs along the feeder bar is two conductor.
It has 24 VAC supply and the common alarm.
The feeder connects in with insulation piercing to the two conductors.
The chassis provides return.

Am I wrong?
« Last Edit: May 27, 2020, 05:21:22 pm by Renate »
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #33 on: May 27, 2020, 07:03:10 pm »
Are you quite sure that the thread-out switches are not actually double pole, DPST?

I say that they are double pole.
The cable that runs along the feeder bar is two conductor.
It has 24 VAC supply and the common alarm.
The feeder connects in with insulation piercing to the two conductors.
The chassis provides return.

Am I wrong?

You are absolutely right, and because of that I put two separated circuits 1 and 2.

This does not change any thing in our problem.
 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #34 on: May 27, 2020, 08:29:56 pm »
This does not change any thing in our problem.
Well, some of this information should have been in the first post.
Your schematic does not show any of this.

Was the goal to switch to current sensing?
How are you even sure that there are bulb bypass resistors? What is their value?
Why would you think that current monitoring would be more reliable than the existing voltage bus?
Is there a problem with the existing boards? With the second poles of the thread-out switches?
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #35 on: May 27, 2020, 09:26:29 pm »
OK:
The machine consists of 4 circuits that control:
1-Yarn in.
2-Yarn out.
3- Broken needles.
4- Safety door open.
but in reality they combined the (1-Yarn in) and (2-Yarn out) in one circuit, which is not good, because (2) needs a specific behavior is different than the others.
because of that, I did what I did.
Now you have an answer to this:


Quote
Well, some of this information should have been in the first post.
Your schematic does not show any of this.

Quote
Was the goal to switch to current sensing?

The goal is to monitor these circuits regardless of the method.


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How are you even sure that there are bulb bypass resistors? What is their value?

I saw it, I don't remember its value, it's just above the bulb resistance.


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Why would you think that current monitoring would be more reliable than the existing voltage bus?

I don't know, the members who answered my question, suggested that.


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Is there a problem with the existing boards?

Yes the part (3- Broken needles) and (4- Safety door open ) doesn't work.


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With the second poles of the thread-out switches?

They combined the (1-Yarn in) and (2-Yarn out) in one circuit, I want to separate them.
« Last Edit: May 27, 2020, 09:30:39 pm by Shaydzmi »
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #36 on: May 27, 2020, 09:48:40 pm »
Correction:

Are you quite sure that the thread-out switches are not actually double pole, DPST?
...
Am I wrong?

Every device has 2 separated switches, so we can call them: DPDT.
 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #37 on: May 28, 2020, 12:06:10 am »
Alright, I think I'm beginning to get a picture.
You've got 84 feeders total, each with an entrance and an exit yarn switch.
The feeder bar cable is a two conductor.

So what you're planning on doing is modifying 84 feeders to split the two switches?
Then what? You've only got two conductors and ground going out.
You could add a second bulb to the feeder (or switch to DC and use diodes).
Then you would have two buses on which you would have to use current detection.

The broken needle detection is simple.
It's just a question of the sensor itself and a latch.
The same goes for cabinet interlock.

Do I have the right picture? Graphic updated to show two bulbs. And yet more modified
« Last Edit: May 28, 2020, 08:22:31 pm by Renate »
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #38 on: May 28, 2020, 03:41:01 am »
Quote
Alright, I think I'm beginning to get a picture.
You've got 84 feeders total, each with an entrance and an exit yarn switch.
The feeder bar cable is a two conductor.
Exactly
Quote
So what you're planning on doing is modifying 84 feeders to split the two switches?
Then what? You've only got two conductors and ground going out.
You could add a second bulb to the feeder
The feeders already have two switches and two bulbs each, all they did was they merged the two conducting wires to go to the board as one wire, so simply I'm going to separate them.
By the way, how can you achieve that with this? (Just for learning purposes)
Quote
(or switch to DC and use diodes).
Quote
Then you would have two buses on which you would have to use current detection.
Yep.
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The broken needle detection is simple.
It's just a question of the sensor itself and a latch.
The same goes for cabinet interlock.
Yes.
Quote
Do I have the right picture?
Yes.

Now, I think it is your turn to give us your ingenious solution!

 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #39 on: May 28, 2020, 01:34:00 pm »
Note: I updated the drawing above.

They merged the two conducting wires to go to the board as one wire, so simply I'm going to separate them.

So you want to remove a feeder from a knitting machine, sit down at a bench, open it up, modify the wiring, put it back together and reinstall it 84 times? ???
It's worth that much to you to tell the difference between the yarn being out at the entrance or the exit of the feeder?
You'll end up with a non-standard feeder that could cause a lot of mischief if it were mixed with others.
And then you have to make a new current sensing board.

Is this a project you're doing or is it a machine that is knitting in production right now?
It's going to take you a while to do this.
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #40 on: May 28, 2020, 01:59:40 pm »
 Oh no no no... Please see the picture:
 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #41 on: May 28, 2020, 05:17:02 pm »
There's some confusion here.

I updated the graphic above to show a second bulb.
If this is not 100% correct, please correct it.

The cable on the feeder ring is two conductors.
Both conductors are already being used.
Both conductors already go to the board.

We're talking in circles here and the problem is not language.
 
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Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #42 on: May 28, 2020, 05:56:06 pm »
There you go :


There is no thing such an alarm wire.
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #43 on: May 28, 2020, 06:05:55 pm »
And there are some photos from inside the feeder, showing the swiches and the resistors across the lamps: (You can tell me how ohms they have)

 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #44 on: May 28, 2020, 07:53:53 pm »
Those are 1.2 k ohm resistors.
If the full 24 VAC was across them it would be 1/2 Watt dissipation.
Since those are 1/4 Watt, that's not what is happening here.

Tell me, from your experience, or actually testing now:
Stick a finger on a switch and make a bulb go on.
Stick a finger in another feeder switch and make another bulb go on.
Did the bulbs get dimmer when you put another switch on?

See, if there are no more resistors anywhere then all the bulb current goes through that 3.3 k ohm resistor on the board.
That would mean that the bulb is running on much less than 24 VAC.
Do you have a replacement bulb number?
Do you have the service manual for this beast?

Note: I've updated again the drawing above.
« Last Edit: May 28, 2020, 08:24:01 pm by Renate »
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #45 on: May 28, 2020, 10:49:36 pm »
Quote
If the full 24 VAC was across them it would be 1/2 Watt dissipation.
Since those are 1/4 Watt, that's not what is happening here.
I didn't understand, can you explain this to me?

Quote
Tell me, from your experience, or actually testing now:
Stick a finger on a switch and make a bulb go on.
Stick a finger in another feeder switch and make another bulb go on.
Did the bulbs get dimmer when you put another switch on?
Yes, they get dimmer and dimmer until they bacome off when 5 or 6 are triggered.

Quote
See, if there are no more resistors anywhere then all the bulb current goes through that 3.3 k ohm resistor on the board.
That would mean that the bulb is running on much less than 24 VAC.
Look, those 168 bulbs/resistors aren't going to the 3.3k ohm, they are going to the 3 big ceramic resistors (you can see them on the board).
The 3.3k ohm is handling just 3 big leds (I assume... tomorrow I'll take a picture of one of them).

Quote
Do you have a replacement bulb number?
When they burn out, usually I replace them with this:
https://www.narva.com.au/products/47508

Quote
Do you have the service manual for this beast?
No.

Quote
Note: I've updated again the drawing above.
Correct.
Thank you.


 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #46 on: May 29, 2020, 12:02:57 am »
24VAC ^ 2 / 1200 ohm = 0.48W
I guess that they always presumed that there would never be full 24 VAC there.
17 VAC ^2 / 1200 ohm = 0.24W

Ok, that control board has been all screwed up.
As I said, the stacked power resistors are bypassed.
There is only the 470 ohm resistor actually doing anything.
But it looks like one end is ground as it goes to the minus side of the big cap.
The AC comes in on a 2 pin connector and each side wraps around the board with screw holes!

The 3 sensor circuits seem to be designed for 24 VAC vs 0V.
It doesn't seem that they would work very well for working with a voltage over a drop resistor or a load.

Can you measure continuity between the feeder cable and the plug that goes into the control board?
Can you see where somebody shorted the two conductors of the feeder cable?
 

Offline Renate

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Re: Need some help building a circuit involving switchs and relays
« Reply #47 on: May 29, 2020, 12:42:05 am »
Ok, I figured it out.
The 3 rectifier bridges: Those are for regular 24 VAC signals like broken needle detector, door open, etc

The control board is only designed for a single feeder bus.
The 470 ohm is the 24 VAC supply.
The detection is done by the ST BTA16 triac.
It triggers on the voltage drop across the 470 ohm.


You know the good thing about these forums? It gives you a lot of chances to be wrong!  |O

So, the big triac, the 47 ohm, the two zeners and the big yellow thermistor are there to trigger and provide the full 24 VAC to all the light bulbs.
It is an independent, self-contained sub-circuit that bypasses the 470 ohm.
Since it triggers late in the AC cycle there will be some spikes across the 470 ohm resistor if a light bulb is on.
It's the TO-92 transistors that are further along that do the actual detection.

There's no reason that the bulbs should dim if 4 or 5 of them are on.
The triac/thermistor bypass could be broken.
« Last Edit: May 29, 2020, 02:20:43 am by Renate »
 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #48 on: May 29, 2020, 03:55:34 am »
Yes, the 3 bridge rectifiers are for: 1- Needle detector. 2- Open gate. 3- Revolution counter.
FYI: Only the revolution counter is working, the rest are broken.

Quote
You know the good thing about these forums? It gives you a lot of chances to be wrong! 
That is you, me I'm always wrong.
The ceramic resistors ARE NOT bypassed, you can look at the board again.

Quote
So, the big triac, the 47 ohm, the two zeners and the big yellow thermistor are there to trigger and provide the full 24 VAC to all the light bulbs.
It is an independent, self-contained sub-circuit that bypasses the 470 ohm.
Since it triggers late in the AC cycle there will be some spikes across the 470 ohm resistor if a light bulb is on.
It's the TO-92 transistors that are further along that do the actual detection.
I didn't understand any of this.

Quote
There's no reason that the bulbs should dim if 4 or 5 of them are on.
There must be a reason though.


 

Offline ShaydzmiTopic starter

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Re: Need some help building a circuit involving switchs and relays
« Reply #49 on: May 29, 2020, 03:59:59 am »
Quote
Can you see where somebody shorted the two conductors of the feeder cable?
The two conductors are twisted right at their end, you can see where by looking at one of the previous photos.
 


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