4
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PLC ladder-logic equation stabilization
In PLCs, my understanding is that one 'tick' represents one pass through the equations; every gate is updated once with respect to its inputs.
I've been working with PLCs for over 30 years but never ...
- 171k
4
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PLC rung definition and evaluation
You are correct in your execution sequence and your statement that a rung can be several lines.
Ladder vs text
In the old days many of the PLCs programmers could switch between ladder and text or '...
- 171k
3
votes
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Updating outputs in PLCs
I had edited my response to your earlier question to cover this lightly. Here's some more detail for a basic PLC.
Task execution order
Typically PLCs task execution order runs as follows:
Read the ...
- 171k
3
votes
What does the % symbol mean on plc addresses?
In IEC 61131 the percent symbol means it refers to an a fixed hardware address. Eg: input/output or some other feature of the PLC hardware.
These addresses may never change, regardless of program ...
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2
votes
can arduino UNO be programmed to measure the analog voltages of 6 resistor ladder network without using switches
simulate this circuit – Schematic created using CircuitLab
Figure 1. Connection setup.
All of these microcontrollers have one internal analog to digital converter and you multiplex (switch ...
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2
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can arduino UNO be programmed to measure the analog voltages of 6 resistor ladder network without using switches
Yes, it can. You can connect the 3.3V as the external ADC reference and use 5 of the 6 available ADC input pins to measure the voltages at each node.
The AREF pin has relatively low impedance and ...
- 384k
2
votes
Accepted
Total capacitance for a ladder network with two capacitances
For each segment, we have two capacitors in series which are then in parallel with a third, so we have a total capacitance of:
$$C_{leg} = C_1 + \frac{1}{\frac{1}{C_2} + \frac{1}{C_1}}$$
We can ...
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2
votes
Ladder Logic for PLC Program
Without knowing what PLC you are using, I'll give you an example with a CLICK PLC. The CLICK PLC makes this trivial as it has built in I/O on the processor and I'm using model C0-02DR-D $139 which has ...
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Updating outputs in PLCs
Let we take into a consideration rack type PLC CPU where other peripheral IO devices are connected trough backplane bus. This bus usualy is a serial communiacation bus like CAN, I2C, RS485,...also the ...
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1
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PLC rung definition and evaluation
Yes, all the branches leading to the output must be evaluated before the output can be set. Actual evaluation, if you're familiar with reverse Polish and stacks, is more like
push A
push B
and
...
- 384k
1
vote
Accepted
What does this symbol mean in this ladder logic rung?
The symbol relates to an SPST toggle / rotary switch.
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1
vote
Accepted
1
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What does this ladder logic schematic showing a coil in parallel(?) with a contact mean?
Pressing FIRE energises relay PR1.
T1 (Timer 1) is always powered. A contact of PR1 starts the timing function. Note that the contract wires do not connect with the L1 and N wires so it's not in ...
- 171k
1
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What does this ladder logic schematic showing a coil in parallel(?) with a contact mean?
The PR1 contact should not truly be connected in parallel with the T1 coil:
If it were, energizing coil PR1 (e.g. by pressing the "FIRE" button) would short Line and Neutral and blow the ...
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1
vote
Accepted
two independent zones from central heating unit
Your logic looks fine.
simulate this circuit – Schematic created using CircuitLab
Figure 1. OP's logic redrawn using changeover contacts. 2-pole relays may be easier to source.
This does ...
- 171k
1
vote
Accepted
What is the difference between these two ladder logic diagrams?
In your first program, it works as you intend when ToggleThis starts at 0. You set Change to 1, and in Rung 2, because ChangePrevious is 0, ToggleThis gets latched to 1. Rung 3 sets ChangePrevious to ...
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TIA portal - failed to establish a connection
Nothing special, TIA is a master of troubles and issues. First, make a correct settings for your PC ethernet NIC, make the IPv4 to be in the same subnet, for example 192.168.0.150. Then plug the cable ...
- 23.7k
1
vote
TLP LogixPro PLC Simulator
First draw a timing diagram. It's better than a wall of text. This is what I think you are trying to do.
...
- 171k
1
vote
Accepted
what is the logic behind these ladder lines
The logic is just clamping each of the variables DM0021, 22 and 23 to the range 0 to 99. If it is inside the limits it leaves it alone.
- 171k
1
vote
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Storage bit in OSF and best way to detect falling edge
This is for Rockwell/Allen-Bradley PLCs, which use all of those instructions.
For those who don't know:
XIC = Examine If Closed. This is a normally open contact. --| |--
XIO = Examine If Open. ...
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How to create a Retentive/Accumulative Timer from On-Delay/Off-Delay Timers
A retentive timer can be built with an On Timer and supporting logic.
A typical TON implementation automatically clears the accumulating value when its input goes false. A retentive timer saves the ...
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vote
Accepted
Proving the output voltage of a resistor ladder only with usage of currents
Redraw the schematic in a slightly less confusing way:
simulate this circuit – Schematic created using CircuitLab
Start at the bottom:
R5 and R6 have the same voltage across them, and have ...
- 1,662
1
vote
Accepted
Understanding ladder PLC logic
If you have a latter version of TIA that allows mixing LAD and SCL you can add a simple code, instead of LAD:
...
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1
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Understanding ladder PLC logic
is it sequential like c/c++?
No, with typical column scan pattern* it is evaluated top-to-bottom and left-to-right. This means, first all of column 1 is evaluated from row 1 to end, then column 2 is ...
- 22.3k
1
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Switching outputs using ladder logic
Your screen grabs are too difficult to read.
It sounds as though you are looking for a 60 s clock with 50% duty cycle. The normal method is to generate a timing sequence as follows:
...
- 171k
1
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Total capacitance for a ladder network with two capacitances
There is probably a compact form based on z-transform generating functions. See the SE question and answer on a related resistor ladder network: Closed form expression for a resistor ladder network.
...
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Total capacitance for a ladder network with two capacitances
As a supplement to the answer by Tom Carpenter, if you have an infinite chain and the series converges, then
$$ C_{leg}(m + 1) \rightarrow C_{leg}(m) $$
$$C_{leg} = C_1 + \frac{1}{\frac{1}{C_2} + \...
- 3,524
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