PLC 101 Toolkit
Eight hands-on explainers that turn the abstract parts of controls into something you can type into and understand instantly.
Number Base Converter
Type a value and pick its base to instantly see it in all other number systems used in PLC programming.
PLCs store all values as binary bits internally. Decimal and hex are display conveniences. BCD encodes each decimal digit in 4 bits, commonly used for numeric displays and legacy hardware.
Scan Cycle Explainer
Pick a phase of the PLC scan cycle to see what happens in that step and where it fits in the loop.
- 1Read Inputs
The CPU reads all physical input signals (digital and analog) and copies their current state into an internal input image table. No input changes are seen by the logic during this phase.
- 2Execute Logic
- 3Update Outputs
- 4Housekeeping
This snapshot approach ensures that logic decisions within a single scan are based on a consistent set of inputs, even if a physical signal changes mid-scan.
A typical PLC scan cycle completes in 1-10 ms. The Execute phase writes only to the output image table, then physical outputs change during the separate Update Outputs phase. Fast-changing signals shorter than one scan time may be missed.
Addressing Decoder
Pick a vendor and type an address to decode each segment into plain language.
Siemens uses byte.bit absolute addressing. %I = digital inputs, %Q = digital outputs, %M = internal memory flags.
Timer Preset Helper
Type a duration and pick your platform to get the correctly formatted timer preset value.
Use the TIME literal T#3s as the PT (preset time) input on a TON, TOF, or TONR block in TIA Portal. The IEC TIME type supports up to T#24d20h31m23s647ms.
Data Type Sizer
Pick a PLC data type to see its bit size, byte size, value range, and platform names.
Signed: -32,768 to 32,767. Unsigned (WORD/UInt): 0 to 65,535.
16-bit integer. INT is the most common PLC integer type. Siemens S7 raw analog values use INT (0-27648 nominal).
ISA Tag Decoder
Type an ISA-5.1 instrument tag to decode each letter into a plain-language description.
ISA-5.1 tag structure: [Measured Variable] + [Function letters] + [Modifier]. "PSHH" = Pressure, Switch, High-High (highest alarm level)
IP / NEMA Enclosure Lookup
Decode an IP code or look up a NEMA enclosure type to understand its protection rating.
IP54: First digit (5) rates solid particle protection (0-6). Second digit (4) rates liquid ingress protection (0-8).
Boolean Ladder Trainer
Set inputs A, B, C and pick a logic function to see if the output coil energizes, plus how it maps to ladder rungs.
All three contacts (A, B, C) are wired in series on one rung. Current flows to the coil only when all contacts are closed.
Series contacts = AND logic. All contacts must be true for the coil to energize.