Comparison

555 Calc vs PLC

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

555 Calc

This utility app helps engineers and hobbyists calculate resistor values for circuits using the Timer IC 555. Simply input frequency, duty ratio, and capacitor values to get the required resistor outputs.

Highlights
  • Calculate resistor values
  • Input frequency
  • Input duty ratio
  • Input capacitor value
  • Timer IC 555 circuit design
Features
Read full description

This App calculates registors value, when designing the circuit using Timer IC 555. How to (1) Input Frequency value. (2) Input Duty Ratio. (3) Input C1 Value. (4) Touch ‘Calculate’ button. (5) Registors value will be displayed. Note. * Set Duty Ratio to 50 ~ 99. * If you set Duty Ratio to 50, R1 value will be set to 0.

About

PLC

Features
Read full description

PLC-Inspector is a professional diagnostic tool for Siemens LOGO! controllers. Read memory, follow changes live and set registers, over Modbus/TCP, directly from iPhone, iPad or Mac. KEY FEATURES • Memory reading VM memory, analog inputs (AI) and analog outputs (AQ) of your LOGO! in real time. • Register writing Enter values in decimal or hexadecimal and send them to the controller. The app checks what the controller reports back and says so separately when the confirmation does not match the request. • Safeguarded writing Write mode has to be switched on deliberately and expires when you leave the view. Before every write there is a confirmation showing register and value in plain text, which can be switched off for a working session. • Bit-level visualisation Every register as a 16-bit value with colour-coded bit display. • Change detection Changed values are highlighted in orange. Jump between changes with the arrow buttons. • Auto-refresh Automatic updates in intervals from 0.5 to 10 seconds. • Multiple stations Manage any number of PLC stations with individual settings. APPLICATIONS - Commissioning and fault finding on site - Mobile process monitoring - Analysis of memory contents - Training and education TECHNICAL DETAILS - Protocol: Modbus/TCP (default port 502) - Reading: Read Holding Registers (FC 03), automatic splitting above 125 registers - Writing: Write Single Register (FC 06) with echo verification - Supported controller: Siemens LOGO! 8 (0BA8) NOTE The app needs a network connection to the LOGO! controller. The Modbus server must be enabled in LOGO!Soft Comfort. Developed by spiritdev Softwareentwicklung GmbH - your partner for industrial software solutions.

Screenshots

555 Calc1 screens
PLC4 screens

Verdict

The call

The clearest difference is ads: PLC at none against 555 Calc's shown. PLC also leads on update cadence (every 2 weeks vs every 20 months). 555 Calc's advantage is iOS requirement (11.0 vs 17.0). On price, in-app purchases and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

555 Calc ships an update every 20 months, PLC every 2 weeks. The most recent releases landed on September 27, 2026 and October 6, 2026 respectively.

Scorecard3 real differences · 7 level
555 Calc versus PLC: the parameters behind the verdict, then further details
Parameter555 CalcPLC
PriceFreeFree
Rating4.0 (3 ratings) — better—
Positive reviews50.0% of reviews—
Number of ratings3 — better—
Update frequencyEvery 20 monthsEvery 2 weeks — better
AdsYesNo — better
In-app purchasesNoNo
MonetizationAd-supported—
DevicesiPhone, iPad, iPodiPhone, iPad, Mac
Requires iOS11.0 — better17.0
Further details — not scored
Size18 MB4 MB
Age rating4+4+
DeveloperJibiki Worksspiritdev Softwareentwicklung GmbH

In-app purchases

None

555 Calc

No in-app purchases

None

PLC

No in-app purchases

Questions

Is 555 Calc free?
555 Calc is free to download, with no in-app purchases.
Is PLC free?
PLC is free to download, with no in-app purchases.
Do 555 Calc or PLC have ads?
555 Calc shows ads; PLC does not.
Which is updated more often, 555 Calc or PLC?
555 Calc ships an update every 20 months, and PLC every 2 weeks. Most recently, 555 Calc was updated on September 27, 2026 and PLC on October 6, 2026.

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