Common DIY Mistakes with Siemens LOGO!
LOGO! is friendly for beginners, but a few mistakes can damage the module or be dangerous. We've gathered the five most common ones — and how to get them right.
5 mistakes beginners make most often
Mixing 24V and 230V worlds
Input modules are built for either 24V (DC) or 230V (AC) — mixing both types in one circuit can permanently damage the input.
A motor wired straight to a relay output
Relay outputs have a load limit. Wiring a motor or other heavy load directly to a relay can burn it out or cause a dangerous overload.
Skipping the simulation
Testing logic straight on real hardware — a program error can trigger an unexpected switch-on or damage that the simulator would have caught first.
230V work without an electrician
Wiring mains voltage yourself without the right qualification — it's dangerous, and in Latvia it isn't legal either.
How to do it right
electrician only
You can safely handle the low-voltage (24V) side yourself, but always leave mains-voltage wiring to a certified electrician.
Check the input type before wiring
Look at the model code and rating plate — DC or AC inputs — and stick to one type throughout the circuit.
Drive motors through a contactor
The relay commands the contactor coil, the contactor switches the motor — that keeps the relay output safely within its load limit.
Simulate first, wire second
LOGO! Soft Comfort has a built-in simulator — test the whole logic on screen before connecting real devices.
Keep more than one copy of the file
Save the program to your local drive, the cloud, and, say, email it to yourself — one location is never enough.
Leave 230V work to an electrician
Low-voltage wiring, programming, and DIN-rail mounting you can do yourself — leave mains-voltage connections to a professional.
Checklist before you start
Five things to check before you connect the first wire.
- Confirmed input type (24V or 230V) matches the model
- Contactor planned for motors and heavy loads
- Program tested in the simulator
- Program file saved in at least two places
- Electrician booked for the 230V connection
Frequently asked questions
Do all LOGO! models have 230V inputs?
No. There are both 24V (DC) and 230V (AC) versions — always check the rating plate of your specific model before wiring.
Can a relay drive a pump or motor directly?
Small, low-power loads sometimes, but for motors and heavier loads always use a contactor — the relay only drives its coil.
Why does simulating the logic before wiring matter?
The LOGO! Soft Comfort simulator lets you see how the program will behave without risking damage to hardware or an unexpected switch-on.
Where should I keep the LOGO! program file?
In at least two places — for example your computer and the cloud or a USB drive — so a single device failure doesn't wipe out the project.
Can I connect LOGO! to mains voltage myself?
You can handle the low-voltage side and DIN-rail mounting yourself, but only a certified electrician should make the 230V connection.
Ready to start without these mistakes?
Browse LOGO! modules and accessories in the shop — pick the right base module for your project.