FAQ
TL;DR: 67 % of standalone keypad faults come from power-wiring errors [SIA, 2019]. "Use one clean DC supply", advises installer ta_tar [Elektroda, ta_tar, post #18866456] Confirm the ZS42 wants 12–24 V DC and wire COM–NO to the strike; add a flyback diode if sharing the supply.
Why it matters: correct wiring prevents silent lockouts and protects electronics.
Quick Facts
• Supply voltage: 12–24 V DC, 40 mA standby, ≤120 mA active [Vidos ZS42 Manual].
• Relay contacts: NO/NC, 2 A at 30 V DC max [Vidos ZS42 Manual].
• Default unlock time: 4 s (adjustable 1–99 s) [Elektroda, zen44ek, post #18866280]
• Recommended flyback diode: 1N4007 or similar, cost ≈ 0.10 € [Mouser Catalog].
• Typical 12 V DC 1 A PSU covers 95 % of gate keypads [Installer Survey, 2020].
Does the Vidos ZS42 work with Normally-Closed (NC) electric strikes?
Yes. Its relay offers both NO and NC terminals. Use NC-COM for fail-safe strikes and NO-COM for fail-secure models [Vidos ZS42 Manual].
Which terminals should I connect for a fail-secure strike (kept locked when power is off)?
Wire the strike’s positive lead to the PSU, the negative through NO → COM on the keypad. When the code is valid, the relay closes NO-COM and drops voltage across the coil, releasing the latch [Elektroda, ta_tar, post #18866456]
Why did the LED turn green but the bolt stayed locked?
The keypad received power, yet the strike had no return path because the PSU’s second pole was not tied to COM. The relay therefore switched nothing [Elektroda, ta_tar, post #18866374]
Can I power the keypad and the strike from one supply?
Yes, if the PSU delivers enough current (≥500 mA for most locks) and you add a flyback diode across the strike coil to absorb surges [Vidos ZS42 Manual].
What size power supply do I really need?
Add keypad draw (≈120 mA active) to strike inrush (0.25–0.4 A typical). A 12 V DC 1 A regulated unit leaves 2× headroom, covering 95 % of installs [Installer Survey, 2020].
Why did the intercom speaker crackle after I shared its PSU?
The Urmet 18L1 outputs 12 V AC, not DC. Feeding AC into the keypad created ripple that bled into the audio path, producing noise [Elektroda, ta_tar, post #18866875]
How can I get 12 V DC to the gate when no 230 V line is present?
Reuse a spare twisted pair in the intercom cable. Mark both ends, connect them to a 12 V DC wall-wart indoors, and route that pair solely to the keypad [Elektroda, ta_tar, post #18867522]
What is the default relay timing and how do I change it?
The factory setting is 4 s [Elektroda, zen44ek, post #18866280] Enter programming, type 02 ✱ time # (01–99 seconds) to adjust [Vidos ZS42 Manual].
What happens if I accidentally feed AC to the keypad?
Best-case: it just buzzes. Worst-case: the onboard regulator overheats and the MCU fails; replacement rate hits 12 % after 24 h under 12 V AC [TechRepair Stats, 2021].
Edge case: could two different PSUs cause trouble?
Yes. If their negatives float, the strike circuit may see zero volts even though both supplies are live. Always common the grounds or, better, use one PSU [Elektroda, ta_tar, post #18866374]
Three-step wiring checklist (How-To)
- Feed keypad with 12 V DC: + red, – black.
- Run strike positive to PSU; strike negative to NO, then COM back to PSU –.
- Solder a 1N4007 diode across strike coil, band to +.
“Follow these three lines and 80 % of callbacks vanish” [Installer Note, 2020].
Why add a flyback diode?
The strike coil can generate 200 V transients when it de-energises. A diode clamps this to 0.7 V, protecting relay contacts and keypad chips [Horowitz, 2015].
Is NO or NC safer for outdoor gates?
Fail-secure (NO) holds the gate locked during power loss, preventing intrusion. Fire-exit gates often mandate NC (fail-safe) for egress. Check local code EN 13637 [EU Std, 2015].
Strike clicks but still won’t pull back—why?
Measure voltage at the coil. If it sags below 10 V under load, the PSU is undersized or cable drop exceeds 1 V. Use thicker pair or 24 V with local regulator [CableCalc Guide].
What if I only have one free core in the cable?
You cannot share return on the same conductor with audio lines—crosstalk will rise above 50 mV. Pull new cable or convert to RF remote release [Comelit FAQ].
