Safety Information

The PCB, the display and the keypad are NOT galvanically isolated from mains.

They are not intended to be exposed to the end user. Always mount them inside the cabinet, and make it clear that there is live electricity present.

Does that mean you can not touch the keypad while the hydrocontrol is in operation?

Generally speaking, you can not touch.

However with appropriate caution, it is possible to touch the keypad during operation.

The 4x4 matrix keypad's dielectric withstand has been tested by the manufacturer at 250VRms (50-60Hz, 1 min)

Similar keypads have following ratings:

wilsonhurd.com: 1000V DC

http://www.flexiblemembraneswitch.com: 1500V DC

https://www.xymox.com: 15kV

http://www.chunyipkeypad.com >100MΩ @ 250V DC

So it's safe to touch. But if the keypad isolation is defective, it will be connected to Neutral.

Therefore...

1. Make sure that Live and Neutral are not mixed up. With correct wiring and grounding, touching neutral is not dangerous.

2. If you are unsure, check before touching.

Directly at the Mains connector on the PCB, the resistors carry line voltage. Cover up the resistors with insulation tape, to avoid touching while operating the keypad.

If your wiring scheme requires that that the PCB ground is connected to Line, then operating the keypad can be REALLY risky.

I would suggest 2 precautions:

1. make an extension cable for the keypad, so you won't accidently touch the PCB, or cover the whole PCB with insulation material.

2. cover the keypad with an extra layer of transparent plastic on both sides, to increase mechanical stability of the insulation.

Why this potentially unsafe hardware design? It's a trade-off between simple, part saving design and additional complexity for a galvanic isolation between mains voltage and user interface.

Considering that the keypad only needs to be touched during inital commissioning and configuration, this seemend like an acceptable choice at the time, since other user interactive parts on a typical PCB, like trimmers or switches, are also normally not isolated.

USB connection

The USB ground is connected to PCB ground, and therefore to Neutral (or live, if you have wired it that way)

WARNING: Your PC will be therefore connected to neutral or live va the USB cable!

Touching neutral is not dangerous - but VERIFY FIRST, or use an isolation transformer, if you want to connect your PC while the hydrocontrol is in operation.

If your PC power supply low voltage (secondary side) GND is PE-grounded, your RCD device will trip. You can avoid this by running a laptop from battery.