This module has a mains referenced antenna

One of the worst shocks I received in my TV servicing days was from an aerial isolating panel which slotted into the top of the cardboard cover at the rear of a KB monochrome TV. It didn't help that it was a wet day, my shoe leaked and there was a strip of exposed stone floor where the customer's carpet didn't quite reach the wall.

Are you sure this is 433MHz and not 50Hz? :-p

Simon Howroyd

Not being an RF expert, I'd guess that a class Y ceramic capacitor between the circuit and antenna might allow decent coupling of RF but block the mains shock risk.

Big Clive

R24 is marked twice on the remote - not that it matters for the circuit, but it does give an indication of quality control.

Zeedijk Mike

Evening Harvey do you have any links? Particularly for something UL rated or comparable.

Mike Page

I noticed from looking at other similar designed 433MHz mains switches that the wire 'helical' is all that they use (sometimes just hanging from the board, others have it dangling outside the case). Does going to the trouble of adding a dedicated mini external antenna really make that much difference to the range, for the purpose of what this will be used for?

Phil in the kitchen

It appears to be the opposite. N being oN and F being ofF.

Big Clive

By enclosing it and marking the antenna as a hazard or disconnecting the coiled black wire at that end and just using the internal antenna.

Big Clive

I’d guess F and N on the remote switch are “Function” and “Non Function”, ie a lock out of the buttons being accidentally pressed. Ewen

Ewen McNeill

Thank-you Clive this is topical for me. Would love to know what antenna isolation is de rigeur.

Mike Page

Reminds me of a "surprise" floating chassis 1970's TV repair.

Dave Davies

How would one go about making this unit electrically safe?

I'm still surprised that antenna is referenced to the mains. I had a similar surprise at work when I found out a (much safer, as it was inside case) antenna was connected to live, not neutral, as were all the debug ports, which is certainly a fun way to start the day. The designers also said that it's standard practice to reference the antenna to mains which is a claim I still doubt to this day, especially as it looked like some layout program glitched and overlapped some fills near the mains-in.

Nanashi Mitame

With the traditional setup it usually powers the circuitry directly from the buttons via diodes. Maybe it's just to provide cleaner switching.

Big Clive

Yeah, the remote is huge. I think it's going for longer range, so the extending antenna is the deciding factor for size.

Big Clive

I think the coil of wire connecting the RF receiver module to the antenna socket IS the helical antenna for that module - perhaps some of the other modules don't have this . Given that the antenna isn't properly matched anyway, a ceramic cap in series with both the core & shield of the antenna would have been equally effective and a lot safer..

Gordo

It's a Chinese design. You get to pick one, or the other, but not both.

Gavin

So aside from an electrocution risk its well designed. Hmm....

Jon Knight

The way the transmitter switches power the IC via the transistor keeps the quiescent current super low. It is for long battery life.

Nuts 'n' Proud

Too bad they didn't add an RF transformer to provide isolation of the antenna. That would be a cheap solution to a potentially lethal problem.

HarveyB

Looks like they have provision for internal antenna, with the wire coil probably soldered to either the ground pad beside the one heading to the connector, or simply left floating. This is a far better implementation of it. As Jason pointed out, it uses a very common EV1527 remote so a much smaller remote should work too, I have 2 of the 4-channel versions of this, each with 2 remotes which came in for about $6 US$ and for what they are they work well. Decent robust, compact and water resistant remotes with stiff but tactile buttons. Stock image below of the commonly available one I have. ( http://securitytechadvice.com/wp-content/uploads/2020/10/80eba97c-e8c5-4b3a-82eb-f4b0cf97ac29.jpg )

Anton

Most are non technical. They will ignore safety feedback or make some random nonsensical excuse. I sometimes leave positive feedback with a description of the issue.

Big Clive

Technically speaking it is, so should be capped by the zeners to a safe voltage with respect to ground. That changes if live and neutral are reversed. I've adjusted the description.

Big Clive

Do you ever pass your observations on to the sellers, and if so, do they ever respond or contact the manufacturers?

EV1527 is a classic. Very hackable. It has 4 inputs, and every combination of the 4 inputs sends a different code. I've used it in projects to give a dozen or more buttons.

Jason Brinkerhoff

I bet that's all sorts of fun conducted EMI.

Sure the Out Side of the antenna isn't clamped to neutral ? Hard to see in the video ?

Oh yeah looking

Michael Thompson