Sat, 02 May 2026 03:52:37 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309891#Comment_309891 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309891#Comment_309891 Sat, 13 Dec 2025 14:22:50 +0000 Rex
Have the replacement panel up and running and since if it activates, it is impossible to hear the external sounder in the house and particularly if entry is from the back.

So this time, I have fitted a sound bomb, if for no other reason that the excessive inside noise is slightly disorienting.

However, I now have a very faint humming from the sounder and wondering if it is induced by the incoming mains.

The red line is roughly the cables from the sounder that go on the bell terminal on the board. These two wires go under the plastic housing and enter the interior just below the terminals. The yellow lines are the mains to the transformer.

I know little about the science of electricity but could the transformer and/or the incoming mains be inducing a micro current in the sounder wires that is causing the sound to hum?

If so, what is the solution? Reroute the wires so they do not cross the incoming mains or go under the transformer? Reposition the sounder?

Grateful for any suggestions.

Compliments of the season to one and all,

Rex]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309892#Comment_309892 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309892#Comment_309892 Sat, 13 Dec 2025 14:49:56 +0000 djh
If your problem is caused by the two yellow wires crossing the red wire, then one solution would be just to twist the two yellow wires around each other. A 'twisted pair' won't induce interference in the same way. Or as you suggest, rerouting the wires would help.

But maybe the interference is generated elsewhere and is already on the red wire. If the circuit design was intended to have a mechanical bell or suchlike on the end then a small ripple wouldn't cause a hum in the same way it might with a piezo sounder.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309893#Comment_309893 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309893#Comment_309893 Sat, 13 Dec 2025 17:42:36 +0000 WillInAberdeen
So irrespective of how the DC wiring is routed, the sounder itself can be picking up the mag field from the transformer and the mains cable.

You can try repositioning the sounder a few feet away from anything mains and see if that helps?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309894#Comment_309894 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309894#Comment_309894 Sat, 13 Dec 2025 19:14:03 +0000 Rex
I will see about repositioning the sounder under the panel and the wires can go straight up to the terminal.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309895#Comment_309895 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309895#Comment_309895 Sat, 13 Dec 2025 20:38:37 +0000 djh Posted By: RexBy mounting it there, the wires are not exposed.Just use a screened twisted pair instead of whatever wire you used and then it doesn't matter whether it's exposed and you can mount the piezo sounder further away.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309896#Comment_309896 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309896#Comment_309896 Sat, 13 Dec 2025 22:44:09 +0000 philedge
If it's still humming when you move it away from the AC, alarm suppliers will have a small PCB mounted relay which you can wire to the bell output and wire the soundbomb via the relay so it only ever gets connected when the bell output is live and switches the relay]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309897#Comment_309897 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309897#Comment_309897 Sun, 14 Dec 2025 07:50:07 +0000 Rex
But.... that did not happen and I'm not about to start running cables up walls. Its a TF house with Fermacel so challenging to chase the cable into the wall.

Disorienting would be nice but my main aim is to ensure that anyone breaking in can hear that they have activated the alarm. As it is, the 3g glazing and Warmcel is extremely good at reducing the exterior alarm to close to inaudible.

Will reposition the sound to below the panel today so the wires are not adjacent to the mains input.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309898#Comment_309898 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18384&Focus=309898#Comment_309898 Sun, 14 Dec 2025 10:06:25 +0000 Rex
Thanks for the suggestions and support from a rather non-electrical, expert DIYer.

Compliments of the season to one and all,

Rex]]>