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For a college project I am implementing heat via the use of one of those heat-pads you can get for lizards. The problem is the heater is direct to the mains.

Am I being dumb or is there a way to allow mains electricity into a PCB to then power the mat directly from the PCB? I am using an IC chip to control the mat.

The mat is 8w at 240v AC

I'm just struggling to work out how to implement the mat into the PCB as I have no idea if its possible wiring earth, live and neutral into a PCB.

Many thanks

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    \$\begingroup\$ Oh, yes, it's done all the time. Doing it safely usually means hiring a professional to apply formal testing and rule-checking. \$\endgroup\$ – Whit3rd Dec 12 '16 at 10:06
  • \$\begingroup\$ I bet the lizard doesn't realize the risk? How is it fitted to the lizard is my main interest - is it worn like a little coat? \$\endgroup\$ – Andy aka Dec 12 '16 at 10:11
  • \$\begingroup\$ @Andyaka Now I have to imagine a lizard in a cute little electric labcoat – you made my day. \$\endgroup\$ – Marcus Müller Dec 12 '16 at 10:22
  • \$\begingroup\$ Yeah and I thought I was being serious LOL \$\endgroup\$ – Andy aka Dec 12 '16 at 10:33
  • \$\begingroup\$ If you follow the rules, do some calculations and follow up on your production, you are allowed to CE mark it yourself. If it's your first time, I would not recommend it. \$\endgroup\$ – winny Dec 12 '16 at 14:46
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Rule number one: If you have to ask, then you should not be messing with mains.

However, if you buy a relay-isolated module with shrouded screw terminals, then it's relatively straightforward to wire the mains side entirely point to point. If you take care to have no stray wire strands at the terminals, adequate wire cross section and insulation rated for mains use, a fuse rated to protect the thinnest gauge of wire used, the relay module screwed down onto an insulating base, segregation of mains and low voltage areas, physical protection for the mains terminals, then it can be fairly safe. Try eBay with a search of 'arduino relay', more there than you can shake a stick at.

If you run mains onto a PCB, you have to take a lot more care over clearances, and protecting the tracks from accidental contact by you. Really, if you have to ask, then don't. The problem is not getting the mains to work. The problem is keeping it safe. The risks are foreseeable, though most noobs don't spot them until after their first mistake (which can be their last). Amongst the risks that you may not foresee are 1500V spikes on the mains, you (or anyone else) forgetting that there's mains on the board and touching the wrong track, you dropping a bit of wire on the board. It's hard work to get mains onto a board safely. Your college Prof and colleagues will be very upset with you if you create an avoidable death or fire, even an unexpected 'bang' in the corner of the lab would be very embarrassing.

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  • \$\begingroup\$ @MarcusMuller thx \$\endgroup\$ – Neil_UK Dec 12 '16 at 10:12
  • \$\begingroup\$ You're perfectly welcome, Neil, but I've not been doing that for you – I did it for the literal love of life :) \$\endgroup\$ – Marcus Müller Dec 12 '16 at 10:18
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It is less expensive, faster, easier and SAFER to use a commercial product for controlling mains power vs. designing it onto your PC board. There are many solutions for mechanical realays, SCR/Triac and SSR (Solid State Relays) for exactly this kind of application. You have not revealed WHY you want to put the mains control circuit on YOUR PC board?

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