How Not To Do PCBs

tmp21AEMy usual stance is to be nice to Itead, I’ve been dealing with them for some time and although I have absolutely no commercial or personal tie up with them, they do send product samples from time to time as do many others - and I usually end up writing decent reports about their products – especially Sonoff controllers which I think are miraculous given the price.

Well, there’s always an exception (but see the new note at the end)

Yesterday I received this neat little board and accompanying radio handset.

tmpA51So over on the top right you see the board, a really neat little 4-relay WIFI-and-radio controlled board complete with spring aerial and on-board test buttons.

This is the kind of board that could end up all over a hobbyists house, turning lights and other devices on and off. And that’s what worries me as hobbyists aren’t necessarily experts in electronics and mains power use.

So – why would I have a problem with this.

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Ok, take a look at the underside – which is clearly left-right reversed from the upper view. The clearances around the relays are fine for mains voltages and they’ve made up for track width with some heavy soldering – not pretty but functional. But here’s the rub – look at the two vertical tracks on the bottom right of the photo – that’s mains power coming in from the connector – to the little power supply.A close inspection at the power supply end shows that the gaps between pins are close – but in practice ok.. but here’s the rub… notice the light green nature of the bottom half of the board – that is ground plane flooding – most commendable – keeps electrical noise down – BUT – what the HELL is it doing right up next to the mains wires??

Those of you from the states might think this is bad but hey, not too bad.. but in countries using up to 250v (we have 250v here) – that is downright dangerous – the slightest damp or circuit board fault or solder beading and BANG.  I am not one of these perfectionists – far from it – I could not tell you how many times I’ve electrocuted myself over my many years messing with electronics (around 50 years amazingly) – but I’m not going near that with 250v mains! So – apart from the fire risk there is also a risk of electrocution from messing with the on-board buttons.

Now – to be VERY fair, I did immediately contact Itead about this (as did Peter Oakes as he has one) and in very strong terms told them my views on this given the high quality of their other stuff. Well, it turns out that in fact that this product is a third party board simply using their little cute power supply left middle) – and they are going to contact the manufacturer.  If you see these boards – I would check that you get a revised version – OR un-solder that power supply – swap the leftmost connector to the spare holes and feed it with 5v instead.

All this REALLY needs is the ground flooding removed from the area around those two tracks – maybe leaving 3mm all round.. and I’d be inclined not to solder the unused middle connector (but that’s just me). Clearly these are early production or even prototypes by the hand soldering – I’m hoping our comments will mean the final production will be useful, SAFE products.

As for the board ITSELF – there are 4 buttons for on and off – and a neat feature – a button to select one of several non-volatile modes – so, for example, the 4 buttons/remote/WIFI might turn individual outputs on or off, or allow only one of 4 to be on at any time, or monostable mode where delays close momentarily only etc. Very good!

Update December 2016: Now, I have to tell you that following on from comments that Peter Oakes and I passed back to Itead, they have, I believe, dropped this product and are working on their own version. I have to say, HATS OFF!

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12 thoughts on “How Not To Do PCBs

  1. I think this will be a good test for ITEAD. if they deal with the issue promptly and with good grace, then it will be a very positive sign No company is perfect, and I personally believe their reaction to screw ups is an important sign

    1. Yes absolutely - I suspect originally 5 v then the company (not ITead) decided to make it dual. Well, they're now aware that it is no good so hopefully a release will come out with that sorted. I will take the PSU off mine and use that for something else - and run this one from low voltage.

  2. I would gladly see the little SMPS module unsoldered and checked for safety. Often these are a security nightmare too.
    Every time I get a chinese power supply, I test it on a megger at 2k5V. At least 10% do not pass the test, some even going into dead short between primary and secondary side, usually because of failed suppression cap being ordinary 1kV or even 500V ceramic instead of self-healing security one.

      1. Hello,
        I use them too, they are OK as far as I can say. Never have seen any of them failed. Nevertheless, I do not trust chinese QC, so I test every single one I use. The good thing about these exact modules is that they use a thick teflon-like insulation on the secondary winding instead of the common thin enamel. This adds a good portion of security.

    1. Hello,
      I use them too, they are OK as far as I can say. Never seen any of them failed. Nevertheless, I do not trust chinese QC, so I test every single one I use. The good thing about these exact modules is that they use a thick teflon-like insulation on the secondary winding instead of the more common thin enamel layer. This adds a good portion of security.

  3. I had a couple of these on order when I read this post. As I live in the US where we "only" use 120V for normal branch circuits I though I'd give it a try with some modifications. The picture shows my crude modifications to the ground plane.

    Now if I just figure out how to load my own firmware. Anyone seen a schematic for this beast?

    John

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