Does anyone have any advice re. setting up lab/workshop?

[BrendanP]

We have recently bought a house in the Latrobe Valley about 130kms east of Melbourne.

Does anyone have any advice re. setting up a electronics lab/workshop? I think some of the more experienced guys must have quite extensive set ups at home or work.

After spending the last 4 years in a one bedroom flat its great to have room to move.
Previously I had a small desk to work on, now I have 6 meters of bench space. My benches are 600mm wide. I have 3 foot fluros above them and then more shelves above that for parts boxes. I have a lot of shelving for folders full of data sheets.

I was thinking of mounting a earthed copper rail around the edge of the benches that I could clip a anti ESD braclet lead onto. I have seen ankle type things you wear that earth the sole of the shoe to the ground but I guess that requires a special floor covering.

Theres a timber floor there at the moment. I dislike carpet because of the fibres and dust it traps. What is best in flooring re. ESD?

The bench surfaces are melamine. Is this bad for ESD?

 

[hippy]

I've not suffered any ESD problems but I may have been lucky. Some things are more static sensitive than others so worth considering at the start.

I'd personally be cautious about earthed copper edging to the desk as that's going to attract loose and bare-ended wire like a magnet. Most wrist straps have a large press-stud and you should be able to find ( or make ) matching recepticals that fit in mains power outlet boxes which can sit next to your mains sockets. Shoe straps require a special floor, probably overkill and expensive, but you could cover your workbench with it, but then you have no insulation on it at all. It's possible to buy anti-static mats which clip to the same points your wrist strap would which is probably better.

When you're earthed you become part of a potential circuit so the most important thing in my mind is proper circuit breakers ( RCD, ELCB etc ) for the entire lab mains power supply. Particularly important when one wrist is grounded and you are proding with the other hand but recommended anyway.

One thing you perhaps need to consider is; is earth earthed ? The last thing you want is to be killed by a faulty appliance elsewhere in the system dumping mains up earth.

 

[moxhamj]

I've never had problems with static either. Concrete floor, usually wearing rubber soled shoes, no carpet anywhere and not wearing synthethics. Wood would be fine too. If you wander round in the new room a bit then touch some metal things and don't get a zap then there is no static.

Have you got room for a computer with broadband access? If so, then no need to have any reference manuals any more.

Re expensive setups, mine isn't really expensive. It has grown by topsy and every piece of equipment was drooled over in catalogues for years before purchase so equipment earns its keep.

Get on Rockby's mailing list (in Melb) and when they have something on special that is great value then buy a few. Eg I've just picked up a whole lot of relays for 50c each. Electus is good also (Jaycar's wholesale division - all the same products but about 30% off). Send them an email and ask for a catalogue.

But you can do a lot with a small protoboard, a picaxe and a few resistors/caps/leds, a multimeter and an old 300Mhz computer.

 

[Rickharris]

I agree with the above - I have had little problem with static & have worked with electronics since 1961. Currently (sorry for the pun) a teacher the kids miss-treat the components in possibly the worse environment there is but we don't get any issues that aren't self made. Components by and large are very cheap anyway.

Avoid the earthed bench, as Hippy infers ,"Ouch", in fact in many electronic labs they go for an earth free isolated supply option to minimise the danger of electric shock. At the voltages you are likely to be dealing with just normal domestic precautions should do.

A good dual bench power supply which allows you to set voltage and current. is useful but a supply of AA batteries is just as stable and flexible.

An oscilloscope I would have said was invaluable but i hardly every get ours out of the cupboard these days.

A DVM cheap enough to have 2.

a Decent set of basic tools. Proto board and strip board for building on.

A basic set of resistors, capacitors. you don't need one of every value at all.

Most importantly a good supplier who will respond quickly to your needs. Sadly, at least in the UK, the corner shop with electronic components in it is long gone but the web is almost as good.

Imagination and the need to solve some problems also helps.

there has been discussion in this forum before so a search may throw up some more information to help you set up.

 

[BrendanP]

Do you guys worry about fume extraction when soldering?

Do you guys worry about fume extraction when soldering? I was thinking of rigging up a small inline duct fan with some small diameter concertina foil tube as a soldering fume extraction system. I have the room to have a dedicated soldering area on the bench so I could do it. Do schools use fume extraction when soldering? DO OHS regs. make fume extraction obilgatory if you are employing people to solder? Do you think its an issue from a medical perspective Dr. Acula?

Ive pretty well given up on suppliers here In Australia. (Apart from the usual stuff like R's and cap's). Anything else I just order it from Mouser in Texas or Futurlec in Thailand. HoBid is also usefull. I can't speak highly enough about Mouser.

I have a CRO and a variable power supply with current limiting. Thats probably the most usefull thing I have.

Good point re. the RCD's etc. My father also mentioned to me to check that earth really is earthed.

I'm concerend re. the ESD issue because I have read that parts can be critically damaged by ESD yet not show symptons immediately. Their service life is drastically shortened or they will not perform correctly. I'm getting ready to small scale manufacture some electronic equipment. I have 'nightmares' about having the gear fail because a part worth a buck failed prematurely because of incorrect ESD practices.

I have also read that the ESD voltage threshhold that many parts can be damaged at is below that that human beings can feel. Maybe I misunderstood that part but I think I got it right. I notice that everything that comes from Mouser is packed in anti ESD bags and foil style plastic envelopes.

 

[hippy]

Do you guys worry about fume extraction when soldering?

No more so than I worry about getting run over by a car. Now oven cleaner; that does scare me :-o

If I were doing a lot more soldering I would perhaps worry more. Then again I smoke, so I'm not exactly paranoid about personal risk. Something's going to kill us no matter what we do. When I was at school, chemistry labs had parquet flooring which was full of who knows what in the cracks and probably did more damage. I recall New Scientist producing a report that showed schools were massively more toxic than commercial laboratories.

I think it's reasonable to consider the damage of solder fumes and I'd say grab some ducting, stick a fan in it and feed it out a wall vent. At least it stops the fumes going in your eyes when crouched over your board.

 

[andrewpro]

There are two things I sorely lack that I truly wish I had... Very organized parts storage, and open space.


You can fill your benches up with doodads, whatsits, equipment, etc but none of that will do a lick of good if you cant work on anything.

Most of my parts are in those cabinets of small drawers. You don't really NEED ESD safe ones. I keep all my chips in that black crosslinked conductive foam stuff inside the drawers and I've never had issues. Get as many of the drawers as you can. Even if half of them are empty, you'll be better off with empty bins than having them all full. When you need ot jsut grab a part, or go "shopping", it's a lot easier when everything has a place.


The only place in the shop that I would have truly stuck in one place is a soldering station. If you can, try to have it powered from a different circuit than any test equipment and power supplies. Those soldering irons can throw a lot of noise into the system.


For the rest, I'd just have good lighting and as much open space as you can. Put a mains plug every 4 to 6 feet if you have the opportunity, and don't put them on the floor! put them where you can get at them. When it comes time to need a power supply, or a scope, or a function generator, or anything just pull it out of storage and plop it down. Or put it all on a cart and wheel it where it's needed.


Just my thoughts.

--Andy P

 

[eclectic]

Nightmares in Oz?

Brendan.

ESD is possibly a nightmare.

But, this lot really IS!!!

Duty. Practicable. Reasonably practicable. ............

http://www.justd.com/ohs.htm

And I'm sure there's loads more!
Best of British and Oz luck mate!

e.

 

[hippy]

Where space wasn't a problem at work and parts bins were elsewhere, it was very handy to have a shelf above the workbench so scopes and so on could be put there without cables cluttering everything and getting in the way. We had sockets just below the shelf so power could go to the bench for soldering irons etc, and slots in the shelf for pushing plugs down through.

As andypro says, you can never have too many of those plastic drawer units. More expensive ones come in various widths which help for larger components. The rule there is organisation. Column sets for capacitors, ditto for resistors ( down in value, across in magnitude ), diodes, crystals, PICAXE's and so on. Include drawers for the common values even if you don't have the components. Labels save so much time. Standard envelope stickies cut to size and hand written work well.

 

[BCJKiwi]

Static and ESD depend largely on low humidity and the ability to generate/conduct it.

As you are in Montana I would expect it would get pretty dry at times so if this is still of concern for you, a small mat and wrist strap connection where you are working is all you should need. When you reach for those components in that shelving/bin system, ensure you touch the bin before you touch the component. If it's in a bag, put the bag on the mat before opening it.

This issue is all about differences - electrons won't flow if there is no potential difference!

If you are still paranoid about ESD and want to get even more paranoid go here;
http://solutions.3m.com/wps/portal/3M/en_US/electronics/home/SupportTraining/ESDTraining/
and click on the
ESD Control Handbook » link on the right.

Just bear in mind the static/ESD detection/mitigation is a big part of 3M's business so they certainly don't downplay the issues!

 

[moxhamj]

Re solder fumes, I tend to have a fan blowing across the desk which blows the fumes away. It depends a bit on eyesight - if you work with the workpiece 30cm in front of you on the bench then the fumes go straight up. But if you put your face right over the soldering then that would be a problem.

One of my best investments was a set of parts drawers with labels on them.

Eclectic, that web link is a nightmare. They are into lawsuits by the second paragraph!

BrendanP, what sort of projects are you making?

 

[BrendanP]

Theres a lot of good advice in everyones replys, many thanks. I have a address label printer I'm going to use to label parts holders and bins. Thanks for the tip re. organising the R's Hippy.

I work in construction so I see how much stuff gets stolen off site, everything from building materials to entire earthmoving gear such as excavators and bobcats. I developed a on site security system that takes a couple of minutes to set up and is easy for untrainned people to use. It nothing very fancy, waterproof sensors that can be placed on or in equipment around the site. When moved they TX a rf signal back to the base station. The base station SMS's and rings the programmed number to alert the user. It has a DTMF recognition IC so the user can acknowledge the reception of the alarm condition by pressing a key on their phone, otherwise the unit trys a second and third number. It also alerts on main power failure, physical movement (tamper) of the base station itself, low on board charge state battery, low battery levels in the sensors. You can also SMS the base station and interrogate it it about most of those parmameters and it will reply.

Learning about and working with the GSM module was the toughest part of the project.

The last part of the project to finish is developing code so the base station logs on each of the sensors when they report in 'situation normal' say, every 20 minutes. Failure to logon triggers a alarm condition.

So as I see it there will be a sub routine in the set up menu that allow the user to log on each sensor. The sensors header info will be written to eeprom. (I have a external eeprom on the pcb. I use extensive setup prompts to make it easy to use via the LCD and there wasn't room in the IC's.

Im unsure how to go about the code that will write the time the sensor reports and then check that time at a certain interval to see if it has reported.

I set up a Pty. Ltd. company structure with a paid up value of AU $100. If the thing fails it isnt the end of the world. Go ahead and sue me, for a hundred bucks! I don't expect failures but I thought I'd add that information to prempt the hand wringers. The ASIC web site has all the information needed to do it. My brother in law is a lawyer and did if for me but I could of done it myself as could anyone else.

 

[demonicpicaxeguy]

small tupperware containers aren't a bad way to go as far as storage goes especially stackable ones, just visit the $2 or 2 pound shop,

 

[moxhamj]

That is a great business idea. You may not need too much more equipment than you already have. Once a prototype is working I presume you would start making these in larger quantities and you could either do this yourself or outsource. There probably is more field testing to do - the RF range could be an issue and putting an RF unit near metal (eg an earthmover) would decrease it further. But that is a field testing issue and probably doesn't need more equipment.

 

[wapo54001]

What is the mains frequency where you are? Especially if 50Hz and you are using fluorescents, I'd consider replacing the ballasts with electronic ballasts -- fluorescent flicker seriously annoys me, actually can give people headaches.

 

[profmason]

I am redoing my workspace over the holiday. I got a new table which allowed me to move to a U shaped system. As was mentioned earlier, you never seem to have enough small drawer cabinets. I am including a quick image of the workspace below. Tables are melamine folding tables, 1x four foot and 2x five foot. Floor surface is a laminated hardwood. I use two 48 bin cabinets and four 12 bin cabinets for part storage. There are also two dedicated storage trays for resistors. (With 36 bins each)
To address a few other things, I use a desktop fume extractor that pulls the fumes from soldering through a carbon filter. My rework station has a fume extraction option that is built into the iron, but I removed it because I want the iron to be as light and maneuverable as possible. At the college we have a IPC certification program which I did for fun last year. We use all lead free solder and a BIG fume extraction system. In my student labs (Where we do much less soldering) we use lead free solder and have microhoods (Looks like a wok on the end of a double jointed arm.)
To echo what people have said previously, the most used things are in order
1. Computer
2. Breadboard
3. Power Supply
4. Soldering Station. (Break down and buy a decent one!) I started with http://www.web-tronics.com/cispdeesdsas.html
and now use http://store.sra-solder.com/product.php?xProd=6267&jssCart=9728b838162c72acd913004518049c5a
5. Good lighting. I love this lamp:
http://ww2.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=34018

On my wish list right now are MORE 48 drawer cabinets!

have fun!

 

[BrendanP]

I'm always impressed by the depth of knowledge and skill of many of the people on this forum. Thanks again for all the good advice.

I actually have a lamp indentical to the one in the link. I also recently bought on ebay a zephyrtornics hot air soldering pencil.

Dr. Acula, I've done quite a bit of work testing RF ranges with the transcievers I use. (Radiometrix units). I have a Winradio reciever which Winradio kindly calibrated for me so I can use the RSSI feature to make comparisons between different antenna configs and so on.

When the unit is in set up mode you can go around and move the sensors, the base station then will activate its external siren/strobe output for 2 seconds. That way the user can easily check the RF link by plugging in a piezo siren and walk around the sensors and giving them a kick or nudge.

Depending on the app. the base station can use either a helical as an antenna or a yagi mounted say on the roof of the site shed. The Radiometrix RF units user guide has a circuit that will detect a antenna tamper attempt/attack.

The base station will also take an N.O. or N.C. input from a hardwired alarm output so it can also be used as a adjunct to a conventional alarm system.

Mains power supply is 50HZ in Australia. Ill see how I can cope with the fluros but I'll change them if the noise irritates me.

 

[Peter M]

ESD can be a problem, whilst working in the telecommunications industry, 3 teams did a rather large hardware/software upgrade. our team used wrist straps, and 1 of the other teams said that it was hog wash - interestingly we had about 2 hardware failures for the hundreds of upgrades, whilst they had numerous failures, some of these were days later - up to you but for a few bucks?

Another simple addition can be a computer power supply (cheap, lots end up in bins) with its outputs conected to banana sockets mounted on the front of your bench. Easy 5v and 12v for proto typeing, short cct proof and it could be used as your earth point for ESD protection as well. This can then free up your more valuable variable PSU for other voltages if required.

soldering fumes, if you do a lot of it can be harmful, I get blood noses if I spend all day soldering without a fan. I too use a fan (120mm computer fan) blowing across where I'm soldering to blow the fumes away.

Good luck with the project should be a winner, Ive had people suggest a very simular idea to me... can't beleive what people will steal... you need heavy machinery to pinch it and no one notices????

 

[manuka]

Brendan: Bulldozers-what happened to the horses!? At least the iron horses shouldn't give you trouble jumping fences. Bravo on the move, although I guess the commute will be an issue eventually...

I'm rather late to the workbench party, & the Forum brains trust has admirably already offered great ideas. Aside from RCD protection,another relates to the workbench surface. I'm a fan of butynol offcuts on electronic workroom benchtops- plumbers & roofers let these go for a few beer. Butynol is pleasant to work on,withstands soldering irons, & has a high resistance to suit ESD wrist straps.

My decades of electronics lab. layouts show you can never have enough horizontal work surfaces, & although typically 900mm high these could be at flexible heights to suit the project. User ergonomics (comfy seating etc) are pretty crucial, as is LIGHTING. Naturally have an internet capable PC handy. There are numerous further tricks of the trade in this game, but you no doubt know many already.

Soldering with classic 60/40 fluxed solder increasingly raises Health & Safety concerns, & at the very least I'd ensure fresh air & practice self discipline to keep food away from the workroom. You don't want to end up a drongo with excess lead in your system. Stan

Footnote: Nimble animals such as cats may leap on the bench & knock things over too. Little kids may help dada in a similar manner. A Kiwi mate recently had his workshop burnt out (~$50,000 worth of damage), when his cat knocked over his hot iron while he down the road getting some parts. Yeah- he should have turned it off. The cynical may laugh, but he was then called out (as a volunteer fireman) back to his own fire... Stan

 

[wapo54001]

Mains power supply is 50HZ in Australia. Ill see how I can cope with the fluros but I'll change them if the noise irritates me.

It's mainly the effect of the low frequency flickering that is most annoying in my case . . .

 

[Dippy]

I'll go along with a lot of above.
I'd add that your choice will obviously depend on your budget and projects.
I've never had ESD problems but I do sometimes use a conductive doo-dah 'just in case'.
I'll go along with a fan for soldering , good extractors are expensive. But not too much of a hurricane or else it'll cool your solder.

I'd also think a bit harder about lighting. Sensitive IR stuff will be interefered with by mains lighting esp flouro.
Make sure your lighting is good, bright and even so that you don't cast too much shadow when your nose is an inch away from your pcb.

Well labelled component drawers, you can get those RAACO wall mounted things.


As said before, PC, osc, mulitmeter and a PSU with variable I/V out (e.g. Thurlby Thandar).
A good toolkit, tweezers, proper temp controlled anti-static soldering iron eg Weller and solder sucker and range of sodler bits.
For smd you'll probably need a proper desoldering station.
Oh and a magnifying glass and a small vice may be handy. (No hippy, not that sort of vice).

The list could go on. I love spending other people's money.

Prediction: Regardless of space and intention your bench will be covered in mess after a few months.

 

[hippy]

My decades of electronics lab. layouts show you can never have enough horizontal work surfaces, & although typically 900mm high these could be at flexible heights to suit the project. User ergonomics (comfy seating etc) are pretty crucial

Excellent advice from Stan. Most desks are around 750mm, lab benches at 900mm ( kitchen worktop height ) allow work standing up ( handy when scopes etc are on shelves above ) and sat down, although you really need a draughtsperson chair ...

http://www.seatstore.co.uk/acatalog/Drafter-MetroL.jpg

It's a bit weird being up in the clouds for a few days and a long step off, but that soon passes. They don't come with wheels so a bit immovable. You probably want bench and desk so you can mix electronics with thinking and design in a normal wheelie chair. You could perhaps have a fold-down bench surface at 900mm over the desk but would need to make sure the 750mm wasn't a knee obstruction below.

If you have friends round, or that rare breed, a partner with an equal interest in your hobby, get two chairs of the right height.

I'd forgotten how much standing up I used to do when working on electronics, so floor surface can be critical there. I recall we just had normal floor tiles, nothing ESD fancy, on a concrete surface. Never suffered any back or posture problems.

Getting decent depth wood for surfaces can be an issue or expense. Kitchen worktop comes in ideal lengths but deeper stuff is expensive. In an alcove which is my (unused) work bench I used a laminated hardboard with honey-comb innards internal door ( initially $2 as one side had a small hole punched in it ). I also learned the value of measure three times, cut once there. I'm sure you can imagine the disaster I had

 

[BrendanP]

Hi Stan, best wishes for the new year. Still going on with the horses but taking a slight detour.... I started playing with the GSM for the nags but this app. suggested itself so here I am.

I'm working down here in the valley, theres quite a bit going on so I shouldnt need to go back to Melbourne at all. There a new de salination plant going in not far away and theres pending an announcement of a new coal fire power station. I'd like to work on a nuclear fuled station buts that a way off for here.

My next door neighbour at the flat I was living in when you visited is a plumber, I'll ask him about the desk top material. Do you know what plumbers usually use it for?

Interesting you mention fire awareness, I was thinking this morning I should get a smoke detector for the room and wire it into the house burg. alarm system which has a dialler on it.

 

[daily]

Bench power suplys and earth

I don't think installing anything attached to mains earth is a good idea. I have blown up the chip and power transistor in my bench PSU by connecting the PSU's output to earth, even though the PSU was supposed to be short circuit resistant. I suggest that mains is removed as much as possible and i think that you should use the 0V rail from your PSU as 'earth'.

(I have managed to replace the damaged parts, the chip was a quad opamp and had split in half, the 2N3055 just stopped functioning)

 

[moxhamj]

Dippy re "Prediction: Regardless of space and intention your bench will be covered in mess after a few months.", I think it was Einstein who said that if a messy bench is a sign of a messy mind, then of what is an empty bench the sign of?

I would be very embarrassed if a photo of my bench ever got out. But I judge my shed by what it produces, not what it looks like.

Re lighting, I have flouros but I also have a desk lamp and when the last 100W bulb blew I replaced it with a compact flouro and one thing that is very nice is that these compact flouros don't get hot so you can get them up close to a circuit without risking burning hands etc.

 

[demonicpicaxeguy]

Dippy re "Prediction: Regardless of space and intention your bench will be covered in mess after a few months.", I think it was Einstein who said that if a messy bench is a sign of a messy mind, then of what is an empty bench the sign of?

I would be very embarrassed if a photo of my bench ever got out. But I judge my shed by what it produces, not what it looks like.

Re lighting, I have flouros but I also have a desk lamp and when the last 100W bulb blew I replaced it with a compact flouro and one thing that is very nice is that these compact flouros don't get hot so you can get them up close to a circuit without risking burning hands etc.

i find those clean white type cfls are the best especially for trying to decifer between orange and red on some of those resistors


it must be that time of the decade i'm also re doing my garage to run my new buisness out of, i'm building a 12 foot bench with shelves against the wall and overhead storage above that

i think it's probably safe to say that almost everyone would be embarrssed if their bench space photo got out

 

[profmason]

Cleaned the bench today. Photos attached (Smirk)

All the stuff on the bench filled 2x 3 gallon tubs (To be sorted later )

have fun!

 

[manuka]

Prof.M-I'm seriously impressed! But no doubt you'll need some odd component in the next few days & have to dump those tubs back on the bench ! My own rather 3D workbench has just had a micro-scare, providing postcard sized space for 4D's stamp sized OLCD (Organic LCD) work out. I'm still getting my mind around these micro SD memory card based products, but PICAXE control looks very feasible. The 4D web site => http://www.4dsystems.com.au has more general details. Stan

 

[D n T]

The dream workshop...

I might sound like an ad for an electronics outlet that used to be owned by a bloke with thick black rimmed glasses who now flys helicopters to the poles (initials D.S.) but anyway...

A couple of things for your workshop, usually from the above
A variable power supply
A deskmount magnifyer lamp - to help you see thee orange stripes on ther resistor
A nice little soldering unit with stable stand
D.S. have a good little set of draws for under 10 dollars with twenty draws for components etc, I have 5 of the things
A fridge for refreshments, and if you need to cool something down, throw it in a plastic bag and into the friodge
A window to look out of, it will help with problem solving
You might want to disconect your smoke detector and put in a stand alone or you might get some visits in the of a heavy consructing session
A fold up bed for when you PICAXE mad mates from NZ come over to visit
All of the above from the other guys.
A big bin so you don't have to empty it often and so you can fish out that note you made with the part number on it that you threw out but now need ( been there done that).
A seat for your wife to sit, have coffee and talk to you while you work, handy, trust me...

 

[Rickharris]

Wife - Talk? - Awww you Ausies always joking!

 

[D n T]

LAB essentials

Hey Rick, at least he would be giving her the opportunity, when she says " you are always in there and we never spend any time together, well, she could bring in a beverage and talk for a while, I mean no one might be listerning but hey. And mates can sit in it when they visit, espsecially from across the creek in NZ

 

[Mycroft2152]

Dippy wrote:

"Prediction: Regardless of space and intention your bench will be covered in mess after a few months. "

I'd say Dippy was an optimist. My bench usually only takes 3 days!

Myc

 

[BrendanP]

Stan.....more moves than a chest board.

Stan, you have more moves than a chest board. The 4D stuff looks interesting.
You're addicted to those little bread boards! I still use the download cable that Andrew gave to me.

Thanks for everyones advice. I'm going to put up another bench at a height suitiable for standing and working at as suggested. And given that its been about 40 degree today Im going to look at putting a aircon in the wall. Hard to think straight when you're sweltering hot.

I'll take some pics in the next couple of days when everything is in its place and post them.

 

[hippy]

I don't think installing anything attached to mains earth is a good idea ... I suggest that mains is removed as much as possible and i think that you should use the 0V rail from your PSU as 'earth'.

The company I worked for had mains isolating transformers which are handy ( apparently ) when working on live mains ( especially lighting control hardware which uses Live or Neutral as its 0V ), but I'm not sure how they interact with real earth or the consequences of being wired to real earth for ESD protection and having 'that accident'.

I agree, remove mains as much as possible. Even though the kit I worked on was invariably mains powered we always removed mains PSU units from what we were working on, put them in safe ( cannot be accidentally touched ) boxes and just ran low voltage into the equipment. Walwart supply is intrinsically safer than including a mains PSU.

I'm not entirely convinced of using PSU 0V as earth as it isn't. In many designs it is simply floating. In fact, multiple floating 0V's coupled with equipment which is genuinely earthed can present some major problems.