Powering Your Lab/Bench - Page 1
Forum section: electronics / general

author: Keith
author_rank: Contributor
timestamp: November 07, 2011, 12:52:29 am
content: Are you guys coming directly of the mains with a power strip to feed your lab/bench? I was curious as I've completed my bench and now will have multiple outlets feeding my equipment rack as well as convenience outlets. The bench itself will have a dedicated circuit feeding multiple power strips(appropriate ratings). I was thinking about purchasing an Isolation transformer to protect myself and my equipment; however, its a few hundred USD. Anyone using or planning to use isolation for their lab/bench? I'm hoping Dave will have a few videos on his new lab construction, bench design, electrical, etc.

author: w2aew
author_rank: Super Contributor
timestamp: November 07, 2011, 01:07:55 am
content: Personally, I keep all my equipment on the mains, and use an isolation transformer when repairing older equipment that may have a hot chassis. I would definitely NOT put the equipment on an isolation transformer.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: November 07, 2011, 01:27:47 am
content: An major part of what to do and what to use about a safe lab electrical installation, it has to do with the age of the building it self,and the quality of the current wiring.Or even the quality of the earth ground it self.All those factors must be inspected by a specialist electrician.About Dave and the new lab, it looks that he found an very modern building, and from what I have seen in his video,he would not have anything major to worry about the electrical installation.

author: McMonster
author_rank: Frequent Contributor
timestamp: November 07, 2011, 01:53:38 am
content: But he will have a lot of work with just every other aspect of building a lab. And judging from the number of instruments in the old lab I think he'll need at least some extension cords anyway. I strongly hope there'll be at least a few videos documenting setting all the things up, I'm starting my new lab this week.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: November 07, 2011, 01:57:07 am
content: Well I would prefer to was down to Australia right now and give him a hand.This is what he needs right now.I know to paint walls too.

author: Psi
author_rank: Super Contributor
timestamp: November 07, 2011, 02:13:36 am
content: I made a box with some mains switches, sockets and neons.Fused at 2A currentlyProvides a convenient switch to power up/down all my gear at once.And also sub switches to power up only selected gear (all power supplies, all soldering tools etc)It's much harder to accidentally leave stuff on when you have a master switch and neon for the entire bench.One of the outputs powers a variac i can use if i need some isolated power

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 07, 2011, 09:57:18 am
content: Quote from: Kiriakos-GR on November 07, 2011, 01:57:07 amso you dont mind losing one hand?

author: JuKu
author_rank: Frequent Contributor
timestamp: November 07, 2011, 10:09:21 am
content: I value myself highly. All instruments and devices under test and development (basically, everything but the computer) are behind an isolation transformer and a leakage current cutoff switch. I also build touch guards for live parts when the covers are off.

author: kripton2035
author_rank: Super Contributor
timestamp: November 07, 2011, 12:10:44 pm
content: I use a main differential interruptor, and a bunch of outlets on itsee the picture :

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: November 07, 2011, 01:21:02 pm
content: Im using APC online ups-es and surge protection installed in breaker box

author: Cj1corbystarlet
author_rank: Contributor
timestamp: November 07, 2011, 01:45:41 pm
content: As a Sparkie during my day job, I'd highly recommend using earthed outlets for most of the work done on a bench, I'd only advocate using a isolation transformer when it is really really really needed.One day i must do a video on the hidden dangers i have seen using iso-trani's in the field, they sound sweet and innocent but i would treat then with utmost respect, just because its not earth referenced (secondary side) doesn't mean it cant kill you in the wrong situation.Ben

author: david77
author_rank: Frequent Contributor
timestamp: November 07, 2011, 02:58:28 pm
content: My lab's powered by its own 10A circuit straight from the main panel. The lights, electric heater and PC are on another 10A circuit, so I can avoid having to traipse around in the dark should I trip the bench MCB. Of course I do use a RCD switch with IdeltaN=0,03A, as is the norm here. I recently bought another one to put the bench on its own RCD, having the lights and the rest of the lab on the same RCD defeats the purpose of two seperate circuits a bit. I haven't got round to installing the second RCD yet.The whole lab bench is switchable from a switch located next to the door where the light switch is, this way I never forget to turn everything off when I leave. Only the PC has its own permanently powered power point.

author: IanB
author_rank: Super Contributor
timestamp: November 07, 2011, 06:48:22 pm
content: Quote from: JuKu on November 07, 2011, 10:09:21 amUsing an isolation transformer does not necessarily make things safer. The protective earth system used on mains supplies is what it says it is; it protects you from certain equipment faults that might otherwise lead to live metal parts. If you power normally grounded equipment from an isolated supply, you could have the chassis floating at a high voltage in the event of a fault without tripping a breaker.Furthermore a leakage current cutoff switch can't do anything on the isolated side of a transformer as there is nowhere for current to leak to. If you place it on the mains side of the transformer than it will do its job fine, but now the isolation transformer is not needed.

author: Unknown
author_rank: Unknown
timestamp: November 07, 2011, 09:52:18 pm
content: Agreed with the recommendations against isolating ground of test equipment, only use an isolation transformer for the DUT and be very careful around it, it will only protect you against a single fault (touching one conductor is fairly safe, touching the other = you get shocked). You can't make equipment double isolated by just using an isolation transformer, there's lots of exposed metal like BNC buses on RF equipment or scopes that is directly connected to input ground, this can be very dangerous if the ground is floating. Scope manufacturers are especially vocal about this, probably due to the number of people being killed by floating scopes.Apart from the grounding issue, you would need multiple isolation transformers, since there is no isolation if you connect all gear to the same transformer.

author: ivan747
author_rank: Super Contributor
timestamp: November 07, 2011, 10:34:42 pm
content: Quote from: Keith on November 07, 2011, 12:52:29 amI hope so too. This may be one of the most interesting videos to me on the blog. I have always wondered how he connects his grounding wrist strap to and his earth bonding post to earth. I wouldn't like to see that connected to a green wire going to the back of a power outlet's faceplate, that would be a bit dodgy. I am expecting to see something like the bonding post on this outlet, but using the proper Australian plug:-----------------On the room I have my desk on there is justonepower outlet. That is inconvenient. Luckily, my desk is right next to it, so no power extensions cords are needed. I use two power strips: one for equipment (I don't have a lot of stuff) and the other one for computer equipment and general use. I also have a small, 3 outlet power strip on the desk so I can quickly plug and unplug things I am testing, as well as chargers.As for voltage and earthing, I don't have much to say, but I will say it anyway: the earth wire is connected and the voltage is really stable at 117V. I have measured it in several occasions and it doesn't seems to change.I also have a 220V outlet (NEMA 6), consisting on two live wires with inverted phases and an earth wire. I am not sure how safe it is to plug 220V equipment into that, specially when the equipment uses polarized plugs.