Advice on setting up a home electronics lab - Living in the UK - Page 1
Forum section: electronics / general

author: andyowenwest
author_rank: Newbie
timestamp: February 15, 2019, 02:45:11 pm
content: I'm soon to be buying a house in the UK and would like to setup an electronics lab in the garage (attached to the house).The type of equipment I'll be using is nothing out of the ordinary:OscilloscopeSoldering Iron (up to 400C)Triple output 10A 30V power supplySignal generatorsAutomotive transformer 240vPC EquipmentThe most risky projects i'm planning on are designing a range of guitar tube amps and some aquarium maintenance automationIn terms of experience I'm a Masters' graduate with 1 year industry experience designing high power GPU IT solutions.As much as (I like to think) I know a bit about electronics I want to try my best to be respectful of the dangers and minimise riskIs there any extra insurance above my standard buildings insurance (with accidental damage) that I need or should consider?What safety devices are essential for a home lab?A few ideas so far are:Ensuring the property has decent RCD protectionSurge protection for the test equipmentAuto shut-off for soldering irons (30 mins?)Isolation transformer (Mainly for the tube designs)ESD mats / wrist bands (not the wireless ones)Let me know what you think, all comments welcome!Cheers,Andy

author: coppercone2
author_rank: Super Contributor
timestamp: February 15, 2019, 02:54:33 pm
content: Yea my advice is to finish a basement, install humidity and floor controls (french drain etc) and get a space 5x bigger then you need with overkill power distribution and ability to move rackmounts around. Once you get 30+ test gears benches start to look stupid.I always called it the wall (like pink floyd)

author: AndyC_772
author_rank: Super Contributor
timestamp: February 15, 2019, 03:01:17 pm
content: Re: insurance, it really depends on whether you're doing this as a hobby, or to make a living.If it's all just for fun, then your home contents insurance should cover it. If you have any individual expensive items then it might do no harm to check they're covered (purely based on value), but that's all.If it's for business, you'll probably find there's an exception which means your kit isn't covered. In that case, you should be able to get separate cover for your equipment as part of the professional indemnity cover that you (should!) have anyway.I have a single policy which covers all my equipment, my professional liability (eg. in case I make a mistake which has expensive consequences down the line), 3rd party liability (someone visits my lab, manages to hurt themselves, and blames me), and product liability (something I've built catches fire and burns the customer's office down).If your're setting up in a garage, don't forget you'll probably want heating - and pragmatically, an unattended heater is probably the most dangerous thing you'll have in the lab.

author: sokoloff
author_rank: Super Contributor
timestamp: February 15, 2019, 03:51:02 pm
content: Consider two power distribution networks, one for devices that can/should be left on all the time and another for devices that you want to be sure are turned off when you leave for lunch or the day/evening. Strongly consider having a clear indicator lamp also attached to the latter circuit.I admit that I don't have this setup in my basement lab yet, but am planning to in the next deep cleaning/revision of the space.For now, I always turn on a specific lamp on the bench prior to turning on the soldering/hot air station, and I always turn off the station prior to turning off the lamp. (I'm a pilot, so have pretty good checklist discipline ingrained.) If the lamp is on, there's possible danger. If the lamp is off, I'm reasonably sure that the station is also off.My intention is to expand that with a wall switch to drive a circuit with differently colored outlets, so even though I intend to turn off all the heating equipment at the equipment, I can also throw the wall switch and be doubly sure that I haven't missed anything.

author: coppercone2
author_rank: Super Contributor
timestamp: February 15, 2019, 05:31:46 pm
content: People got paranoid since someone here had the fire.But again rackmount is one of best fire spread preventers so long you dont have battery banks in there.The hot air station is a giant hazard compared to anything else. Soldering iron too, but if you have a rubber non plastic esd mat on a metal surface it. Gets infinitely harder to start a fire. Biggest problems are plastic boxes and flamable wiring (teflon and silicone is your bet)

author: tggzzz
author_rank: Super Contributor
timestamp: February 15, 2019, 06:08:08 pm
content: Ensure you have the appropriate scope probes for whatever you are probing - especially anywhere "near" mains.

author: nctnico
author_rank: Super Contributor
timestamp: February 15, 2019, 06:14:29 pm
content: Forget about the isolation transformer. It will render the RCD useless. Better get a differential probe; these aren't very expensive nowadays. MicSig has a model which offers excellent value for money.

author: apis
author_rank: Super Contributor
timestamp: February 15, 2019, 06:20:54 pm
content: Quote from: coppercone2 on February 15, 2019, 05:31:46 pmTrue, a good thing to do is probably keep fuel far from any heat source, so even if something goes wrong and catches fire it can't spread. No fuel, no fire. Fuel == plastics, paper/wood/cotton, some chemicals.

author: coppice
author_rank: Super Contributor
timestamp: February 15, 2019, 06:22:10 pm
content: Quote from: nctnico on February 15, 2019, 06:14:29 pmWhile an isolation transformer defeats the effects of an RCD placed before the transformer, you can always add a second RCD after the transformer.

author: apis
author_rank: Super Contributor
timestamp: February 15, 2019, 06:24:04 pm
content: Quote from: nctnico on February 15, 2019, 06:14:29 pmNot useless, superfluous. If you use an isolation transformer what would you need an RCD for?

author: coppercone2
author_rank: Super Contributor
timestamp: February 15, 2019, 07:50:46 pm
content: a live chassisI built my own variac, it has a ground neutral disconnect switch but the physical ground is always wired in. I might put another switch to disconnect that.If you have a neutral option switch, what you can do is use the isolated variac as a high performance filter and variable power source, otherwise float it.

author: Berni
author_rank: Super Contributor
timestamp: February 15, 2019, 08:20:45 pm
content: As people said make sure you have plenty of room around the lab.As the hobby goes on it often involves getting a fair bit of cheap used test equipment. The old gear is very big and heavy so you better have some solid shelving or have space to put in a big rack cabinet or two. You also tend to eventually accumulate a big collection of components that needs a good deal of space to keep sorted properly and as usual you will want a place to store projects, or useful large parts or equipment that is a shame to throw away. This means even more shelves. Oh and did i mention you will need shelves? Yeah you need shelves.The workbench you also want to be pretty large, ideally 2m wide or more and at least 60cm deep. You also want to have more shelves behind the bench to keep the most often used equipment and tools. Not having those lay on the bench gives you back a ton of bench space. If you want to have oldschool gear there you also need the shelves behind the bench to be at least 50cm deep.Isolation transformer is nice to keep around but ONLY if you know what you are doing with mains and exactly how and why electrical shocks happen. Otherwise it can give you false sense of security in a dangerous situation. But if you do know how to use them they are great for mains work because not only do they let you touch 1 thing in any piece of equipment without a bang or shock, but they also limit the current in the event of something going wrong. A typical 250VA isolation transformer will only deliver about 15A of short circuit current, makes for a good spark and fizzle and that's it. But making a short on direct mains from the wall can deliver 100 to 1000A of short circuit current, resulting in a loud bang, melted metal and the surrounding area charred black from the arc flash and metal oxides.You do still have to be realistic about it, but if you can make a choice, its a good idea to put the lab in a room that is 15 m2or more. Don't worry if the room looks empty and wasted at first, the space will come in handy later.

author: apis
author_rank: Super Contributor
timestamp: February 15, 2019, 08:28:13 pm
content: Quote from: coppercone2 on February 15, 2019, 07:50:46 pmA variac isn't an isolation transformer.If you have an isolation transformer you won't get ground currents. An RCD can only protect you from ground current faults, so it would be pointless together with an isolation transformer. Saying you shouldn't use an isolation transformer because it makes the RCD useless, while technically correct, misses the point of why you would be using a isolation transformer or an RCD in the first place.

author: nctnico
author_rank: Super Contributor
timestamp: February 15, 2019, 10:08:40 pm
content: Quote from: apis on February 15, 2019, 06:24:04 pmTo not receive a shock when you touch live wires. If you use an isolation transformer you need to setup the entire room for that purpose and have training. The primary problem is that the safety precautions spread like an oil stain over your entire workspace. Otherwise it is very easy to ground the equipment through other equipment without the leakage current going through the RCD and thus create a potentially lethal situation. With a (mains rated) differential probe you minimise the risk area and if you touch something the RCD will safe you.

author: coppercone2
author_rank: Super Contributor
timestamp: February 15, 2019, 11:49:03 pm
content: Quote from: apis on February 15, 2019, 08:28:13 pmi said I built my own variac. it has a autoformer in series with a transformer. i call the unit a variac (variable voltage impedance limited AC source) that consists of a transformer and a variable autoformer. Variac is a trade name for a device. It's pretty catchy. I suppose you can call it a iso-variac.You can still short the neutral with a switch or contactor to remove the isolation but preserve the surge current protection, filter characteristics.I don't know if they make one component isolated version that does not require two transformers, using a single magnetic loop.However with two components, you can put filter networks before and after the isolation transformer and leave the output through the variac directly (L-output stage filter topology I guess). This is what a medical filter transformer does (not to be confused with a medical isolation transformer). Commercially there exist units like my home made one IIRC.

author: nick_d
author_rank: Regular Contributor
timestamp: February 19, 2019, 01:24:20 am
content: I haven't actually taken any special precautions in carrying out my electronics hobby/learning.Yes, our place has an RCD. The last time I managed to trip the RCD was at my parents' place when I was learning about transformerless power supplies (capacitive droppers). It actually scared me a bit, and I haven't returned to that project.Apart from that, I just have an ordinary analog CRO and old Weller soldering iron (not in the best nick, running on string and duct tape), which are unplugged and stored in boxes when not in use. Probably the best I can suggest is: get a lot of cardboard boxesI think the isolation transformer is also a great idea, mainly for the current limiting as has been mentioned. In fact, I use an old 240V -> 120V dropper when I am working on SMPS stuff, since the lesser voltage also gives some additional safety. And for first power-up I would halve it again, since most parts of the SMPS are not particularly sensitive to what voltage is being used, others can be modified to compensate.My suggestion is to treat it case by case. If you feel additional precautions are needed for a particular project, then implement those precautions. And also, if you keep your equipment unplugged when not in use, then I don't think there is any significant fire risk.cheers, Nick

author: tggzzz
author_rank: Super Contributor
timestamp: February 19, 2019, 08:34:19 am
content: Quote from: nick_d on February 19, 2019, 01:24:20 amIf you use an isolation transformer after an RCD, the RCD no longer acts as an RCD - because in fault conditions there is no differential current in the RCD.There are many discussions of this topic on this forum; many but not all of the posts are correct.QuoteIf you halve the input voltage, you double the input current. Many components in pre-built SMPSs cannot withstand that.Why double the current? Because theoutput poweris constant.

author: Berni
author_rank: Super Contributor
timestamp: February 19, 2019, 09:05:56 am
content: Quote from: tggzzz on February 19, 2019, 08:34:19 amMost SMPS are designed to be 110V to 240V universal input so it wouldn't hurt it. While the lower input voltage makes for less inrush current into the mains side filter capacitor and the capacitor ends up charging to a lower voltage so there is less energy stored in there to potentially explode components. When you are fixing a dead PSU you have no idea what could be wrong with it so less power and energy being around is welcome if a violent fault condition happens (And it can get quite violent in faulty SMPS supplies).If you are not fixing the actual PSU itself but instead fixing whatever the PSU is powering then you don't use a isolation transformer in the first place. Just keep the lid on the PSU, and make sure earth is still connected to ground before you plug it right in. The PSU is designed to be used like this in while the ground connection makes sure if the PSU does fail in a bad way during your repair the current goes to earth and trips breakers rather than giving you a shock on a 5V rail that suddenly floats on top of 220V AC.I find poking around the PCB of a live running mains powered SMPS to be quite scary so i always use a isolation transformer for those, makes me feel safer and if i do screw something up the resulting explosion is much less dramatic.

author: tggzzz
author_rank: Super Contributor
timestamp: February 19, 2019, 09:13:30 am
content: Quote from: Berni on February 19, 2019, 09:05:56 amI don't disagree, but nick_d halves the voltage "again", presumably to 55V.

author: OwO
author_rank: Super Contributor
timestamp: February 19, 2019, 09:27:35 am
content: First of all I wouldn't rely on insurance to cover anything especially hobby stuff, even in normal households insurance is a pain to deal with and you would be lucky if you manage to get any compensation in an accident. Assume that nothing will be covered (except maybe cost of repairing the house at most) and don't have anything expensive in the same room where you solder.In this day and age there is no need for very expensive test equipment even if you are doing RF circuit design, so I don't see the need for equipment totaling more than $1000 in a lab where you don't work with RF at all.What I would consider basic set up for an electronics lab (from order of most essential to least):1. Temperature controlled soldering iron. I have just a $10 one that I've used for years and has seen plenty of abuse, never had a problem with it.2. Hot air station. A 858D or other sub-$50 one is perfectly adequate, but always cut power to it when you are away (switching it off is not good enough, you need to cut power to it).3. Power supply; this is optional depending on what voltages you work with. Everything I do is either USB powered or 12V powered, so I still haven't yet gotten a lab power supply.4. Oscilloscope; any cheap one will do. I would personally go for a new Rigol but if you can find good deals on used ones they are fine too (fully working ones only. Broken ones are not worth your time)

author: OwO
author_rank: Super Contributor
timestamp: February 19, 2019, 09:43:35 am
content: In my case I have an RF lab so I also have a cheap VNA and SDR receiver. If I felt like spending more money *maybe* I'd get a Rigol spectrum analyzer. As it stands there is no more than $1000 worth of equipment in the lab:- Soldering iron and misc materials (flux, solder, wick, etc) - $20- Hot air station - $40- Power supply - $50- Scope - $300- SDR - $100- VNA - $300That adds to $800 total. If I wanted to measure phase noise of a circuit I don't buy a $5000 spectrum analyzer, I build two such circuits and mix the signals and look at the phase noise of the result. I have built quite many RF products with this minimal lab layout.

author: nick_d
author_rank: Regular Contributor
timestamp: February 19, 2019, 10:36:34 am
content: Wow my casual comments about voltage dropping and SMPS caused some controversy, I didn't expect that. I will try to clarify my original post.Firstly, I meant to say that IF you are using an isolation transformer, there is no reason it must have a 1:1 turns ratio, the one that I use is a smallish one in a 2:1 ratio which means that it produces a US voltage from an Australian voltage, and being small it won't provide a big current in case of short circuit. I find this to be more useful and safer. Obviously, you can't draw a huge current from the SMPS while powered from this.Secondly, I meant to say that IF you are designing your own SMPS, then it's highly likely that something will blow up when you first power it on, and what I use in this case has about a 5:1 turns ratio and thus produces 48VAC from 240VAC. Supposing the eventual SMPS will be powered from 100~240V and will produce 12V, then with my temporary 48VAC supply I adjust the feedback network to produce only 6V temporarily. Therefore, the waveforms are more or less realistic except that all voltages are halved. Obviously, it does not test inductor saturation, etc.Getting back to the topic though, I mentioned this to illustrate that a lot can be done to improve safety just by raiding the parts bin, you don't need an expensive setup.cheers, Nick

author: bd139
author_rank: Super Contributor
timestamp: February 19, 2019, 10:59:35 am
content: Lots of people doing things the hard way here.If you're playing around with fixing SMPS supplies, you don't have to run them on AC. It's dangerous and stupid TBH.The first thing the SMPS front end does is convert the AC to DC for the switching converter. Thus if you stack three 30V bench supplies in series or get a 100V supply (most labs need these anyway!) that'll give you 90V at a couple of amps which is enough to bring up most devices quite happily, the whole set up is entirely floating so you can probe without things exploding and you can put sensible current limits on the supplies to stop runaway destruction. You can test enough of the AC front end with that to be confident it'll work or not afterwards as well. Just swap the input polarity and if it works both ways round it will most likely work.I've got three DC bench supplies I have paid less for (£120) than a safe isolation transformer. Your safety is worth £120!The isolation transformer doesn't necessarily help here as it is still capable of delivering masses ofpowerto the DUT which is what makes things explode.

author: coppice
author_rank: Super Contributor
timestamp: February 19, 2019, 11:29:27 am
content: Quote from: bd139 on February 19, 2019, 10:59:35 amThat's a rather simplistic view of an SMPS. How are you going to investigate the power factor correction when running from DC? Some SMPSes won't even start from DC these days because of the power factor correction stuff. Some sophisticated SMPSes won't start from DC because they have a very small auxiliary linear transformer supply to run the control circuitry before the mains supply soft starts. Those will just short out a DC source.

author: bd139
author_rank: Super Contributor
timestamp: February 19, 2019, 11:56:33 am
content: True - it's a naive approach but that is realistic here. Most of the cheaper SMPS modules don't have PFC or anything fancy like that. If they are more complicated than that, time is money and failing SMPS is a risk to the device being powered so I'd just go for FRU replacement and replace the supply or bypass and sub for a new SMPS module.You can usually bypass the PFC if you want to as well. Most of the failures I've seen in SMPS are switching or feedback related or just worn out components which are wholesale strip and replace on the line side. Apple are fun - theirs just blow holes in the controller IC

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: February 19, 2019, 12:01:29 pm
content: If working on valve/tube gear you should ideally have a fully insulated bench surface (wood is OK if dry) and an insulating floor or mat where you stand or sit. Definitely don't stand on concrete.The thing you absolutelydon'twant to have, when doing any powered tests, is any part of your body earthed. No matter how careful you are there is always the risk of touching something with 500v on it, and yourself being earthed is the difference between, 'Ouch' .. and being put in a 6ft hole in the place the current through your body returned to.It follows that earthed test equipment is a personnel hazard when working on exposed high voltage. Don't touch metal knobs or panels, or earthed scope probes if you can avoid it. I really wish scope manufacturers would change their ways over this. Having an earthed probe in your hand is about the most dangerous thing you can do when testing live high voltages. Particularly if it's in theotherhand, not the one which gets the shock.There have been several deaths on stage through a performer holding an earthed metal microphone in one hand and playing a guitar in the other connected to an amplifier whose earth had come off and touched the live. It's the hand-to-hand shock which is most likely to kill since it goes through the heart muscle. Wireless mics have been a huge safety benefit here. Eliminating the one earth prevents the circuit being closed if the guitar becomes live. As have sensitive fuses in guitar leads. (but they need to blow with ~20mA or so to be any help)Also, an RCD DOES NOT protect you against this risk when working on amplifier guts. It cannot sense current 'lost to earth' if that current came from a transformer secondary. (Though it would help in the stage performer situation)Fire: In my 40+ years in electronics I've never seen a soldering iron start a fire. They generally don't get quite hot enough to ignite things. Hot air guns are a somewhat worrying issue though; there have been quite a few reported cases of them going out of control and becoming red or even white hot. I'd advise making sure any such tools are unplugged when not in use. (On some models the on/off switch is not a proper mains switch and should not be relied on)Safety is achieved by understanding the risks.

author: OwO
author_rank: Super Contributor
timestamp: February 19, 2019, 12:40:38 pm
content: I just prefer to not deal with mains ever. If a PSU is bad just replace it (or fix obvious faults like bad caps).

author: bd139
author_rank: Super Contributor
timestamp: February 19, 2019, 12:43:57 pm
content: Sensible. Replacement is usually cheaper in time and energy. I must have spent 6 hours fucking around with a Tek 2235 PSU recently. That’s a DS1054Z in cash for me.

author: Berni
author_rank: Super Contributor
timestamp: February 19, 2019, 12:56:00 pm
content: That depends on what sort of PSU it is.If its a usual 12V 5A thing that runs as soon as you give it mains yeah replace it unless its a easy fix.If for example its more like the PSU from my old Tekteonix AWG2041 then not so much. Just the PSU in there is about the size of a small toaster and has 3 or 4 extra PCBs sticking out of the main PCB and everything surrounded in complex bent aluminum to get the heatsinking on to all the stuff and hold the extra boards. There are like 6 or more supply rails, some linearly post regulated, there is a standby rail and the PSU turns on via a power on signal and provides a power OK signal back. Googling the original manufacturer of the PSU module retrievals they went out of business by now, there are no schematics and ebay doesn't find any spares.In such a case its worth going to pretty long lengths to fix such a complex unobtanium PSU. In the case of my Tek signal generator the PFC transistor blew up and has taken out some of the PFC components with it and blew up the soft start circuit that's before it. Got it fixed and was well worth the effort.But yeah only attempt repairing a SMPS if you know what you are doing, they are dangerous things.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 19, 2019, 02:26:07 pm
content: Quote from: coppice on February 15, 2019, 06:22:10 pmAn RCD after an isolation transformer will be useless - as the transformer secondary is floating, all the current from it will inherently be balanced, so nothing that happens after the RCD can cause an imbalance to trip it.

author: andyowenwest
author_rank: Newbie
timestamp: February 28, 2019, 08:54:45 am
content: Thanks to everyone who has commentedThere's been some really good advice here that will definitely be useful to myself and others in the futureI'm due to move in around 3 weeks time. My plan is to document the process of building a basic lab and extract some top tips from here and start building a home-lab blogIll post back when I start making progress!CheersAndy

author: HalFET
author_rank: Frequent Contributor
timestamp: February 28, 2019, 10:30:41 am
content: Quote from: OwO on February 19, 2019, 09:43:35 amGet another power supply is my main advice, always get one power supply more than you think you need. And when working on valves I also like to have a period scope, mostly because if I do inadvertently blow it up somehow (haven't done so yet though), it'll be a pretty easy fix. Also, wouldn't you want a signal generator if you are going to be working on audio? I have three signal generators and I'm still always short a signal generator when building circuits.But a few non obvious ones that are nice to have:Solder fume extraction (you can buy old units for less than 50 bucks and it's totally worth it).High brightness light you can aim at things, if possible one of those magnifiers with a ring light around it.A stereozoom microscope with a long work distance.A wire rack.Storage boxes for components.Bench vice with turnable head.A voodoo doll with a skeleton made out of discarded resistors that were soldered together.A system to put your rolls of wire and cable on. I currently have three pieces of MDF bolted together as a U bracket with a piece of PVC tubing for this.An old computer you don't mind blowing up for interface testing.Boxed 1:1 isolation amplifier so you can feed things in and out of your computer's soundcard safely.Isopropyl alcohol and acetone.A pyrex oven dish or something else protect your desk from things that might go hot/catch fire.CO2 fire extinguisherBucket of sandSafety gogglesDremel or column drillScotchbrite pads to quickly remove soldermask.HacksawScalpelAn old AM radio (you damn well know why)Kapton tapeWidlarizer/hammerA benchmeter which can measure currents above 1A for longer than ten seconds.Glue and hot snot gunSelf-healing cutting matOk, maybe the voodoo doll isn't strictly necessary, but I definitely recommend the solder fume extraction, safety goggles, CO2 fire extinguisher and a bucket of sand (for lithium battery containment).