Building A Current Limiter

[Gary_S]

How do i do this? I've got all Gerald Webers books and they describe it but i'm from the UK so some of the hook up is gonna be different.

Is there anyone on the forum from the UK who's built one that can give me some advice?

It's not really as much advice about building it's more where to source the female extension things. I've never seen anything like that for sale here in the UK. The only extension cords available have the actual cord already attached and all wired up. The extension sockets they talk about for the current limiter need to be just the bare socket and then you attach a mains cord and hook the connections up with hook up wire.

Once you have that hooked up you plug a laml with a 100W bulb into one of the sockets and your amp into the other one.

I think that's how it goes but i don't know where to source those parts from (the socket things i mean, i know where to get everything else)

Plus do you need to get a metal enclosure to house it? or can you just have the sockets loose without having them held inside something.

This is where a picture would be worth a thousand words; to see a video of someone actually building it would answer my questions. I've searched YT and everywhere for current limiter videos but there's nothing that shows in detail one being built.

I want to get this built sometime because it's a handy thing if you've down surgery on your amp and need to test it.

[sluckey]

Here's a bare bones unit that does the job just fine. All you need is an extension cord and a lamp socket.

http://home.comcast.net/~seluckey/amps/misc/Amp_Scrapbook.pdf

EDIT for coinroller:  http://sluckeyamps.com/misc/Amp_Scrapbook.pdf

[Gary_S]

Cheers Sluckey that's great and just what i've been looking for!

Many thanks for the link.

[jjasilli]

Here's the schematic of my light bulb limiter.

Also G Weber instructions,. from an earlier thread: 
*Plug the amp in to the light-bulb limiter, turn it on in 'standby' mode (if available)
*Switch standby to 'play'. If the lamp lights brightly, this indicates a short somewhere in the
amp.
*Remove power tubes, one at a time. If the light stays bright, that tube can be replaced in
the amp. If the light dims, the tube you just removed is shorted. If none of the tubes
appears to be shorted, go to the next step.
*Remove all power tubes together. If the light dims, the problem is probably in the bias
supply. If the light remains bright, the problem is (probably) a bad rectifier, sorted power
transformer, or shorted filter cap - see next step.
*Now switch the amp to standby mode. If the light goes out, the problem is in the filter
caps. If the light keeps shining bright, the problem is is the transformer or the rectifier -
see next step.
*Remove the rectifier (or disconnect the diodes if it's a hard-wired solid-state rectifier). If
the light dims, the rectifier is bad. If the light stays bright, the problem is probably in the
power transformer.

[Gary_S]

Thanks jjasilli i appreciate the info you posted. The current limiter seems a really useful tool to have in the toolbox.

[PRR]

Do you understand that UK uses different wire colors than the US?

The most important one is Ground/Earth. Since this is green here and Green/Yellow there(?) it should be pretty clear.

In the US there are two "live" wires, originally black rubber. In theory one of them is painted white (today we have white and black plastics). Inside the wall they now check that you got it right. But out at the appliance (amplifier, lamp limiter) it is safest to treat both as "live". In the UK various other colors are standard: brown, blue, and I gather they are changing them again. Still the same rule: anything other than Green(/yellow) is treated as "live", it should not matter(*) which is which.

(*) If wiring a screw-base lamp socket, you really want White on Shell. White is ideally less-live, and less-deadly to touch, such as the too-exposed screw on a lamp base. However it seems UK is tending toward recessed 2-pin lamps? (Or are stores just pushing them harder?) And for a workbench lamp-limiter, you will just be careful, and un-plug before changing the lamp.

The world changes. This limiter trick requites incandescent lamps. Not these new small fluorescents. Not LED lamps. ("Halogen" is good old incandescent with magic gas and is fine for the limiter.)

[Gary_S]

Do you understand that UK uses different wire colors than the US?

The most important one is Ground/Earth. Since this is green here and Green/Yellow there(?) it should be pretty clear.

In the US there are two "live" wires, originally black rubber. In theory one of them is painted white (today we have white and black plastics). Inside the wall they now check that you got it right. But out at the appliance (amplifier, lamp limiter) it is safest to treat both as "live". In the UK various other colors are standard: brown, blue, and I gather they are changing them again. Still the same rule: anything other than Green(/yellow) is treated as "live", it should not matter(*) which is which.

(*) If wiring a screw-base lamp socket, you really want White on Shell. White is ideally less-live, and less-deadly to touch, such as the too-exposed screw on a lamp base. However it seems UK is tending toward recessed 2-pin lamps? (Or are stores just pushing them harder?) And for a workbench lamp-limiter, you will just be careful, and un-plug before changing the lamp.

The world changes. This limiter trick requites incandescent lamps. Not these new small fluorescents. Not LED lamps. ("Halogen" is good old incandescent with magic gas and is fine for the limiter.)

Hi PRR, yeah the colours are different over here for the wiring and we have a different system i know that, but thanks for reminding me because you can never be too careful round electricity. Here it's brown live, blue neutral and the earth is green and yellow striped.

The problem is now here in the UK do you know it's getting practically impossible to get standard bulbs?!!!!! Seriously! What they are doing is totally phasing out the use of standard 100W and 60W light bulbs in favour of these horrible energy efficient bulbs that when you turn a light on at first it's very dull and then gradually lights up until it reaches it's proper brightness.

It's supposed to be energy efficient but sometimes i wish they'd leave well alone. I don't know if one of those bulbs would work as well in the limiter?

I'm sourcing the parts just now and i know where i can get everything to build it apart from a small metal enclosure to house it in. I was on ebay last night and saw a few things but not really what i'm looking for.

[kagliostro]

No way to use neon or led lamps

may be you can use some halogen, lower voltage, filament lamp in series

or

may be you can use a 20W 220v with an in series resistor

I hope someone can give an explanation about this

---

Also in Italy now is difficult to find 100W or 60W filament lamps

to put 3 filament 20W 220v lamp in parallel isn't the same as to have one filament 60W 220v lamp


K

[PRR]

> one of those bulbs would work as well in the limiter?

MUST be a hot wire! Not fluorescent gas, not LED.

> in the UK .... is totally phasing out the use of standard 100W and 60W light bulbs in favour of these horrible...........

In the US also. I bought the last pack of 100W bulbs at my grocery store. 60W are legal for another year.

I do not know your new law.

Here, "efficient incandescent" will stay legal for now. It only has to be 20%(?) better than the cheap bulbs of the last 100 years to qualify under law. By changing the Argon filler gas to a halogen gas (and a few other things) you easily get the light of "100 Watts" for only 78 Watts of electricity (and FIVE times the price but double the life and reduced total operating cost-- we don't care in a lamp-limiter).

"Specialty" lamps stay legal. I've always lit the bathroom mirror with four "globe" bulbs. They are slightly expensive, but the light is good. Theater dressing tables are often lit with lots of 25W globes, for broad light spread and consistent light color so no make-up surprises. These are still available here in 100W. Plain old incandescent, just bigger bulb.

The "space capsule" PAR bulbs will be around a long time. For lighting a garage entry, total hours of waste is low so a hi-efficiency lamp is not needed. Millions of outside light sockets won't take any other shape and deliver that much light. LEDs will eventually take-over this app, but not at $49 (versus $5) and they'll never pay-back in electric saved. PARs remain available as stage-lights, though I note LED "PARs" are now available, and might help get more dramatic light in a poorly-wired club.

> 3 filament 20W 220v lamp in parallel isn't the same as to have one filament 60W 220v lamp

For light: when you buy a 20W you already said "I do not want a lot of light". They often go in "minor" places like closets. 20W are often designed for less light and longer life (or cheaper material!). In my garage, three 40W sure do not equal one good 100W. Two 40W cast a nice glow around the side door, but one 100W is BRIGHT over a larger area.

For lamp-limiter: three 20W parallel is near-enough one 60W. It just gets crowded.

> a small metal enclosure to house it in.

Electric supply stores have functional boxes already tested for electric, heat, and fire issues. However the English have IMHO funny names for them. Pelmet? Pattress? Henley? They use the same words in Hong Kong, so it must be well-established terminology.
http://www.ukelectricalsupplies.com/boxes-and-enclosures.htm

I've been frustrated finding UK electric info. This forum may be interesting:
http://www.electriciansforums.co.uk/forum.php
It is supposed to be "Professionals Only!" but I see they tolerate 'fools', if only to advise them to get a local expert. (At Mike Holt forum, if someone appears to be non-Pro they get locked out.) If they know you are working on a benchtop box under constant watch, they might confirm wiring and know what boxes are suitable.

[Gary_S]

In the US also. I bought the last pack of 100W bulbs at my grocery store. 60W are legal for another year.

I do not know your new law.

In the US this is happening with the bulbs also? and Italy too!  Must be an all over agreement in order to help the environment. Trouble is these new energy efficient lightbulbs are not as good. I put in a 100W one and it is dim and dingy compared with a regular 100W bulb. I wish they didn't do that and things just carried on as before.

Question about grounding the device: i spoke with someone recently who told me that i could even use like a plastic box as a chassis box for the current limiter. But the thing is; in the instructions i have on building the device you have to take the earth lead from your mains cord and it has to be connected to both female outlets in the chassis box and then a ground has to be taken from the outlet and has to be actually grounded on the metal chassis itself. Obviously you can't do that if you don't use a metal box as your chassis.

Is there a danger issue if you don't use a metal enclosure and don't have that chassis ground?

As far as the law here PRR regarding the bulbs; i think it'll probably be the same as it is in most countries now, they seem to be phasing ordinary standard bulbs out now and you cannot get them in stores anymore. Good thing you bought up a small stock of what was left because the old one's are much better quality, lighting wise. I didn't know that this was even planned, this phasing out of the older bulbs. Had i known i would have done the same thing and went round and bought up a good stock of them.

[jjasilli]

Is there a danger issue if you don't use a metal enclosure and don't have that chassis ground?  Yes, this is always a danger, no matter what the device -- even lighting fixtures & power tools, etc., etc.  The problem is that a wiring fault or malfunction can cause a metal chassis to "go live" with house current.  Anyone one who touches it can be electrocuted.  So a metal chassis should have its own earth ground connection; hence the 3rd wire now required in house wiring.   

[PRR]

Any exposed metal in a building with electricity "must" be tied to power service "ground/earth". That way it can't charge-up from stray leakage, and if bad insulation makes it "hot" it will blow a fuse in the basement.

Yes, you can use plastic boxes. My whole garage is plastic boxes. 3-conductor cable carries Ground from service panel to each box. Switch and outlet boxes, our switches/outlets have a metal frame which must be grounded (and obviously the 3rd-hole of each outlet). Lamp sockets all plastic; here I ignore the ground wire. But the boxes do not have to be grounded: can't get a shock from plastic, and these boxes are Approved For Purpose which means they are robust enough that they won't break easily and let juice out.

[Gary_S]

Yes, you can use plastic boxes. My whole garage is plastic boxes. 3-conductor cable carries Ground from service panel to each box. Switch and outlet boxes, our switches/outlets have a metal frame which must be grounded (and obviously the 3rd-hole of each outlet). Lamp sockets all plastic; here I ignore the ground wire. But the boxes do not have to be grounded: can't get a shock from plastic, and these boxes are Approved For Purpose which means they are robust enough that they won't break easily and let juice out.

Thanks PRR. Do you think i'd be better using an ABS box then rather than a die cast aluminium one?  if i can use the plastic type box it sounds as though it would be more convenient, not having to be grounded like the aluminium. Plus the metal boxes were more expensive where i've been pricing them from.

[Gary_S]

So i have all the parts now, just waiting on the two female outlets to arrive and then i can wire it up.
Only thing is the 100W lamp; all the lamps here take a 60W bulb. Never see any that have 100W. I'll have to look around and see what else i can get  

[John]

I believe even a 60 watt will let you know something's wrong. So far I haven't used mine to troubleshoot, just for start up- anytime I do anything inside. I have no faith in myself. 

[Gary_S]

Ok so now i have all the components here for building the current limiter. One question i have is this, this might sound dumb! but anyway!!! you're putting these sockets in series, so the question is regarding the ground wire from the mains cable: you have to connect that to the socket nearest the ground cable but it has to run from there to the ground connection on the second socket too. What's the best way of doing this? can you connect the ground wire to the ground of the first socket and then run some hook up wire to the second socket ground connection or what's the best way?

Here's the thing i'm building so that you understand what i'm waffling on about!

http://www.recycledsound.net/10_Build_a_Current_Limiter.pdf

[Gary_S]

Ok so now i've finished building this current limiter. It was a bit fiddly and awkward, purely because of the type of sockets i used. I used metal clad single sockets, you guys will know what i mean. The back of the socket screws back on after you've finished wiring it. Only trouble was feeding the wires from one socket to the next and still be able to get the backs of the sockets screwed on after you're finished. So there's knockout holes on the sides and you knock the holes out with a punch or similar tool. I used these holes to feed the wires through from one socket to the next. It was fiddly and if it hadn't been for having to negotiate those holes it would have been a breeze.

Now i'm using a plastic box as a chassis for this thing so i don't need to ground it but these metal clad sockets have a terminal at the bottom of the metal box that you can obviously connect a ground wire to. i didn't do that i ran the ground connection from the first socket ground terminal and then hook up wire from there to the second socket ground.

Is it ok not to add another ground to the bottom of those clad sockets if the connection is already made via the centre terminal on the socket?

[PRR]

Don't get me started.......

> metal clad single sockets, you guys will know what i mean.

No, I do not.

I've been spending time looking at UK wiring devices and practices.

I am quite baffled.

(True, some devices I put up with would look baroque to you.)

Yes, the UK's basic domestic socket is the safest in the world.

But other devices appear to me to be cheezy, poorly described, poorly cataloged in internet stores. Yes, there is much that locals "just know" and I do not. But the regulations leave much unsaid.

I really got hot when I discovered that recessed ceiling lighting is not designed to have insulation over it. And that this is only noted in fine print on the slip of paper everybody throws away. What happens is the fixture overheats, insulation melts, people are shocked and wood burns. In the US, this became an issue in the 1970s, by the 1980s all such fixtures AND most insulation had clear instructions and permanent markings not to insulate above unless rated. And I recently noticed that "all" the recessed ceiling fixtures I could readily buy here _ARE_ rated "IC" (Insulation Contact).

Moreover, a UK "Product Of The Year" is a junction box which can be concealed loosely above a ceiling near things like those tinderbox recessed lamps. The recess ceiling fixtures here _have_ a remote junction-box off the side of the top, suitable for Y-ing one circuit to multiple fixtures.

> if the connection is already made via the centre terminal on the socket?

Ohm-meter from the (un-plugged!) wall-plug ground pin to any/every metal you can touch. If everything is under one ohm (allowing for meters that don't read 1 ohm well), call it good.

(There's actually a UK/BS-specified test, and a standard "earth loop impedance test instrument". Total phase+earth impedance should be more like 0.05 Ohms.
http://claydons.org/public-html/elec/testing.htm
http://www.tlc-direct.co.uk/Book/8.6.2.htm
http://www.test-meter.co.uk/17th-edition-test-equipment/loop-testers/
However if your connections look good, they probably are good. A low-Ohm reading confirms that what you thought was connected really is connected.)

An additional safety factor is that you only use this for smoke-testing. Limited exposure and a strong sense of "Whoops!". So you might never touch the metal-clad while there is power(?). This is of course different from a device in everyday casual use.

[Gary_S]

Don't get me started.......

> metal clad single sockets, you guys will know what i mean.

No, I do not.

http://www.ebay.co.uk/itm/METAL-CLAD-1-GANG-13A-1G-WALL-SWITCHED-SOCKET-BACK-BOX-METALCLAD-/230770241415?pt=UK_DIY_Material_Electrical_Fittings_MJ&hash=item35bafa6f87

[PRR]

Clearly needs to have low-low-ohms to the source Earth pin. Surely has provision.

In the US we would perhaps use an ugly combination of a green screw, a jumper wire, and a wire-nut. Wire-nuts appear to be unknown in UK practice. This is probably a Good Thing.

CEILING ROSE 250V 6A has just the one(??) earth-screw. I do not know if it takes two wires (from the source, and to the load).
 

[Gary_S]

Clearly needs to have low-low-ohms to the source Earth pin. Surely has provision.

On the sockets for wiring you have the terminals like what we normally have in the UK for a standard 13 Amp plug. Three terminals; Live neutral and Earth or ground. From my mains cord which is a three strand cord, again with Live, Neutral and Earth, i connected it up via the diagram i linked to earlier. The ground wire was connected to the socket, just like you would wire a standard plug.

Some electricians think it's better to take a fly lead from the actual earth terminal in the plug and connect it to a fixed metal earth that's on the very bottom of the metal clad socket.

This is a kinda gray area as most electricians i've read on the subject say that the extra fly lead to the bottom of the clad socket is not necessary as long as you have the earth/ground wire from your mains cable connected to the earth terminal in the socket.

Our wiring color is different in the UK to you guys: we have brown for live, blue is neutral and green and yellow striped is earth/ground. I think the US is black white and green wires?

[drgonzonm]

This is dumb question, Are any heater lamps available?  I just checked out the listings of one of the local big box stores, and they have 125w heat lamps available. 

I would consider checking with an ag store someone who provides parts for incubators.