Light dimmer voltage?

I'm looking forward to reading some of the answers to your post. Welcome by the way...

You've got it right, and thanks for the correction on testing current. Makes sense in hindsight.

Would still like to know why the measured voltage did not vary when changing the dimmer setting. Does this test also require a load?

<...Does this test also require a load?...>

Certainly, otherwise the full line voltage will be seen at the terminals of the voltmeter no matter what the dimmer setting, as the voltmeter setting is a high input impedance device. A 12Ω 1000W load for the dimmer would have made all the difference. Even a 120Ω 100W load (such as a light bulb) would give a more understandable result. A voltmeter with an input impedance of, say, 250,000Ω however........

The old dimmer is now knackered.

Write it off as a learning exercise, buy another one, and don't operate the new one into the short circuit that the ammeter setting represents!

Shyam,

You are of course correct as to voltage readings.

I laughed out loud when I read about burning up the dimmer by placing the dead short of a 20 amp shunt across the dimmer rather then in series. The reason the multimeter did not blow was simply that it was protected with current taking the path of least resistance through the large 20 amp shunt rather then the rest of the meter circuitry.

The assumption of course was that the tiny wall case dimmer held sufficient resistance to serve as a dimmer instead of realizing that these days, rather than a movable tap resister, we dim stuff by phase chopping and other means not dependent on a big old resistance box as you pointed out.

Nonetheless, I would have thought that a mechanical engineer would have enough knowledge of electrical circuits not to get caught that way.

j.

Hi Jack Jersawitz

Light dimmers of tomorrow if not already today may be very likely to be MOSFET or IGBT and these will work on AC/DC power easily. Old things gone with the days as power saving factor and keep working on from very low voltage to very high makes these circuit devices versatile. In my house all CFL lamps works on AC/DC right from 90V to 300V and I will really like if they can start working even on 12V battery and can also take 230V AC from same socket. It is all possible due to high frequency chopping capability of these devices and remaining highly efficient to > 90%. Who will use resistance damper type dimmers now?

Chopped power can make 12V bulb to perfectly work on 110V/230V mains. If you drop all that voltage in resistance then you are going to have room heater below each bulb. You also have methods like slow start and slow stop to avoid inductive burn up and also watch out for cold and hot resistance difference of the filament.

Earth is warming up so keep a tag on power loss.

Thanks for excellent advice.

I am converting a 20 US gal. electric water heater to a boiler to experiment with distilling ethanol. Getting this simple power control working is the final step.

Sounds like fun ,but be careful,don't forget the relief valve!

Wise warning but not needed - it's an open system. The distillation column vents to open air.

But I am beginning to wonder if I have any grounding concerns...

Dude seriouisly...distilling ethanol and popping (fortunatley only) dimmers all in the same post? Please evaluate your home owners insurance

And as stated the white wire is neutral which returns the unused power to panel. So if no power is used you are backfeeding everything back to the switch. The result....well you know as well as I do the result.

You wrote:-

And as stated the white wire is neutral which returns the unused power to panel.

If this was intended to be a joke, I do not find it funny. It could lead to misunderstandings for other people with little knowledge and even less understanding in this area....

If it shows your personal knowledge of AC electricity, you are a dangerous man....to yourself and anyone near you at the time you "Pop your Clogs!".....

Please do tell Andy. What is a white wire on a 110V/120 AC system where you come from?

Yes it is to ground - but it is not to be confused WITH ground. It is grounded through the panel (not the chassis/j-box etc.)

The white wire is neutral, it has nothing to do with "returning unused power to ground"! The same power that is running from the phase connection, is also running through the neutral connection, it is changing direction either 50 or 60 times each second, depending upon where you live in this world.

Neutral is connected to the center point of a 3 phase star output, usually a transformer, but it could be a 3 phase generator, due to the fact that it is connected to ground at the local substation for safety reasons, it should only have at worst a volt or two on it, depending upon the balance of the loads on the three phases and the distance to the substation.....it can have more and if something goes wrong, it could be dangerous....

For example, if the ground connection was removed, it would float to a much higher (killing level possibly) voltage.

Remember that the same current that flows through the phase to the load, is identical to that that is flowing through the neutral from the load. When the phase reverses, the current flowing from the neutral is identical with that flowing through the load to the phase connection.....

It would appear that your knowledge of mains AC is severely limited, may I with all due respect say you should not mess with it ever as it has a habit of biting the hand that touches it......

so if I understand you...

You claim a neutral only on 3 phase, and that it has nothing to do with ground?

You appear to not have sufficient training in this area to understand either what you are saying or my answers.

Sadly for you this is NOT the place now to learn either high school physics or Electrical Engineering 101....

May I suggest that you go back to school and major in El.Engineering, then you can look back and laugh about your comments here and see why I cannot help you further.

My major concerns are that you or others reading your comments, with even less understanding of the matters than yourself, might get a bad shock or worse.

Therefore I am calling a sensible halt here and now.

If the subject was brain surgery, I am sure you would understand more quickly that one cannot become a surgeon by reading a Blog, well the same is true for an electrician or an electrical engineer!!!

Though in my experience, sadly many electricians have only learnt enough just to do their job, but have learnt nothing more deeply than that about the science of electricity.....not that what we are talking about is difficult, it is not, but if your background did not prepare you fully, its a big hurdle......

I studied Electrical Engineering to beyond S level in the Royal Navy and later in the OU a degree. I was using the knowledge gained daily at the same time with full (do not take it wrongly!) "Hands on experience".....yes I did get a few shocks......but I was lucky......With Ships rolling and working on live equipment that is par for the course!!!

Abasile,

Others have gently warned you but let me be a bit more forceful.

STOP!!! STOP!!!

You have adequately demonstrated here in two or three posts that outside your own area of mechanical engineering you are completely ignorant.

I speak thusly because you must STOP! Do not proceed!

You will put yourself and possibly others at extreme risk!

You obviously have no knowledge or even common sense about the electrical components you are attempting to use. Like keys to a car in the hands of a drunk somebody should take away the multimeter and lock up the tank you propose to use to heat and distill liquids that are highly flammable and therefore potentially explosive.

The electric heater you speak of seems to be the heater in a hot water tank you are adapting for your still. I am surprised none of the other esteemed, who in the past have demonstrated good knowledge of electrical circuits, have here picked up on that.

You propose to use a thousand watt lighting dimmer to control a hot water heater.

Usually, a 20 gallon tank heater is wired to a 240 v.a.c. 30 amp circuit. Do the simple math. Volts times amps equals watts. That heater is better then 6 times the load that dimmer is capable of handling.

Further, you are proposing to load that heater with flammables that usually provide plenty of vapors.

Yet that heater has on it thermal controls that, depending on the particular heater, may involve switching contacts that are purely thermal mechanical, i.e., they are capable of producing a spark when they operate.

Further. You wonder about grounding the circuits. You obviously are, at least where electrics are involved, just another tinkerer. STOP! Don't do it.

There also seems to be some dispute here as to wiring.

That heater is almost surely a 240 v.a.c. device which means it gets fed from a 2 pole breaker a black wire, which if measured to neutral is 120 v.a.c. and a red wire, also 120 to neutral, but across the red and black 240 volts.

Somebody here says that the white wire, which is normally the neutral, returns unused electricity to the panel. Nonsense!

Stop reading the Brown's gas imbeciles who talk about using the unused electricity to generate Brown's gas; actually the gas they are generating has nothing to do with Brown's mix of hydrogen and oxygen.

You hook a device to a power circuit the device demands and draws from the circuit however much it needs up to the limits of the circuit wherein you kick a breaker or burn out the alternator if not protected, or more likely, start a little local fire in your local wiring.

Until recently a two twenty supply encompassed a red and black wire, as above stated, and a white wire connected to the neutral bus in the panel which usually is also connected to the ground through a heavy wire attached to, at least, an eight foot rod driven into the ground. In say, the water heater under discussion, the white wire might also have served as ground.

The rules have recently changed because under certain conditions and in certain types of equipment, that white wire could also become a load carrier between the device and the panel.

To circumvent such possibilities it is now mandated that systems entail four wires, the two hot wires and the neutral, plus a grounding conductor that cannot under any circumstance become hot for obvious reasons.

But as to the original subject of this thread; again STOP.

Stick to re bar, I beam, and concrete. You display an abysmal knowledge of electricity. It is likely you are just as bad at chemical functions and reactions.

STOP! STOP! STOP!

j.

You should try using a hotplate control from an old stove. They usually work on a time on and off basis rather than reducing voltage

You didn't get any voltage change as the circuit wasn't drawing enough current to effectively allow the TRIAC to turn on (generally, SCR's are not used in lighting dimmers, due to cost)

Place a Incadescent light globe across the output terminals of the dimmer, and place your meter in parallel with the light globe (measuring the voltage across the lamp) now adjusting the dimmer, you should see (light and voltage) changing.

I would doubt that your dimmer would handle much over 50-100W before it too goes South for the winter, and the vital smoke leaks from its storage canister inside the device.

I agree with your first two statements the third however I don't understand. The poster stated it was a 1000W dimmer so would be able to handle up to a 1000W heater load (resistive). That is not a large heater by any means so hopefully he verified the rating of the heater.

Shawn

Dear abasile

in case you have not already thrown that dimmer out of the window, why not have a look at the components that have charred, if not beyond recognition to give up smell. if there is a fuse you would have checked it; if its a capacitor ,it would show ,if its a diac that looks like a small diode ,its unlikely to give up smoke smell.hows about the Triac which you would know because it has got to have a heat sink associated,quite often in case of dead short circuit triac innerds would show; if not and if you are lucky could it be the Printed circuit board Tracks(in case there is one) and associated hookup wire that generated the burning smell.

may be we can salvage the dimmer !

Thanks for your patience.

pkd.

Hello p.k.datta

Hardly worth salvaging the dimmer in the US.

Cost of one is around US$4.00

Kind Regards....

A 1000W dimmer will cost a bit more then $4.00 in the US. When the dimmer was shorted it was most likely the Triac that failed which is probably either a TO-220 or TO-247 device that is pop riveted to the yoke or plate of the dimmer. If you do try to replace it to resucitate your failed dimmer make sure to use a little thermal grease on the Triac to properly conduct heat from the device to the heat sink.

Shawn

I am not sure but I think when trying to test your current you need to put the meter in series if not using a shunt. However if the meter is rated in Milli amps you might blow it so I would use a amp probe. this is for ac. A hall effect meter for DC of much amperage. The others will say if I am wrong. It just hit me, why not go to the local dump and take out the controls and elements from an old electric stove and fool around with them. You might end up using 240 volts to make it really get hot but it will cost less then 120 volts if you are going to use it a lot. Or buy a 240 volt hot water element that looks like it has the same amount of inches as the stove element. Or pull out old elements from the dead water tanks at the dump while you are there and set your test meter on diode test for sound to check if they are burnt out.This might make it easier to make a water proof connection.Just an old welders ideas, Good luck.

Can you please explain how you measured the current?.

Your meter will still probably read 118 volts even with the dimmer at 10% on condition. Many dimmers work like a "chopper" circuit allowing part of the waveform through to the load and so your meter will still see peak voltage and display 118V.

Regarding measuring current, as all before have said, you need a load in the circuit, and it is probable that you have also blown the protection fuse inside the meter. (Go and check it on something less dangerous like your car headlight circuit or similar to verify that the meter is still OK.)

On the other hand, looking at your primary objective (alcohol) be careful and measure the temperature of your condensation column. No matter how good your brewing technique, it's possible to get methanol in the brew and that will come out in the first condensate before the ethanol and then finally water.

What you do with the alcohol afterwards is up to you, but methanol is great for yard lights, flares and so on.

Most 'inexpensive' dimmers are 'choppers' and basically let current flow starting as the AC crosses 0V for a portion of the cycle where it 'chops' off the power. When the supply voltage crosses back to zero, it starts conducting again. What the dimmer really does is set the amount of time after zero voltage crossing until the 'chop' of the power to the output happens. This is really power efficient for resistive loads, but electronics on the output has problems. Since most heaters and all incandescent lights are resistive, it works well.

If you are trying to do 'fine adjustments', a $4 dimmer might not be a good choice, but it is worth a try.

I question how you were trying to measure the current. Amp meters for AC are often inductively coupled (a loop of some kind goes AROUND the hot wire (typically) to the load), or it is measured like DC, measuring the voltage drop across a KNOWN resistance. The known resistance is often inside a multi-meter, or it could be an external 'shunt'. In any case the resistive load needs to be IN LINE with the current. Panel mounted amp meters often have external shunts bolted onto the back of them (at least they did in the 'olden days' :)

If you are going to measure AC current regularly, I suggest you invest in a clip on Amp meter (they often have a VOM built in as well).

I hope this helps a little... JC (I am not an engineer nor do I play one on TV)

This is essentially correct, but what you are desribing is "Reverse Phase Control" dimming and uses FET's. Standard Phase Control waits some amount of time after the zero cross and then begins to conduct and will remain "On" until the zero cross when the Triac will commutate off. One of these two methods is how most of the dimmers available today work. Standard Phase Control is used for incandescent and magnetic low-voltage lighting, Reverse Phase control is used for electronic low-voltage and can be used for incandescent as well but is usually lower power and more expensive then standard phase control so is not often used for incandescent lighting.

Shawn

I learned back in the days of analog meters to never use the 20A range on the meter. The low current range - 2A - was usually fused. The number of times I have seen those fuses blown told me that current measurement was too dangerous to risk a meter on. The 20A range never has a fuse, so the shunt resistor acts as a fuse. ( definition of a fuse - the most delicate item in a circuit). If you need to know current - put your own shunt R in the circuit or use a clamp on inductive probe. Either of those is cheaper than a new meter.

Usually it is not varying the voltage, but current. Maybe you do a wrong method of current checking. You may not put multimeter directly in close-loop. You need a "load" to define the current that flowing through it. If i'm not wrong, the current should be 118 Amp if it's directly checked, surely it's high enough to burn your device.