I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't work. I set
the meter to 20v DC & tried to measure the voltage at the porcelain cable
connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at the time
& still got nothing.

Is my multi meter broken or is a digital meter no good for this sort of
thing? If the latter, what do I need to buy?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't work. I set
the meter to 20v DC & tried to measure the voltage at the porcelain cable
connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at the time
& still got nothing.

Is my multi meter broken or is a digital meter no good for this sort of
thing? If the latter, what do I need to buy?

Try switching it to AC... :-)

--
Frank Erskine

"Frank Erskine" wrote in message
...
On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't work. I
set
the meter to 20v DC & tried to measure the voltage at the porcelain cable
connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at the
time
& still got nothing.

Is my multi meter broken or is a digital meter no good for this sort of
thing? If the latter, what do I need to buy?

Try switching it to AC... :-)

Seconded.

Adam

In article ,
"ARWadsworth" writes:

"Frank Erskine" wrote in message
...
On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't work. I
set
the meter to 20v DC & tried to measure the voltage at the porcelain cable
connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at the
time
& still got nothing.

Is my multi meter broken or is a digital meter no good for this sort of
thing? If the latter, what do I need to buy?

Try switching it to AC... :-)

Seconded.

If it's an electronic transformer, you still won't get an accurate
reading, as test meters aren't designed for ~20kHz AC and a grotty
waveform. You should get something somewhere between 6 and 18V though.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 24 Oct, 17:52, (Andrew Gabriel) wrote:
In article ,
* * * * "ARWadsworth" writes:





"Frank Erskine" wrote in message
.. .
On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't work. *I
set
the meter to 20v DC & tried to measure the voltage at the porcelain cable
connector. *Nothing.

Tried to measure the voltage on the one next to it, which was on at the
time
& still got nothing.

Is my multi meter broken or is a digital meter no good for this sort of
thing? *If the latter, what do I need to buy?

Try switching it to AC... :-)

Seconded.

If it's an electronic transformer, you still won't get an accurate
reading, as test meters aren't designed for ~20kHz AC and a grotty
waveform. You should get something somewhere between 6 and 18V though.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

Yes - I tried measuring the output voltage of a single to three phase
invertor with a DVM and did guess that 600vac, or so, wasn't quite
right. A more modern DVM gave me 280vac and a traditional AVO 8 gave
240vac,

Rob

Frank Erskine wrote:
On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't
work. I set the meter to 20v DC & tried to measure the voltage at
the porcelain cable connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at
the time & still got nothing.

Is my multi meter broken or is a digital meter no good for this sort
of thing? If the latter, what do I need to buy?

Try switching it to AC... :-)

Doh!

What a pillock I am. Automatically assumed 12v would be DC.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

On Fri, 24 Oct 2008 17:29:19 GMT, "The Medway Handyman"
wrote:

Try switching it to AC... :-)

Doh!

What a pillock I am. Automatically assumed 12v would be DC.

You aren't alone! (

I read an re-read your post wondering what could be wrong. Gave up in
the end.

(Anybody want to buy a well used DMM?)
(With AC scale)

On 24 Oct, 19:41, EricP wrote:
On Fri, 24 Oct 2008 17:29:19 GMT, "The Medway Handyman"

wrote:
Try switching it to AC... :-)

Doh!

What a pillock I am. *Automatically assumed 12v would be DC.

You aren't alone! *(

I read an re-read your post wondering what could be wrong. Gave up in
the end.

(Anybody want to buy a well used DMM?)
(With AC scale)

You've also got to bear in mind that some electronic transformers are
of a design that requires there to be a reasonable load before any
output occurs. This is just a characteristic of switch mode power
supplies, not a design aim.

Rob

robgraham wrote:
On 24 Oct, 19:41, EricP wrote:
On Fri, 24 Oct 2008 17:29:19 GMT, "The Medway Handyman"

wrote:
Try switching it to AC... :-)

Doh!

What a pillock I am. Automatically assumed 12v would be DC.

You aren't alone! (

I read an re-read your post wondering what could be wrong. Gave up in
the end.

(Anybody want to buy a well used DMM?)
(With AC scale)

You've also got to bear in mind that some electronic transformers are
of a design that requires there to be a reasonable load before any
output occurs. This is just a characteristic of switch mode power
supplies, not a design aim.

Ah. So they need a 'known to be working' bulb (sorry lamp) to be there?

I'm just looking for a simple & reliable way of knowing if I need to change
the SMPS.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

The Medway Handyman wrote:
Frank Erskine wrote:
On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't
work. I set the meter to 20v DC & tried to measure the voltage at
the porcelain cable connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at
the time & still got nothing.

Is my multi meter broken or is a digital meter no good for this sort
of thing? If the latter, what do I need to buy?
Try switching it to AC... :-)

Doh!

What a pillock I am. Automatically assumed 12v would be DC.

Not entirely... worth noting that many lighting "transformers" these
days are in fact switched mode power supplies. Some of these will
shutdown in the absence of a load, so measuring the voltage without a
bulb present may also get you nothing even if using the correct range.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
The Medway Handyman wrote:
Frank Erskine wrote:
On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't
work. I set the meter to 20v DC & tried to measure the voltage at
the porcelain cable connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at
the time & still got nothing.

Is my multi meter broken or is a digital meter no good for this sort
of thing? If the latter, what do I need to buy?

Try switching it to AC... :-)

Doh!

What a pillock I am. Automatically assumed 12v would be DC.

You may not get an accurate reading with some DVMs on the AC range either
as SMPS run at a much higher frequency than mains. And may not give any
output at all in the absence of a load.

Just for guidance SMPS are quite light and usually shaped so they'll fit
through the downlighter mounting hole. A true transformer will be much
heavier - and likely larger too. Most these days are SMPS.

--
*He who dies with the most toys is, nonetheless, dead.

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't
work. I set the meter to 20v DC & tried to measure the voltage at
the porcelain cable connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at
the time & still got nothing.

Is my multi meter broken or is a digital meter no good for this
sort of thing? If the latter, what do I need to buy?

Try switching it to AC... :-)

Doh!

What a pillock I am. Automatically assumed 12v would be DC.

You may not get an accurate reading with some DVMs on the AC range
either as SMPS run at a much higher frequency than mains. And may not
give any output at all in the absence of a load.

Just for guidance SMPS are quite light and usually shaped so they'll
fit through the downlighter mounting hole. A true transformer will be
much heavier - and likely larger too. Most these days are SMPS.

Thanks Dave (& John).

That makes perfect sense, I used the word 'transfomer' almost in a generic
way. Seems that SMPS are described as transformers even by TLC
http://www.tlc-direct.co.uk/Main_Ind...ers/index.html

Are these really SMPS's?

To further my education :-) how does an SMPS work in simple terms? I
understand how a transformer works more or less, how does an SMPS achieve a
similar thing?

What about wall warts? Is a Nokia phone charger an SMPS?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

In article ,
The Medway Handyman wrote:
Just for guidance SMPS are quite light and usually shaped so they'll
fit through the downlighter mounting hole. A true transformer will be
much heavier - and likely larger too. Most these days are SMPS.

Thanks Dave (& John).

That makes perfect sense, I used the word 'transfomer' almost in a
generic way. Seems that SMPS are described as transformers even by TLC

http://www.tlc-direct.co.uk/Main_Ind...ers/index.html

They call them electronic transformers and the 'proper' transformers
toroidal - which is actually a type of transformer. I've seen low voltage
lighting true transformers which weren't toroidal.

But it makes some sense to call them all transformers because they do the
same job. And most won't be interested in any differences internally.

Are these really SMPS's?

The electronic ones, yes.

To further my education :-) how does an SMPS work in simple terms? I
understand how a transformer works more or less, how does an SMPS
achieve a similar thing?

Like for like, transformers gets smaller as the frequency increases. So
an SMPS converts the 50Hz mains frequency to something like 30,000 Hz. So
a much smaller and cheaper transformer can be used.

What about wall warts? Is a Nokia phone charger an SMPS?

Most are these days. When you make things by the million the material
costs are important and the saving in expensive copper for the windings
etc can easily exceed the complexity of making the thing. As well as
making it smaller for a given output. It's also simple to make an SMPS
that will work with virtually any input voltage and give a constant output
- not so with a normal one.

--
*Is there another word for synonym?

Dave Plowman London SW
To e-mail, change noise into sound.

The Medway Handyman wrote:

That makes perfect sense, I used the word 'transfomer' almost in a generic
way. Seems that SMPS are described as transformers even by TLC
http://www.tlc-direct.co.uk/Main_Ind...ers/index.html

Are these really SMPS's?

Yup, too small and light to be an iron cored transformer.

To further my education :-) how does an SMPS work in simple terms? I
understand how a transformer works more or less, how does an SMPS achieve a
similar thing?

There are quite a number of different designs, but the general principle
generally goes something like rectify the mains and use it to drive an
oscillator producing an output at many times mains frequency. Use this
in a much smaller step down transformer (transformers gain efficiency as
the frequency rises). In the case of a lighting transformer there is no
need for much else - you can use the LV HF waveform directly.

What about wall warts? Is a Nokia phone charger an SMPS?

Almost certainly. This is one of the factors that makes the "switch off
your mobile phone charger to save the planet" arguments kind of pointless.

Note with the TLC transformers, these will give a voltage output with no
load (I tested one of the individual lamp 50W ones the other day. The
reading was also a good approximation to 12V using my DMM (although this
was a "true RMS" clamp meter).

If you want a reliable way to test an electronic transformer you might
find it worth making up a small test jig using some high power wire
wound resistors. You could then use them in series with your DMM on its
current measuring range (assuming it will read at least a couple of
amps). That ought to be enough to ensure the transformer starts ok.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"The Medway Handyman" wrote in message
om...
Dave Plowman (News) wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't
work. I set the meter to 20v DC & tried to measure the voltage at
the porcelain cable connector. Nothing.

Tried to measure the voltage on the one next to it, which was on at
the time & still got nothing.

Is my multi meter broken or is a digital meter no good for this
sort of thing? If the latter, what do I need to buy?

Try switching it to AC... :-)

Doh!

What a pillock I am. Automatically assumed 12v would be DC.

You may not get an accurate reading with some DVMs on the AC range
either as SMPS run at a much higher frequency than mains. And may not
give any output at all in the absence of a load.

Just for guidance SMPS are quite light and usually shaped so they'll
fit through the downlighter mounting hole. A true transformer will be
much heavier - and likely larger too. Most these days are SMPS.

Thanks Dave (& John).

That makes perfect sense, I used the word 'transfomer' almost in a generic
way. Seems that SMPS are described as transformers even by TLC
http://www.tlc-direct.co.uk/Main_Ind...ers/index.html

Are these really SMPS's?

To further my education :-) how does an SMPS work in simple terms? I
understand how a transformer works more or less, how does an SMPS achieve
a similar thing?

What about wall warts? Is a Nokia phone charger an SMPS?

Most phone chargers are SMPS these days but the Nokia
might be an exception. If yours look like mine
http://myweb.tiscali.co.uk/infoweb/nokia.jpg
then it defiantly has a conventional transformer inside
I'm sure I saw identical ones blister packed in a
Supermarket recently.

--
Graham.

%Profound_observation%

On Oct 24, 8:30*pm, "Dave Plowman (News)"
wrote:
In article ,
* *The Medway Handyman wrote:





Frank Erskine wrote:
On Fri, 24 Oct 2008 15:37:46 GMT, "The Medway Handyman"
wrote:

I have a digital multi meter from TLC
http://www.tlc-direct.co.uk/Products/TMM3800.html

I had to change some 12v 35w halogen lamps today & one wouldn't
work. *I set the meter to 20v DC & tried to measure the voltage at
the porcelain cable connector. *Nothing.

Tried to measure the voltage on the one next to it, which was on at
the time & still got nothing.

Is my multi meter broken or is a digital meter no good for this sort
of thing? *If the latter, what do I need to buy?

Try switching it to AC... :-)
Doh!
What a pillock I am. *Automatically assumed 12v would be DC.

You may not get an accurate reading with some DVMs on the AC range either
as SMPS run at a much higher frequency than mains. And may not give any
output at all in the absence of a load.

Just for guidance SMPS are quite light and usually shaped so they'll fit
through the downlighter mounting hole. A true transformer will be much
heavier - and likely larger too. Most these days are SMPS.

--
*He who dies with the most toys is, nonetheless, dead. *

* * Dave Plowman * * * * * * * * London SW
* * * * * * * * * To e-mail, change noise into sound.- Hide quoted text -

- Show quoted text -

Not only switching power supplies!!!!!

A year or two ago we repaired a car battery charger (can't remember
what the problem was). To check we then hooked up a DMM to the output
switched on and got some real funny voltage readings. Seemingly ow
voltage IIRC.

Oops what's going on? Until we suggested that what the digital meter
was seeing from the battery charger output was completely unsmoothed
and unfiltered rectified voltages varying between zero and some sort
of rectified peak AC voltage. We would have been better off using an
analog meter!

Sure enough when we hooked up a spare car battery charging current
flowed into the battery and the voltages made sense.
A suitable charging voltage for lead acid batteries is around 2.3
volts per cell (maybe a little higher). So for the so called "12 volt
car battery" 6 cells at 2.3 volts each = 13.8 volts. That's very close
to the 14 volts often mentioned.

Commercial outfits often float their batteries (just maintaining them
at full charge) at either 2.15 or 2.17 volts per cell. Doesn't sound
like much of a difference but avoids boiling the life out of a fully
charged battery.

So 6 x 2.15 = 12.90 (British Telcomm.) and 6 x 2.17 = 13.02 (Old AT&T
and Bell System Spec.) Except these were usually for telephone
exchange battery strings for a nominal 48 volts. i.e. 24 x 2 = 48
volts.