12v DC supply

[kevinlms]

6 minutes ago, Junctionmad said:

The question posed is simple , the fact is the answer is not , so can 16vac output be used to power a nominally 12v dc turntable , the correct and only answer is “ it depends “ ( on a number of factors and you need far more info to answer the question correctly ) 

 

 

Agreed. The initial question and follow up show a lack of understanding by the OP (nothing wrong with that, it is the whole point of asking questions - to learn).

 

I even asked earlier, as to what sort of turntable it was and there has been no answer. MOST turntables are 12 Volt DC, but IIRC the Fleischmann one is AC.

 

However it seems we will never know...

[sharris]

43 minutes ago, Junctionmad said:

The question posed is simple , the fact is the answer is not

 

I'd say the answer to the question as posed is simple (I need 12V DC - implied in the title - to power my turntable, but my controller only gives 16V AC)

 

My answer to that question would involve a bridge rectifier, a 12V voltage regulator and a couple of capacitors, and if I was feeling generous, a reversing switch.

 

Like all engineering answers, it would be an answer to the question posed, but not the answer to the question that the customer should have asked. Incomplete specifications are probably the most expensive (and a very common) mistake a customer can make.

 

[Mallard60022]

7 hours ago, Junctionmad said:

The question posed is simple , the fact is the answer is not , so can 16vac output be used to power a nominally 12v dc turntable , the correct and only answer is “ it depends “ ( on a number of factors and you need far more info to answer the question correctly ) 

 

 

Totally agree and thanks for your mild response. However this sort of what is quite a basic question, is often replied to with such over complicated answers that it just totally puts off someone from bothering.  Don't know why it is this particular part of the Forum within which that happens? 

I am lucky in that I can just ask a couple of really experienced friends who have simple and straightforward advice. 

I am very sorry to have to say that too many people on these and other Forums just think they know better than others and just have to go on and on and on and it is tedious.

I would, by the way, in no way accuse you of this as I do not even know you.

All the best.

A. Luddite.

[Mallard60022]

The last few posts are again, absolutely correct and kindly put. Let us just agree that it is a skilled person in 'teaching' (in this post case, explaining) that can negotiate with a questioner to attempt to find out exactly what they want to do or achieve. Not all have this skill; they have great knowledge but can not really understand that someone else can't quite 'get it'. 

If, of course the questioner never responds, then the case is closed, as they are either scared off by  some complicated first responses or just have gone away. Pity really.

I suppose I have been fortunate to experience a whole range of 'teachers' in my long and varied careers and I know the ones I respect and the ones I would never even ask to tell me the time of the next bus...….

Edited September 18, 2019 by Mallard60022

[melmerby]

8 hours ago, kevinlms said:

 MOST turntables are 12 Volt DC, but IIRC the Fleischmann one is AC.

 

Correct, along with AFAIK it's cousin the Märklin one

[DCB]

9 hours ago, sharris said:

 

I'd say the answer to the question as posed is simple (I need 12V DC - implied in the title - to power my turntable, but my controller only gives 16V AC)

 

My answer to that question would involve a bridge rectifier, a 12V voltage regulator and a couple of capacitors, and if I was feeling generous, a reversing switch.

 

Like all engineering answers, it would be an answer to the question posed, but not the answer to the question that the customer should have asked. Incomplete specifications are probably the most expensive (and a very common) mistake a customer can make.

 

How would you wire the regulator?    If you are moving into the above £1 budget range wouldn't a circuit controller be a better solution?

 

I would hang a Lucas "12 volt" Zener diode across the outputs like I used to in the 1970s on Triumph and BSA bikes but they regulate to give 13.8 to 14.2 volts max so back to square one I fear.

[Crosland]

15 hours ago, SHMD said:

Most answers on all forums are not of mercantile quality - and that is the price of an open forum. (Moderated or not.)

Some answers are dangerous - to varying degrees - and some are priceless (and that is why we ask), some are just wrong.

 

 

The problem is some, from certain posters, are priceless for all the wrong reasons. Do I keep stum and say nothing, or correct them to avoid others being completely confused?

 

I was once, some years ago, accused by a mod of only ever posting to tell people they were wrong  I am happy to let the wrong posts go unchallenged, f that's what people want.

 

[Crosland]

52 minutes ago, DavidCBroad said:

How would you wire the regulator?    If you are moving into the above £1 budget range wouldn't a circuit controller be a better solution?

 

Follow the datasheet? A LM7812 is less than a pound but I wasn't aware the OP specified any price constraints.

 

I was going to say using a Zener is a cheap and nasty solution but have you seen the price of a "Lucas 12V Zener"?

[DCB]

19 minutes ago, Crosland said:

 

Follow the datasheet? A LM7812 is less than a pound but I wasn't aware the OP specified any price constraints.

 

I was going to say using a Zener is a cheap and nasty solution but have you seen the price of a "Lucas 12V Zener"?

If I bought a 12 volt Zener from my local electronics shop it wouldn't come with a data sheet.   I just wondered how one would wire it?   Does it need a heat sink etc.

[sharris]

18 minutes ago, DavidCBroad said:

If I bought a 12 volt Zener from my local electronics shop it wouldn't come with a data sheet.   I just wondered how one would wire it?   Does it need a heat sink etc.

 

Electronic components rarely come with a datasheet. Back in the 80s and 90s I used to have a bookshelf full of databooks with datasheets from Texas Instruments, Motorola, Intel and suchlike. I still have some of them, but mostly I find them online these days - e.g. RS and Farnell have datasheets on the components they sell.

[SHMD]

21 minutes ago, DavidCBroad said:

If I bought a 12 volt Zener from my local electronics shop it wouldn't come with a data sheet.   I just wondered how one would wire it?   Does it need a heat sink etc.

 

There is not a simple answer to this, but this link will help you understand what you will need to do (ie - lots of calculations):-

 

https://www.electronics-tutorials.ws/diode/diode_7.html

 

 

Basically, using a Zener Diode to regulate voltage is awful as the heat dissipation for the resistor and zener have to be done for all extremes of operating conditions.

 

 

Kev.

(..but you could just ditch the resister and hope that the PSU's source impedance will be enough..)

((DO NOT TRY THIS AT HOME!))

 

 

[SHMD]

4 hours ago, Mallard60022 said:

 

I am lucky in that I can just ask a couple of really experienced friends who have simple and straightforward advice. 

 

 

 

 

..who probably know your abilities, equipment, resources and requirements and only need a little prompting to come up with "your" right solution.

Asking a question on a forum will have none of this context and thus will result in a lot of faffing about.

 

Maybe Andy should add a new Forum Rule that only correctly (guessed or otherwise) answers should be posted to save time and please OPs!

 

 

Kev.

(DavidCBroad has lots of straight forward simple advice and lots of experience...)

 

[melmerby]

40 minutes ago, sharris said:

 

Electronic components rarely come with a datasheet. Back in the 80s and 90s I used to have a bookshelf full of databooks with datasheets from Texas Instruments, Motorola, Intel and suchlike. I still have some of them, but mostly I find them online these days - e.g. RS and Farnell have datasheets on the components they sell.

Back in the day you could buy a complete folder (later several folders) full of RS datasheets, with the RS part numbers. Individual sheets were free for the asking from an RS counter.

Manufacturers used to give books of data sets to people who used their components (companies, not private individuals)

Like you I still have some, including CMOS from Philips (74HC & 40XX)

These days most info is online for everybody to use

[Junctionmad]

Ah yes rows of yellow TI books followed by rows of blue National books , them were the days when men were men and sheep were worried 

[Crosland]

6 hours ago, DavidCBroad said:

If I bought a 12 volt Zener from my local electronics shop it wouldn't come with a data sheet.   I just wondered how one would wire it?   Does it need a heat sink etc.

 

??? You were the one suggesting a zener. Now you say you don't know how to wire it!

 

I give up.

[melmerby]

5 hours ago, SHMD said:

(DavidCBroad has lots of straight forward simple advice and lots of experience...)

 

 

6 hours ago, DavidCBroad said:

If I bought a 12 volt Zener from my local electronics shop it wouldn't come with a data sheet.   I just wondered how one would wire it?   Does it need a heat sink etc.

 

5 minutes ago, Crosland said:

 

??? You were the one suggesting a zener. Now you say you don't know how to wire it!

 

I give up.

[Crosland]

7 hours ago, SHMD said:

(DavidCBroad has lots of straight forward simple advice and lots of experience...)

 

 

Such advice as using LEDs without current limit resistors.

 

 

[sharris]

3 minutes ago, Crosland said:

 

Such advice as using LEDs without current limit resistors.

Now, now, Crosland, let's not open that one again! 

[Mallard60022]

7 hours ago, SHMD said:

 

..who probably know your abilities, equipment, resources and requirements and only need a little prompting to come up with "your" right solution.

Asking a question on a forum will have none of this context and thus will result in a lot of faffing about.

 

Maybe Andy should add a new Forum Rule that only correctly (guessed or otherwise) answers should be posted to save time and please OPs!

 

 

Kev.

(DavidCBroad has lots of straight forward simple advice and lots of experience...)

 

Take your point. They also can see my blank look (frequently!!!)

P

[DCB]

15 hours ago, Crosland said:

 

??? You were the one suggesting a zener. Now you say you don't know how to wire it!

 

I give up.

I suggested I would put a Lucas zener across the outputs and said why it wouldn't work. The Lucas "12 volt" Zener Diode controls to 13.8 to 14.2 volts and is rated at something like 7.5 amps and there are some in my shed..

I would like a wiring diagram for a modern zener diode as suggested, the old one is just connect negative to negative and positive to positive and screw it to a heatsink.

 

[SHMD]

Did you look at that website?

 

https://www.electronics-tutorials.ws/diode/diode_7.html

 

 

Kev.

 

[St Enodoc]

My advice to the OP, if he's still reading this, is to forget the turntable and run tank engines or diesels.

[Junctionmad]

48 minutes ago, DavidCBroad said:

I suggested I would put a Lucas zener across the outputs and said why it wouldn't work. The Lucas "12 volt" Zener Diode controls to 13.8 to 14.2 volts and is rated at something like 7.5 amps and there are some in my shed..

I would like a wiring diagram for a modern zener diode as suggested, the old one is just connect negative to negative and positive to positive and screw it to a heatsink.

 

To use a Lucas zenner , you need to understand the context and circuit as it’s applied to motorbikes of the 70s. Simply “ connect negative to negative .........” would fry everything 

 

this is not meant to be patronizing , but electronics is a profession and a science precisely because there is design knowledge needed to use anything , unfortunately well intentioned people feel that , “ it’s only volts and amps “ , sure I understand that. Hence the simple questions but the answer is complex 

 

a big zenner like the Lucas one , equally needs a big power series resistor , without it,   once the current goes over the avalanche region , the power supply will be effectively shorted , the value of the resistor needs to take in to account the desired operating region of the particular zenner and the desired load current 

 

( again the issue of a simple question and a complex answer based on design criteria ) 

 

for lots of reasons its its a terrible solution ( and it was on bikes too  and has been replaced by regulators ) 

 

the easiest and simplest  solution for for a few pennies is rectify it ,  then use a common 12v linear regulator ic , assuming the heat dissipation is within spec and the load is compatible ( easy isn’t it :D) 

 

i am reminded of the quip 

 

Lord Finchley tried to mend the Electric Light
Himself. It struck him dead: And serve him right!
It is the business of the wealthy man
To give employment to the artisan. 

 

Hilaire Belloc

 

 

Edited September 19, 2019 by Junctionmad

[Ravenser]

1 hour ago, Junctionmad said:

To use a Lucas zenner , you need to understand the context and circuit as it’s applied to motorbikes of the 70s. Simply “ connect negative to negative .........” would fry everything 

 

this is not meant to be patronizing , but electronics is a profession and a science precisely because there is design knowledge needed to use anything , unfortunately well intentioned people feel that , “ it’s only volts and amps “ , sure I understand that. Hence the simple questions but the answer is complex 

 

a big zenner like the Lucas one , equally needs a big power series resistor , without it,   once the current goes over the avalanche region , the power supply will be effectively shorted , the value of the resistor needs to take in to account the desired operating region of the particular zenner and the desired load current 

 

( again the issue of a simple question and a complex answer based on design criteria ) 

 

for lots of reasons its its a terrible solution ( and it was on bikes too  and has been replaced by regulators ) 

 

the easiest and simplest  solution for for a few pennies is rectify it ,  then use a common 12v linear regulator ic , assuming the heat dissipation is within spec and the load is compatible ( easy isn’t it :D) 

 

i am reminded of the quip 

 

Lord Finchley tried to mend the Electric Light
Himself. It struck him dead: And serve him right!
It is the business of the wealthy man
To give employment to the artisan. 

 

Hilaire Belloc

 

 

 

So if you connect a turntable to a 1970s motorbike and start up the motorbike, the turntable will rotate??? Or am I misreading the thread?

[DCB]

9 minutes ago, Ravenser said:

 

So if you connect a turntable to a 1970s motorbike and start up the motorbike, the turntable will rotate??? Or am I misreading the thread?

To the electrics in theory yes if it has Lucas electrics with a Zener Diode.   Not an optimal solution. Just make sure there is a 1 amp fuse between bike and turntable or a short could quickly melt all the insulation.

 

Could be an issue with neighbours, starting the bike before turning a loco.

 

Good idea, need thinking though some more.