Does anyone know if it would be practical to geta 24V ac 50 Hz power
supply from a stand-by battery?

I'd think there'd be an inverter involved but are these easily
available for this output? The aim is to run an electronic device
during power failures, but getting a different device might be easier
than getting 24V ac.

Aidan wrote:

Does anyone know if it would be practical to geta 24V ac 50 Hz power
supply from a stand-by battery?

if you make your own invertor. Or you could buy a 24v dc to sine mains
invertor and add a 24v transformer onto it.

I'd think there'd be an inverter involved but are these easily
available for this output?

no

The aim is to run an electronic device
during power failures, but getting a different device might be easier
than getting 24V ac.

quite likely. But your 24v ac device will most likely run quite happily
off 24v x 1.41 - 3v = 31v dc. Sometimes theyll even accept a range of
voltages. I cant think of too many 24v appliances that would need ac.

Dont ask electronic questions on ukdiy. You can, but its at your risk,
this isnt a tronics group, theres little expertise here on it.


NT

Aidan wrote:

Does anyone know if it would be practical to geta 24V ac 50 Hz power
supply from a stand-by battery?

I'd think there'd be an inverter involved but are these easily
available for this output? The aim is to run an electronic device
during power failures, but getting a different device might be easier
than getting 24V ac.

I would be tempted to see if the electronic device can be modified to
feed it DC (since there is a fair chance it converts its AC input to DC
at some point anyway).

Failing that an invertor will do the trick, although many will produce
240V not 24. A change to their tansformer may fix that however depending
on the design.


--
Cheers,

John.

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

Does anyone know if it would be practical to geta 24V ac 50 Hz power
supply from a stand-by battery?

What is it? Maybe it will run off DC too?

Apart from that, finding a cheap inverter may be difficult. Probably easier
to buy a 24VDC - 230VAC inverter (v. cheap) and a mains power supply for
it.

Christian.

In an earlier contribution to this discussion,
Aidan wrote:

Does anyone know if it would be practical to geta 24V ac 50 Hz power
supply from a stand-by battery?

I'd think there'd be an inverter involved but are these easily
available for this output? The aim is to run an electronic device
during power failures, but getting a different device might be easier
than getting 24V ac.

Do you have any means of running it at present? If so, you presumably have a
240v/24v transformer which you power of a battery to mains inverter. Having
said that, most cheap inverters require 12v DC input rather than 24v. What
is your battery?
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

John Rumm wrote:
Aidan wrote:

Does anyone know if it would be practical to geta 24V ac 50 Hz power
supply from a stand-by battery?

I would be tempted to see if the electronic device can be modified to
feed it DC (since there is a fair chance it converts its AC input to DC
at some point anyway).

It should run on dc without modification. As the OP didnt think to tell
us what it was, we can only guess.

I made a mistake earlier, it'll want 24x1.41 = 34v dc, so 36v lead
acids should do fine.


NT

It's a BMS outstation, a computer type device intended to monitor &
controls heating & stuff.

On the pcb, it has an encapsulated transformer 0-24V pri/0-18V sec,
adjacent to the power input. The power is from a 24V ac mains
transformer. Also 4 electrolytic capacitors, but nothing I recognise as
an rectifier. There's a small battery on the pcb, but it's just to
maintain the RAM & programmed settings. The device fails if the 24 Vac
goes off. I'd like to monitor inputs and keep the alarms working. The
control valves are also 24 V ac, but I wouldn't intend maintaining the
power supply to these.

You could probably achieve what I want with PLCs but I'd have to learn
how to programme those, so that's relegated to plan B!

In an earlier contribution to this discussion,
Aidan wrote:

It's a BMS outstation, a computer type device intended to monitor &
controls heating & stuff.

On the pcb, it has an encapsulated transformer 0-24V pri/0-18V sec,
adjacent to the power input. The power is from a 24V ac mains
transformer.

In that case, use the *same* mains transformer running from an inverter -
like I suggested earlier.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On 23 Sep 2005 08:21:16 -0700, wrote:


Dont ask electronic questions on ukdiy. You can, but its at your risk,
this isnt a tronics group, theres little expertise here on it.

You are proving the point I assume?



--
Peter Parry.
http://www.wpp.ltd.uk/

Aidan wrote:
It's a BMS outstation, a computer type device intended to monitor &
controls heating & stuff.

On the pcb, it has an encapsulated transformer 0-24V pri/0-18V sec,
adjacent to the power input. The power is from a 24V ac mains
transformer. Also 4 electrolytic capacitors, but nothing I recognise as
an rectifier. There's a small battery on the pcb, but it's just to
maintain the RAM & programmed settings. The device fails if the 24 Vac
goes off. I'd like to monitor inputs and keep the alarms working. The
control valves are also 24 V ac, but I wouldn't intend maintaining the
power supply to these.

You could probably achieve what I want with PLCs but I'd have to learn
how to programme those, so that's relegated to plan B!


Going through an inverter will be much less efficient than direct DC
injection.
There MUST be a rectifier; almost certainly the secondary of the traffo
will be connected straight to it (maybe via a fuse) so trace the pcb
tracks. If you can't find it just disconnect the secondary of the traffo
and connect your DC feed to wherever the secondary previously went - the
rectifier may run a little warmer but this is very unlikely to be a
problem - and if it DOES get too hot you'll be able to find it

If you want this as a back-up system , rather than replacing the mains
supply, you'll need to find the rectifier and connect the new DC supply
to its output via a diode.

Dave

wrote:

I would be tempted to see if the electronic device can be modified to
feed it DC (since there is a fair chance it converts its AC input to DC
at some point anyway).


It should run on dc without modification. As the OP didnt think to tell
us what it was, we can only guess.

You are assuming it has a full wave bridge rectifier on its input...
(fair assumption certainly, but not guarenteed).



--
Cheers,

John.

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

Dave wrote:

There MUST be a rectifier; almost certainly the secondary of the traffo
will be connected straight to it (maybe via a fuse) so trace the pcb
tracks.

Thanks all. There is a small fuse tucked out of sight above the
transformer. I'll dismantle one and see if I can follow the circuit &
measure some voltages.

Aidan wrote:
Dave wrote:

There MUST be a rectifier; almost certainly the secondary of the traffo
will be connected straight to it (maybe via a fuse) so trace the pcb
tracks.

Thanks all. There is a small fuse tucked out of sight above the
transformer. I'll dismantle one and see if I can follow the circuit &
measure some voltages.

24v ac solenoids will generally run happily on 12v dc.

NT

John Rumm wrote:
wrote:

It should run on dc without modification. As the OP didnt think to tell
us what it was, we can only guess.

You are assuming it has a full wave bridge rectifier on its input...
(fair assumption certainly, but not guarenteed).

No I'm not.


NT

wrote:
John Rumm wrote:
wrote:

It should run on dc without modification. As the OP didnt think to tell
us what it was, we can only guess.

You are assuming it has a full wave bridge rectifier on its input...
(fair assumption certainly, but not guarenteed).

No I'm not.

Yes, you are.
A device with (for example) a transformer in the input circuit, as this
one turned out to have, will simply blow fuses if you connect DC to it.

wrote:

24v ac solenoids will generally run happily on 12v dc.

No solenoids. All are modulating motorized control valves, 24V ac
power supply with a 0-10V control signal.

No battery at present, besides the coin-sized one on the pcb.

Ian Stirling wrote:
wrote:
John Rumm wrote:
wrote:

It should run on dc without modification. As the OP didnt think to tell
us what it was, we can only guess.

You are assuming it has a full wave bridge rectifier on its input...
(fair assumption certainly, but not guarenteed).

No I'm not.

Yes, you are.

No, I wasn't, thats why I said I wasn't. Its not hard to run through
the various possibilities and see that what I said is consistent with
them. Note I said 'should' not 'will'.

The possibles:

full wave rec: ok on dc. Most likely option, until we knew it was tf
input.
half wave: again dc fine
ac loads: some ok on dc, some not, but these comprise a very small
percentage indeed of 24v electronic loads.

So clearly we can say a 24v ac input box of tronics should run on dc -
but not will, as there will be the ocasional one that wont.


A device with (for example) a transformer in the input circuit, as this
one turned out to have, will simply blow fuses if you connect DC to it.

of course. Just think the options thru.


NT

On 24 Sep 2005 08:52:41 -0700, wrote:

So clearly we can say a 24v ac input box of tronics should run on dc -
but not will, as there will be the ocasional one that wont.

Obviously a well researched bit of work. Of the dozen or so devices
I have immediately to hand which require 12-24VAC precisely none will
run off 12-24VDC (or any other DC supply of any voltage).

A device with (for example) a transformer in the input circuit, as this
one turned out to have, will simply blow fuses if you connect DC to it.

It will? Of those dozen or so devices I have none would "blow a
fuse" if used on DC. None of those with transformers would blow a
fuse. About half would probably be damaged though including many
with transformers which would not blow a fuse.


--
Peter Parry.
http://www.wpp.ltd.uk/

Peter Parry wrote:

On 23 Sep 2005 08:21:16 -0700, wrote:



Dont ask electronic questions on ukdiy. You can, but its at your risk,
this isnt a tronics group, theres little expertise here on it.


You are proving the point I assume?



Actually, there's rather a lot.

Peter Parry wrote:
On 24 Sep 2005 08:52:41 -0700, wrote:

So clearly we can say a 24v ac input box of tronics should run on dc -
but not will, as there will be the ocasional one that wont.

Obviously a well researched bit of work. Of the dozen or so devices
I have immediately to hand which require 12-24VAC precisely none will
run off 12-24VDC (or any other DC supply of any voltage).

A most unusual situation. Of all the low v kit in this house that takes
ac from wallwarts, not a single one is unable to run happily off dc.


NT

In article .com,
wrote:
A most unusual situation. Of all the low v kit in this house that takes
ac from wallwarts, not a single one is unable to run happily off dc.

Use one with a higher voltage. If it uses an AC low voltage supply, then
all the regulation is internal. A DC supply will happily pass through the
rectifier etc, but if of the same nominal voltage won't be high enough to
make the regulation work.

--
*It is wrong to ever split an infinitive *

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

Having said that, most cheap inverters require 12v DC input rather than
24v. What is your battery?

Maplin sell a range of cheap inverters that are available in 24VDC at no
extra cost. I have a (12V) one myself and it seems pretty OK, given that it
only cost 20 quid.

Christian.

Christian McArdle wrote:
Maplin sell a range of cheap inverters that are available in 24VDC at no
extra cost. I have a (12V) one myself and it seems pretty OK, given that it
only cost 20 quid.


That sounds promising & I have an expedition to Maplins planned.
Ta.

I have a (12V) one myself and it seems pretty OK, given that it
only cost 20 quid.

That sounds promising & I have an expedition to Maplins planned.

I should mention that it was in a 50% sale at the time, though.

Christian.

In message , Andy
Champ writes
wrote:

A most unusual situation. Of all the low v kit in this house that takes
ac from wallwarts, not a single one is unable to run happily off dc.


I have seen a lamp with fibre optics fed through a plastic flower - and
a synchronous motor to make it twinkle.

I've got a xmas tree that does that ... somewhere

--
geoff

wrote:

A most unusual situation. Of all the low v kit in this house that takes
ac from wallwarts, not a single one is unable to run happily off dc.


I have seen a lamp with fibre optics fed through a plastic flower - and
a synchronous motor to make it twinkle.

Andy

Aidan wrote:

That sounds promising & I have an expedition to Maplins planned.
Ta.


They have quite a decent web site. Much easier to phone ahead and make
sure they have the thing!

Andy