transformer based DC power supply safer than switching power supply?

I have a broken table tennis robot (shoots ping pong balls). I found that it
has two DC power supply (12V x 2), and one of them failed.

The easiest solution is to use a spare computer PC power supply to replace
the defective one.

My only concern is this. The power supply in the robot is transformer based.
A PC power supply is transformer-less switching circuit, which means no A/C
isolation from the mains. Would this make the resulting device less safe?

james wrote:

> I have a broken table tennis robot (shoots ping pong balls). I found
> that it has two DC power supply (12V x 2), and one of them failed.
>
> The easiest solution is to use a spare computer PC power supply to
> replace the defective one.
>
> My only concern is this. The power supply in the robot is transformer
> based. A PC power supply is transformer-less switching circuit, which
> means no A/C isolation from the mains. Would this make the resulting
> device less safe?

A PC power supply provides Isolation from the incoming AC mains !
Whatever gave you the idea it didn't ?

--
Best Regards:
Baron.

On Sun, 31 May 2009 17:41:19 GMT, "james" <(E-Mail Removed)> wrote:

>I have a broken table tennis robot (shoots ping pong balls). I found that it
>has two DC power supply (12V x 2), and one of them failed.
>
>The easiest solution is to use a spare computer PC power supply to replace
>the defective one.
>
>My only concern is this. The power supply in the robot is transformer based.
>A PC power supply is transformer-less switching circuit, which means no A/C
>isolation from the mains.

If you know so little about mains isolation and SMPS design, I'd
suggest keeping to ping-pong, and let someone else fix the unit. A
SMPS is fully isolated.

>Would this make the resulting device less safe?

Well, were someone who knows what they are doing to fix it, it would
be just as safe.

On Sun, 31 May 2009 16:18:27 -0400, "Michael A. Terrell"
<(E-Mail Removed)> wrote:

>
>Baron wrote:
>>
>> james wrote:
>>
>> > I have a broken table tennis robot (shoots ping pong balls). I found
>> > that it has two DC power supply (12V x 2), and one of them failed.
>> >
>> > The easiest solution is to use a spare computer PC power supply to
>> > replace the defective one.
>> >
>> > My only concern is this. The power supply in the robot is transformer
>> > based. A PC power supply is transformer-less switching circuit, which
>> > means no A/C isolation from the mains. Would this make the resulting
>> > device less safe?
>>
>> A PC power supply provides Isolation from the incoming AC mains !
>> Whatever gave you the idea it didn't ?
>
>
> The PC power supply case & common are connected to ground, and can
>short out other power supplies.

True, but the other supplies had better not have their cases hooked to
anything other than ground.

On Sun, 31 May 2009 17:41:19 GMT, james wrote:

>I have a broken table tennis robot (shoots ping pong balls). I found that it
>has two DC power supply (12V x 2), and one of them failed.
>
>The easiest solution is to use a spare computer PC power supply to replace
>the defective one.
>
>My only concern is this. The power supply in the robot is transformer based.
>A PC power supply is transformer-less switching circuit, which means no A/C
>isolation from the mains. Would this make the resulting device less safe?

Just a thought: if you replace the transformer(s) with a much lighter
switching supply, doesn't the machine get too light so it becomes unstable?
May be it depends on the transformer weight for inertia.

Mat Nieuwenhoven

james wrote:

> I have a broken table tennis robot (shoots ping pong balls). I found that it
> has two DC power supply (12V x 2), and one of them failed.
>
> The easiest solution is to use a spare computer PC power supply to replace
> the defective one.

Wrong ! It is not rated at a suitable power.

Graham
--
due to the hugely increased level of spam please make the obvious adjustment to
my email address

PeterD wrote:

> If you know so little about mains isolation and SMPS design, I'd
> suggest keeping to ping-pong, and let someone else fix the unit.

Well said Sir.

due to the hugely increased level of spam please make the obvious adjustment to
my email address

Mat Nieuwenhoven wrote:

> On Sun, 31 May 2009 17:41:19 GMT, james wrote:
>
> >I have a broken table tennis robot (shoots ping pong balls). I found that it
> >has two DC power supply (12V x 2), and one of them failed.
> >
> >The easiest solution is to use a spare computer PC power supply to replace
> >the defective one.
> >
> >My only concern is this. The power supply in the robot is transformer based.
> >A PC power supply is transformer-less switching circuit, which means no A/C
> >isolation from the mains. Would this make the resulting device less safe?
>
> Just a thought: if you replace the transformer(s) with a much lighter
> switching supply, doesn't the machine get too light so it becomes unstable?
> May be it depends on the transformer weight for inertia.

Uh ?

Graham

--
due to the hugely increased level of spam please make the obvious adjustment to
my email address

On Mon, 01 Jun 2009 12:08:31 +0100, Eeyore
<(E-Mail Removed)> wrote:

>
>
>Mat Nieuwenhoven wrote:
>
>> On Sun, 31 May 2009 17:41:19 GMT, james wrote:
>>
>> >I have a broken table tennis robot (shoots ping pong balls). I found that it
>> >has two DC power supply (12V x 2), and one of them failed.
>> >
>> >The easiest solution is to use a spare computer PC power supply to replace
>> >the defective one.
>> >
>> >My only concern is this. The power supply in the robot is transformer based.
>> >A PC power supply is transformer-less switching circuit, which means no A/C
>> >isolation from the mains. Would this make the resulting device less safe?
>>
>> Just a thought: if you replace the transformer(s) with a much lighter
>> switching supply, doesn't the machine get too light so it becomes unstable?
>> May be it depends on the transformer weight for inertia.
>
>Uh ?
>
>Graham

Every action creates an equal and opposite reaction. So it fires a
ping-pong ball forward, and as a result the opposite energy is
directed in the other (rearward) direction.

With an SMPS there is no question that that will launch the machine
into the next room with sufficient force to cause personal injury or
even death to anyone unlucky enough to be in the way.

The resulting ripping of the power cord from the machine will then
allow live wires to arc on the floor, igniting the carpet and causing
a fire.

The resulting fire will destroy the house, and then spread to the next
house.

The ambulance which was called for the person struck by the machine
will be involved in an accident, blocking the route for the fire
trucks.

The fire will spread to near by houses, and continue to spread
unabated until the entire city is consumed.

The authorities will assume (incorrectly, perhaps) that the
destruction of the city was cause by terrorism and will call for war
against the guilty parties.

There will be no survivors...

On Mon, 01 Jun 2009 09:39:42 +0200 (CEST), Mat Nieuwenhoven wrote:

>On Sun, 31 May 2009 17:41:19 GMT, james wrote:
>
>>I have a broken table tennis robot (shoots ping pong balls). I found that it
>>has two DC power supply (12V x 2), and one of them failed.
>>
>>The easiest solution is to use a spare computer PC power supply to replace
>>the defective one.
>>
>>My only concern is this. The power supply in the robot is transformer based.
>>A PC power supply is transformer-less switching circuit, which means no A/C
>>isolation from the mains. Would this make the resulting device less safe?
>
>Just a thought: if you replace the transformer(s) with a much lighter
>switching supply, doesn't the machine get too light so it becomes unstable?
>May be it depends on the transformer weight for inertia.

On second thought, this might be a desirable side-effect if it makes the
machine just slightly unstable: the paths of the pingpong balls become more
unpredictable, enhancing the training experience :-)

Mat Nieuwenhoven