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From: Matt on 9 Dec 2009 14:01
Hello all,
I was hoping someone might be able to help with a problem I've been
having with a TV lift I built. I have an actuator that raises and
lowers a TV for the bedroom. It's wired with a DPDT switch. I'm
using a 12V 5A power supply. When I first plug it in, it works fine.
However, after a while, nothing happens when I flip the switch.
Any ideas on if this is a power supply problem and what the remedy
would be?
Thanks in advance.
Matt
From: GregS on 9 Dec 2009 14:39
In article <bcd0e9d5-d9ba-4379-8b8d-45b8f370424d(a)k17g2000yqh.googlegroups.com>, Matt <matthew.n.johnson(a)gmail.com> wrote:
>Hello all,
>I was hoping someone might be able to help with a problem I've been
>having with a TV lift I built. I have an actuator that raises and
>lowers a TV for the bedroom. It's wired with a DPDT switch. I'm
>using a 12V 5A power supply. When I first plug it in, it works fine.
>However, after a while, nothing happens when I flip the switch.
>Any ideas on if this is a power supply problem and what the remedy
>would be?
>Thanks in advance.
>Matt

Try turning off the supply. That should be pretty much it. I
am assuming there is a simple EOT or turn off switch on top and bottom
when it reaches those points.

greg
From: John Fields on 9 Dec 2009 14:41
On Wed, 9 Dec 2009 11:01:25 -0800 (PST), Matt
<matthew.n.johnson(a)gmail.com> wrote:

>Hello all,
>I was hoping someone might be able to help with a problem I've been
>having with a TV lift I built. I have an actuator that raises and
>lowers a TV for the bedroom. It's wired with a DPDT switch. I'm
>using a 12V 5A power supply. When I first plug it in, it works fine.
>However, after a while, nothing happens when I flip the switch.
>Any ideas on if this is a power supply problem and what the remedy
>would be?

---
If your DPDT switch doesn't have a center OFF position, then when the
lift gets to either the full up or full down position the motor's rotor
will be locked and the power supply will be driving a very low
resistance and outputting a lot of current.

If you're lucky and your power supply has a crowbar in it (or current
or thermal overload protection of some sort) then it'll just shut down
until things cool down or you unplug it and then plug it back in.

If that's what's happening what you need is a circuit which senses when
the lifter gets to its limit(s) and then disconnects the AC side of the
supply from the mains or the DC side of the supply from the load until
the next time you throw the switch.

Either that or replace the switch with one that has a spring loaded
toggle which goes to the center OFF position when you release it.

JF
From: Jan Panteltje on 9 Dec 2009 15:52
On Dec 9, 8:01 pm, Matt <matthew.n.john...(a)gmail.com> wrote:
> Hello all,
> I was hoping someone might be able to help with a problem I've been
> having with a TV lift I built.  I have an actuator that raises and
> lowers a TV for the bedroom.  It's wired with a DPDT switch.  I'm
> using a 12V 5A power supply.  When I first plug it in, it works fine.
> However, after a while, nothing happens when I flip the switch.
> Any ideas on if this is a power supply problem and what the remedy
> would be?
> Thanks in advance.
> Matt

How many push ups did you do before trying that switch again?
It is the law of conversation of energy,
and push ups make you stronger so you can overcome the switch counter
force.
From: Matt on 9 Dec 2009 16:00
On Dec 9, 1:41 pm, John Fields <jfie...(a)austininstruments.com> wrote:
> On Wed, 9 Dec 2009 11:01:25 -0800 (PST), Matt
>
> <matthew.n.john...(a)gmail.com> wrote:
> >Hello all,
> >I was hoping someone might be able to help with a problem I've been
> >having with a TV lift I built.  I have an actuator that raises and
> >lowers a TV for the bedroom.  It's wired with a DPDT switch.  I'm
> >using a 12V 5A power supply.  When I first plug it in, it works fine.
> >However, after a while, nothing happens when I flip the switch.
> >Any ideas on if this is a power supply problem and what the remedy
> >would be?
>
> ---
> If your DPDT switch doesn't have a center OFF position, then when the
> lift gets to either the full up or full down position the motor's rotor
> will be locked and the power supply will be driving a very low
> resistance and outputting a lot of current.
>
> If you're lucky  and your power supply has a crowbar in it (or current
> or thermal overload protection of some sort) then it'll just shut down
> until things cool down or you unplug it and then plug it back in.
>
> If that's what's happening what you need is a circuit which senses when
> the lifter gets to its limit(s) and then disconnects the AC side of the
> supply from the mains or the DC side of the supply from the load until
> the next time you throw the switch.
>
> Either that or replace the switch with one that has a spring loaded
> toggle which goes to the center OFF position when you release it.
>
> JF

Thanks. The switch does have an OFF position. The actuator has built-
in limit switches at both ends, but I was operating it in the middle
of its range when the problems occurred. I'll try a rocker switch
that stays in the off position, but I'm not sure that was the problem
since I could raise, lower and leave it in the OFF position.
Thanks for the input.
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