Power supply problem (?)

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

--- 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

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.

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.

Is the power supply properly sized for the motor? It could be going into thermal shutdown, or the motor could have a thermal cutout if it's too small for the job.

Is this a recent problem?

Good Luck! Rich

I don't know what type of power supply you're using how ever, I'll take a guess and say it's a switch mode type that is shutting down from lack of load after some time. Since it appears that you don't seem to be super technically inclined, I'll offer you a simple test solution. Place a 12 volt lamp across the output of the supply and let it burn.. If the unit remains working after that, it confirms my theory how ever, if the lamp drops out on you when not attempting to use the supply to move the unit, then you have a bad supply..

Also, inductive loads on some supplies will cause them to shut down, the lamp load should also cure this problem. If all works, then you can use a resistor in the lamps place. You could also put a back EMF diode on the output of the supply incase you do have a little kick back issue.

That power supplky seems a little light, I guess it depends on how hard the TV is to move. It could be the power supply overheating and going into protective shutdown. if you haven't already try adding some sort of counterweight like are used on lifts

The specs on the actuator I'm using say 12 VDC, 5Amp current draw at full load. It's rated for 150 lbs and is lifting about 30 when the TV is loaded. The power supply I'm using is one you'd use for an LCD screen. It seems to lift things fine at first, but when it's been inactive for a while, it doesn't start again.

I'll try place the lamp across the output and see what happens. (To answer one poster's remark, Yes, I'm an electronics neophyte with no formal training in the subject.)

Thanks again to all for the input.

When you say actuator I think of lead-screw type.

Can you check the PS voltage to see what it is doing?

An eccentric or cam (think piston crank) may require much more current at the middle of the range than the ends.

Where did you find it and what was it's original purpose? It may be binding or have some problem like rust.

I've had a satellite dish actuator on my bed for some time now. It raises the headboard side to make reading easy. 24 VDC 6 amp supply. One switch sends it up/down the other switches off the supply from the mains. Immensely powerful - I mounted one toggle switch so it is off in the up position in case my arm gets caught in it.

LCD power supplies aren't known for gorilla power. It may just be over current and limiting output - lamp will tell you that.

A work around may be to have the supply charge a large cap to 12 volts then when you raise or lower it would dump the stored energy and get things started.