Help with killing power from 12v trigger

[Kash007]

Hi all.

New to the forum so thanks in advance.

Scenario:

Tv with usb output > (5v to 12v adaptor) > 12v trigger used for opening and closing a motorised tv brackets

Situation:

Tv on = tv bracket opens as expected
Tv off = tv closes after prolonged period of about 3 - 5 minutes

I believe this is because of the residual power being present and fading after this time.

Because of this residual power, the signal to the 12v trigger is still present hence the bracket stays open.

My question is, is there anything I can put in line to kill any or dissipate any of this residual power to close the circuit much quicker?

Ideally I’d want the bracket to close as soon as the tv is turned off.

Unfortunately it’s a stand alone tv with no amp or any other hardware that has a 12v trigger built in.

The bracket does come with a remote control but I don’t want to have to use another remote if I don’t need to. And buying an ‘all in one’ programmable remote control is another solutions but an expensive and long winded one.

The Current set up nearly works perfectly - it’s just the delayed closing that’s not ideal. There’s no setting on the tv where I can specify Usb Power options on the tv either

 

[Andy™]

resistor could be used to discharge capacitors quicker but youll need to get a value enough to discharge it qucik enough but still high enough not to add too much additional load when its on

or it could simply be that the TV intentionally keeps the USB on for a short time after in which case not much you can do

 

[Kash007]

resistor could be used to discharge capacitors quicker but youll need to get a value enough to discharge it qucik enough but still high enough not to add too much additional load when its on

or it could simply be that the TV intentionally keeps the USB on for a short time after in which case not much you can do

Thought as much.

Thanks for the reply!

 

[Geoff1946]

Easy experiment: Get a USB splitter, (2way), and plug anything USB powered that you have into the spare way. e.g.led light, battery charger, anything that will take a bit of power. If that eliminates or even reduces the delay then so would a resistor.

 

[Kash007]

Easy experiment: Get a USB splitter, (2way), and plug anything USB powered that you have into the spare way. e.g.led light, battery charger, anything that will take a bit of power. If that eliminates or even reduces the delay then so would a resistor.

now why didnt i think of that! thanks man!

will keep you posted on the outcome.

 

[Bruspark]

Lots of current TV's don't actually switch off when in standby, and may spend time updating programme guides etc before sleeping. It might be worth connecting a usb powered light or similar to the outlet and seeing if /when it goes off. My TV also powers up randomly when off to look for updates and Programmes to record.

As this is a pain I use a 'smart socket' strip that reacts to major power draw from the TV or Amp on one socket to power the other sockets up. Then then powers Subwoofers etc , Plug in power adapters to drive 12V triggers and mood lighting

 

[Arthurdent]

If you pull the 12v adapter out of the 5v usb but leave it connected to the screen lift does it close immediately or exhibit the same problem.

I would expect a step-up buck converter to have a reasonably chunky capacitor on its output, but then I would also expect a simple screen trigger to draw at least a few mA either directly driving a relay or through and optocoupler or something. So if it runs that long then I would think the TV is not just delivering residual from a capacitor its intentionally driving the output; perhaps to give an external HDD time to flush cache and spin down for example after sending it a power off.

I recently just swapped a 12v relay for a 5v relay in a 240v screen trigger, the rest of the components were fine as is. But my usb port shuts down sharpish.