114. TV ON Switch
The Pinscape Controller has a feature that lets you send a "Power On"
command to your TV(s) when the overall system powers up. This feature
can solve the problem that some TVs have when used in pin cabs, namely
that they don't power on automatically when they're plugged in again
after being unplugged.
This feature is only needed if your TV doesn't remember its power
state when you plug it back in after it's unplugged, and
using the sort of one-button power control setup as described in
. That power control setup effectively
unplugs the TVs and other devices from AC power when the PC is off, so
each time you turn the PC back on, the TV thinks it's being plugged
back in to the wall outlet after being unplugged. Some TVs
automatically power up and return to displaying the last video source
when this happens, but many just go into standby mode. The Pinscape
TV ON feature is meant to solve this problem for TVs that go into
standby mode, by explicitly sending a "Power On" command to the TV at
system startup to get it back into operation.
Do I need it?
Before going on, you should make sure you actually need this feature.
Some TVs need it and others don't. And regardless of TV, there's no
need for it unless you're using one-button power control of the sort
described in Power Switching
Assuming you're using that sort of power switching, here's how to
test your TV to see if it needs help powering on at system
- Set up the TV as a monitor on your PC, using the input on the TV
(HDMI, etc) that you intend to use when it's in your cab. Turn
everything ON and make sure it's all configured so that you see
the Windows desktop on the TV.
- With the TV still ON, pull the plug out of the wall socket.
- Wait a few minutes.
- Plug it back in, and don't push any buttons on the TV.
- Did the TV turn back on and show the Windows desktop again?
If the answer is yes, you don't need the "TV ON" feature. A
smart power strip is all you need to control this TV and get it to
power up in sync with the PC.
If the TV stays off or goes into standby mode, you do need the
TV ON feature. This TV won't turn on after being unplugged until it
receives an explicit "Power On" command, which is exactly what the TV
ON feature provides. You'll still need the switched outlet to control
its line power, but you'll also need the TV ON feature to get
it to wake up again each time power is restored.
Be sure to check each TV you plan to use in your cab, since some
might need the TV ON feature even if others don't.
You can approximate this test without the PC if necessary. Just tune
the TV to an over-the-air channel instead of using the PC as a video
input. The important thing is that there's some kind of active video
source, since some TVs will go into standby mode when there's no input
and wake up when there is. The test with the PC as video source is
the most reliable, because that's the exact setup you'll have in the
cab, but most TVs will behave the same way with all video sources.
What if I'm still shopping for a TV?
Some cab builders try to avoid this whole issue by only buying TVs
that pass the test above. So you might be wondering if there's an
easy way to tell when shopping. Unfortunately, I've never seen a
manufacturer or store mention it anywhere, and I don't think it would
occur to most buyers to ask. It's not even safe to assume that
similar models from the same manufacturer will behave the same way.
If you want to be sure before you buy, you'll have to either find a
store that's willing to let you test a floor model, or find a friend
or forum member who has the exact model you're considering.
What this feature doesn't do
The TV ON feature doesn't
control power at the plug, and it
can't turn OFF your TVs. For both of those functions, use the
techniques described in Power Switching
. The TV ON feature
is meant to be used in conjunction with
the switched power
strip described in that chapter. TV ON isn't a replacement for the
switched power strip; it's just an add-on to deal with TVs that don't
automatically turn back on after being unplugged.
How it works
The TV ON feature works by having the Pinscape software send a
"Power On" command to the TV a short time after the computer turns on.
To physically send the command to the TV, there are two possibilities:
- By wires soldered to the switch terminals of the ON button on the TV
itself. We connect these wires to a relay controlled by the Pinscape
device. The Pinscape software pulses the relay shortly after
the computer turns on. The TV registers this as an ON button press.
- By IR remote control. We connect an IR LED to the Pinscape unit,
and position the LED so that it points at the TV's remote control sensor.
The Pinscape software can be programmed to transmit the TV's remote
control ON code at the proper time.
The Pinscape software sends the ON command a few seconds after the
computer starts up. The delay is necessary because most TVs ignore
commands for a few seconds after being plugged in. The exact amount
of time needed varies by TV, so the delay can be can be adjusted in
the Pinscape software configuration.
Using Windows commands
The normal way to use the TV ON feature is to let Pinscape do
everything automatically using the power sensing circuit
described below. If you're using the expansion boards, that's built
in, so I'd go that route. If you're using a standalone KL25Z, though,
the sensor circuit might be more trouble than you want to go to.
So let me offer an easier alternative: use Windows commands.
Here's the idea:
- Create a .BAT file
- Put commands in the .BAT file to turn on the TV (see below)
- Put a shortcut to the .BAT file in your Start Menu > Startup folder
When Windows starts up, it'll run this .BAT file because it's in
your Startup folder, so this will have roughly the same effect as the
power sensor circuit. We just let Windows tell us when the system
is starting up rather than detecting it electronically.
The commands all involve the utility program PinscapeCmd.exe, which
you'll find in your Pinscape Config Tool folder. In the command examples
below, we'll pretend this folder is named C:\Pinscape, but
it doesn't have to use that exact name. Just substitute your folder path into the
commands below if you're using something different.
If you're using the hard-wired TV ON switch, the command looks like this:
The TVON sub-command briefly pulses the TV ON relay, just like the
Pinscape software would do by itself at system startup when the power
sensing circuit detects that the system has just been powered on.
If you're using an IR remote control instead of the hard-wired switch, do this:
That transmits the IR code in "slot 1" in your learned IR command list.
If you're going to teach Pinscape multiple IR commands, change the "1"
in SendIR=1 to whichever slot contains the right ON command
for your TV.
One more detail: if you have more than one Pinscape unit in your system
at the same time, you have to tell PinscapeCmd which unit you want to
send the command to. You do this by adding Unit=2 (or whichever
unit number you want to address) right after the PinscapeCmd
C:\Pinscape\PinscapeCmd Unit=2 TVON
Power sensing circuit
The Pinscape expansion boards have some special circuitry built-in
that detects when the system is powering up. This is a little more
complicated than it sounds because of the way PC power supplies work.
USB-powered devices like the KL25Z generally continue to receive 5V
power even when the PC is off. That means that the Pinscape software
can't tell from USB power alone when the system is powered on or off.
As far as Pinscape's USB power goes, the power is always on, even when
the overall system is off. Similarly, the Pinscape software can't
assume that a KL25Z reboot means that the power status has changed,
since the KL25Z can be rebooted at random times, such as when you
update option settings, or if you should unplug it for some reason.
If you want to use Pinscape's automatic TV ON system without
the expansion boards, you have two choices:
- You can make Windows run a batch script when the system boots, as described above ("Using Windows commands")
- You can build a replica of the power sensing circuit used on the expansion boards
The first option (a Windows batch script) is easier, but if you prefer
to let Pinscape handle things automatically, read on for details
on building the power sensing circuit.
Note that this entire scheme depends on following the switched
120V power plan outlined in Power Switching
. In order
for this to work, you must be using:
- A "soft" power switch for the main PC
- A switched outlet that's controlled by the PC power
- A secondary ATX power supply that's plugged into the switched outlet,
for powering feedback devices and other systems apart from the PC
If you're already familiar with that design, read on. If not, you
should go back and read about it in Power Switching
because some of the material below won't make sense if you're not
using the same design for the main power switching system.
Here's the schematic for the sensing circuit. Again, this
is built in to the expansion boards, so you won't have to
build this separately if you're using the expansion boards.
- Connect GND to a Ground pin on the KL25Z (see KL25Z Pin Out)
- Connect 3V3_KL25Z to a 3.3V pin on the KL25Z (see KL25Z Pin Out)
- Connect GND2 to the secondary power supply ground (the one
plugged into the switched outlet)
- Connect +5V_PSU2 to the secondary power supply +5V
- Connect PSU2_STATUS_SENSE to the KL25Z GPIO port assigned as "Power status
input" in the Pinscape Config Tool settings
- Connect PSU2_STATUS_SET to the KL25Z GPIO port assigned as "Status latch
output" in the settings
You can use any free GPIO ports for the connections listed.
The expansion boards use PTD2 for the power status input (PSU2_STATUS_SENSE)
and PTE0 for the latch output (PSU2_STATUS_SET).
Configuring settings for the power sensing circuit
To configure your standalone TV ON circuit, run the Pinscape Config
Tool. Go to the Settings page, and scroll down to the TV ON
Click on the Power status input box to select the GPIO
pin you wired to PSU2_STATUS_SENSE. Then click on the Power latch
output box to select the pin wired to PSU2_STATUS_SET.
If you're using the IR transmitter instead of the hard-wired TV ON
relay switch, you can simply set the Relay output box to
Not Connected, to tell the software that no pin is connected
to that function.
The Startup delay time is the amount of time in seconds that
the software will wait after system startup to send the TV ON signals
to the TVs. This is used for both the relay switch and the IR
signals. Adjust this as needed to make sure that the system waits
long enough for your TVs to initialize. Most TVs aren't responsive to
any control inputs for a few seconds after they're plugged in, so this
delay is intended to give the TVs long enough that they're ready to
handle the ON signal when Pinscape sends it. If your TVs usually work
but seem to miss the signal some of the time, adding a few seconds
to the delay might make it more reliable.
When you've entered all of the settings, click "Program KL25Z" at
the bottom of the page to save the changes to the device.
Setting up an IR transmitter/receiver
If you're going the IR route, the minimum requirement is an IR
transmitter, to send IR commands to your TV(s). But you'll almost
certainly want to set up an IR receiver as well, so that Pinscape can
"learn" commands from your remotes. It's possible in principle to
program the remote control codes by hand, without the learning
function, but it's surprisingly difficult to find published
information for the exact model of TV you're trying to control. And
even if you can find published codes, they're hard to make sense of
because no one can agree on a universal standard format. The learning
function is by far the easiest way to figure out what codes your exact
TV is using, because it lets Pinscape read the codes directly from
your remote control.
See IR Remote Control
for instructions on setting up the IR remote
control features with Pinscape.
Once you've installed the IR transmitter and receiver hardware, you can
set up the TV ON feature through IR as follows:
- Teach Pinscape the remote control code for your TV's "ON" button,
following the procedure in IR Remote Control ("Learning IR commands
from your remotes")
- Click the TV ON icon ()
in the row for the "ON" button code
- Be sure to save settings by clicking "Program KL25Z"
Once you activate the TV ON icon for a code, Pinscape will automatically
transmit that code at system startup, when the power sensing circuit
detects that power has just been turned on. Remember that you must
use and configure the power-sensing circuit for this to work (the circuit
is built in to the expansion boards, but you have to build it separately
if you're using a standalone KL25Z).
Connecting a hard-wired TV ON switch
Warning: I no longer recommend this approach. Even though it's
the original solution I used in my own cab, I'd recommend avoiding it
and using the IR transmitter solution instead. Hard-wiring the
power switch requires opening up the TV, and modern flat-panel
TVs are just too delicate for this to be a good idea. The IR
solution is completely non-invasive.
If you're absolutely dead set on this approach, though, read on.
The main expansion board has wiring for up to two TV switches.
The connectors are on the JP4 pin header, labeled "TV ON".
Connect the first TV's power switch to the pair of pins in the "column"
under the label TV1. Connect the second TV's power switch to the
pair of pins in the column under the label TV2.
You can just run ordinary wire between the expansion board pins
and the switch on the TV. These carry only low-power switch signals,
so you can use a fairly thin wire like you'd use for wiring cabinet
buttons, such as 24 AWG.
Standalone wiring (no expansion boards)
If you're using the expansion boards, the relay switch is built in.
If you're not using the expansion board, you can build the same
circuit yourself. Here's the schematic:
- Connect GND to a Ground pin on the KL25Z (see KL25Z Pin Out)
- Connect +5V_PSU2 to the +5V of your secondary power supply
- Connect GND2 to the ground (black wire) of your secondary power supply
- Connect TV_SWITCH to the GPIO pin you're using for the TV relay
You can use any GPIO pin to control the TV relay. The default used
on the expansion boards is PTD3, but you can use a different pin if
that one is in use. You'll have to configure whichever pin you select
in the Pinscape Config Tool. In the Config Tool, go to the Settings
page, then scroll down to the TV ON section. Click the Relay
output box to set the appropriate GPIO pin.
Wiring the TV switch
You'll have to be comfortable with taking
the TV apart at this stage, because we have to connect some wires to
the On/Off button.
There are no generic instructions for taking a TV case apart, so you're
on your own for this part. Your goal is to open the case and expose the
little circuit board containing the On/Off button.
Needless to say, use extreme caution with this step. In modern LCD
TVs, the LCD panel and polarizing filter are very thin, brittle
plastic sheets and often have no structural support other than the
outer case, so it's very easy to crack them during the removal process
or after the case is off. Removing the case will also void the
warranty, so you're assuming the entire risk of breaking something
Once you get the case open, you should find a little circuit board
located under the area where the buttons on the case are situated.
It's usually long and narrow, and looks something like this:
The red arrows in the photo above show the soldering points for the
button leads. The little squarish silver objects are the buttons.
These are normally situated immediately under the exterior plastic
buttons on the TV's bezel; pressing on the exterior plastic button has
the effect of pushing down on this metal part, which is the real
Once you find this circuit board, identify which button corresponds to
the On/Off button on the outer case. Do this by position: just find
the inner button that's situated underneath the On/Off button on the
case. You can also do this by counting buttons from right to left,
since there should be the same number of silver buttons on the circuit
board as plastic buttons on the case.
Next, identify the switch leads. There are probably four leads to
these switches, one at each corner. On the TVs I've looked at, the
leads are in pairs that are electrically connected together, so there
are really only two wires here even though it looks like four. Put
your multimeter in continuity test mode and check the leads in pairs.
Find a pair that are not connected normally, but that become
connected when you press the button. These are the leads you want
to solder to.
The next step is possibly even more delicate and tricky than opening
the case. You have to solder wires to the button leads you just
identified. To do this, use fine hookup wire, 24 AWG or thinner.
Strip a very short length of insulation from the ends, around 1/8".
Melt a little solder onto the end of the wire. Position the end of
the wire at the desired contact point. Now get out some tape (I used
thin strips of masking tape here) and secure the wire to the board a
couple of inches away from the contact point. The idea is to hold it
in place at the desired position before soldering so that the solder
can just flow over the junction with everything already positioned
properly. Once everything is in place, heat the end of the wire for a
few moments, long enough for the solder to melt and flow onto the
switch lead. Remove the soldering iron carefully and try to hold
everything very still for a few moments so that the solder can
solidify over the junction point. If all went well, the wire should
stick to the switch lead. The connection will be delicate at best, so
you'll want to secure the wire with a couple more pieces of tape to
minimize mechanical stress on it.
TV On/Off switch with wires soldered to leads
Repeat this process for the second lead. Once both are soldered and
held securely in place with tape, test your work with the multimeter.
Use continuity test again. Connect the meter leads to the free ends
of the wires you just soldered. The meter should read open/no
connection. Press the button, and the meter should read
closed/connected. If that works, you're set. Put the TV case
back together, taking care to run your newly attached wires out
a suitable opening.
Now just connect the two wires from the TV's switch to the
appropriate TV ON pin pair on JP4 on the expansion board (see the
illustrations above). The order of the wires doesn't matter:
you can connect either switch terminal to either pin in the
TV ON pair.