Power supply problem on touchscreen contoller

I have an old IRIS 4d/35 system with touchscreen capabilities and display is CRT type.

Recently we upgraded the system to run on LCD displays where we needed to provide the touchscreen controller with a separate power supply since the power for the controller was previously drawn from the CRT power supply.

However when a new switching power supply was used the touchscreen did not work. Reverting back to the supply from the CRT works flawlessly.

The supplies required for the touchscreen controller are 12V, -12V and 5V. The CRT power supply had a common ground and so does the new switching power supply.

Any idea what could be the problem with the new power supply. Any advise would be very much appreciated.

Reply to
vernondopaul
Loading thread data ...

Perhaps the switching supply is not able to supply enough current via one or more outputs, and is shutting down.

Many off the shelf supplies will deliver a hefty dose of 5v, much less in the way of +12v, and often way less than the +12v figure for the -12v.

Gareth.

Reply to
Gareth Magennis

I've checked on this and this is what I found.

The original power supply is proving 5V - 2A, +12V - 0.3A, -12V - 0.2A While the replacement power supply 5V - 4A, +12V - 2A, -12V - 0.5A

Has the common ground of the +12V and +5V effect on the -12V in anyway?

Reply to
vernondopaul

Well the new power supply seems well capable, so either there is something you have missed re: common grounds, or perhaps its the power up sequence that might be wrong, and the various devices are not communicating/booting together properly.

Dunno.

Gareth.

Reply to
Gareth Magennis

What do you mean by proving? Do you mean "reading the labels on the power supplies?" With the system operating, what voltages did you measure? If you got the right voltmeter readings, look with a scope to see if it's really DC. Power supplies have a minimum load requirement. Sometimes that's supplied inside. Other times, you're required to provide some minimum external load for everything to work out right.

However when a new switching power supply was used the touchscreen did not work. Reverting back to the supply from the CRT works flawlessly.

Exactly what was the symptom of "did not work?"

Does this mean that you left the touch screen attached to the LCD and only swapped out the power supply?

Depending on the mechanical configuration, noise from the LCD backlight might affect the touch screen. You can check this by distancing the touch from the lcd.

Reply to
mike

providing.

The touchscreen did not respond to any touch inputs.

Yes that's what I did.

Will check the output with a scope since the voltages are not far apart in comparison.

Reply to
vernondopaul

is CRT type.

provide the touchscreen controller with a separate power supply since the power for the controller was previously drawn from the CRT power supply.

not work. Reverting back to the supply from the CRT works flawlessly.

5V. The CRT power supply had a common ground and so does the new switching power supply.

would be very much appreciated.

Does the touchscreen use a high "static" voltage (ultimately via the CRT accelerating voltage) as part of its operation ?

Reply to
N_Cook

CRT type.

provide the touchscreen controller with a separate power supply since the power for the controller was previously drawn from the CRT power supply.

work. Reverting back to the supply from the CRT works flawlessly.

The CRT power supply had a common ground and so does the new switching power supply.

be very much appreciated.

When we upgraded from CRT to LCD the touchscreen was upgraded at the same time. I suspect the problem is with the power supply as reverting back to the original solves the problem.

Reply to
vernondopaul

CRT type.

somehow your post was stuck somewhere for about 15 years.

not sure about the touch screen problem though.

I have to ask- what is this thing still being used for??

Reply to
Cydrome Leader

Are you saying the touchscreen placed on the LCD panel works fine when powered by the old power supply? If so, then that eliminates the LCD drive signals as a concern for fouling up the signals on the touch panel. CRTs have some noise on the front, but the shadow mask generally isolates the front from a lot of noise. LCDs are REALLY noisy beasts, with 50V pulses on a zillion "wires" on the front of the panel.

But, assuming it really is only the power supply that is different, then it is either the power-up sequence or noise. Possibly the new supply voltages come up in a different sequence than the old one, or there is noise on one or more of the voltages.

Jon

Reply to
Jon Elson

Will check on the sequence on power up, thanks Jon.

Reply to
vernondopaul

CRT type.

provide the touchscreen controller with a separate power supply since the power for the controller was previously drawn from the CRT power supply.

work. Reverting back to the supply from the CRT works flawlessly.

The CRT power supply had a common ground and so does the new switching power supply.

be very much appreciated.

Reply to
vernondopaul

CRT type.

Cydrome,

the 4d/35 is being used on a flight simulator. The company is planning to replace the iris system but I would still have to maintain the old simulator.

Reply to
vernondopaul

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.