Almost dead TMD100

[peterh_DK]

Hi there one of my PLC's has "almost" died. When I connect the power , the green power led next to J1 only lights up partly.  It is sort of half dimmed or blinking. Any idea waht that means. I replaced the PLC and got the system going again but is the board dead?

/Peter

[support]

Does it short out the power supply when connected? i.e. Is there still 24V across the two power terminals when the PLC is connected. If not, then it is likely that there is damage to the board. Contact support@tri-plc.com for more details discussion of the status of your board.

There is a self-test webpage that you can refer to:

http://www.tri-plc.com/selftest

[peterh_DK]

Well this has puzzled me for sometime, but now I can replicate the problem. The PLCs seem ok.
I have 24V 1000ma Powersupply connected to the PLC AND a Fargo telecom Modem (http://www.fargotelecom.com/Products/Fargo/Maestro_100.pdf)
The power consumption of the modem is 310 mA at 5 V ( don't know how much at 24V)
IF I Connect the PLC + Modem to the power supply and then connect to the main 220V Then everything is fine
But

IF I first connect to the 220V wall socket and then to the Modem and PLC ( at the same time)  then the PLC won't power up

But all I have to do is remove the mains cord and replace it again then everything powers up .

Any Ideas what I am missing?

[support]

Why don't you measure the voltage at the PLC's power terminal when it doesn't power up and you probably have an idea. Most likely the whole setup may draw in-rush current that exceeds the power supply maximum current capacity and it simply shut down. When you unplug the main and re connect the main again, the current may rise at a rate that allows the devices to function properly.

Change a power supply to one of higher capacity if that's the case.

[peterh_DK]

Thanks I'll try that

[support]

You may also try add a 1 to 5 ohm resistor to the power supply + terminal to slow the rate of current rise if it is indeed high in-rush current during power on that is straining your power supply.