Question about GPO amps and clamping a relay with a LED

[Whoosh]

Hi there,

I have been reading several manuals for the LK204-205 series of LCD's which looks very interesting, especially the GPO's and the fact that they have a serial connection which should be easy to program and operate under the whole variety of Windows OS's.

After reading the manual for the PC model, which can take 12V and has 750mA GPO's I still have a question. Is the 750mA per GPO or for all combined ? I checked several decent fans and using P=I*U*0,8 I came up with roughly 210mA per fan. So, if the 750mA is for all GPO's combined that would mean 3 or 4 fans instead of 8.

Having said that, I also reasoned that I need some kind of failsafe in case the LCD (or the program operating it) doesnt function that would default all fans to on, which could be done with relays in which case there shouldnt be a problem with that 750mA anyway.

About clamping the relays, I am an electrical no-no ;-), could I clamp them with a LED ? And if so, does it matter where you clamp them ? I mean, could I put the clamp close to the GPO or does it have to be close to the relay ? If the location doesnt matter, it would be great to put them close to the GPO and have the LED in the bracket :-)

Thanks in advance!

[Cheese]

After reading the manual for the PC model, which can take 12V and has 750mA GPO's I still have a question. Is the 750mA per GPO or for all combined ? I checked several decent fans and using P=I*U*0,8 I came up with roughly 210mA per fan. So, if the 750mA is for all GPO's combined that would mean 3 or 4 fans instead of 8.

Yes the formula you need is Power = Current x Voltage and so EACH GPO in the -PC can power up to a 9W fan (a very big fan!) and this is per channel, so you could hook up 8 fans one per GPO - or usign the fans you quote you could hook up three per channel and power 24 fans with the -PC!!

Having said that, I also reasoned that I need some kind of failsafe in case the LCD (or the program operating it) doesnt function that would default all fans to on, which could be done with relays in which case there shouldnt be a problem with that 750mA anyway.

Failsafes are always good, most people don't connect all their fans to the gpo's though... I think the default position for the fan is on but you'd have to check with someone else.

Cheers,

r.

p.s. don't clamp a replay with an led, use a normal diode and it doesn't matter how close to the relay it is. Though with the -pc you won't need relays....

[Whoosh]

Thanks a bunch for the info! With 750mA per GPO the PSU would be the limiter :-) and noted using a normal diode instead of a LED.

You are right, I wouldnt connect the CPU fan to a GPO, but probably all casefans.

Does anyone know whether the GPO's are defaulted to on or off and if this default can be changed ?

Best rgrds

[Henry]

The GPOs are OFF by default and the settings cannot be changed in memory...