The powerdistro box (powered by a MO display)

saxgod · Post by **saxgod** » Thu Aug 01, 2002 5:19 pm

I've been working on a PowerDistro Box (a little box to plug in devices so they can be switched on and off by the GPO's of a MO display (using the LK202-25-V).

It isn't entirely finished and you can see my logbook (to read about my progress) over <a href="http://casemod.saxgod.be/powerdistro">here</a>

I'm going to copy paste a part of the page (containing the schematic and my words about it). Please respond if you think I made a mistake somewhere, so I don't blow anything up

You 'may' also respond if you think something else

hehe

Ok here we go :
--<cut>--
<img src="http://casemod.saxgod.be/powerdistro/po ... br>Created this schematic so you can see what I'm planning to do. I'm going to hook up transistors to the GPO's, and switch the ground connected to relays with them. On the schematics I found in that thread on the MO-Forums there was a 4.7K resistor in front of the transistor. But after talking with Henry it seems that this is the resistor thats already on the PCB of the LCD between the a actual GPO's and the GPO header. The relays have switch over contacts, which are connected to manual switch over switches (like a normal house circuit with 2 switches for 1 light). When the manual switch is in the drawn position, the outputs will only activate when the GPO is turned on. In the other position the output will be default on, and will be switched off when the GPO is turned on. I have implemented this because Henry told me there is no possibility in the LCD to turn on the GPO's by power up. Since I am going to connect a cold cathode and some fans and other things to it, I want the fans and light to be on at powerup. Also this makes that the relays don't have to be charged all the time, but only if I want the lights or fans off. After the switches there are 2 sockets for each output. A 12V and a 5V socket. I have done this by switching the ground through the relays contacts and switches, because in the PSU of your computer the 12V and 5V DC nets have the same ground anyway. After the sockets is a status led, also switched by the same ground, and connected (with all the other leds parrallel) to the 5V DC via a resistor.
 I was thinking to use a <a href="http://casemod.saxgod.be/powerdistro/2N2222.pdf" target="_blank">2N2222</a> transistor because it can handle 600mA max. I estimate that the relay will use a 200mA peak when switched on and then will drop to 50mA for it to stay switched on. Relays will probably just be velleman's 12V with switch over contacts (<a href="http://www.velleman.be/Product.asp?lan=1&id=343879" target="_blank">JZC-22F</a> (has 37mA normal consumption) or other). The manual switches will be <a href="http://www.velleman.be/Product.asp?lan=1&id=337929" target="_blank">ON-ON toggle switches</a>. I Already have the sockets, and leds will be bloo or another (cheaper) color

I'm not sure about putting the leds in, because I am going to put the powerbox right behind the display, above my cdrom, and you can't see the leds there (I was first planning to place it next to my mobo and you could see it trough the casewindow then. Maybe I'll put a new plexi in the top of my case, but thats for later hehe

. (ps. maybe it is safer to keep the whole GPO circuit on 5V, and we could use <a href="http://www.velleman.be/Product.asp?lan=1&id=17774" target="_blank">this relay.</a> The down side of this is that it uses as much power as the 12V relays (450mW), so the used mA will go up (80mA).)

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thats it..

[ This Message was edited by: saxgod on 2002-08-01 17:20 ]

Post by **Aniso** » Thu Aug 01, 2002 7:10 pm

I have not looked at it well, but right off, I would say that your transisters are "backwards". The GPO switches TO ground - it is open collector. If you want to use NPN transisters, you will need to provide pull-up resistors. Also, you need current limiting resistors on each of the bases of your transisters (unless you use NPN and pull-ups).

I believe there is something on this in the (or a) manual.

Post by **Aniso** » Thu Aug 01, 2002 7:13 pm

On 2002-08-01 19:10, Aniso wrote:
I have not looked at it well, but right off, I would say that your transisters are "backwards". The GPO switches TO ground - it is open collector. If you want to use NPN transisters, you will need to provide pull-up resistors. Also, you need current limiting resistors on each of the bases of your transisters (unless you use NPN and pull-ups).

I believe there is something on this in the (or a) manual.

OK, sorry, I was thinking -PC model. Still, you DO need more resistance than what is on the board (240 ohms). I would recomment putting a 4.7K resistor in there.

saxgod · Post by **saxgod** » Fri Aug 02, 2002 4:37 am

Hmm yeah.. Henry told me that those 4.7k resistors where on the LCD, so I didn't include them.. I don't know much about transistors I just took them over from this thread: http://www.lcdforums.com/forums/viewtop ... forum=1&21

I noticed while booting my pc that the led I put on GPO1 was on from powerup, till LCDC started and began steering the display. So I guess that actually all GPO's are default power on until the host tells it to turn off (initializing the display ?). Will need to think about that. Maybe I don't need the manual switches etc..

[ This Message was edited by: saxgod on 2002-08-02 04:38 ]

Post by **Aniso** » Fri Aug 02, 2002 10:32 am

Yes, that other thread is excellent information that I had forgotten about!

I actually thought it was GPO4 or 5 that was on at powerup... Whichever one it is, it is always the same, but the rest will be off at powerup.

As for these resistors, it sounds like Henry did not quite understand the question. There are resistors there on the PCB, but they only limit current to 20mA. You need to limit current to around 1mA. The data sheet probably indicates something like 5mA base current for 100mA collector current in full saturation mode (1K), but my experience is that the base resistor on a small transistor (like 2n2222) does not have to be smaller than 4.7K. Certainly 240 ohms is too small and will probably result in transistor smoke (which smells oh so nice!).

"It is always a good time to think about your ground connections again"
- Me

saxgod · Post by **saxgod** » Fri Aug 09, 2002 12:10 pm

I have a LK202-25V, so what connector does the 'GPO' mean in this schematic
<img src="http://www.matrixorbital.com/temp/forum ... _relay.jpg">

my display switches to ground
<table bgcolor="white"><tr><td>
<img src="http://www.matrixorbital.com/manuals/lk ... tr></table>

I don't understand how connecting the ground via the 4.7k resistor to the base can trigger the transistor to switch the relay to ground ..
or am I missing something here.. please respond asap

cya sax

[ This Message was edited by: saxgod on 2002-08-09 12:11 ]

[ This Message was edited by: saxgod on 2002-08-09 12:11 ]

Post by **linear** » Fri Aug 09, 2002 2:06 pm

What I though I heard Aniso say was that the outputs on the -PC were active low, and the other models were active high. Interfacing to the active-low would be different than the yellow diagram.

saxgod · Post by **saxgod** » Fri Aug 09, 2002 3:06 pm

Yeah .. been thinking about that for a couple of hours and remembering something about pull up resistors I learned a long time ago in school.

then I came up with this; (ps the led is polarized wrong, you need to turn it around

)
<img src="http://casemod.saxgod.be/powerdistro/realthing_gpo.jpg">

I build it and it works

yeah!

<img src="http://casemod.saxgod.be/powerdistro/25.jpg">

[ This Message was edited by: saxgod on 2002-08-09 15:31 ]

saxgod · Post by **saxgod** » Sat Aug 10, 2002 4:53 pm

Almost finished.. just some details to take care of.

<img src="http://casemod.saxgod.be/powerdistro/33.jpg">

And it works!