Sourcing or sinking I/O

[todster]

If I wanted to connect the outputs of this to a sourcing device where would the best place be to pull the common +5v from? What would be the max I could draw current wise? The device connected to the outputs will be  TTL sourcing inputs to another PLC. The inputs are rated at 3.7ma with an off state current of 4.1ma. Possibly there is another way of doing this that is simpler?
 

 

[rossw]

If I wanted to connect the outputs of this to a sourcing device where would the best place be to pull the common +5v from? What would be the max I could draw current wise? The device connected to the outputs will be  TTL sourcing inputs to another PLC. The inputs are rated at 3.7ma with an off state current of 4.1ma. Possibly there is another way of doing this that is simpler?
 

1746ig16.GIF

 
When I've done this, I've usually pinched the +5 from pin3 of either the temperature or humidity sensor connector.
 
I think you bought one of my terminal boards recently? It should be getting very close to delivered about now.
That has a +5 screw connector at the end of the input screw terminals (Gnd one end, +5 the other), and if you're using the 5V to power the opamp there is a second +5 connection at the end of the analog inputs screw terminals too.

 

[todster]

Thanks Ross. I'd forgotten you had done that with your board. The card I have has 16 inputs so I'm wondering if the +5v is limited by the power supply or the W/C 5v regulator.
The pdf for the W/c also says the outputs have a max current when used either sourcing or sinking. Not sure what they meant by sinking.

 

[CAI_Support]

WebControl board has a 5V regulator which providing limited current. If your relay board taking current from WC board, please make sure that is not overheating the 5V regulator.

 

[CAI_Support]

WebControl 5V is regulated by a LM2940S regulator IC.  WebControl 8 board takes 250mA without any sensor.  If your power supply providing 9V power to the WC board, the regulator IC will be okay without too much heat.  Regulator's thermal performance is 60 C/W with max  junction temperature 125C, which means that if more than 2W power consumed on the regulator IC, you must add heatsink, when room temperature is 0 degree C.  With 9V power supply through it to regulated to 5V, there are 4V voltage drop on the regulator.  At 250mA, that is 1W.  If your room temperature is 60 degree C, that is already near the max power rating.  Luckily, most of us live in a room temperature about 30C or 80F, so that the regulator can operate without heatsink no additional load. 

 

[CAI_Support]

Ross' new terminal board has an on-board regulator, which can be used for additional relay boards. 

 

[rossw]

Ross' new terminal board has an on-board regulator, which can be used for additional relay boards. 

 
I'm mostly happy with the new boards.
I've put a rough web page together so I can keep notes, updates, pictures etc in one place.
 
http://webcontrol.rossw.net
 
You can see where the 7805 regulator goes, along with room for heatsink. Schematic and board layout also on this page.

 

[CAI_Support]

Ross,
 
I did not see 7805 soldered on the board.  Is the lower part 3 pin soldering pads for 7805?

 

[rossw]

Ross,
 
I did not see 7805 soldered on the board.  Is the lower part 3 pin soldering pads for 7805?

 
No, I didn't solder a regulator on the board for the photos - the pictures are of the "standard" configuration.
 
Bottom left there is a patch labeled "IC2" on the silkscreen. That's where the regulator would go.
There is a jumper across input to output that needs cut if you're using the onboard regulator. There is a space for a bypass cap on input and output to either side of it also. (I'd intended to mount them on the underside of the board to leave the heatsink clear)
 
I'll probably fully populate a board and take some additional pictures later.

 

[todster]

With 8 outputs on each board and 16 inputs on the plc card, if I wanted to use 2 boards I should have a common 5 v power supply. I guess this is where the board from Ross will come in handy. Does the kit include the 7805 or do I need to order one from mouser or digi?
In the future when a board is sent in for update, is it possible to have it set to dhcp default? I can then set up the reservation on dhcp server by mac and not have to go thru hoops to set it up. Besides, my wife hates it when I do it with her laptop. She blames me for anything that happens after that.

 

[rossw]

With 8 outputs on each board and 16 inputs on the plc card, if I wanted to use 2 boards I should have a common 5 v power supply. I guess this is where the board from Ross will come in handy. Does the kit include the 7805 or do I need to order one from mouser or digi?
In the future when a board is sent in for update, is it possible to have it set to dhcp default? I can then set up the reservation on dhcp server by mac and not have to go thru hoops to set it up. Besides, my wife hates it when I do it with her laptop. She blames me for anything that happens after that.

 
I'd have sent you a 7805 if I realized that was your aim. No, it's not in the kit because I figured most people wouldn't use it.
Fortunately, they're cheap and easy to get hold of. Even check your scrapbox, likely you'll have a heap in there already
 
Early boards had DHCP set by default.
I'd REALLY like to see the boards take an IP by DHCP if there is a DHCP server on the network, but if there is none - then use whatever is configured.
This way, you could send them as 192.168.1.15 as you do now, but those of us with DHCP servers don't have to fiddle with them when we set up a new one

 

[todster]

If I had realized then that I was gonna do this I'd have asked you about it.

 

[rossw]

Ross,
 
I did not see 7805 soldered on the board.  Is the lower part 3 pin soldering pads for 7805?

 

 
As you can see, plenty of room to bolt a heatsink to suit your needs.

 

[CAI_Support]

Ah,  that is a good place, user can add heatsink if he decided to.
Since ther WebControl board using SMD components, there is no easy way for user to add heatsink for the regulator.

 

[todster]

Received the board today. Very nice Ross. Glad I had you solder the amp on. I'm not too sure I could have done that. Gotta get one of those magnifying lights I guess.