Terminal boards for WebControl

[rossw]

I didn't clearly explain. I have the 7805. I cut the trace and installed it. I'm powering it with 24Vdc from the PLC I'll be serially talking to. I jumpered from the 5V output of the 7805 to the power to the analog amp. I currently have no plans to use the analog but may in the future. Currently the analog with the 5V applied outputs a static 3.6v with nothing connected to the board and not connected to the WC.
 I already scratched it between the cap and the V+ ( where it says GND TP1). I already scratched where indicated when I installed the 7805. From what I can tell the 7805 still feeds 5v to the WC on pin 13. I don't mind feeding the W/C the 5V as long as I know that the common source for both is exactly that, common. Which is why I want to get a 7808 or something along that line to power the WC and the RW breakout board from the 7808.

 

 
On the image above, the RED shows the power trace from the +V pin on the analog connector going to the bypass cap, the regulator and the opamp.
The YELLOW is the jumper link across the regulator (if not fitted), joining that to the WC board +5V
The PURPLE is the +5V part of the board that is either powered from, or powers, the WebControl board, TTL input pullups etc.
The GREEN is the common ground between all parts of the board.
 
The reason you're only getting 3.5 (probably 3.7 or 3.8V) from the opamp is that it's not a rail-to-rail device. It can go to ground fine, but it can't pull higher than about 1.2V from the + rail. At 5V - 1.2 = 3.8V, and is the primary reason I added the regulator, so we can power the opamp from +12V so the amplifiers can drive a full 0-10V to the analog inputs (without having to modify the WC board), while also providing 5V to the WC logic and not overheating the onboard regulator.

 

[todster]

Thanks Ross. Thats what I figured. When or if I use the analog I'll use another 780x to set my analog to what I want. I just wasn't comfortable giving it 20volts on the analog.

 

[CAI_Support]

WebControl analog inputs have protection circuit built-in. It will not be able to tell the difference between over range or full scale, however, any over range will not damage the analog input.  The connector may not take more than 200V.  However, Ross' board will never feed that muich voltage anyway.
 
.

 

[nbright]

Just got some of these boards.  What will I need to do to use some gypsum plug moisture sensors? Dry and at 5v input, i get around 1.8v output.

 

[rossw]

Just got some of these boards.  What will I need to do to use some gypsum plug moisture sensors? Dry and at 5v input, i get around 1.8v output.

 
What is their span? So you get 1.8V output "dry", what is it "wet"?

 

[CAI_Support]

Gypsum sensors are for soil moisture measurement.
I would think when it is wet, it will output higher voltage.

 

[rossw]

Gypsum sensors are for soil moisture measurement.
I would think when it is wet, it will output higher voltage.

 
I'd expect their resistance to drop.
So it depends if they are connected between ground and input, with a pullup resistor (in which case the voltage would go down)
or from input to supply with a pulldown resistor (in which case it'll go up!)

 

[CAI_Support]

If user uses Gypsum sensors with 1.8V input, I think analog input can direct to the analog input through the terminal board. Do you see need for any amplifying?

 

[rossw]

If user uses Gypsum sensors with 1.8V input, I think analog input can direct to the analog input through the terminal board. Do you see need for any amplifying?

 
Depends on the span.
If it goes from say 0 to 2.5V then amplifying will give a far greater precision (using all 10 bits of ADC instead of only the bottom 8 bits)

 

[CAI_Support]

I guess we will need more information from NBRIGHT.

 

[Automate]

Thanks rossw, got my kit today

Shipped on 2/18 received in US on 2/28 via International Airmail - Letter

 

[rossw]

Thanks rossw, got my kit today

Shipped on 2/18 received in US on 2/28 via International Airmail - Letter

 
You're Jim? First to use the online purchase - didn't know who you were, had to hope it all worked ok!
Thanks for the update. There's a few others should have got theirs by now that I haven't heard from.

 

[todster]

I'm thinking of making another board similar to yours but with more parts. Be fun to try etching one. I'm starting to go bald anyways :unsure:   .
What I want is to add room for a 7808 or a 7809 and a UDN2987. The 2987 should give me a clean board without pull up or down resistors for a sourcing output. I'll use the 7809 to power the W/C board from 24 volts as well as using it for the UDN and the analog. When the 7805 is added to your board, does it increase the output current limit on the outputs?
What program did you use and how difficult was it to figure out the program?

 

[rossw]

I'm thinking of making another board similar to yours but with more parts. Be fun to try etching one. I'm starting to go bald anyways :unsure:   .
What I want is to add room for a 7808 or a 7809 and a UDN2987. The 2987 should give me a clean board without pull up or down resistors for a sourcing output. I'll use the 7809 to power the W/C board from 24 volts as well as using it for the UDN and the analog. When the 7805 is added to your board, does it increase the output current limit on the outputs?
What program did you use and how difficult was it to figure out the program?

 
If you're going to power from 24V, don't use a linear regulator. Or, use a switching reg to something closer to the linear regs voltage, just to reduce dissipation.
There's little point powering the WC board from 8 or 9V if you're using the terminal board - 5V to the WC logic is all *IT* wants, and 8 or 9V isn't enough to drive any opamp (even rail-to-rail ones) to the 10V for full analog input.
The output drive current is limited by the LVC4245 driver/level-shifter. It's specs say its outputs can each sink or source 24.5mA but the entire device absolute maximum dissipation is a little over 800mW so thats more likely the limiting factor anyway.
The UDN2987 is an output driver - which means you'd need wires or links from the outputs up onto the daughter board. I personally think you'd be better off making a separate output board with suitable pitch connectors to screw straight into the output connectors on the WC.

 

[todster]

I'd been debating using stubs into the outputs but was worried about stability. I'm not using the analog currently and probably not in the foreseeable future, although that could change. I'm more interested in  the temps and humidity right now. I was mainly interested in powering the board from 1 source instead of having multiple. I was wondering about whether the 5v from your board would power up the W/C via the 24v.
My thought was to put terminals above the outputs and use loops up into the inputs for the 2987. I stumbled onto the 2987 and liked it because the inputs on my plc are sinking.
Now I'm going to have to look at something compact for a switching ps to 12v.
I already have a separate board right now with the ULN2003's but it requires pull ups and got unsightly rather fast. It also requires inverting the inputs on the plc. Not a big deal to NOT the inputs in the program. I usually put all the inputs into internal bits, so I could do the inversion then.