BCS-460 wiring (ground) question and PID temp display connections

[TrickyDick]

Hi,

Built a cart and control panel for conducting temp controlled fermentations using modified plastic (for now) conicals, the thread for that is here (https://www.homebrewtalk.com/f51/diy-glycol-chilled-plastic-conical-fermenters-413406-new/)

I added PID temp display modules and my question concerns getting those working.
Right now the debug light is flashing, which means that they aren't getting data from the BCS. I believe I have the addresses correctly set and the appropriate settings enabled in the BCS webpage. I think my problem is the wiring.

The PID display modules have four connections: 12vdc, GND, and SCL & SDA, the latter two connect to the BCS exp0/exp1 ports. I forget which goes to which at the moment. But both are connected appropriately as far as I know(*). The other two supply DC power.

I think that the BCS power does not utilize the GND terminals (of which there are several and I believe all common) for -12vdc. It has a wall wart power brick for its 6 VDC power. There is a 12vdc psu in my enclosure operating a driver board and the PID display modules. I think I need to connect the PID display modules GND, to the BCS GND. It seems that this would not deliver any power to the PID modules however.

I can post some pictures later and possibly a basic wiring diagram. Was wondering if I need to run the BCS off the same psu as everything else (which would require a resistor circuit or potentiometer). My thinking is that this would establish a common ground to the BCS? Does the BCS rail conduct its -VDC? I do not think it does, but not sure. Also unsure if I could run a -12vdc to the the BCS GND without Causing a problem.

The * indicates that the manual and the PCB on the PID modules have changed. My PCB is a bit different pin configuration than the manual states for the SDA/SCL pins.

Otherwise, my initial testing indicates that everything else is working, just no temp display on the control panel.

Thanks for any help!

TD



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[trimixdiver1]

Hi,

Built a cart and control panel for conducting temp controlled fermentations using modified plastic (for now) conicals, the thread for that is here (https://www.homebrewtalk.com/f51/diy-glycol-chilled-plastic-conical-fermenters-413406-new/)

I added PID temp display modules and my question concerns getting those working.
Right now the debug light is flashing, which means that they aren't getting data from the BCS. I believe I have the addresses correctly set and the appropriate settings enabled in the BCS webpage. I think my problem is the wiring.

The PID display modules have four connections: 12vdc, GND, and SCL & SDA, the latter two connect to the BCS exp0/exp1 ports. I forget which goes to which at the moment. But both are connected appropriately as far as I know(*). The other two supply DC power.

I think that the BCS power does not utilize the GND terminals (of which there are several and I believe all common) for -12vdc. It has a wall wart power brick for its 6 VDC power. There is a 12vdc psu in my enclosure operating a driver board and the PID display modules. I think I need to connect the PID display modules GND, to the BCS GND. It seems that this would not deliver any power to the PID modules however.

I can post some pictures later and possibly a basic wiring diagram. Was wondering if I need to run the BCS off the same psu as everything else (which would require a resistor circuit or potentiometer). My thinking is that this would establish a common ground to the BCS? Does the BCS rail conduct its -VDC? I do not think it does, but not sure. Also unsure if I could run a -12vdc to the the BCS GND without Causing a problem.

The * indicates that the manual and the PCB on the PID modules have changed. My PCB is a bit different pin configuration than the manual states for the SDA/SCL pins.

Otherwise, my initial testing indicates that everything else is working, just no temp display on the control panel.

Thanks for any help!

TD



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I do PLC stuff, but the gnd might be for the communications only (the shield) that covers the comm wires. If thats what you asking, then do not connect your power supply negative to this.

 

[TNugent]

I'm sure you saw this on the BCS page but I thought I'd add it here as well. Seems to me that you need to run a jumper from the ground on the 12v power supply to one of the ground terminals on the BCS.

BCS -PID-Disp
=========
GND -GND - Also connect External Power Supply GND (V-)
Exp0-SCL
Exp1-SDA
-----12V - External Power Supply


The GND from the BCS, PID-Disp, and external 12v power supply must all be connected.

 

[TrickyDick]

Thanks for the help. I'm worried doing that will fry something.

The DIN mount PSU and the BCS PSU are different units and with different voltages. It seems a bad idea to "cross the streams" and connect the -12VDC to the BCS GND. I have been thinking that it might be a better idea before I tried this, to try to run the BCS from the 12 volt DIN mount PSU via a voltage reduction circuit or a potentiometer. There are a lot of other things connected to the ground on the BCS that I cannot recall at the moment, I think even the two 120 volt SSRs.

By the way, do you have a link to the BCS page you are referring to?

Oh and one more thing. It seems you're saying to connect the three connections on the PID to the BCS and the power 12v+ to the PSU with an additional jumper from the BCS ground to the PSU 12v-. Is this correct? The reason I'm asking is that the DIN PSU also has a chassis ground. I don't know

The BCS ground terminal I do not think is a vdc- bus for the BCS since its brick type PSU is only 6 v. It's been a long time since I had any electrical or electronics theory courses. Maybe I should put a volt meter from the din PSU to the BCS GND to see if there is any potential, and also from the pid display GND terminal to the PCS GND terminal.

Bah! I am getting too old to understand this stuff anymore. Maybe I just make the connection and see what happens. It will either work or it won't. Hopefully nothing blows up.

TD


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[TNugent]

I'll try and find that page again, it was under the documentation link but I'm not at my computer right now. The way I see it ground is ground. I have everything in my panel that has a ground all connected to the same ground post including the BCS. No other voltage will travel thru to the BCS unless the circuit is completed somehow

 

[TNugent]

http://wiki.embeddedcc.com/index.php/External_7-Segment_Display

 

[TrickyDick]

Well,

Got home, did a few things (crack open a beer, sip, repeat), and then connected the BCS to the chassis ground along with the 12VDC- on the PSU connected to ground. Temp Displays now show the temps!

Not sure why I was so freaked about it all. Need to power up the other stuff to ensure everything is working correctly, but at this point, not sure why it wouldn't.

Thanks! I think I read that the BCS didn't have a true chassis ground. Odd that so many things share a common ground without interference.

Anyways, looks like I'm all set now!

Thanks again!

TD

 

[TrickyDick]

Here is a pic. I haven't fully finished it up, and no temp set points, and no fermenting beer, but the PID displays are working. Thanks! Have a dial thermo on the coolant.

TD


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[TNugent]

I wish I added those to my panel when I built it. Not sure I could fit them in now but it would be handy to see temps at a glance like that.

 

[TrickyDick]

Yeah, that's sort of why I went the extra step to put them in. It's possible I might keep an old notebook PC in my basement, but, maybe not, just to be able to access the BCS. Plus the panel is really bare with just a switch and a light. Needed to have something to look at besides the super cool Michigan State Spartans block S my friend put on when he painted it.

The coolant reservoir has a dial thermometer gauge in the coolant tubing, so it'll only be accurate when there is coolant flowing. The BCS apparently can only support three of these PID displays.

Well thanks for helping me solve my problem!

TD


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