My Automated E-Herms Build (LabJack)

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cruelkix

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Just wanted to say this is extremely cool, and congrats on your pimp system. I don’t know much about electrical, but listen to CodeRage, your system is far too cool for you to get hurt using it.
Thanks for the kudos man. Yeah I will def be doing most of these things before I brew again. I'm really glad I posted all this stuff so CodeRage could tell me how much I screwed up!;) (but in complete and total seriousness as well!)
 
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Perpendicular intersections are okay, when you run signal wires parallel with high current carrying wire is when you start to induce noise. Best practice is to keep them far away.

That's what I was saying. If you have to have them cross, at least you have them perpendicular. Glad to see it's not giving you any issues. I'm scared away from USB for life after the headaches I've had with it from our equipment. Nice build!
 

LabJackSupport

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Noticed a couple items I can comment on related to the LabJack U3.

I was under the impression that the Digital I/O lines could only supply 3.3V and you are switching a 4-32V SSR without amplification. Am I missing something, or does it just work anyway?
In the first picture of post #21, I can see that the analog outputs (DAC0 and DAC1) are sourcing current to a couple SSRs. They can provide 5 volts and plenty of current.

Following the wires from that picture to the 3rd picture, it looks like some FIO (digital I/O with 550 ohms of source impedance) are connected to more SSRs in the sourcing configuration. This looks like the SSRs are being turned on with 3.3 volts (with 550 ohms in series), and thus is not meeting the specs of the SSRs, but likely is providing enough current to light the internal LED and turn on the SSR anyway. The proper way to connect would be the sinking configuration described in Section 2.8.1.4 of the U3 User's Guide, where the I/O lines provides ground for our 5 volt supply:

http://labjack.com/support/u3/users-guide


I don't know what your experience with USB is and if you've ran this yet, but from my experience at work, god help you with those power lines running that close to the USB wires. You have an almost perpendicular crossing and that may help, but from my experience on a daily basis with the USB communication in our industrial equipment (Genius design) you have headaches ahead. Hopefully this is not the case, but just remember this if/when you USB interface starts going whacko.
I would agree that Ethernet (which we also offer) is generally more robust (it is isolated unlike USB), but we get good performance from USB also.

The most common "strange" problem we see seem to be related to electrical arcs and the USB host. For example, a mechanical relay with no snubber is used to control an inductive load like a motor, resulting in ugly arcs when the motor is stopped in particular. This arcs radiates an EM transient to the USB host, or perhaps some combination of radiation and conduction through common ground brings it to the host. The host then forgets a device is connected and requires you to plug/unplug to get it back. We don't see this too often, and it can be addressed when someone is seeing it.

One other thing we see is related to a USB suspend bug in Windows XP. I recommend everyone turn this off for a simple fix to this:

http://forums.labjack.com/index.php?showtopic=4510
 
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cruelkix

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Following the wires from that picture to the 3rd picture, it looks like some FIO (digital I/O with 550 ohms of source impedance) are connected to more SSRs in the sourcing configuration. This looks like the SSRs are being turned on with 3.3 volts (with 550 ohms in series), and thus is not meeting the specs of the SSRs, but likely is providing enough current to light the internal LED and turn on the SSR anyway. The proper way to connect would be the sinking configuration described in Section 2.8.1.4 of the U3 User's Guide, where the I/O lines provides ground for our 5 volt supply:

http://labjack.com/support/u3/users-guide
Its funny how you forget things that you did on purpose. The other SSRs I bought do not have an LED and CAN turn on with only 3 volts supply. This is why I have them wired the way I do and am not having any issues supplying the required voltage. Sorry. I should ahve been able to answer that earlier but I forgot I did that on purpose!:D

Regardless. Thanks for the link for other people to use if they need it!
 

cpeneguy

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What temp sensors are you using and where did you purchase them. Im in the process of gathering all the materials to go all electric and fully automated. Getting tired of filling propane tanks and brewing in the 90 degree heat.
 
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cruelkix

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What temp sensors are you using and where did you purchase them. Im in the process of gathering all the materials to go all electric and fully automated. Getting tired of filling propane tanks and brewing in the 90 degree heat.
I used 3 of these guys.

Then I bought 3 of theseCompression Fittings to punch through the side walls of my keg.

I put the temp probes into SS Temp Probe Tubes and slide them in and out of the compression fittings.

I used a little thermal compound when i slid the temp sensors into the temp probes. Soldering the wire to the end of the temp sensors was a pain in the butt and I ruined one, but i am terrible at soldering small stuff/anything (shaky hands).

All in all it cost like $50 for all 3 (minues the compression fittings of course, with them its like $100). If you can find some really small gauge wire (like 24) it makes life easier. I used shrink wrap and epoxy to seal the end of the SS probe to make it as water tight as possible.
 

cpeneguy

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Thanks for taking the time to respond and give me so much information. I've been trying to track down what types of sensors to use and such for a while.
 
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