Inquiry about Power via Pi vs HM


 
J

JoeRo

New member
Greetings,

I've been lurking in these forums for quite some time, and I finally pulled the trigger. My kit arrived and I assembled it yesterday. I haven't done anything like this in 20 years, and I loved it! It took me quite a bit longer to assemble than I thought it would, but I loved every minute of it (except maybe the two hours I drove around town looking for a Solder Plunger to fix a small mistake I made).

For some reason, I neglected to order probes and a power supply. While I'm waiting for those to arrive, I had a question I thought I'd throw out there.

I followed the directions, including the recommendations, and I powered it up the first time using the Micro USB port on the Pii. The HM lit up and, after tuning the LCD, I even had a display. Having not even touched a soldering iron in years, I was bit surprised everything came up on the first try! Using the Pii power supply, I configured the wireless and made sure everything seemed to be working.

I understand that one of the reasons it's recommended to power it via a Pii is to prevent any problems from ruining the Pii itself. It's my understanding that there is some protection if there are problems *IF* the Pii is supplying the power.

Using Pii power, the HM turned on. I saw bogus temps on the display (I wasn't concerned as I didn't have any probes). It appeared that the HM was functioning correctly. Am I safe to assume that I should be good if I power it through the HM itself? I understand I might have some issues to work out, but my fear is that I'm going to power it on (using the HM power jack) and it's going to start smoking. Am I past that worry, or is it still a possibility?
 
The 12V barrel connection to the HM will power it just fine. I didn't know there were voltage checks in place, but that is definitely good to know. I ran my base board only HM on the USB for a few hours while I configured the web interface.

As for your wacky readings, I might recheck your solder joints on the jacks. When I have no probes in the HM, it reads 'off' in the interface. Your joints may have some resistance and therefore registering a reading. Whatever probes you buy, make sure to select the manufacturer of them in the web interface. But that may also be the result of the 5V input of the Pi vs the 12V when you go thru the HM.

I finished mine a couple weeks about and added a rotodamper and blower. Can't wait to get this thing going!! My wife has told me I can do a pork butt once I build the Christmas yard display she dreamed up...I feel like Steve Wozniak and she's Steve Jobs....
 
Now you have me second guessing my soldering job...

I built the thermocouple version of the board, but I installed a resistor that I wasn't supposed to install. I'm having a hard time removing the K port to get at the resistor, so I took a pair of wire cutters and cut the resistor out. I'm still getting temps, though. They should be 0 with nothing plugged in?

I guess I'll just box it up and check it out when I get my probes and power supply on Wednesday. Thanks for the info -- you helped me find that resistor that I shouldn't have installed! :)
 
the standard probes should show "off" when no probes are plugged in. If you have a Thermocouple HM board and have selected Type: Thermocouple for Probe 0 (Pit Probe), you should see "No Pit Probe", but if you do not set Probe 0 to TC then you'll probably see a false temp for the pit.
 
I did some maintenance and I think things are looking better.

I started by cleaning the board with alcohol. There was some flux still on the board. I'm not sure that was causing a problem, but it's gone now. While cleaning, I noticed a few questionable solder points. I pulled out the iron and set it to 350 and re-flowed every point. I definitely fixed a few issues.

Now, with thermoworks probes select in the configuration, I'm getting the following

Probe 0: Thermocouple - when set to the thermoworks probe, it reads 17 -- setting it to thermocouple changes to no pit probe.
Probe 1: Off. It was reading 10 degrees or so, and slowly dropped down to OFF.
Probe 2: Off/Negative values. It was also reading 10-15 degrees, and slowly dropped to OFF. After a few minutes, it started reading negative. It's hanging around -2.
Probe 3: It was sitting around 17 degrees, and it's slowly climbing. After a few minutes, it's now at 19.6 degrees.

Any suggestions on where to look? I'm expecting that Probe 2/3 should read OFF as well.
 
I don't think you said which version HM board you are building? V4.2 or 4.3?
Either way, the probe circuits are rather simple, on the 4.2 board their traces are very short and confined to the area between the probe jacks and the ATMega. The only components between the probe jack and the ATMega are the 100K Resistor and .1uf capacitor that make up the RC filter, and the standard probes have the 10K pullup resistor connected as well. The last four pins on the ATMega are the probe inputs, counting from the corner Probe 0 (pit) through Probe 3 (on the fourth pin from the corner). On v4.2 boards the resistors in question are the ones standing up along with the .1uf capacitor in the same area. Make sure solder on these components and the last four pins of the ATMega are solid, and clean that area really well with isopropyl alcohol and a soft brush (let dry before you power the board up).
The TC behavior you describe sounds normal, I would guess that one is working properly.
 
4.2

I think it's a resistor, and I know which one, but my iron died. Just got the darn thing, too, and it's just flashing an 8 instead of a temp. Looks like I'm going to be down for a bit until I get my iron working or replaced.

Thanks for all the help guys, it's much appreciated!
 
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