Voltages the the rPi


 
A

Andy Williams

New member
All,

Not sure what I did, but in the process of troubleshooting why my blower wasn't working I shorted out my rPi :(

Fortunately, I have another rPi but before I go plugging this one in, I want to make sure I haven't messed anything else up. I've checked the voltages from the gpio connector and pin 2 is reading 5v. Pin 1 is not reading anything but I'm not sure if that is normal or not.

Also, on C5 I'm reading 5v but on C6 I'm not reading anything. Does C6 not get voltage until the rPi is plugged in? I tried reading the schematic -- I'm in over my head a bit with that.


Thanks!

Andy
 
Yeah both C6 and the Pin 1 are 3.3V which is fed back from the Pi to the HeaterMeter board. We supply the 5V, it supplies the 3.3V (unless IC4 is installed, then we do both).
 
Thanks Bryan!

One other question; before I blew up my rPi, I was not getting any voltage to the blower via the RCA jack. I did measure 12v on J4 when going to the ground of Q1/MOSFET. However, I wasn't reading 12v on any of the other RCA connectors. Am I missing something?

Also -- I see some pinouts on J4 -- Are those two for using wires to connect the blower instead of the RCA jack?


Andy
 
I'm not sure I'm understanding you 100%, but you should get 12V on the J4 pin labeled 12V as well as if you stick the multimeter probe inside the RCA jack. The other pin in J4 should read as open, as should the outside metal part of the RCA jack. Yeah, J4 is if you want to make your own fan connector instead of using the RCA jack.
 
Sorry for being cryptic!

In more generic terms, how can I troubleshoot why I'm not getting power to the blower when I'm supposed to. I thought that measuring say the inside of the barrel against the outside of the barrel would give me 12v. Is that correct and if so, what can I measure to figure out why I'm not getting that 12v.
 
I'm now running power to the blower via J4 and when I measure the voltage I'm getting around 8.4-8.5 volts. When I connect the blower, it doesn't work. After I remove the blower, and check with my multimeter, I don't see any voltage. MOSFET power supply bad?

I'm using a 12v 1.5amp wall wart from Radio Shack.
 
You can't really measure the voltage at J4, because the "ground" pin floats so it isn't ground all the time. Depending on the multimeter it may or may not be accurate at all. Without the fan plugged in, it is an open circuit so that makes sense why you're not getting any voltage without it plugged in. That you're seeing at 8.4V, if that's ballpark accurate, that's plenty for the blower to run.

Do you have a computer fan or something you can test with? You can also solder a 1K resistor inline with a LED (doesn't matter which leg) then apply it to J4 to see if it lights up. I assume your blower output is set to 100% for these tests, right?
 
I did test and the fan works fine. Taking a closer look, I'm almost positive that I put the MOSFET in backwards. Looking at the assembly pictures, the flat metal part (heat sink?) lays flat on the PCB?

If I did put it in backwards is it now toast?
 
Yep, it should be with the metal side down.

jpRD4k5.png
 
Nope that looks perfect-- on the right side, installed the right way, and the hole even lines up! The diode is even facing the right way above it, which is something that I considered but clearly isn't an issue. I'm at a loss here, I'm not sure what the problem could be.
 
Oh durp that's what I get for replying first thing out of bed and before the coffee. Thanks for posting that photo, that's a great macro shot.
 
Success! I'm up and running!!

Feel like a kid in a candy shop with $500 in my pocket!

I'm online and working: http://fivewilliams.net:8000

Just need to build a fan assembly/case now.

Thanks *so much* for all the hard work and effort put into this project. Hopefully I'll be able to contribute going forward.

Edit: just monitoring the temp of a room right now. Can't wait for cooler weather here in the FL panhandle.
 
Nice!

I sent my friends my external URL for my heatermeter and now I get emails from them asking me what I'm cooking and when they should come over ;)
 
My goal in the next few weeks is to put together a front facing www site to point everyone. That www site will also poll the heatermeter for updates as well as keep all the historical updates and settings.

I started a test cook a few hours ago and the results have far exceeded my expectations! No tuning whatsoever and temps are rock solid. Have my 3 other food probes measuring grate temps to see how my UDS works with a heat diffuser. So far so good!

Live readings at the aforementioned URL :)
 
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