HeaterMeter v4.0 for RaspberyPi / Standalone


 
haha wow! Actually, that's the image from the first post in this thread. It was all I had available at the time! Yeah, a nice graph of a running smoke would be a better representation than just my testing graphs. Still pretty cool.

Also, good news everyone! I just was talking with Laen from OSH Park fame and HeaterMeter PCBs are now going to be carried on the OSH Park Store. This means shorter delivery times AND you only have to buy one board if that is all you want. Great news all around. I'll be making a separate post to pimp their store.

John, it is funny that you say that I taught you something. In the programming world, I've always told new hires "If you want to learn something, do a project you enjoy" and that's just what that has been for me. I wanted to learn embedded programming. I wanted to learn "circuits" (my dad was an electronics officer on a P-3C in the Navy and it always fascinated me). Nothing teaches like getting involved in something you really want to do. I'm glad all of you have been here to keep me motivated to keep coming up with new ideas!
 
Bryan Mayland said:
Golly, that is so crazy high. HeaterMeter will display "No Probe" for readings which are really close to reference voltage (1-2 ADC 'ticks'). The voltage divider you've got going there is:
1.1M / (1.1M + 10k) = 0.991 = 3.2703V

While that should give a reading (1014 out of 1023) that's still pretty close to the top end. Looking at the curve for that probe, they seem particularly unsuited for reading temperatures below 100F. You'd be able to get much more accurate readings by choosing different biasing resistors for the probes.

That said, you should still be getting readings out of HeaterMeter. Without the system powered on, try checking the resistance between the metal braid on the probe wire the ground on the probe pin header (with the probe plugged in). It should read 1 ohm or less. Also try taking the same reading with the probe touching the HDMI shield which you say gives you a reading. They should be the same value.

EDIT: Oh hey you've already tested that. They shouldn't read open, that's for sure. Check to make sure the probe pin is seating properly in the jack. You should get near-0 ohm resistance between pin 1 of the probe jack header and the braid of the probe cable.
Click to expand...

Sorry, took the night off to watch the baseball game.

For resistance between the probe jack header and the braid of the cable I'm showing open for 3 out of the 4 ET-732 probes that I own. One of the probes does around 2k ohms, but I believe this probe is actually bad (which is why I own the other ones), because when I touch it to the probe cable to the HDMI housing it shows like 900 F for a temperature.

I am pulling the probes out a couple of mm out to get them to click in as D Peart mentioned.

If I change the 10K resistor to a 20k resistor this will change the calibration curve slightly, correct?

Are the rPi and the HeaterMeter board grounded together somewhere?
 
Bryan Mayland said:
haha wow! Actually, that's the image from the first post in this thread. It was all I had available at the time! Yeah, a nice graph of a running smoke would be a better representation than just my testing graphs. Still pretty cool.

Also, good news everyone! I just was talking with Laen from OSH Park fame and HeaterMeter PCBs are now going to be carried on the OSH Park Store. This means shorter delivery times AND you only have to buy one board if that is all you want. Great news all around. I'll be making a separate post to pimp their store.

John, it is funny that you say that I taught you something. In the programming world, I've always told new hires "If you want to learn something, do a project you enjoy" and that's just what that has been for me. I wanted to learn embedded programming. I wanted to learn "circuits" (my dad was an electronics officer on a P-3C in the Navy and it always fascinated me). Nothing teaches like getting involved in something you really want to do. I'm glad all of you have been here to keep me motivated to keep coming up with new ideas!
Click to expand...

That is good news on the OSH Park Store :-).
 
Maverick probes showed up, plugged one into my Igrill, and no surprise the temp/resistance curve is different, maverick was -25f at room temp, and -100f or so at 200f.

Bill
 
Alan,

If you change the resistor on the board to 20k, then you just need to change the value in the configuration web page from the default 10k to 20k. The PID coefficients do not change.

dave

Alan Erickson said:
Sorry, took the night off to watch the baseball game.

For resistance between the probe jack header and the braid of the cable I'm showing open for 3 out of the 4 ET-732 probes that I own. One of the probes does around 2k ohms, but I believe this probe is actually bad (which is why I own the other ones), because when I touch it to the probe cable to the HDMI housing it shows like 900 F for a temperature.

I am pulling the probes out a couple of mm out to get them to click in as D Peart mentioned.

If I change the 10K resistor to a 20k resistor this will change the calibration curve slightly, correct?

Are the rPi and the HeaterMeter board grounded together somewhere?
Click to expand...
 
Has anyone adapted the HeaterMeter to control an electric hotplate? I've made a terracotta bbq smoker that I think should be good for an all-day smoke without any attention except maybe one or two wood chunk replenishments. But temp control will be crucial for unattended use.

I would guess it should be pretty easy to adjust from a variable fan control to an on/off hotplate control using a solid state relay to control (in my case) 240V. But I'm not a code expert and it's a long time since any PID experience ;-). Cheers, -Dave
 
Yep. check the Sous vide thread where Evan has posted a good writeup on it. I've built a SSR-controlled outlet as well, putting an RCA jack for an input and just using an audio cable to connect it to the HeaterMeter's blower output. All you've got to do in the configuration is set the min fan speed to 100%.
 
Bryan Mayland said:
Yep. check the Sous vide thread where Evan has posted a good writeup on it. I've built a SSR-controlled outlet as well, putting an RCA jack for an input and just using an audio cable to connect it to the HeaterMeter's blower output. All you've got to do in the configuration is set the min fan speed to 100%.
Click to expand...

That is nice to know, because that is the same setup you would use for a simple intake damper that only had open/closed binary action :-).

Bill
 
Also just a general note. The Microsoft Wireless 800 keyboard/mouse combo has some widely reported issues with the Raspberry Pi...some google will confirm this if you doubt my word :-), many many other people have experienced the same issue. Might save somebody ELSE from snagging one for their rPi and expending some %^$#@& trying to use it :-). It types endless characters when you try to even login. This may be a driver issue that will eventually be fixed.

I have a Logitech wireless keyboard/mouse that worked just fine.

Bill
 
Looking at my setup, which is on a 512 rPi...it looks like it only uses 256 of the memory ??

kkI3X.png
 
Bill D aka Willbird said:
Looking at my setup, which is on a 512 rPi...it looks like it only uses 256 of the memory ??
Click to expand...
I wouldn't know because my Pi only has 256MB. It is probably something that has to do with the older rPi bootloader being hard-coded to 256MB total memory or the "memory split" actually just telling the core how much to allocate for user RAM. We use the 224 split so 224 is all you'll get. Not that the the LinkMeter OpenWrt will ever use anywhere near that. As you can see you have about 10MB in actual use but it can peak at up to 16MB!
 
Dave D said:
Has anyone adapted the HeaterMeter to control an electric hotplate? I've made a terracotta bbq smoker that I think should be good for an all-day smoke without any attention except maybe one or two wood chunk replenishments. But temp control will be crucial for unattended use.

I would guess it should be pretty easy to adjust from a variable fan control to an on/off hotplate control using a solid state relay to control (in my case) 240V. But I'm not a code expert and it's a long time since any PID experience ;-). Cheers, -Dave
Click to expand...

My Dad and I modified my Mom's Bradley electric smoker for her birthday. The stock elements on these Bradley's are terrible (1) because they take forever to get the smoker hot (2) they burn out easily and cost $30 to replace (3) they run on a thermostat so the temperature varies +- 30 degrees. We basically used the Linkmeter and a 40A SSR from ebay with one of those charcoal lighter heating elements you can get from the hardware store $10-12US. Here are some photos:

2012-10-29.jpg


2012-10-29.jpg


This thing has been setup in this manner and used weekly for a year or more and works 100x's better than the stock smoker.
 
Perfect, thanks! Will give that a try in a couple months when I get to my new house. In the meantime I think I'll order a HeaterMeter PCB and a RaspPi, as I don't have one yet... ;-)

Looking forward to watching my bbq cook on a smartphone from work. Though maybe I need to get a smartphone first.

Bryan Mayland said:
Yep. check the Sous vide thread where Evan has posted a good writeup on it. I've built a SSR-controlled outlet as well, putting an RCA jack for an input and just using an audio cable to connect it to the HeaterMeter's blower output. All you've got to do in the configuration is set the min fan speed to 100%.
Click to expand...
 
Dave S, that is a great idea to use a charcoal lighter. Simpler, cheaper, and probably less failure-prone than using a disassembled electric hotplate like what's in my current (fully manual) smoker. How do you have that element setup exactly? Looks like a metal shield between the charcoal lighter and hunks of wood that you lean against it, or is there something I'm missing?

Would love some details because I'll probably try this in a large square terracotta pot, with a terracotta lid. My thought would've been to put the charcoal lighter in the bottom with a chip pan on top, but maybe you've done some experimenting.

Dave S (GeoDave) said:
My Dad and I modified my Mom's Bradley electric smoker for her birthday. The stock elements on these Bradley's are terrible (1) because they take forever to get the smoker hot (2) they burn out easily and cost $30 to replace (3) they run on a thermostat so the temperature varies +- 30 degrees. We basically used the Linkmeter and a 40A SSR from ebay with one of those charcoal lighter heating elements you can get from the hardware store $10-12US.
Click to expand...
 
Dave,
Very nicely done on the Bradley, when my brothers craps out I'll give him that idea. My electric element crapped out this weekend when I was making jerky so I need to get a replacement. I hadn't thought of the charcoal starter. I'll give that a shot.

thanks,
dave

Dave S (GeoDave) said:
My Dad and I modified my Mom's Bradley electric smoker for her birthday. The stock elements on these Bradley's are terrible (1) because they take forever to get the smoker hot (2) they burn out easily and cost $30 to replace (3) they run on a thermostat so the temperature varies +- 30 degrees. We basically used the Linkmeter and a 40A SSR from ebay with one of those charcoal lighter heating elements you can get from the hardware store $10-12US. Here are some photos:

This thing has been setup in this manner and used weekly for a year or more and works 100x's better than the stock smoker.
Click to expand...
 
Dave D said:
Dave S, that is a great idea to use a charcoal lighter. Simpler, cheaper, and probably less failure-prone than using a disassembled electric hotplate like what's in my current (fully manual) smoker. How do you have that element setup exactly? Looks like a metal shield between the charcoal lighter and hunks of wood that you lean against it, or is there something I'm missing?

Would love some details because I'll probably try this in a large square terracotta pot, with a terracotta lid. My thought would've been to put the charcoal lighter in the bottom with a chip pan on top, but maybe you've done some experimenting.
Click to expand...

I too was thinking of making my own electric smoker after seeing these starters in the hardware store. My Dad first tried to use a hot water heater element after I told him I thought he should try the Brinkmann electric charcoal starter. The hot water heating element ended up melting and almost causing a fire...so don't try that. Those elements like to be in water! I was still living in Seattle when he installed the element so I don't have any more picture but he basically removed the handle by drilling out the rivets and removing the wires. The ends of the element ended up fitting very nicely in the existing heating element socket. He then screwed the starters shield to the back of the smoker using a metal screw. This slightly offsets the element from the back wall of the smoker. Works and fits great.

The bowl and wood are in front of the element. In case you didn't know, Bradley smokers have a little box that advances their proprietary wooden bricketts onto a hot plate which creates the smoke. After a given amount of time the used bricketts are advanced into the bowl of water.
 
If one required a larger fan to run, say 2A, would I only have to change out the 1n4001's for 1n4007? I ran the system last weekend on the weber 22, and found the small fan only took 10 minutes to get the coals up to 225F. Now I wonder about my stoker. My feeling is it will be okay with the smaller fan, except in the winter. It tends to get a little cold at nights here.
 
Larger 1N00X diodes are rated for higher reverse voltage, not higher current, and the max voltage they should see is 12V. They're all rated for 1A continuous, so you could put 2 in parallel I suppose. They don't carry current all the time though, just when the fan turns off and for a short instant after. At least that's my understanding of how freewheeling diodes go.
 
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