LinkMeter v2 Homebrew BBQ Controller - Part 1

[D Peart]

Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
I can change the set point on via HM and see the change in LM, but if I change the set point or even probe names on LM I don't see them get updated on HM, instead a few seconds later they get overwritten to their previous values.

You can try seeing if it is a web problem by ssh/telnetting in and running a set command from lmclient
<pre class="ip-ubbcode-code-pre">
lua /usr/lib/lua/lmclient.lua LMST,sp,225
</pre>
That should set the setpoint to 225. If that works then something is up with the web interface. If that doesn't work then try setting it directly through the serial port
<pre class="ip-ubbcode-code-pre">
echo -e \\n/set?sp=225 > /dev/ttyS1
</pre>
If still nothing, then sounds like something is screwed up with the serial. Try removing the HM board and connecting the router RX/TX together and seeing if you can echo things to it with the instructions I posted on the previous page.

Changing topic! A workaround to the time being off until Openwrt fixes it upstream. Go to the web interface and go to System -> Startup and add a line to the rc.local at the bottom. First, go to the list of time servers and pick one that is up and near you geographically then add to the rc.local (before the exit 0)
<pre class="ip-ubbcode-code-pre">
rdate servername
# example
rdate nist1-ny.ustiming.org
</pre>
Your clock will be synced on bootup with the time server. </div></BLOCKQUOTE>

The lua resulted in an OK response, but the set point never changed.

The echo command never returns. I double checked my serial connections and they appear correct. I'm not sure what has changed since I know this worked before. I'll have to hook it up to the computer and see what I can see.

dave

EDIT: Reflashing HM fixed it.

 

[D Peart]

Bryan,

I'm trying to use the probes from the ET-732 Maverick thermometer. I went and got all the points of the resistance v temp, plugged them into the calculator and got my A,B,C coefficients.

Unfortunately I still get No Pit Probe. If I plug them into the probe ports for the ET-73 probes, I get 19 degrees, so I know they can work.

Ideas on how to figure out what is wrong?

Here is the data I gathered.
F, R
25, 4.96e6
30, 4.1e6
35, 3.74e6
40, 3.45e6
45, 2.9e6
50, 2.5e6
55, 2.28e6
60, 2.05e6
65, 1.86e6
70, 1.57e6
75, 979e3
80, 810e3
85, 753e3
90, 593e3
95, 572e3
100, 432e3
105, 401e3
110, 362e3
115, 312e3
120, 317e3
125, 292e3
130, 254e3
135, 225e3
140, 199e3
145, 179e3
150, 161e3
155, 143e3
160, 125e3
165, 116e3
170, 103e3
175, 93.7e3
180, 83.4e3
185, 75.8e3
190, 68.8e3
195, 60.1e3
200, 55.9e3
205, 51.5e3
210, 46.3e3
215, 42.1e3
220, 38.1e3
225, 35.0e3
230, 32.1e3
235, 30.1e3
240, 26.8e3
245, 24.3e3
250, 22.6e3
255, 20.8e3
260, 19.17e3
265, 17.45e3
270, 16.04e3
275, 15.02e3
280, 13.88e3
285, 12.78e3
290, 11.74e3
295, 10.85e3
300, 10.07e3
305, 9.27e3
310, 8.52e3
315, 7.95e3
320, 7.4e3
325, 6.89e3
330, 6.4e3

The calculator gave me:
4.3934e-4, 2.08342e-4, 1.2004e-08

The data at 115 and 120 seem bad to me, but removing them doesn't fix it.

Ideas? Did you figure out your own coefficients for the ET-73 or did you find some place to get them?

I emailed Maverick Customer Service hopefully they will be willing to share the coefficients, or have a data sheet for their specific thermistor like we get from Mouser.

thanks again
dave

 

[Bryan Mayland]

Originally posted by D Peart:
The calculator gave me:
4.3934e-4, 2.08342e-4, 1.2004e-08

Which calculator are you using? I copy-pasted that into a CSV file and loaded it in AN2395's TableGenerator and got
0.000230503,0.000143905,2.39823E-007

 

[D Peart]

Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
The calculator gave me:
4.3934e-4, 2.08342e-4, 1.2004e-08

Which calculator are you using? I copy-pasted that into a CSV file and loaded it in AN2395's TableGenerator and got
0.000230503,0.000143905,2.39823E-007 </div></BLOCKQUOTE>

Well that is frustrating, I'm using the calculator you linked to. I run TableGenerator.exe.

EDIT: The temp is in degrees F, not Celcius.

dave

 

[Bryan Mayland]

Originally posted by D Peart:
EDIT: The temp is in degrees F, not Celcius.

Oh nice, looks like the values don't update if you change the units after you load the file. Now I get the same values you had. Maybe try commenting out the "sanity check" lines 156-157 in grillpid.cpp and see what values come out. (Line numbers are approximate because my code is a little different right now)

 

[D Peart]

Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
EDIT: The temp is in degrees F, not Celcius.

Oh nice, looks like the values don't update if you change the units after you load the file. Now I get the same values you had. Maybe try commenting out the "sanity check" lines 156-157 in grillpid.cpp and see what values come out. (Line numbers are approximate because my code is a little different right now) </div></BLOCKQUOTE>

-22F! for some reason I don't think that is correct

I've got a set of ET-73 probes on order, I was just hoping to use these ones if possible.

dave

 

[D Peart]

Originally posted by D Peart:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
EDIT: The temp is in degrees F, not Celcius.

Oh nice, looks like the values don't update if you change the units after you load the file. Now I get the same values you had. Maybe try commenting out the "sanity check" lines 156-157 in grillpid.cpp and see what values come out. (Line numbers are approximate because my code is a little different right now) </div></BLOCKQUOTE>

-22F! for some reason I don't think that is correct

I've got a set of ET-73 probes on order, I was just hoping to use these ones if possible.

dave </div></BLOCKQUOTE>

Got the ET-73 probes in and they seem to be working just fine. Bryan, where did you get the coefficients for these probes?

thanks,
dave

 

[Bryan Mayland]

Originally posted by D Peart:
Got the ET-73 probes in and they seem to be working just fine. Bryan, where did you get the coefficients for these probes?

Bob had them in his original posting. How did you perform the measurements for the ET-732s? You didn't have them plugged into anything besides the multimeter did you?

 

[Bryan Mayland]

Oh hey on the good news front, I have a fix for the time sync problem. I'll have a new trunk firmware out once I get my new hard drive (tomorrow hopefully) and restore the backup and get my development system back up and running.

 

[D Peart]

Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
Got the ET-73 probes in and they seem to be working just fine. Bryan, where did you get the coefficients for these probes?

Bob had them in his original posting. How did you perform the measurements for the ET-732s? You didn't have them plugged into anything besides the multimeter did you? </div></BLOCKQUOTE>

I took a pot of vegetable oil, cooled it to 10 degrees, then as it warmed up, I took measurements of the probe very 5 degrees and the temperature with a digital thermometer placed adjacent to the probe in the oil. I then added heat until I got to 390F.

Those are the values in that table. I then plugged them into the coefficient calculator and got the coefficients.

I also checked the temperature with a dial thermometer at the same time.

On a good note, I did hear back from Maverick and I may be able to get the resistance/temp data from them. Hopefully I'll hear tomorrow.

dave

 

[Bryan Mayland]

Originally posted by D Peart:
I took a pot of vegetable oil, cooled it to 10 degrees, then as it warmed up, I took measurements of the probe very 5 degrees and the temperature with a digital thermometer placed adjacent to the probe in the oil. I then added heat until I got to 390F.

Haha, actually I meant the resistance measurement part, not the temperature part. I was just making sure there wasn't something else attached to the probe or you had it plugged into something else which might have been forming a separate circuit that was altering the resistance you were measuring.

One thing you might want to try (at room temperature) is plugging in a probe and measuring the voltage at the right end of the 10k resistor vs ground. From that voltage measurement you can calculate the resistance and subsequently the temperature. It would take the whole ADC conversion out and verify its results.

Also verify that the probes are wired correctly, that when inserted the metal casing of the probe registers as ground. Maybe the ET-732s are wired differently than the others?

 

[D Peart]

Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
I took a pot of vegetable oil, cooled it to 10 degrees, then as it warmed up, I took measurements of the probe very 5 degrees and the temperature with a digital thermometer placed adjacent to the probe in the oil. I then added heat until I got to 390F.

Haha, actually I meant the resistance measurement part, not the temperature part. I was just making sure there wasn't something else attached to the probe or you had it plugged into something else which might have been forming a separate circuit that was altering the resistance you were measuring.

One thing you might want to try (at room temperature) is plugging in a probe and measuring the voltage at the right end of the 10k resistor vs ground. From that voltage measurement you can calculate the resistance and subsequently the temperature. It would take the whole ADC conversion out and verify its results.

Also verify that the probes are wired correctly, that when inserted the metal casing of the probe registers as ground. Maybe the ET-732s are wired differently than the others? </div></BLOCKQUOTE>

For resistance measuring I just hooked up the probe directly to the ohm meter and read the resistance there.

 

[D Peart]

Heard back from Maverick. They had the T vs R tables for the ET-73 probe, but not the ET-732. So looks like that route is not going to work.

Looks like I'll have to abandon my hope of using my ET-732 probes for something that already works

dave

 

[Bryan Mayland]

Originally posted by D Peart:
Looks like I'll have to abandon my hope of using my ET-732 probes for something that already works

I'd say just figure out where it is going wrong. I mean you've got all the data necessary to check it out. If you're getting -22F then that means we're calculating the resistance as being on the order of like 100-1000 megaohms.

What I'm looking at is in the TableGenerator, when I load those numbers, the left scale of the graph is in KOhms. Is your resistance at 75F really 1 megaohm?

 

[Bryan Mayland]

I've just posted a new snapshot up on
http://capnbry.net/linkmeter/snapshots/trunk/

WRT: Fixes date/time sync problem when starting up
WRT: Fixes (?) inability to join a wireless network via the web interface due to "internal server error" on the scan page
WRT: Update to OpenWrt r29473/LuCI r8081
HM: Fix bad formatting on a couple LCD config items
HM: Add min LID OPEN time, 30s
HM: Add /set?lo /set?ld for lid offset and duration setting via serial
HM: Fix a small issue where the HM config is garbled coming into LM on boot
HM: Add 10ms duration when blinking wireless receive LED

I tried flashing via the web interface and the sysupgrade but both failed for me, so I ended up having to TFTP flash it. Remember to save your back up your LM config!

 

[Jay Bremner]

Hey Bryan,
First off I want to say NICE WORK!! Been lurking around this project trying to decide if it is within my capabilities and I think I have decided to try it. I have one question for you though....how hard would it be to build this project using an arduino uno board instead of building the board from scratch? What are the pros and cons of building it from scratch...is it a space issue?, etc.....

Looking forward to your reply and hopefully some guidance during this project!
Thanks again Bryan (and also a shoutout to Bob)

 

[Bryan Mayland]

Originally posted by Jay Bremner:
how hard would it be to build this project using an arduino uno board instead of building the board from scratch? What are the pros and cons of building it from scratch...is it a space issue?, etc.....

Building the board is actually pretty easy, there's not a whole lot of components especially because the voltage regulation is done on the Uno board. The problem is the space. You can't stack a shield on top of the Uno board and get it to fit back inside the WRT54GL enclosure. If you were to make a new enclosure, all the parts you need could probably fit on maybe a 1.5"x3" piece of perfboard (assuming no RFM12). As an alternative to perfboard, you could also build the parts you need on the stock PCB and just wire it to the Uno.

 

[D Peart]

Originally posted by Bryan Mayland:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
Looks like I'll have to abandon my hope of using my ET-732 probes for something that already works

I'd say just figure out where it is going wrong. I mean you've got all the data necessary to check it out. If you're getting -22F then that means we're calculating the resistance as being on the order of like 100-1000 megaohms.

What I'm looking at is in the TableGenerator, when I load those numbers, the left scale of the graph is in KOhms. Is your resistance at 75F really 1 megaohm? </div></BLOCKQUOTE>

I just checked and at 72.0 F I get 1.170 mega ohms. I looked at the ET-73 sheet and it reports:

rmax 43.40k
rnom 40.82k
rmin 38.35k

That is a substantial difference.
dave

 

[Bryan Mayland]

Originally posted by Dave S (GeoDave):
I assume the lmremote sketch is to be used with another arduino and an LCD. Looks really cool...that is why i bought it!

The lmremote sketch is actually a transmitter for remote probes back to HeaterMeter. One could definitely add data transmission though to the base and make what you're talking about with relative ease. Adding buttons and stuff to change the configuration from such a device would be a pain though.

 

[Bryan Mayland]

Originally posted by D Peart:
I just checked and at 72.0 F I get 1.170 mega ohms. I looked at the ET-73 sheet and it reports:

rmax 43.40k
rnom 40.82k
rmin 38.35k

That is a substantial difference.

Yeah it sure is. From my calculations based on that, 72F is 1015 (out of 1023) on the ADC. I'm wondering if there's enough error in the single-precision floats, the fixed resistor, and the probe itself to cause a reading of -22F.

Now that I look at it, it doesn't look like a tremendous difference. I'm guessing the problem is that that 1015 is 4.96V, which may be too close to the 5V reference voltage to get an accurate reading?