LinkMeter v2 Homebrew BBQ Controller - Part 1

[Dave S (GeoDave)]

Originally posted by Bryan Mayland:
My IKEAs are working OK at room temperature where they read right on for ~75F but I haven't tested them at grill temperature yet. I kinda want to write a sketch to have it do the "LUA implementation of Levenberg–Marquardt algorithm for a 2-pass (rough estimate, refine) multi-iteration determination off coeffs" from the TODO list.

EDIT: I use the standard 10k resistors.

Yes, standard 10k are fine.

The problem appears when you use the Maverick and IKEA probes at the same time. Electrically speaking they are separate...right? Is there something on the software side that would explain this? Issues is consistent between Linkmeter v3.1 and MiniLink v1.0.

 

[D Peart]

I use the two different Maverick probes at the same time without issue. I just have to make sure I have the proper coefficients loaded on a per probe basis.

dave

Originally posted by Dave S (GeoDave):
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bryan Mayland:
My IKEAs are working OK at room temperature where they read right on for ~75F but I haven't tested them at grill temperature yet. I kinda want to write a sketch to have it do the "LUA implementation of Levenberg–Marquardt algorithm for a 2-pass (rough estimate, refine) multi-iteration determination off coeffs" from the TODO list.

EDIT: I use the standard 10k resistors.

Yes, standard 10k are fine.

The problem appears when you use the Maverick and IKEA probes at the same time. Electrically speaking they are separate...right? Is there something on the software side that would explain this? Issues is consistent between Linkmeter v3.1 and MiniLink v1.0.

I will say that I do like these probes. They are super cheap and seem to work well. They were fine at 225F. </div></BLOCKQUOTE>

 

[Dave S (GeoDave)]

Originally posted by D Peart:
I use the two different Maverick probes at the same time without issue. I just have to make sure I have the proper coefficients loaded on a per probe basis.

dave

Coefficients are set correctly. I will have pit and probe1 Ikea. When I plug Maverick 72 into probe2, maverick is correct but Ikea probes read 300-400F.

 

[Bryan Mayland]

Originally posted by Arwin:
Bryan: can you explain me the difference between using 10k and 50k for the probes? As far as I understood, the fixed resistor should be around the same as the resistor of the probe at 25 degrees C. so that's why I used the 50k, but actually I don't know the influence..

The fixed resistor affects the resolution and effective range of the temperature returned. Here's a graph I did way back when that shows what temperatures can be read with a couple different resistors and probes.

Looking at just the Maverick probe, you can see a 6.8k ohm resistor can measure slightly higher temperatures at the cost of losing some resolution across the entire range. Using the Steinhart calculator, with the IKEA probes and a 50k resistor at 200F, each ADC "tick" is about 1F. If you use a 10k resistor, each ADC point is 0.29F.

 

[Joe Loyd]

Originally posted by D Peart:
When I had my LCD issues I was getting D instead of A as well. I had to swap out to the other diode to get it working.

After that I didn't have any issues with that one. The other two I built still have garbled LCD issues periodically and I have to power toggle them to get it cleaned up. I usually get the issue when I plug in a probe, this action causes the LCD to garble sometimes.

dave

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Joe Loyd:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bryan Mayland:
...
Is it possible you have your D4 and D6 reversed? I'm fairly certain that it wouldn't display anything at all if you did, but 'A' is 100 001 and 'D' is 100 100. As with all these LCD issues I just don't know what to do because it is so random. It is unusual that yours prints D consistently instead of A though. Are your D0-D3 connected? Have you tried with them disconnected?

No, D4 and D6 are correct. I disconnected D0-3 with no change, sill all "D"s.... </div></BLOCKQUOTE> </div></BLOCKQUOTE>

Thanks Dave, which diode did you change, D4?...

 

[Bryan Mayland]

Originally posted by Dave S (GeoDave):
Coefficients are set correctly. I will have pit and probe1 Ikea. When I plug Maverick 72 into probe2, maverick is correct but Ikea probes read 300-400F.

They are separate but all share the same ground connection (the sheathing of the cable). I just tried IKEA probes and maverick probes at the same time and I don't have any strange numbers.... until I touch the wires together. When their cables touch, the maverick probe gets low numbers and the IKEA probe goes offline. So yeah there's definitely a problem with them.

 

[D Peart]

D2, it should be connected between pin 13 of the shift register and pin 6 of the LCD

dave

Originally posted by Joe Loyd:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
When I had my LCD issues I was getting D instead of A as well. I had to swap out to the other diode to get it working.

After that I didn't have any issues with that one. The other two I built still have garbled LCD issues periodically and I have to power toggle them to get it cleaned up. I usually get the issue when I plug in a probe, this action causes the LCD to garble sometimes.

dave

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Joe Loyd:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bryan Mayland:
...
Is it possible you have your D4 and D6 reversed? I'm fairly certain that it wouldn't display anything at all if you did, but 'A' is 100 001 and 'D' is 100 100. As with all these LCD issues I just don't know what to do because it is so random. It is unusual that yours prints D consistently instead of A though. Are your D0-D3 connected? Have you tried with them disconnected?

No, D4 and D6 are correct. I disconnected D0-3 with no change, sill all "D"s.... </div></BLOCKQUOTE> </div></BLOCKQUOTE>

Thanks Dave, which diode did you change, D4?... </div></BLOCKQUOTE>

 

[Bryan Mayland]

Yup, I've opened up the Fantast unit and inside the circuit that measures the temperature looks like this, with the "44k" resistor being the probe:


Every 5 seconds, the bottom wire gets a burst of ~1.3kHz 1.5V pulses followed by a sawtooth wave of 0.5V to 1V. The top one starts with the saw wave then goes to the square wave. If no probe is plugged in, only the bottom one does the 1.5V square wave and nothing else. The top just goes high for a short time.

So yeah completely different circuit and probes are wired backward wrt the Maverick probes, with the tip being the cable exterior.

 

[Arwin]

Alright, so that's why I didn't notice anything strange; I just dont't have any other probes than Ikea

and now I think of it, I had problems with touching the probes and changed the wiring. Altough I was thinking that I had done something wrong, but now it becomes clear that I had not but the probes are wired backwards...

 

[Joe Loyd]

Originally posted by D Peart:
D2, it should be connected between pin 13 of the shift register and pin 6 of the LCD

...

Swapped it for a 1N5817 but that resulted in a blank instead of the "D"...Hmm, well it's a good excuse to order a DSO, not sure how much more I can do with a simple o-meter...

 

[D Peart]

Joe,
It will go blank if you installed it backwards. I'd double check that first.

Though any reason for a DSO is a good one

dave

Originally posted by Joe Loyd:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
D2, it should be connected between pin 13 of the shift register and pin 6 of the LCD

...

Swapped it for a 1N5817 but that resulted in a blank instead of the "D"...Hmm, well it's a good excuse to order a DSO, not sure how much more I can do with a simple o-meter... </div></BLOCKQUOTE>

 

[Joe Loyd]

Originally posted by D Peart:
Joe,
It will go blank if you installed it backwards. I'd double check that first.

Though any reason for a DSO is a good one

dave

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Joe Loyd:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
D2, it should be connected between pin 13 of the shift register and pin 6 of the LCD

...

Swapped it for a 1N5817 but that resulted in a blank instead of the "D"...Hmm, well it's a good excuse to order a DSO, not sure how much more I can do with a simple o-meter... </div></BLOCKQUOTE> </div></BLOCKQUOTE>

Thanks, confirmed it's in the right way

 

[Dave S (GeoDave)]

It has just occurred to me that I have WAY too many Linkmeter compatible routers and parts. My wife is starting to look at me like I am insane. I would feel better if they were getting some use.

So I am selling the following:

1. WRT54G v3...make me an offer. I will throw in a partially populated MiniLink v1.0 beta board. The board has enough parts on it to fully function. The router has never been opened so you will need to cut holes for the probes and blower mount. You will also need to wire the 12v line coming from the routers power plug.

2. WRT54GL v1.1...make me an offer. This one comes with a fully populated v3.1 board. I have not cut holes for the LCD, button, temperature probes, or blower fan plug.

If anyone is interested, send me an e-mail david.shaeffer@gmail.com. You pay shipping from Seattle.

My ultimate goal is to use my WRT54GS v1.1 with a MiniLink v1.1 board as my Linkmeter.

 

[Kyle Christensen]

Quick question. For some reason (I don't recall if it did this before) my linkmeter reads 257F without a pit probe attached. Is that normal?

Now I realize I'd never not have a pit probe attached, but I thought it was a little strange.

 

[D Peart]

If your pit probe is not attached it should say no pit probe.

With it reading 257F, that sounds like you have a short for that probe. Check with an ohm meter and read the resistance of the pin header for that probe.

It should read open, but I suspect you have a bridge short or something.

dave

Originally posted by Kyle Christensen:
Quick question. For some reason (I don't recall if it did this before) my linkmeter reads 257F without a pit probe attached. Is that normal?

Now I realize I'd never not have a pit probe attached, but I thought it was a little strange.

 

[Joe Loyd]

Originally posted by Joe Loyd:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
Joe,
It will go blank if you installed it backwards. I'd double check that first.

Though any reason for a DSO is a good one

dave

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Joe Loyd:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
D2, it should be connected between pin 13 of the shift register and pin 6 of the LCD

...

Swapped it for a 1N5817 but that resulted in a blank instead of the "D"...Hmm, well it's a good excuse to order a DSO, not sure how much more I can do with a simple o-meter... </div></BLOCKQUOTE> </div></BLOCKQUOTE>

Thanks, confirmed it's in the right way </div></BLOCKQUOTE>

Ah, finally success on the third try!...I found a bad trace, from the AT to probe #2. Not actually the cause of my LCD woes but where's one there's probably more. So I stripped it and swapped the parts over to last of my three Dorkbot boards. And (drum roll)...nothing. Yep, this one, like my first, didn't even display "D"s, just a blank screen... Then I remembered that I still had the replacement D2 mounted so I swapped it back to the 1N4001 and was rewarded with a "No Pit Probe Installed"... Now, on to the button board...Thanks again to D Peart & Brian for the help!....

 

[Kyle Christensen]

Originally posted by D Peart:
If your pit probe is not attached it should say no pit probe.

With it reading 257F, that sounds like you have a short for that probe. Check with an ohm meter and read the resistance of the pin header for that probe.

It should read open, but I suspect you have a bridge short or something.

dave

Apparently I have something goofy with my probe wiring. So when I wired these up, I grounded all 3 of my probe jacks together, then connected a 10k resistor to the ground and the top pin of the pit probe jack. The other top pins of the other probes are unused. Then I have each bottom pin running to the HM board.

Photo: http://dl.dropbox.com/u/119708/probejacks.jpg

The probe reads fine when I plug it in, but when it's unplugged it doesn't read "No Pit Probe". If I unplug the probe connector from the LM board, it reads "No Pit Probe". What did I goof up?

 

[Justin-TX]

First of all I have been following this thread for awhile now and I would like to thank all the contributors. There is just an overwhelming wealth of knowledge here.

So I just ordered the v3.2 boards and all the components and they should be here within a few days. My first question is, is it normal for the voltage from the power supply to be around 14v? I just don't want to damage the heat meter board by feeding it to much voltage.

Secondly, I was wondering if some people would be so kind as to post some pictures of how they have mounted their fans. Or maybe just point me in the right direction if this has been posted already. I did see looking back through past pages that Auber instruments sells a nice fan with a mounting system but $50 plus shipping seems kinda steep just for the fan.

Thanks
Justin

 

[D Peart]

Kyle,
Are you using the v3.1 board? It will have the 10k pullup resistors on it.

Can not use the 10k resistor you show on the probes as it will mess everything up. Each probe needs its own dedicated 10k resistor connected to VDD.

dave

Originally posted by Kyle Christensen:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by D Peart:
If your pit probe is not attached it should say no pit probe.

With it reading 257F, that sounds like you have a short for that probe. Check with an ohm meter and read the resistance of the pin header for that probe.

It should read open, but I suspect you have a bridge short or something.

dave

Apparently I have something goofy with my probe wiring. So when I wired these up, I grounded all 3 of my probe jacks together, then connected a 10k resistor to the ground and the top pin of the pit probe jack. The other top pins of the other probes are unused. Then I have each bottom pin running to the HM board.

Photo: http://dl.dropbox.com/u/119708/probejacks.jpg

The probe reads fine when I plug it in, but when it's unplugged it doesn't read "No Pit Probe". If I unplug the probe connector from the LM board, it reads "No Pit Probe". What did I goof up? </div></BLOCKQUOTE>

 

[Bryan Mayland]

Originally posted by Kyle Christensen:
Apparently I have something goofy with my probe wiring. So when I wired these up, I grounded all 3 of my probe jacks together, then connected a 10k resistor to the ground and the top pin of the pit probe jack. The other top pins of the other probes are unused. Then I have each bottom pin running to the HM board.

Photo: http://dl.dropbox.com/u/119708/probejacks.jpg

The probe reads fine when I plug it in, but when it's unplugged it doesn't read "No Pit Probe". If I unplug the probe connector from the LM board, it reads "No Pit Probe". What did I goof up?

Ah yes. That is a really pretty piece of wiring you did there. Unfortunately it makes a fixed voltage divider (assuming your orange wire has the 10k resistor in series as well). The extra pin on the jacks is contacted when there is no probe inserted in them so what you end up with is
ATmega -> 10k resistor -> x -> 10k resistor -> Ground

We read from where the X is so when no probe is in it, you get a fixed 2.5V at the ADC. This is advantageous in that you can put a thermistor on there and have it read ambient temperature (if your coefficients are set for it). I'd not put it on the Pit probe jack though.

But yeah if you take that off (assuming you have the other 10k resistors in place) you should be good to go.