True wireless thermometer

[setitandforgetitsmoker]

one end is in the pillar block on the opposite end of the motor the other end of the shaft is mounted on a plate with the motor which is is two brackets angled from the fixed part of pit the brackets are carrying the weight of the racks on one end other end can be left as is.

 

[kookie]

I get what setitandforgetitsmoker is saying. I think this is basicly what he is getting at. Going off of Jet deck's pic of his pit. On the side facing you, extend the shaft and move the bearing out and mount on a bracket that is mounted to the up rights and not the top tube. Now you can mount a plate or bracket on to the shaft itself to mount the transmiter on it and run the probe wire down the shaft and tie it to it and then you can use the probe on the shelves. Make sure to leave some slack on the wire. This way the transmitter is outside the pit housing and it rotates with the shaft. I think this should work.

Kookie

 

[richtee]

Ahhh. Small hole in the side. 'K.

 

[setitandforgetitsmoker]

ritchee tried to upload a small drawing and it would not let me but kookie was close to what i was trying to get at. i would also look into a temp controller of some sorts with multiple thermocouple inputs it would not be used for temp control but would be a alot easier than messing with multiple units and i have found thermocouples on pid units to be more accurate that remote temp probes. hope this helps thank you

 

[richtee]

I guess you could also break the rings and attach probes to each section, "Multiplexing" your readings from multipe probes to a single Tx. Dunno the stabilization time for the Tx to get a reliable reading, but it's not like the carosel is spinning 30 RPM or anything..Hmm @ 1 rpm 3 probes, just shy of 1/3 min connected each, maybe 18 seconds.

As far as contact resistance, with a phospor-bronze brush, it would be minimal, but I do agree this would be the sticking point of this arrangement.

 

[minichef]

Let me chime in about the sensor theory. You can have 3 standard types of sensor, thermocouple, RTD and thermistor. The thermocouple as mentioned is dissimiliar metals that produce a voltage (talking milivolts here) not resistance depending upon the temperature they are placed. With thermocouples you need to worry about the junctions you create after the probe junction, this causes error in your temp reading. The error will depend upon the temperature difference between the two points. If the only other junction is at the temp control no need to worry as the controls should have compensation built in to eliminate this error.
RTD and thermistor are resistive sensors, as the temp changes the resistance goes up or down. I would opt for RTD or thermistor sensor for the slip ring idea, less sensitive and easier to cancel error.

Just my thought,

 

[richtee]

And most digi's use the RTD/thermistors I believe. I honestly think this will work. Keeping the contacts outside the smoker proper will increase it's reliability as well... Per Setit-.

 

[jet_deck]

This is a block of Calsil. I cut a piece of it about the size of a kids shoebox, then cut it in half long ways, and hollowed out an area in each half, so that the Tx portion of the unit would rest in it, protected from the heat, and just let the wire and probe run out of the heat protected "box"
To test, last night, put the oven on 450*, and put the probe in the hollowed out block and left it for 30 min, it was not an accurate test, because the "L" shaped probe was larger than the hollow area, and i had about 1/8" gap between the two halves with the probe in between. After 30 min, the probe read only 130. I figure on a hot sunny day, beside the pit the Tx would be almost this hot anyway. Will try to test again tonight.

 

[richtee]

Like I mentioned... a brisket or stubborn butt'll go durn near 20 hours... maybe with multiple units you can swap out during a mop...

 

[jet_deck]

I hollowed out the Calcil properly for the probe to fit in. Oven at 400*, probe showed 130* and climbing after only 20 min. I guess i could back the oven down to 250 and see what happens