Homebrew PCBs

Which one?

RE:
  approach in favor of a purchased controller with a type K 
thermocouple. This cost USD 8.99 on e-bay from China. I have not yet put 
it into service because of the melted gears.
On 12/30/2016 01:04 PM, Harvey Altstadter hrconsult@... 
[Homebrew_PCBs] wrote:
>
> Rob,
>
> The Passive IR gun type thermometer is only used for making initial 
> measurements, not for a feedback type control system. The PIR 
> thermometers have a distance to spot ratio. The Sparkfun unit 
> mentioned previously has a ratio of 12:1, meaning that at a distance 
> of 12 inches, the detector is reading the temperature in a 1 inch 
> circle. The thermistor and thermocouple approaches measure the 
> temperature at the point of contact, a much smaller area. With the PIR 
> thermometer, I could not read the rollers in my laminator at all 
> because they are surrounded by the heater structure except where the 
> paper path is. Those slots were too narrow for either of my PIR 
> thermometers. Another issue with the PIR thermometers, usually ignored 
> in the advertising, is that the emissivity of the surface being 
> measured has an effect on the readings. In plain English, this means 
> that two surfaces made with different materials could be at the same 
> temperature, but give different readings on the PIR. Surfaces with 
> multiple materials, if they fall in the reading area, will give a 
> reading that integrates the two readings, rather than providing a true 
> reading.
>
> I tried to use the RepRap thermistor in my original control circuit, 
> and found that while it works, the resistance vs temperature curve is 
> very flat near 200�C, making the controller action sluggish. I 
> abandoned the thermistor approach in favor of a purchased controller 
> with a type K thermocouple. This cost USD 8.99 on e-bay from China. I 
> have not yet put it into service because of the melted gears.
>
> As far as the location of the thermistor in the Royal laminator, this 
> is a mechanically simple location to use, and if we think about it, we 
> understand that there is no need to measure the actual temperature of 
> the rollers, at least in the original application of the laminator. As 
> long as the temperature drop between the heater and the roller is 
> known, the system can be calibrated for proper operation with the 
> thermistor mounted on the heater structure. The Harbor Freight unit 
> uses mechanical thermoswitches mounted on the heater structure.
>
> In our toner transfer case, it is not clear (at least to me) that 
> measuring at the heater is sufficient. Since we are putting single or 
> double sided thermally conductive boards of different sizes through 
> the rollers, I am not sure that the temperature drop is sufficiently 
> constant that we don't have to measure the temperature at the roller. 
> I was experimenting with this when my gears turned to mush.
>
> Harvey
>
>
> On 12/30/2016 8:24 AM, Rob roomberg@... [Homebrew_PCBs] wrote:
>>
>> Where do you mount this device without destroying it and melting 
>> solder on the supporting
>> chips in the toner work PCB heating  path?
>> How far do you mount it from the desired location where you are 
>> pinpointing temperature measurment?
>>
>>
>>
>>
>> While I would agree that a Non contact passive infrared rules..........
>>
>> I would like to some day compare the accuracy of the $20 passive 
>> infrared with
>> the K type thermocouple and a simple thermistor.
>>
>> Noting that my ROYAL laminator heater control was done by a contact 
>> thermistor clamped to the aluminum heat shield
>> behind a roller heater.
>>
>>
>> When I was looking into thermocouple circuits and supporting chips it 
>> looked like about $15 gets that done
>> and
>> 5 cents buys a thermistor....
>> or maybe a dollar if it has wires.
>>
>> New Reprap NTC 3950 Thermistor 100K with 1 Meter wire for 3D Printer TSCA
>>
>>
>> On 12/30/2016 09:02 AM, AncelB mosaicmerc@... [Homebrew_PCBs] 
>> wrote:
>>>
>>> Non contact passive infrared rules...
>>> Get one of these...
>>> https://www.sparkfun.com/products/9570
>>>
>>> ------------------------------------------------------------------------
>>>
>>
>
>