Homebrew PCBs

Rob,

The link that I purchased from is inactive, but this is the same unit:

http://www.ebay.com/itm/12V-24V-Digital-Temperature-Controller-Board-Thermostat-K-Thermocouple-Probe-/182145097075?var=&hash=item2a68b19d73:m:m-d0W2aqMiE7N3CDhyhvxFwIT 
has the thermocouple in a bolt, but I also bought several pieces of the 
bead type in case I need to have the thermocouple in contact with the 
roller. The one I bought operates from 12 VDC. A small wall wart would 
do, or as in my case, I bought a 110VAC to 12 VDC converter module from 
ebay. Very little current is needed. One like this would do: 
http://www.ebay.com/itm/85V-265V-to-6V-12VDC-6W-9W-2-3-x3W-900ma-12V-LED-Driver-Power-Supply-/251651394313?hash=item3a97978b09:g:CPcAAOSw1DtXI3rk 


Harvey
On 12/30/2016 12:28 PM, Rob roomberg@... [Homebrew_PCBs] wrote:
>
>
> 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
>>>>
>>>> ------------------------------------------------------------------------
>>>>
>>>
>>
>
>