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Old 2nd Mar 2021, 10:10 pm   #1
TonyT53
Diode
 
Join Date: Mar 2021
Location: Reading, Berkshire, UK.
Posts: 2
Default Weller DS801 and DS3105 temperature sensor

I have a DS801D de-soldering station with the DS3105 iron that I acquired many years ago and only tested recently finding that the temperature control of the unit was not working as expected.

Thanks to the information in the Jul 2017 post 'Weller DS801 temperature setting' from Chriswood1900 on this forum I found that the DS801 functions as I would expect when I substituted a 100R pot in place of the temperature sensor in the iron (labelled '22R PTC heat sensor' in the schematic).
The DS801 appeared to be working as intended (by monitoring the final op amp output) with the 100R pot varying from around 22R to 55R, corresponding to the temperature control being set at 50C and 450C respectively.

The temperature sensor in the iron was tested and found to have a resistance of around 1R5 at 20C and around 25R at 300C. I therefore assume that the sensor is faulty or the iron is not the correct one for the DS801.

I've not been able to locate a part number for the temperature sensor (pink wires attached in the picture) and I would appreciate any information or where I could get a replacement.

Many Thanks
Tony
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Old 3rd Mar 2021, 3:02 pm   #2
Electronpusher0
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Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,287
Default Re: Weller DS801 and DS3105 temperature sensor

From the resistance values you give for the controller at 50 and 450C it seems that the controller is designed for a sensor element that has the same resistance temperature characteristic as the EC1201P iron ie
0 deg C - 20Ω
200 deg C - 36.5Ω
400 deg C - 51.8Ω

The values you get for the iron do seem low. Do check to make sure that the sensor in the iron is not actually a Thermocoule.

The reason I say this is that I tried to plot the temperature / resistance curve of an iron assuming that it was a thermistor by using a dvm to measure the resitance and got very similar readings to you only to discover that it was actually a thermocouple and the mV output was causing the dvm to give a varying value with temperature that was unrelated to the resistance.

Peter
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Old 3rd Mar 2021, 9:03 pm   #3
TonyT53
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Join Date: Mar 2021
Location: Reading, Berkshire, UK.
Posts: 2
Default Re: Weller DS801 and DS3105 temperature sensor

Hi Peter,

Thanks for the quick reply.
I thought it was highly likely that the iron was paired with the DS801 but from what you say it may not be.
I was hoping someone would recognise the model DS3105 iron and the picture of the sensor to confirm what I had.
I'll check to see if the sensor is a thermocouple.

Tony
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