After some good working weeks, I think that the IC1 (TLV2741) has gone to the “big ol’ junkyard in the sky”…
My VM110 is used to take the temperature from a little melting-oven and switches the oven with a solid state relais. So far…it worked for about 2 months… Yesterday the VM110 told my software a non-varying temp of about 5°C. The oven heated, but my software did not recognize. So I had to stop that melting process to fix the problem… :-((
I looked about the Temperature-controller, but it delivered the right voltage. I think, that the IC1 is “in the bobo”.
Where can I buy this IC? I did not find it in Germany?
Strange that the Op-Amp has failed.
You were lucky not to overheat the melting oven…
BTW: The operation amplifier IC1 is of type TLV274 (on the IC seems to read TLV274I).
The TLV274 is quite common op-amp and you may find it easily from Germany too…
The exact type for plastic DIP package is now TLV274IN.
Datasheet: focus.ti.com/lit/ds/symlink/tlv274.pdf
it was really last second…
My temp-controller is a Type J and is for using up to 750°C.
After I switched off the oven, I took my external Temp-Controller and had a temp of nearly 720°C in there… I recognized just in the right time…
Thank you for the Data sheet… I had a second problem as well, because of the noise. I thought about a little capacitor of 220 µF to fix the unsteady measurement…
I have to solder it at Pin 1 or 7 …is that right??
To reduce the noise you may connect a capacitor from pin 3 or from pin 5 to GND.
Do not connect capacitor to pin 1 or 7. Operation amplifier becomes unstable if a capacitor is directly coupled from its output to GND. See the TLV274 data sheet on page 12, chapter " Driving a capacitive load".
There is said:
" … for capacitive loads of greater than 10 pF, it is recommended that a resistor be placed in series with the output of the amplifier…"
If you connect 220uF from pin 3 or 5 to GND the time constant will be (due to R6, R7) 100k x 220uF = 22 seconds. This means that you have more than one minute delay until you get valid temperature reading after connection the K8055 on. I think lower capacitor value (1 to 10uF) will do the job too.
I had not seen this passage …uuups…