Title: How to find the problem?[sparkybg's HAKKO classic and T12/T1
Post by: Ryan111 on July 25, 2016, 07:01:24 pm
Post by: Ryan111 on July 25, 2016, 07:01:24 pm
Hi fellas
About a year ago, I started to make a soldering iron based on Sparky's classic soldering iron. but unfortunately after about 3 month, I gave it up because I got busy. now I just started it again. I did everything and everything is working very well save one part. thermocouple and Op-Amp! I just have problem with this part. this is a picture of my board:
This picture shows the +input of Op-Amp:
This picture shows the -input of Op-Amp:
And this picture shows the output of Op-Amp:
The problem is that the output of thermocouple isn't correct. e.g. I measured +&-input and output of the Op-Amp and those green and black wires that are the output of the handpiece's cable and are +&- of the thermocouple. I measured all of these due to GND and the result was this:
Green wire: 0.333v
black wire : 0v
the +input of the Op-Amp: 0.275v
the -input of the Op-Amp: 0.011v
the output of the Op-Amp: 3.2v
The supply is 3.3v. as you can see the result isn't correct. What's the problem in your opinion? please feel free to ask any question.
Another question, How can I find the problem? I just have a VC9805 Digital Multimeter (http://http://www.ebay.com/itm/VC9805-Digital-Multimeter-C-F-Inductance-Capacitance-Resistance-Thermometer-Ohm-/321664459835). I really stock. I attached the schematic+two layers of the PCB.
About a year ago, I started to make a soldering iron based on Sparky's classic soldering iron. but unfortunately after about 3 month, I gave it up because I got busy. now I just started it again. I did everything and everything is working very well save one part. thermocouple and Op-Amp! I just have problem with this part. this is a picture of my board:
This picture shows the +input of Op-Amp:
This picture shows the -input of Op-Amp:
And this picture shows the output of Op-Amp:
The problem is that the output of thermocouple isn't correct. e.g. I measured +&-input and output of the Op-Amp and those green and black wires that are the output of the handpiece's cable and are +&- of the thermocouple. I measured all of these due to GND and the result was this:
Green wire: 0.333v
black wire : 0v
the +input of the Op-Amp: 0.275v
the -input of the Op-Amp: 0.011v
the output of the Op-Amp: 3.2v
The supply is 3.3v. as you can see the result isn't correct. What's the problem in your opinion? please feel free to ask any question.
Another question, How can I find the problem? I just have a VC9805 Digital Multimeter (http://http://www.ebay.com/itm/VC9805-Digital-Multimeter-C-F-Inductance-Capacitance-Resistance-Thermometer-Ohm-/321664459835). I really stock. I attached the schematic+two layers of the PCB.
Title: Re: How to find the problem?[sparkybg's HAKKO classic and T1
Post by: sparkybg on July 25, 2016, 07:42:52 pm
Post by: sparkybg on July 25, 2016, 07:42:52 pm
From what you measured, the op-amp behaves exactly how it should. The input at the + of the opamp should be millivolts if thermocouple is attached there.
Title: Re: How to find the problem?[sparkybg's HAKKO classic and T1
Post by: Ryan111 on August 22, 2016, 06:12:01 am
Post by: Ryan111 on August 22, 2016, 06:12:01 am
[quote author="sparkybg"]From what you measured, the op-amp behaves exactly how it should. The input at the + of the opamp should be millivolts if thermocouple is attached there.[/quote]
Hi sparkybg
Thanks for reply
I have a question
Why these thermocouples don't have any "Cold-Junction Compensation"? I think the problem is that my circuit doesn't have any cold junction.
Hi sparkybg
Thanks for reply
I have a question
Why these thermocouples don't have any "Cold-Junction Compensation"? I think the problem is that my circuit doesn't have any cold junction.
Title: Re: How to find the problem?[sparkybg's HAKKO classic and T1
Post by: sparkybg on August 22, 2016, 09:03:25 am
Post by: sparkybg on August 22, 2016, 09:03:25 am
Cold junction is fixed at 22 (or 23, I don't remember) degrees Celsius. The compensation is done in firmware and is not your problem. Maximum deviation you can get is 22 degrees Celsius. You have general electrical problem somewhere.
Title: Re: How to find the problem?[sparkybg's HAKKO classic and T1
Post by: Ryan111 on August 25, 2016, 08:32:19 pm
Post by: Ryan111 on August 25, 2016, 08:32:19 pm
I just did four experiments/tests.
1.
I applied heat by a lighted match to the tip and it showed at output 1.7mV and
it went down after several second.
http://img4.uplood.fr/free/joad_20160825_174651.jpg (http://img4.uplood.fr/free/joad_20160825_174651.jpg)
2.
Again I inserted the tip into the handle and again applied the heat by match and
I got the same result like the first experiment/test.
http://img4.uplood.fr/free/z6ll_20160825_175032.jpg (http://img4.uplood.fr/free/z6ll_20160825_175032.jpg)
3.
again I soldered the handle to my controller board and didn't turn it on and applied
the heat but didn't get any result. just 0V! just like this:
http://img4.uplood.fr/free/lnva_20160825_185403.jpg (http://img4.uplood.fr/free/lnva_20160825_185403.jpg)
4.
I plugged in the circuit and measured the two lead of the handle and found out there
was 334mV. ok, I applied the heat and measured the voltage just like above and the result was 335mV and it went up to 336 after around 20 second and after a minute it went up to 337. no change again!
it's interesting to me. instead of going down, it goes up!
1.
I applied heat by a lighted match to the tip and it showed at output 1.7mV and
it went down after several second.
http://img4.uplood.fr/free/joad_20160825_174651.jpg (http://img4.uplood.fr/free/joad_20160825_174651.jpg)
2.
Again I inserted the tip into the handle and again applied the heat by match and
I got the same result like the first experiment/test.
http://img4.uplood.fr/free/z6ll_20160825_175032.jpg (http://img4.uplood.fr/free/z6ll_20160825_175032.jpg)
3.
again I soldered the handle to my controller board and didn't turn it on and applied
the heat but didn't get any result. just 0V! just like this:
http://img4.uplood.fr/free/lnva_20160825_185403.jpg (http://img4.uplood.fr/free/lnva_20160825_185403.jpg)
4.
I plugged in the circuit and measured the two lead of the handle and found out there
was 334mV. ok, I applied the heat and measured the voltage just like above and the result was 335mV and it went up to 336 after around 20 second and after a minute it went up to 337. no change again!
it's interesting to me. instead of going down, it goes up!
Title: Re: How to find the problem?[sparkybg's HAKKO classic and T1
Post by: sparkybg on August 25, 2016, 09:49:43 pm
Post by: sparkybg on August 25, 2016, 09:49:43 pm
What is the resistance between the terminals of your tip you are measuring?
Title: Re: How to find the problem?[sparkybg's HAKKO classic and T1
Post by: Ryan111 on August 26, 2016, 07:43:43 am
Post by: Ryan111 on August 26, 2016, 07:43:43 am
[quote author="sparkybg"]What is the resistance between the terminals of your tip you are measuring?[/quote]
It's around 8.7ohm while the handle is soldered on the board but I think if I un-solder the handle, the resistance would be this amount.
I did two tests/experiments again:
1. I desoldered the handle(its terminals) from the board and plugged in the board and measured the voltage of the pads that I solder the terminals of the handle on it and it was 320mV.
2. Again I soldered the terminals but this time in reverse direction(the green wire to GND and black to the +Heater unlike earlier that I soldered the green terminal to the +Heater and the black terminal to the GND) and everything was ok but the output unlike earlier is negative. e.g. instead of showing +1.7mV it showed -1.7mV.
It's around 8.7ohm while the handle is soldered on the board but I think if I un-solder the handle, the resistance would be this amount.
I did two tests/experiments again:
1. I desoldered the handle(its terminals) from the board and plugged in the board and measured the voltage of the pads that I solder the terminals of the handle on it and it was 320mV.
2. Again I soldered the terminals but this time in reverse direction(the green wire to GND and black to the +Heater unlike earlier that I soldered the green terminal to the +Heater and the black terminal to the GND) and everything was ok but the output unlike earlier is negative. e.g. instead of showing +1.7mV it showed -1.7mV.