It's quite possible that when the output switches that noise gets picked up on the thermal-couple. You could shield the line from the thermal-couple, or you might try a .1ufd in parallel with R11. This will make the op amp less responsive to high frequency noise.I got it working! I used the LT 1635, checked the pinouts, talked with the electrical engineering professor who recommended the part, plugged it in with the same resistor values and voila! Maintained 33.1 degrees Celsius all night, and super fast response from the thermistor if I spray it with key board air can or hit it with a heat gun. Super happy!
One last question and comment on this. It seems to have a fair amount of noise as you can see from the next picture. It doesn't seem to really effect the performance but if it's an easy fix, I would like to fix it. But I'm also of the mindset that if it aint broke, don't fix it. It seems to change when I move the power leads to the peltier and also when I move the leads for the thermistor. Should I wrap wires with something and ground them? Or should I not worry about it since it does work.
Lastly I just wanted to thank everyone that has responded to my questions and made suggestions. This was my first time posting in this forum and it was nice to not get condescending, belittling comments. I have seen that a lot in other forums with people who are not well educated or informed on what they are asking about, and it was nice to just get knowledgeable well-informed answers.
Yes.Where on the 555 should I add the big capacitor? between pin7 (V+) and ground?
I'm guessing you added the cap in parallel with the resistor?????
That's what I thought as well. Still a little noisy considering it has a .01 and 1k feeding it. Now I'm wondering about the other trace only being 1/2 volt.The green trace is the opamp output to pin 5.
Looks like your ready to go. Matbe you could put it in the fridge and make sure the temperature holds, but I think it should.Yeah I added the capacitor in parallel with the 1k resistor, it's a .1uF capacitor though not a .01. I also added a large 33uF capacitor on the V+ pin for the timer. Maybe I misspoke earlier but the green wave is not pin5 on the 555. The green wave is pin6 or threshold on the 555 which also has a .1uF to ground.
Do you see any problems with this, the way its set up now? I do plan on shielding the wires once I design and mill a board for it, which I'm confident will reduce the noise.
by Duane Benson
by Duane Benson
by Duane Benson
by Duane Benson