Hi,
I design a new extruder control PCB. It has AD595A thermocouple ic and a tip122 transistor for driving the heather with PWM.
It works but I saw that when the PWM starts there became a lot of noise with my temperature readings. If it does not active my readings are fine.

Is there a way to solve this issue?

Regards,
Nuri Erginer

... filtering the noise with caps or RC-networks or have a better look on the GND-arrangements ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I use 100nf cap between analog 0 and GND but it did not solve the problem

I found that the AD595 is very sensitive to supply rail noise, so if you get the 5V from a switch mode PSU you will need to filter it. Details here: [hydraraptor.blogspot.com]

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[www.hydraraptor.blogspot.com]

I will try the same solution to night nophead

I will inform you the results

Thanks alot

Here is the result I use 1 k resistor and 25uf cap. It is still noisy while the PWM is active. As you see when it is not active there is a smooth reading. PID is also working on arduino

Do I need bigger cap?

Regards,
Nuri Erginer

It looks like a ground problem to me. You need to route the ground current from the heater so that it does not generate voltage drops in the ground path between the AD595A and the Arduino ground pin.

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[www.hydraraptor.blogspot.com]

... make the Ground-connections shorter and thicker (resolder GND-trays) and use a smaller cap, not bigger ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Nophead you are the best!!
I just solder a wire from the heater transistor ground to the main ground Above is the result.

Viktor I will try a smaller cap thanks.

Edited 1 time(s). Last edit at 07/02/2010 06:45PM by nerginer.