Potentiometer working weird with SSR

Other Hardware General Electronics
1

I have a pot connected to the Arduino Uno and a thermocouple shield which you can find out more at https://www.tindie.com/products/artisanaltech/tc4-coffee-roaster-shield-tc4-plus/.

The pot seems to be sending the right values to the software because I get 0 - 100% according to the knob position. No issues there and by the way, it's controlling a heater.

Where I have issues is the Arduino sending signals to the SSR. At slightly above 50%, somewhere before 1 o'clock, the heater is running at full power as can be seen from the ammeter reading. Then when I go further, it drops some before rising on a more gradual curve until it stops at 5 o'clock.

2

What are the signals, exactly? How do you derive the signals? How long a time are the signals present?

3

I believe the output (OT1) on the TC4+ shield drives the SSR with pulses since the Arduino sketch had control method configured as ICC.

4

An electric heater has such a SLOW response that you should only control it with an OFF-ON lever to the SSR.

5

How is that pot connected ?

6

To 5v, Gnd and A0.

7

It's an open coil heater array.

8

So, how many seconds does it take to change temperature?

9

Extremely fast. Within seconds. Anyway, after some questions from an oversea friend, the problem might be my Arduino board. I've tried with two pots connected to the 5v pin and can't get more than 3v out of it. Not at the same time of course.

10

Then, after initial heat, turn it on/off t 1 second intervals for testing. change the intervals until it works as desired.

What does the 5 volt pin show with NO pot connected? Can we guess you are using at least a 10k pot?

11

Please do not cross post.

12

That was indeed about a rotary encoder on the same board. I didn't want to mix the two issues together since one was an analog pot and the rotary encoder was digital.

13

Yes, using a pretty decent quality 10K linear pot. The funny thing is the 5v header is outputting 5v but when connected to a pot, the highest value on the multimeter was 2.8+ with the 10K pot and 2.9+ with a 500K pot before the multimeter said OL.

I get the same thing regardless of whether I'm powering the Uno with my laptop, phone charger or a 12V supply through the DC jack.

14

If the pot is, indeed, the ONLY device connected to the Arduino, then the 5 volt regulator is defective.

15

Is there another regulator besides the one that's beside the DC jack port? I read that the regulator is bypassed when the board is powered by USB and I do get a nice 5v.

16

No, but the regulator is only needed when input is 7 volts or more. The Arduino MUST have 5 volts from somewhere. What voltage are you applying to the DC jack?

17

"I get the same thing regardless of whether I'm powering the Uno with my laptop, phone charger or a 12V supply through the DC jack."

But I've been powering it from my laptop all this while since it's working with a Windows based software too.

18

Just in case anyone has a similar problem, the cause is my (possibly) fake Arduino Uno R3 not being able to supply 5v through a 10K resistance. That's why it dropped to 2.8+ V. With a 100K and 500K pots, I could get the full 5V fine.

19

10 k will draw a tiny current that should not have any influence on regulated voltage.
Is it a maybe a pot of 10 ohm? Usually those have a wound resistor. You can feel that they do not move smoothly when you turn them.
Or did you destroy your regulator by an accidental siortsge?

20

No idea for now, buddy. The Arduino was just lying around for over 2 years gathering dust before I gathered enough funds and willpower to complete the project. It's a pity that it couldn't supply enough to a 10K resistance because I was planning to try it with a rotary encoder too but that's also a 10K device.

As for the pot's resistance, pretty sure it's 10K. Have checked a few times with a multimeter. It's not a cheap pot and feels very nice.