Problem with PID controller

[69daytona]

Built one from instructions here when this started for my Lee pot, it has been working great until today, now it won't keep pot anywhere near set temp.

Anyone have this problem? Could it be just worn out thermocouple?

[bangerjim]

At the ridiculous cheap prices......buy several spare t/c's. Those ones are so cheaply made, they can fail easily and frequently.

Or buy a industrial grade t/c like I use in my designs. They run over $100 or so. But last for....well....forever. Industrial companies do not go low dollar like on here!

Stick it in salt/ice water and see if reads 32F and lower. Salt water with ice in it can get to around 29F or lower under the right conditions.

To test the controller, you would need a MilliVolt source test instrument (t/c simulator) like I use to test functionality with.

bangerjim

[JonB_in_Glencoe]

Have you checked the parameters?
Are they the same now, as before, when it was working?

Yes, it could very well be the T/C

[JeffG]

I've had to replace a thermocouple on mine, was having the same symptoms.

[69daytona]

Bought a couple new TC, turned my pot on with the old one to get it hot enough to get it out of lead switched to the new TC turned pot back on and now it cycles but won't stay on long enough to get the pot hot, acts like the paid control isn't working right.
Have a new pid control on order.

[69daytona]

Went back out and turned it on while resizing a bunch of brass and it came up to temp but then kept on going, hear to turn the temp control down on pot to get it to go down.
still wants to climb way past set temp.

[Norbrat]

Are you sure it's not your SSR? They are known to fail "ON", so the PID might be signalling it to turn off, but it can't.

[Mike W1]

From Auber's Q&A

To check the controller.

a. The first thing to do is to verify the controller is OK. This can be done very easily.
Just use a copper wire to short the terminals for the TC input (e.g connect terminal 4
and 5 for 2342 or 2352; connect terminal 6 and 7 for 1512, and connect terminal 9
and 10 for 2363). The reading of the controller should be about the ambient temperature,
where the controller is located.

If that is the case, the controller is fine. To be 100% sure the controller is fine; check
the parameter setting for the input type. Make sure it is set to K type.

If reading does not show ambient temperature, change all the parameter to the initial
setting listed in the instruction manual. If it still not shows ambient temperature, the
controller is defective.

If “a” passes, go to next step.

b. The next thing to do is to verify the system (the controller and the sensor) is OK.
You need to remove the TC from your installation, connect it directly to the controller
(without extension and connectors). Dip the TC in ice/water mixture (70%: 30%). The
sensor body need to be complete immersed. Read the temperature in 5-10 minutes.
The reading should be close to 0 °C or 32 °F. You can also do this in boiling water.
The reading should be close to 100 °C or 212 °F at sea level. Important, you can not
calibrate the system in the air because some of the sensors may take 30 minutes to
response in the air.

If the system fails to pass “b”, then the TC may be defective.

If the system passed test “a” and “b” then, the problem is the set up.

Disconnect any load from the output of the PID.
Turn unit on, should display "EEEEE" followed by
it's boot up sequence. If the probe is out in the
open air, the display should begin reading the
ambient room temperature. Let the unit sit and
check every so often to see if it turns off. It should
stay on 24/7. If you happen to see it turn off, flip
the switch and turn it back on. If it does not come
up and run through the check right away, it could
be a heat problem with the PID. Also make sure
that your wiring connections are all good.
If the PID unit stays on with no load, try it again
with the pot. If you have an amp clamp, you can
get an idea of the current that the pot is pulling
from the unit. We can work from there, but first
make sure the PID unit stays on with no load.

Temperature sensors -- there are RTD's or
thermocouples. If yours is a K type thermocouple, and
"The brand the OP has says EEEE = 'out of range' ", then
you probably have a loose or intermittent connection
on either the PID on the thermocouple terminals
or somewhere up to the thermocouple junction
itself. Else you could have a thermocouple that is
not rated for 700F. I would recommend you look
at the connections associated with the
thermocouple. Hope this helps.
Also a dirty connection on the power feed to the
PID could make the PID crash due to repeated
voltage collapses when the load is connected.
From Auber's Q&A

4. Can I test a SSR with a multimeter?
4.1) Q: When there is no input for the SSR, I can still measure a live voltage on output of the SSR.
Does that mean the SSR is defective?
A: Not necessarily. The SSR is a semiconductor device that has a leak current. The leakage is
less than in the 10-30 mA range. Larger capacity SSR has higher leakage than the small capacity
SSR. If you measure the output voltage at an open circuit condition, you will get a live voltage
that is the same as the AC input. (This is the typical case when user tests the output with a voltage
tester).That does not necessarily mean the SSR is burned through. However, if there is a load
(more than 10 Watt, such as a heater) on the output, you should not detect any significant voltage
because it is drained by the load.

4.2) Q: When I measured the resistance of the output of SSR, it changed from mega ohm to 1-20 kilo
ohm range when an input trigger is applied. Should it be zero ohm?
A: No. It should not. This is because almost all AC SSR on the market has a zero voltage crossing
detection circuit. It will not turn on (change resistant to zero) unless it detects an AC voltage that is
changing the flow direction (across zero voltage). The zero voltage detection function is for protecting
inductive loads. Without an AC load, the output resistance will never change to zero. It should be
noted that changing the resistance from mega ohm to kilo ohm does not mean the SSR is good. But
It tells you it has not been burned open and is responding to input.

4.3) Q. How to test an AC SSR?
A. The most reliable way is connect the output with a 40W light bulb. If the light bulb responds to
the input trigger, the SSR is fine.

Check for voltage on the control side of the SSR
it should be between 4 and 30 volts DC
Check for voltage on the LINE side of the SSR. this is the wire that goes
to the incoming power (the plug)
As stated above, use a standard household lamp and plug into the outlet
to test if its switching on.

Most of the SSR that I use have a LED indicator light on the to show when they are activated.
Even with the light active, it may still not be switching but it does help on trouble shooting.

[69daytona]

Thanks Mike. I will test it once grandkids leave. If it tests good will use the new one to build a control for mold heater or lube heater.