Board locks up or resets

[W0VHA]

I've got a CAI WC board that likes to lock up or reset to defaults every now and again.  I'm pretty sure it's due to transients on its' inputs, but I'm not sure what to do about it.
 
It seems to go wonky when the chiller that the board is monitoring starts up or shuts down, so I imagine voltage is being induced into the temp sensors. (I haven't put a scope on it yet, though)
 
Any sugguestions on how to keep this from happening? (cabling is shielded, >8" from power, and crosses power at right angles)
 

 

[CAI_Support]

Which version firmware do you have on that board?  We heard two people told us that before on older firmware. But have not heard that on the later firmware.
Please check to make sure power supply is providing enough power.  Not stable power sometimes causes the CPU executing error.  In the later firmware, we added space to guard configuration storage in our code, so that even CPU running to a wrong place, it will not cause problem.

 

[W0VHA]

Firmware is 3.02.17a.  Power supply is a 10AMP,9vdc industrial power supply, that's supplying two other WC's without problems (I really think it's a noise issue on a data line, I just haven't been able to narrow it down)

 

[CAI_Support]

3.02.17a firmware should be a stable one.  Your power supply surely sounds good.  If you have two other boards without problem, could you please send this one back to our office, so that we can test out for you?  We want to see them so that if that is a problem then we can fix it.

 

[W0VHA]

Boards are OK (I've swapped boards with a known good one, and the problem follows).

 

[CAI_Support]

If boards are okay, then send one to us to see if a different firmware working better.

 

[W0VHA]

Problem solved.  Transients were the problem, and putting surge protection in the lines between sensors/IO and the board has solved the problem.
 

 
Methinks the WC boards might need some better IO clamping/isolation.  Definately something to look at for WC32 if/when it comes out.
 
 

 

[CAI_Support]

Thanks for letting us know.  What kind of surge protection chip/circuit was those?  Maybe we could have them implemented on the daughter board.

 

[pittom]

Same problem here,tried diffent board same problem

 

[CAI_Support]

Same problem here,tried diffent board same problem

W0VHA already found solution by adding optical isolator to the input filtering the noise coming from the TTL input lines. Could you please try the same to see if the problem is caused by external noise?

 

[pittom]

ok will try and let you know

 

[Tschmidt]

W0VHA already found solution by adding optical isolator to the input filtering the noise coming from the TTL input lines. Could you please try the same to see if the problem is caused by external noise?

Just to be clear those are not optos, they clamp input transients to ground.
 
I’ve had similar problems with the WebControl I used for wood heat controller.
http://www.tschmidt.com/writings/2ndgen_woodheat_controller.pdf
 
In my design I clamped the 1-wire I/O with 1N4148 diodes to Vcc and Ground and have occasional lock ups when dehumidifier turns on. Looks like that was not as effective as the out board protection. I have a simple go/nogo power line monitor and it never reported over/under/transient condition on the line.
 
I don’t know how the 1-wire interface is implemented, I assume it is bit-banged and the problem is firmware gets confused if it sees certain 1-wire states, but that is just a guess.
 
Dehumidifier died so I no longer have a way to produce the problem.
 
/tom

 

[CAI_Support]

Hi Tim,
 
Thanks for your posting. W0VHA wrote to us directly told us using opto isolator fixed problem.  Maybe the picture showing is something different than the TTL input.
 
The 1-wire interface is different from TTL input, it does not have any filtering capability, but has bus directly tied to a CPU input pin.  Because 1-wire signals could bounce on that bus back and forth causing CPU misidentify the signal, we added the 1-wire timing adjustment field in later firmware.  If you ever found the 1-wire bus could cause lockup, please try to adjust the 1-wire timing to avoid the bounced signal confusing the 1-wire decoding logic.
 
If your firmware does not have the 1-wire timing adjustment, please try to get firmware updated.  Over the years, we have added a lot of new features to the firmware, in addition with a lot of fixes to make it running reliable.