Arduino based irrigation controller misbheaving at a particular site.

[boylesg]

I don't even no where to begin with this one.

I have designed an Arduino Mega based irrigation controller.

The hardware is just a Mega, with a data logger shield, an ESP13 shield and a 8 x relay board.

It has been working impeccably at 4 sites.

But I have taken it to this one house and all hell breaks loose.

Just seemingly random and unrelated break downs.

The 3A DC to DC converter keeps shutting off due to the thermal over load protected being triggered.

Today I could not get any of my relays to turn on at all.

They require digital low to be sent to the digital pins to turn the relay on along with the solenoid valve connected to it.

The digitalWrite is DEFINITELY being called correctly and LOW is appearing on the pin.

Except that the LOW was around 2.5V, not low enough to trigger the relay.

Now what could possibly prevent an Arduino digital pin from reaching 0V????????

I brought the whole controller home and it works impeccably again.

I am at a total loss! Have not idea where to even begin in diagnosing this problem.

Can anyone point me in the right direction.

- - - Updated - - -

Poor household ground connection?
High level of noise in the household or neighborhood power supply?
Unusual RF interference at this particular location.

It can't be a problem with my hardware because I have it is working impeccably at my house right now.

E.G. digitalWrite(38, LOW) makes 0.3V or so appear on digital pin 38.

But when I did the same at this other site digitalWrite(38, LOW) made 2.4V appear on pin 38.

 

[wwfeldman]

"The 3A DC to DC converter keeps shutting off due to the thermal over load protected being triggered."

what is it designed to use as input?
check that the bad location has that input

I blew up an HP Arbitrary Function Generator by plugging it into 220V when it was set for 110V
only had to move a switch on the back - it kept shutting down and I kept turning it back on

does your device depend on earth ground to return current, or not?
does the bad location depend on earth ground to return current, or not?

is the output of your DC to DC converter isolated from the input?
are the grounds tied together?

please provide (at least) a block diagram showing all the connections to the outside, including relays
a complete schematic would be better

 

[BradtheRad]

* Try attaching a pulp or pull-down resistor where you see noise at a terminal. 1 Mohm is a reasonable value to start. Don't make it low enough to affect operation.

* Check where sensor wires are high impedance. Ambient mains hum may be present in the troublesome house. If mains hum reaches high impedance wiring, the wiring picks it up like an antenna.

Normal operation might be regained by finding the correct strategic location to attach a resistor or capacitor to a supply rail.

 

[boylesg]

Are these likely to make any difference?

https://www.bunnings.com.au/arlec-p...VjxiPCh22EAS-EAQYBCABEgJxy_D_BwE&gclsrc=aw.ds

It is powered by a 24VAC 1A plug pack.

24V AC powers the solenoid valves.

And some of the current goes through a 3A bridge rectifier and 2200uF cap and into the DC to DC converter modules that supplies 5VDC for the electronics.

So the electronics is isolated from the mains.

The two grounds of the DC to DC converter module would be internally tied together?
That is what I have been assuming anyway.

 

[boylesg]

This is the most important bits of the schematic I guess. All the Arduino connections are trivial.



What could cause an Arduino to output 2.5V as LOW??????

 

[KlausST]

Hi,

What could cause an Arduino to output 2.5V as LOW??????

* Not driven at all (input, floating)
* weak pull down with external current to HIGH.
* switched as ouput, driven LOW, but too high external current
* driven as ouput, PWM (or randomly switching), and measured with a slow (averaging) measurement tool

Klaus

 

[wwfeldman]

the surge protector will make a difference only if one or more of the MOVs are bad (low resistance or shorted)

are you using the same 24VAC 1A plug pack at home and at the "bad" location?

if the ground on the input side of the DC to DC converter is connected to the ground on the output side, they are not isolated.
this allows a potential sneak path for current

 

[boylesg]

the surge protector will make a difference only if one or more of the MOVs are bad (low resistance or shorted)

are you using the same 24VAC 1A plug pack at home and at the "bad" location?

Don't know what you mean by MOV....you will have to enlighten me.

Have been using standard 24AC, 1A, bare ends plug packs from Jaycar.

And I brought the entire device (irrigation controller and plug pack) home and have been testing it here.

So far both have been behaving impeccably.

So I just don't know where to begin in finding a solution to this problem.

- - - Updated - - -

if the ground on the input side of the DC to DC converter is connected to the ground on the output side, they are not isolated.
this allows a potential sneak path for current

According to my multimeter and with an unconnected DC to DC converter, there is no continuity between the input GND and the output GND.