Silo monitoring project

Good day All,

I want to get into using the AUTOMATION HAT for projects and I have just a basic question about this unit and getting started.

First: I don’t see any documents on if this Unit is AC or DC on the input ports.

I know that ADC can only be DC since analogue signals cant work on AC systems

My plan is to wire Industrial grade Silo monitoring equipment to Rasberry Pi and Pi zero and use inputs and outputs of the AUTOMATION HAT to replace a PLC.

The idea is rather than having a massive and expensive PLC I will use multiple small units accross the Production plant to monitor and control the system. All the components except for the pressure sensor is AC hence my question above.

After that, I’m going to make a program that will receive all the small inputs from the multiple Pi’s and send them using WIFI to a central PC or even another PI for processing and control.

I am new to Hardware monitoring and control but not software.
So I will get back to this post on any ideas and progress.

Sounds like a big project, super cool though, best of luck!

My read / assumption is DC only. Me personally, I would assume DC unless told otherwise. There is a contact us link on the shop page if you want to e-mail Pimoroni for the info.
Yes, sounds like a cool project.

Those are logic inputs, so should be DC. Here’s an ELI5 intro to the Automation Mini hardware itself:

@lexfiend I had gone looking for that, looked in the wrong place though, I went to the Learn section.

Since I’m new to Electrical wiring I would like to ask your help on if this is wired correctly.
The below is a 0.8mV/Kpa Pressure sensor used on top of a Silo.
This is the only Analogue device of the whole system.
If the output from the device is higher than 6V it should trigger an alarm.
Joke: If the output is higher than 8V run for your life. Silo will explode at any minute.

Here is the picture of the board:

Ah. It was a link off the official Automation HAT tutorial:

I haven’t taken Electronics 101, but I suspect both HAT and sensor would need a common ground, for your readings to make any sense.

The Level Indicator sensor itself has its own true Earth Ground. The mean: sensor connects to Metal Silo-Metal is connected to mother earth.
Both circuits is on the same PCB but they don’t share any connections.
Basically this is a motor that if it finds any resistance(powder based product) it will disconnect its switch(that looks like a plastic white pin at the top) the plastic pin will rotate to the left and press in the switch on the right.
Basically its a fancy light switch.

Yes, and again, nada E101, but wouldn’t the sensor signal be referenced against the HAT/Pi’s own idea of ground, which is not necessary Earth Ground?

Oh ok, The right side has earth ground and runs the motor.
on the left is a basic light switch.
the motor circuit does not contact the sensors circuit on off switch in any way.
I updated my previous post to make more sense I hope.

I’m talking about the pressure sensor that you mentioned, the one that goes “8V we DIE!”

If that sensor doesn’t share the HAT/PI’s reference ground, then 8V from the sensor may well be read as 4V by the ADC. That…would not be good.

I’m guessing that powering the Pi from the same source as the sensor (maybe via a buck converter) would eliminate this issue, but I’m still waiting for a proper EE to jump up and shout “you IDIOT! WTF are you talking about?!?!” :grin:

1 Like

OHHH My bad I was talking about the level indicator.:P
Makes more sense now.

The picture does not show it but there is a Yellow cable under the board that runs to the unites metal plate.
I can remove that wire and attach it to Ground on the Automation HAT.
Will that solve the issue?

I didn’t know that can make a difference Thank you.

Ummm, a tiny voice1 just went “forcing grounds together is a Really Bad Idea”.

(reaches for the tannoy) EE TO FORUM 9, EE TO FORUM 9 PLEASE!

1 Almost everything I’ve come close to knowing about basic electronics was from a college friend decades ago, who despaired of getting me interested in EE at the time. That’s his voice rattling around in my head, in a half-sneering “So now you get interested in EE? All that wasted time…”

1 Like

Anything that is already connected to earth ground, I would leave connected to earth ground. You will need a common ground reference from anything sending a signal to the automation hat.
Think of it this way, if you try to measure a battery with a volt meter, one lead goes to the plus and one to the negative of the battery. Remove the negative lead and the voltmeter stops reading the voltage.
I would connect a wire to the terminal where the wire “going to” earth ground is connected on the device. And the other end to the automation hats ground pin.

1 Like

OK the next part is weird.
This unit is attached to a mechanic leaver that acts as a valve. When closing the valve the electronic component(switch) is pressed in and the PLC picks up that the valve is opened or closed.
Max rating is 230v 3a ~
My dumb ass question is why is this AC only when it is basically this unit is just a fantasy light switch. Shouldn’t it be able to accept both AC or

Another less serious note question.
I’m new to the Pimoroni community. Do people here tend to like programming more then electronics wiring?

If it’s just a mechanical switch it should be fine with AC or DC.

It seems to me that most of the “help me” threads are programing related. Mostly just trying to get that just bought item working. Help with python code etc.

There are some how do I make this work with this threads, like yours.

From time to time I like to post what I have built. And my code if anybody is interested. My background is in electronics, I’m a retired electronic technician.

Wouldn’t it be a good idea to check for a potential difference between the two grounds first, since one is a signal ground and the other effectively a power ground? If there is, I would think you’d end up with a current flowing from one side to the other, which can’t be good.

Remember that the components listed here is outside in the open. Sealed by IP55 or higher containers from the outside elements. If there is a storm then the electric components can be damaged if it does not have a propper ground. If I connect earth ground to circuit ground and lightning strikes then is it possible that all my components like the hat and pi will be fried?

“If” the earth ground is a separate ground connection (only grounds the case) from the signal ground, you want to use the signal ground.

Here in Canada on any appliance that has a three prong plug, that third prong goes to ground, earth ground. And in the fuse box, the neutral and ground are connected together. You can debate if that’s good or bad in reference to a lightning strike but it is what it is. I personally don’t think it will matter, your going to have dead tech anyway.

If you have an ohm meter you can check to see if the earth ground and signal ground are one and the same. They usually are. If they are the same (wired together) it doesn’t matter which one you use.

If two pieces of equipment are a fair distance apart, you can have different earth ground potentials. I do believe its referred to as a ground loop. Something like that. It’s 6AM here and I only just got up. Haven’t had my fist cup of java.
Anyway, if you just reference to earth ground and only run the one signal wire, you can end up with issues. Run a second wire linking signal ground from both devices and things will be much better. They have a common reference that doesn’t change.

The earth ground is IMHO, there to protect you, not the equipment. Especially with mains AC powered devices. If something goes wrong inside and the live feed contacts something its not supposed to, it gets shorted to ground and trips the breaker or blows the fuse.

If I got something wrong there feel free to correct me. I’ve been out of the loop (retired) for a fair number of years and my memory isn’t what it used to be. ;)