Having arduino detect if primary power fails using power sharing controller chip

Projects General Guidance
1

Hi all,

I'm working on a solar tracker project and run in to some questions.

I have a working solar tracker controller system. I'm using a arduino mega as the main control piece, and GPS, RTC, etc to support it. The panel is moved by two 24V DC motor with encoder and limit switch for position control. So I'm good there.

The power supply is 24V 10A DC, powering two 24v motors for panel movement, then it's stepped down to 5V to power a Naked Mega (a bare minimum arduino mega made by a guy from Taiwan).
We want to implement a battery system that allows a hot swap in case of primary power source failure. We also want the system to move the panels to a flat position as soon as primary power fails (using battery).
So the process would be:
system powered by the grid;
if grid fails, the system will instead draw power from the battery;
as soon as the arduino knows it's drawing power from battery (or grid has no power), move the tracker to stow(flat) position, then it can safely wait till the battery dies.

Thanks Paul for pointing out. The system is powered by a 24v Transformer (down from a 110V grid). We want to have a battery (24v) backup, so hot-swap would be "if the primary power (from transformer) fails, the backup power (battery) will take place". And I would like my arduino to detect this and have a response.

Below is what I found that may help

http://www.cartft.com/catalog/il/1330

I'm sending messages to them to ask about detail guidance on that, but I'd like to ask you guys if you have any other suggestions.

In my mind, I want to be able to get a chip that allows automatic hot swap, and have a digital pin (through a step down resister circuit from 24v to 5v) connecting the power source and the arduino mega. The first link above seems legit, but I don't have enough experience in EE to be sure.

I appreciate any suggestions.

Geng Qin

2

Lots of words about "hot swap" but no mention of what is being swapped!

Paul

3

Paul_KD7HB:
Lots of words about "hot swap" but no mention of what is being swapped!

Paul

Thanks for pointing out. I have changed the description.

4

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html

You may need some panel position information feedback so you know where the panel is and move it to mid-position when you have the system go over to backup power.

Thanks.. Tom... :slight_smile:

5

Now I see you want an uninterruptable power supply (UPS) giving 24 volts DC.

To me, hot swap, means the ability to remove an operating piece of equipment from a system and plug in a replacement piece. Such as a removable disk drive. Or a system controller board.

Why won't a standard computer UPS box powering the Arduino system through a 24 volt power supply work for you?

Paul

6

So what happens if the mains drops out for 10 secs, then recovers?
Do you want to continue parking the panels and ignoring power recovery?

Why not monitor the battery voltage, and only park the panels when the battery capacity is getting low... ie soon won’t be able to drive the parking cycle.
Ignore the mains supply - it’s charging the battery anyway - so the battery will let you know soon enough if the mains has gone!

Less motor activity, also monitors the battery condition etc...

7

lastchancename:
So what happens if the mains drops out for 10 secs, then recovers?
Do you want to continue parking the panels and ignoring power recovery?

Why not monitor the battery voltage, and only park the panels when the battery capacity is getting low... ie soon won’t be able to drive the parking cycle.
Ignore the mains supply - it’s charging the battery anyway - so the battery will let you know soon enough if the mains has gone!

Less motor activity, also monitors the battery condition etc...

For the first question, I'm thinking the system would go back to normal operation when it detect a recovery from the primary power.

The battery monitoring one is an interesting thought. But I don't really know how to do that... I'm assuming it's not as simple as putting the battery in parallel. Would that be similar to a Uninterruptible power supply?