Powering Off The Ez-b At Low Battery Warning

 
#1

I'm looking to implement a way where as the EZ-B moniters the LiPo battery voltage, it will trigger a script to say "Low battery. Robot is powering down" when the low battery warning activates, and proceeds to switch the EZ-B off, possibly triggering a relay so it breaks the connection between the battery and EZ-B, and then I can charge the battery without disconnecting it from the EZ-B.

The problem I run in to trying to figure this out is re-initialising the relay to re-establish the power connection, as I would need the EZ-B to operate the relay which at this point would be in its "Off" state so it wouldn't trigger the relay. I'm normally pretty good figuring this sort of thing out, but I can't get my head around this one.

Has anyone done something similar to what I'm looking to do? If so, I'd love to hear your solutions.

#2

How about something like a monentary switch push button. You press it and it bypasses the relay to power on the EZ-B which then sets a digital pin high to re-energize the relay and you can release the switch.

My only concern is how much of a battery life hit will you take keeping a digital pin high and the relay energized.

If you expect the robot to be unattended so fully discharging the batteries is a real worry, than probably worth figuring something out.

Alan

#3

I kind of had the same thought. Also, Never ever charge a lipo unattended. It always leads to bad things happening.

#4

steve G

rs media has this.he says all systems powering down or
the batt in my feet needs changing

#5

Due to the compact size of the EZ-B v4, there is absolutely zero room left on the PCB for a battery power relay. If anyone has seen an EZ-B v4, it is probably the most compact PCB I've ever seen Smile

As for powering down the EZ-B with a low battery, a solidstate relay can be connected to a digital port. Using EZ-Script, you can use the GetVoltage() command to get the most recent voltage from the EZ-B v4

Here is one from SparkFun, but it only does 8 amps - which is not enough juice for a Revolution robot: https://www.sparkfun.com/products/10636

#6

Thanks for the advice guys. I think you may be on to something Alan. Using a momentary switch to temporarily bypass the relay might be an option. Two reasons why I'm looking to do this, is 1) I don't want to manually disconnect and remove the battery every time it needs recharging, and 2) I would eventually add a auto dock and charge feature so this is where I would need the batteries connection to the EZ-B cut while it recharges.

I'm aware about the safety of recharging a LiPo battery unattended and I use a Ballance charger with an auto cut of feature which reduces the chance of "bad things happening".

The amperage is actually something I didn't fully take in to account while thinking about this so thanks for the heads up DJ. So it does look like a relay is the way to go. Just to be clear, when I was asking about the auto power cut off, I wasn't asking about having it added to the EZ-B, as you really have done an amazing job designing the v4 to be as powerful and as compact as it is, and know that adding a relay to the board to carry out this fiction would take up to much real estate. No, this is something I want to add myself for the possibility of designing a "dock and charge" on my current and future projects.

I suppose what I'm ultimately looking for is a convieniant and safe way to recharge a LiPo battery that is still connected to an EZ-B, much like a laptop or mobile/cell phone does (The device can still have the battery connected, and even be used). Maybe this could be a future EZ-Robot product module, that could be designed to connect to the EZ-B's power base connector that could be that could be added to the product range and sold in the shop. Just an idea.

But for now, my current project has a Roomba for a drive base, so when the LiPo gets to 6v or so a final script is triggered to say" I'm going to recharge", and send a "dock" command to the Roomba which I know how to do, then powers off the EZ-B as the Roomba seeks the docking station. Once I get this figured out Incan build on it from there.

Anyway thanks again for your input guys. Smile