willpearson
Posts: 8
Joined: Mon Nov 20, 2017 4:48 pm

Power for Pi zero w + Picon zero motor controller

Mon Nov 20, 2017 4:58 pm

Hi,

Well I'm about to buy my first pi for a joint project with my boys. I wonder if someone can tell if what I'm planning is possible?!

I'd like to use a pi zero, with picon zero pHat to make a small differential drive robot/car. I'll be looking for motors than run at around 200rpm at 6v ( I think this is about right). I plan to use 4 x rechargeable AA batteries (so 4.8v).

The pico zero seems to have lots of options as to where to draw the power from, and whether to use several power supplies or one. This is the bit I'm struggling with.

I assume the 4.8v will be close enough to 5v to run the pi zero, and the picon zero.

If the motors are too big - can they draw too much current and damage either board? Or will they drop the voltage (or current?) and just cause the pi to reset? Should I abandon this plan and up the voltage, or add a separate power supply to keep the power to the pi separate?

Any help much appreciated as I'm desperate to buy soon!

Will

mattmiller
Posts: 1953
Joined: Thu Feb 05, 2015 11:25 pm

Re: Power for Pi zero w + Picon zero motor controller

Mon Nov 20, 2017 9:35 pm

Ideally, separate supplies for the motors and and a Pi are the best option as motors can draw lots of current at times and this can lead to voltage dips which can lead to your Pi re-booting/locking up if just running off one power source

This is more noticeable when the batteries become a bit discharged - i.e you can be perfectly OK for 1st 30 mins and then thinkgs get more problematical

I run both my PiConZero bots from separate batteries for the Pi and the PiConZero board

User avatar
Imperf3kt
Posts: 1300
Joined: Tue Jun 20, 2017 12:16 am
Location: Australia

Re: Power for Pi zero w + Picon zero motor controller

Mon Nov 20, 2017 9:46 pm

What you want is possible, but it opens a truly huge can of worms regarding battery management.

As a start, I'd suggest using two 18650 Lipo or li-ion batteries and a step down converter, opposed to NI-CD. These will give you 3.7v each cell.

Now for the can of worms, you must ensure the Pi never gets more than 5.2-5.25v ever.
You will also need to load balance the batteries so they discharge evenly.
You will need a way to force the Pi to elegantly shutdown once critical battery levels are reached - you can NOT just pull the power.
You need a way to detect when that critical point is reached (a non-trivial task)
The motors will require sufficient power, make sure the max current draw of all the motors combined, plus your Pi and other devices connected, do not exceed the battery's output limit. I suggest running them off their own batteries.


With the proper parts and assembly, your device might tun for a couple of hours at most.
User experiencing technical difficulties.

willpearson
Posts: 8
Joined: Mon Nov 20, 2017 4:48 pm

Re: Power for Pi zero w + Picon zero motor controller

Tue Nov 21, 2017 2:27 pm

OK warnings gratefully accepted!

I'll look at 2 power supplies then. 4 x nicad AA for the motors (i have spares and a charger already).

Now for the pi... I bought a ubec - https://www.modmypi.com/raspberry-pi/po ... -converter

It's an ugly looking thing but I think it's the right piece of kit (happy for nicer, more compact alternatives). So I'm planning either an alkaline PP9 or two CR2032's in series (I acquired a load of spares).

And attach the ubec to pins 4 and 6 on the pi, or add a micro usb plug and plug it in the pwr usb.

Am I winning now?

B.Goode
Posts: 6426
Joined: Mon Sep 01, 2014 4:03 pm
Location: UK

Re: Power for Pi zero w + Picon zero motor controller

Tue Nov 21, 2017 2:43 pm

The description of the PiCon Zero on the designer's website looks straightforward to me. https://4tronix.co.uk/blog/?p=1224

But if further clarification is needed, the proprietor of 4tronix is knowledgeable and helpful and really knows the products he sells. He is occasionally a contributor to these forums.

Although the business is relocating just now, you might get a reply from their Contact address: https://shop.4tronix.co.uk/pages/contact-us

DraDragon
Posts: 10
Joined: Wed Nov 22, 2017 9:57 pm

Re: Power for Pi zero w + Picon zero motor controller

Thu Nov 30, 2017 8:28 am

Another option would have been to use a solid USB Power-Bank. Those have voltage regulation built in. Charging is also easily.
Just don't buy the cheapest variant as they often lie about actual capacity.

User avatar
Imperf3kt
Posts: 1300
Joined: Tue Jun 20, 2017 12:16 am
Location: Australia

Re: Power for Pi zero w + Picon zero motor controller

Thu Nov 30, 2017 7:57 pm

DraDragon wrote:
Thu Nov 30, 2017 8:28 am
Another option would have been to use a solid USB Power-Bank. Those have voltage regulation built in. Charging is also easily.
Just don't buy the cheapest variant as they often lie about actual capacity.
Not really an option. The motors alone will need more Amps than one of those things can deliver. Besides, that still won't help stop the SD card corrupting because it turned off unexpectedly.
User experiencing technical difficulties.

Return to “Add-ons”

Who is online

Users browsing this forum: No registered users and 4 guests