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Author Topic: Power Struggle  (Read 393 times)

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glitchyGhost

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Power Struggle
« on: April 19, 2018, 04:42:12 pm »
Hi All

My first post here, I shall try to be concise. 

I am making a Porta-Pi Arcade.  I have a Pi3, PiHat LCD (both powered by a single micro USB), LED lights and USB Amp are also attached to a couple of Rpi PowerPack V1.2's http://www.raspberrypiwiki.com/index.php/RPI_Lithium_Battery_Expansion_Board_SKU:435230

Please refer to the attached, crude schematic. 

Currently, 1 battery runs the Pi w LCD Hat, the other intended to run all peripherals (LEDs/USB Amp etc).
The LCD draws 5V from the Pi. Although the LCD has a dedicated micro USB charge- it makes no difference to power consumption when used or not (apparently) since its all drawn from the Pi.  Which is fine I guess.  The Pi/LCD run great with everything connected and runs on battery for 3-4 hours.  Presumably, the 2nd battery isn't being drained/used as much, so would be great to incorporate a cleverer way of maximizing battery usage.  I suppose I could swap out which battery is used each time, but not exactly ideal.   I realize there are probably better ways of doing this, but I am on a budget and love using the things I already have to hand.

I need help with the following: 

1) To tap into the battery power switches - reconnect them to a single On/Off Rocker switch.  The switches have 6 legs each and the rocker is a standard 2 pin.  I'm sure there's help somewhere online already for that, but its a part of this overall issue.

2) To somehow 'trick' the battery circuit packs into allowing me to play the system whilst charging? - board limitations only allow for these batteries to power an alone Pi3, via SSH whilst in charge mode (The PMU kicks in- It will power up and run, but the Pi-Hat LCD requires too much power, so I get a lightning bolt - its still playable but indicates an issue and I fear for the batteries lives.

3) Redraw a schematic I can follow to recreate what I want using the same or additional parts - not opposed to buying a PowerBlock from here: http://www.retrobuiltgames.com/diy-kits-shop/arcade-parts/power-block-pcb/ but I'm sure I can do what I need with what I have. I am not interested in barrel Jacks.  I like the Micro USB idea and have all the parts I need.  I will happily resolder, or modify the boards as required - if any solution is even possible.

Hope you can help.

Thanks in advance!
« Last Edit: April 19, 2018, 05:02:34 pm by glitchyGhost »

DaOld Man

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Re: Power Struggle
« Reply #1 on: April 21, 2018, 12:39:56 pm »
Hi glitchyGhost and welcome to the board!!

Thats a toughie there.

But for number 1, you could use a double pole double throw switch. (2 switches in one.)
Do you have  a picture of the switch you currently have? You say the switches have six pins so they are probably already DPDT.

Also the problem with not being able to play while charging is probably due to the batteries sucking all the power. You might try a larger power supply (such as 5 amps or more).
Or it could be you have some undersized USB cables. I put a Pi3 in a sega genesis case and the lightning bolt kept coming on. I was using the suggested wall wart for the Pi3, so I brought out the old multimeter and ran some voltage tests.
I found that I was loosing almost a volt on a micro usb cable that I ran from the pi to a connector on the outside of the case.
I replaced this cable with a beefier one and all is well now.
The first cable I used had small conductors, which was creating a voltage drop to the Pi.
It probably would have worked with a Pi2, but the Pi3 requires more power. More power means more voltage drop on the wires supplying the juice.
« Last Edit: April 21, 2018, 12:52:03 pm by DaOld Man »

glitchyGhost

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Re: Power Struggle
« Reply #2 on: April 21, 2018, 03:48:24 pm »
Thanks for the reply!

I have been told by the manufacturer that the battery charger's PMU chip, which controls the unit, is not designed to allow charging whilst using the Pi, unless via SSH with no peripherals.  It clearly almost works however, just needs an additional power 'boost' - I am using a high-quality cable and charger (5V 3A) which has never let me down so far, I suppose I could go 12V DC Barrel route, but this means more expenses, a step down converter board etc.  Anyone out there who knows of a way around this, please let me know.  Perhaps I just need to buy a different battery solution for this project ultimately (*sigh).

So, resided to the fact that for now, when in use its batteries only, when they run out (I have a battery/voltage meter installed) - I shut down and charge it up.  I guess! Not ideal.

The only thing I need help with is how to 'extend' the power switches (on both battery pack units) to an external switch mounted on the arcade.

Not sure if you can make out the battery switch in the photo?  They are the 6 tiny legs I am referring to - I am assuming that 2 of these pins can be soldered to 2 wires then soldered to the rocker switch, should do it? 

I have a multimeter ready to go.  I can see that the front row of 3 legs are actually too close to the actual plastic switch -so would probably melt the thing, but the other 3 are exposed and ready to be soldered to, potentially.  I am unhelpfully ignorant when it comes to wiring and circuits - something I am hoping to improve on!  I have both SPST and DPDT available.  Probably would be better as 2 individual switches - switch 1 for battery 1 (Pi/LCD) and switch 2 for the LEDs/Amp.  So if I could be guided on how do achieve this, that would be great.

Thanks again

DaOld Man

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Re: Power Struggle
« Reply #3 on: April 21, 2018, 10:52:50 pm »
Yes I see the switches you are talking about now.
Are all 6 pins on the switches being used?
Can you post a schematic of that board?

glitchyGhost

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Re: Power Struggle
« Reply #4 on: April 21, 2018, 11:28:13 pm »
Well by the looks of it, although this is a complete guess, I'd say the upper side (in picture) of the pins are in use, with the left being Off, the right being On, the traces aren't really clear and the underside has no solderable points or traces at all.
 I have attached the close up - the best I can do. 

I did find this info though which pretty much sums up the boards flaws - this is actually the 1st version, not the 1.2.

http://wiki.sunfounder.cc/index.php?title=Raspberry_Pi_Lithium_Battery_Power_Pack



glitchyGhost

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Re: Power Struggle
« Reply #5 on: April 22, 2018, 12:08:51 am »
Continuity test reveals the legs are linked top to bottom as expected- each leg beeps when its opposite leg is touched, the On leg (on the right) only beeps when the switch is turned to On.

So I am thinking solder black wire to the left pin and red to the right pin back to a SPST - this should work?

Or I'm about to kill it!

DaOld Man

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Re: Power Struggle
« Reply #6 on: April 22, 2018, 08:44:28 am »
I dont know, the picture you linked to looks a little clearer, but it looks like a SPDT (3 terminals). If thats the case, and all 3 terminals solder back to a trace on the board, you have to remove the switch on the board for your new switch to work properly. And if that is the case, you will have to run three wires to the new switch.
(Not a simple on off switch but a On On switch).
But without a schematic or the board in my hand so I can check the tracing, I really dont know.

  
 

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