PowerBoost 500 Charger and On/Off Switch


#1

Hi All,

In need of some technical help here! I am building a Raspberry Pi based tablet system and wanted a power button and battery so I could use it on the move. I bought a LipoPoly battery and a PowerBoost 500 Charger - Rechargeable 5V Lipo USB Boost @ 500mA+ I also bought one of these switches:

I followed the instructions on the Adafruit website around how to install the on/off switch: https://learn.adafruit.com/adafruit-powerboost-500-plus-charger/on-slash-off-switch

I’m pretty sure the switch I bought is a ‘break-before-make’ switch? and so soldered in all pins to Vbat, En and Gnd. However whenever I flick the switch the power doesn’t turn off, it is always powered by the battery whichever position the switch is in.

Can someone help?

Thanks!!


#2

Here are a couple of pictures


#3

I wouldn’t have used the third terminal you have soldered to the Bat pin. I would have cut that third pin off flush on the switch before soldering it in. Like they did in the tutorial you linked too.
I have a PowerBoost 1000c and have my switch wired to the GND and Enable contacts. I put a ground on the EN pin to turn off the powerboosts up converter. The charger part still works.


#4

Hi alphanumeric,

Thanks very much for your response, much appreciated! This was my second attempt, for the first attempt I did exactly as you said, clipped off the third pin and only soldered EN & GND but got the same result. No matter which position the switch was in power was always provided to the board. Do you know why that would be?

Cheers!


#5

The Battery charge section stays on and the Yellow and Green battery charge state LEDS will be on. Only the up converter Blue LED goes off. Is that what your seeing? If the blue LED is staying on something is wrong?
I prefer it that way myself. My Pi is hard wired to the powerboost and can’t easily be unplugged. It’s all in an enclosure. I often switch it off and leave it plugged in to recharge the battery.
I also have it setup so I cab run the Pi off of the power supply instead of the power boost. I bypass the powerboost. In this mode the powerboost is off and the battery is recharging.


#6

Hi alphanumeric,

Thanks for coming back to me. Yeah that’s exactly it the blue power LED turns on as soon as I plug it in and then remains on no matter what position the switch is in (I can also see that power continues to be supplied to the pi through the usb out irrespective of switch position). When I plug in the power supply the yellow charge light goes on for the battery as expected. I wonder if it could be a faulty board? Which switch did you use?

I’d be interested in how your set up is wired as i’d also like to bypass battery and use power supply sometimes (whilst charging). Are you able to share a picture?

I’m looking for a small button/switch that I can mount externally on my project (without the need to drill) and wire into the powerboost to control on/off. Do you have any suggestions?

Many thanks!


#7

My build pictures are here, https://1drv.ms/f/s!AjOYwiwlwDtpgsVkNRFKrcQ8HARM0Q
My switch may be hard to describe and or find. Its a double pole double throw with a twist.
It has three positions. It goes something like this. In the down position Pin 1 is connected to pin 2 and pin 4 connected to pin 5. ignore the dots, they are just spacers to get things to line up. The editor takes out spaces.
1 4
.|. |
2 5
. .
3 6
then in the center position pin 1 is still connected to pin 2 but pin 5 is now connected to pin 6
1 4
.|
2 5
…|
3 6
then un the up position pin 2 gets connected to pin 3 and 5 stays connect to 6
1 4

2 5
.|. |
3 6

I just happened to have some left over from my days working as an electronic technician. The way my switch works is in the center position my power boost is off, and the Pi is not getting any power, its off. All that’s on is the battery charger. Down ties the Pi to the power supply and the powerboost stays off. Up switches the powerboost on and ties the Pi’s input to the powerboost.

You could do it with two switches. One single pole double throw. Wire the Pi’s +5V to the center common terminal. Then power supply on one terminal and powerboost out on the other.
Then a switch to turn on off the power boost.

The other button in the picture is my shutdown button. Its a momentary contact normally open push button wired to a GPIO PIN. I have my python coed to do an OS shutdown when its pushed.


#8

Wow thanks alphanumeric, that looks too complicated for me :)! Lol

I’m speaking to Pimoroni to see if I got a faulty board, I followed the adafruit tutorial but just didn’t work as expected. To be honest just want to be able to power on/off my project with a switch.

I’m actually looking to surface mount a small momentary button on the outside of the project to turn power on and off through the powerboost. If I used one of these could I solder the wires to the powerboost pin out to control on and off, if so do you know how I would wire it?:

Cheers!


#9

I do believe that is a momentary switch. It only makes contact as long as its pushed down, it doesn’t latch into an on position. Its like a doorbell button. Not what you want. This will work better https://www.adafruit.com/product/1400 to turn the 5V out on off.
But be advised, if you wire a switch to the +5V out of the powerboost, your going to run your battery down as the upconverter will keep running. It will slowly discharge the battery even with no load.
The enable pin is the proper way to do it. For that you want something like this, https://www.adafruit.com/product/1092 If you want low profile etc.

My switch is wired to my powerboost via wires. As a test just take a jumper lead with two male pins, or two bare ends. Touch one to one of the ground pins and the other end to the enable contact. If it doesn’t turn off its defective.


#10

Hi alphanumeric,

Great thanks for the advice :)! Perfect will order one of those tactile switches and give it a go, does it matter which wire is soldered to GND and which to EN?

Pimoroni have been great and are sending me out a replacement PowerBoost board as using a jumper between GND and EN on my current board does not change its state and it stays powered on.

I have one final q for you if you don’t mind :), I need to use a usb cable from the PowerBoost into the micro usb screen power socket however I don’t have enough room in my project to use the usb out socket on the PowerBoost. If I cut off the end of an old usb cable can I solder the red + and black - to the pin out on the PowerBoost rather than using the usb output? If so do you know which pin outs I would use :/?

Many thanks for your help!!


#11

No it doesn’t matter which wire goes where. Button on is a short between the two wires. Basically just one long wire. Button off is an open circuit, as if nothing was there.


#12

From the Adafuit site https://learn.adafruit.com/adafruit-powerboost-1000c-load-share-usb-charge-boost/pinouts
USB - this is the micro USB 5V power pin. It’s the pin that is used to charge the battery, NOT the output power! You can use this if you want to grab power from the microUSB port when it is plugged in
BAT - this is the battery input, connected directly to the JST connector. For most Lithium batteries, this will range from 3.0V when near-dead to 4.2V when fully-charged. Higher voltages will let you draw more current and in general, are more efficient. Try to keep the wires going to this pin nice and short - 3" or less is best!
VS - this is the load shared output from the battery charger. When there is 5V coming in from the micro-B USB power plug, this pin will have approx 5V on it (less a little due to the internal resistance of the charger chip’s MOSFET). When there’s no USB charging, the Vs pin will be the same voltage as the Bat pin.
GND - this is the power ground. This boost converter is not ‘isolated’ - the ground input is the same as the ground output
5V - this is the boosted output. When the board is running, the voltage will be 5.2V approximately. It may dip down to 5V as the current draw starts to go up (over 500mA). When the board is disabled, this output is ‘floating’ but you should still try not to apply a voltage to it while the board is disabled. There’s a blue LED connected to this pin which will let you know when there’s power output

Use the contact labelled 5V and the one labelled G right next to it. It’s what I did. That’s the 5V and ground from the USB power out jack.


#13

This might be bad time to ask but is 500ma going to be enough to drive a PI and the display? What model Pi are you planning on using?


#14

Hi alphanumeric,

Great, many thanks again for the advice. Bits and pieces are arriving today so i’ll give it a go and let you know.

I’m using a pi3 and the rpi 7inch Touchscreen Display. Do you think 500ma will be enough?

Cheers!


#15

No, I don’t think that will be enough. The Pi will draw ~400ma all on its own.


Even a powerboost 1000c might not be enough.
I think you’ll need something like this https://shop.pimoroni.com/products/mp2636-power-booster-charger-module
Only problem is that doesn’t have the enable pin etc. Not brought out to a usable contact anyway.
The Pi foundation recommends the 2.5A power supply for a PI with the Pi Foundation 7 inch touch screen. I have one of the original version one screens mounted to a 3B+. I 10A supply with it. Overkill, but I wanted a big beefy supply with lots of extra capacity. It’s my breadboarding rig.


#16

Ahhhh :) lol! I do have a 1000c PowerBoost too. This is the screen I bought

Hmm so with the mp2636 board I couldn’t have an on/off switch?

Wondering if it would just be easier to use a power bank to power the pi and screen rather than trying to have integrated power in the tablet? But have no idea what powerbank and cable would be the best to use, what do you think?

Cheers!


#17

No the mp2636 doesn’t have any extra breakout pins. I plan on buying one at some point and seeing if I can find an enable pin on the chip to solder a wire too. I don’t like just the one mounting hole much either. It’s the only one I’ve come across with more than 1A out though. I’ve been hoping that Adaruit would do their own version powerboost with that chip.
I have very limited experience with power banks. I have a couple here I bought on sale that I think are 1A out? They might be only 500ma? I only ever ran a PI Zero from them. I don’t have one handy at the moment to check it. One down side to most power banks is you can charge the battery and power something with it at the same time. Like you can with the powerboost.
One option you have is to run your display off of one powerboost and the Pi off of another. Its not ideal, but just an option I’ll mention. Let the Pi and screen share a common ground but keep the two +5V feeds separate.
My only portable Pi project runs headless, no keyboard mouse or display. And its just an A+ and Sense Hat. My powerboost 1000c can run them both with no issues. I don’t see any low volt warning when setting it up, or tweaking my python code with a monitor attached. I use a TV for a monitor.


#18

Just came across this, http://www.instructables.com/id/MINI-LAPTOP/ Might be worth a look see.


#19

Hi alphanumeric,

Thanks very much for your responses, much appreciated!

I did find a larger powerbank with 3.1A output that would work but it’s much too big to go in the project.

Thinking of buying an mp2636 board to go into the project and just pull the battery in and out as and when I need…not ideal! One quick question is there anyway to attach a switch to the battery before it provides power to the mp2636? Something like a mini power controller board in between?

Cheers!


#20

Would this work :/?!

Cheers!