At minimum, the power bank needs something to turn the circuit on and off. I was hoping someone would come up with a clever way to sense whether a USB plug was inserted, and enable the chip only when something was plugged in, so it could run completely on its own. But that hasn’t happened, so the main MCU would need to enable/disable it instead.
One thought was to enable the powerbank whenever the main LEDs were on, so to charge a phone you’d put the lantern in moon mode or battcheck or something, and then plug in the phone. But this would also reduce efficiency, especially on the lowest modes, and it could be a little weird that simply plugging in a device isn’t enough to actually make the powerbank function work.
For full powerbank control, the MCU needs to actually communicate with the powerbank chip over I2C or something, and that’s definitely going to require more pins and more ROM. But this isn’t strictly necessary, if we just let the powerbank use all its default settings. For that, it only needs an on/off switch of some sort.
There’s also the option of adding a second MCU, which would do nothing except watch the USB port and control the power bank. It’s probably a good option, since it would make all that completely independent. Simple and robust. But that’s not happening in this version.
I did suggest a chip that could do the charge and powerbank without MCU connection, and can cope with flakey intermittent solar input, and has a pedigree, and is available, and inexpensive.
But I can’t remember. It’s here in the thread somewhere. Just look up my posts, It’ll be there.
I admitted I might be wrong, but the design I see above looks like it is power bank and charging capable with a single IC, which is U4. I do recall that the current firmware hosted on the ATTiny85 has limitations in controlling all that could be done in this driver. I don’t see a driver that is providing just a charging function. I am pretty certain that the design is the same as the one DEL generated a year or more ago, and was provided to Lexel.
But to be certain we need Lexel to clarify this IMO.
I know we discussed dropping the power bank for this model in the team chat, but i was sure we all agreed to keep the charging feature, which is a key feature needed in this type of light as a very usable feature for long-term use & off-grid use. (will hope he chimes in on that soon.)
Powerbanks are simple stuff, though they do need a good standalone power management chip.
No need to tie it into the MCU unless you want (and know how) to reconfigure things into the latest high power charging and discharging modes. 5V at 1-2A through up to three outputs is usually enough.
Aww, that’s a bummer. I was really looking forward to the power bank functionality. I understand if it can’t fit the equipment/schedule for this first version, and USB charging is still nice, but still. Bummer. Thanks for all the hard work though guys, I’m still interested in the one I’m on the list for.
AT&T came up with a USB charger that would have “zero” vampire draw in 2010.
I think it had a solid-state relay before the rectifier/transformer and a capacitor after, and when the capacitor was full, it’d open the relay.
Plug USB device into charger, capacitor discharges, relay closes, device charges.
Unplug USB device, capacitor reaches charge threshold, relay opens until USB device is plugged in or the measurement circuit discharges the capacitor beyond the trigger threshold.
I may still have one of them laying around somewhere.
v2.0 designed, sleep over it and see if any errors accured
updates:
Power bank stuff removed
+ TP5100 2A charge chip installed
added on battery side a solder pad to switch between 0.75 and 1.5A
added + and chrg and full pads for Charge light indication
+ AMCs can now individually added or removed by pads on the battery side 3 AMCs per channel fixed up to 7 can be unlocked by bridging the solder pads with solder blob
May I request that 0.75A charging be the default, to minimise the chance of crashing a small solar panel?
I’m sorry to see the powerbank function go, but I’m still planning to buy at least one of these. I’ll decide what to do next once I’ve been able to play with the first one