I currently try to make one. PCB is nearly finished, but I need to find an ATTiny25v rev. E in qfn package. I maybe will order from different shops, maybe some have the revision E.
Thanks Jensen567, you are almost certainly right.
If I could make it simpler, cheaper, higher output with a custom driver that would be great, but custom firmware is the place to start for sure.
Oh I’m so sorry, I forgot to to write it down and tell you! You have to solder bridge the middle pad to one of the outer ones. It must not be left open. Do NOT short out all 3 pads. There’s a small “E” of enable, and a “D” for disable power save mode. You can look at the datasheet to learn a bit more about the two modes.
It’s there for better efficiency at low currents. Since your running it at 1.4A, short the middle one with the “D” next to it (I think it could have a bit higher efficiency). You can enable it if you want, but I would only activate it if I’m under 150mA.
Edit: The 6mA is mostly because of the OpAmp quiescent current. It’s about 4.6mA typically.
I can troubleshoot them if you want, here are some pictures of the board and the schematic. Could you check all the traces? The pictures help you which pads are connected, check them for continuity. Could you make some photos of your boards as well? Link: https://imgur.com/a/315u7
If someone finds a mistake, please tell me.
Note: the one airwaire (coloured yellow) is there because Eagle won’t let me create polygons without something in it with the same signal. I placed a pad there on the bottom layer, so this one airwire can be ignored.
In the schematic, the pad on the input is called Bat-, it should be Bat+.
Was about to comment, R1 looks like sense resistor so I think 20m was 20 milliohm, 206 is 20 megaohm, so would make sense if no light with 20 meg in series with the emitter.
I currently don’t have, but I can order some, wanted to make a mouser order this weekend for the new MP3431 board anyway. If you want I can buy some 20mOhm resistors and send them to you.
Do you have higher resistor values in the milli ohm region, just to check if the board works?
The 0.02mm² wire won’t work, 1.4A through that is a bit too much (50mA is the maximum current for that size). For now, maybe a 0.1Ohms 0805 resistor fits. Just to make sure it works (and it should put out around 300mA). I can order some resistors for you, no problem.
And with 20MOhm, you were driving an LED with around 1.5nA :laughing: