I can’t find my link to Matt’s Smart Switch, I guess I lost or deleted my subscription to it. Any updates there?
I have a question for Comfychair, how do you mount your little electronic switch in the tail of a light?
Can someone more experienced with the BLF17DD help me, please?
I'm pulling my gray hair out trying to figure out why low voltage mon. is way off on the BLF17DD board I built up. When the cell falls below maybe 4.10v, the firmware starts cranking down output, using the 130 and 120 values as JC uses. So it thinks the battery is much lower than it really is -- pretty much useless. I've double/triple checked the circuit and it match's a Nanjg driver perfectly (diode configured in correct position, R1 and R2 are all good, etc.).
This is a straight FET build, not a zener mod build, just one battery - it's in a Convoy L4 host. This is my 3rd BLF17DD build (pre v2.0 ), and first time I noticed this, though I didn't do much at all in low voltage monitoring testing on the others.
Should this work ok? Maybe a bad chip or something?
I’ve got more than a dozen of em running and haven’t encountered that. I don’t tend to run cells down so far as to have the driver shut it down, but I’ve had em down to 3.8V or a bit less with no issues.
Edit: Could one of the voltage monitor resistors have bridged, causing a mis-read? (I’d suspect the 1920)
Thanks Dale - I've been buzzing out everything, just can't find a problem. According to checking against the Nanjg, it all looks perfect. Hhmm - gotta double check the resistor values.... Maybe I screwed up, or ordered the wrong size... I'll check now. thanks!! Sometimes I look for the hard things, and it's the obvious things I miss 
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I haven’t built a BLF17DD. You should be able to measure those resistors in-circuit to determine whether they are out of spec due to damage or being faulty. That seems like the most likely culprit to me. I guess too much vdrop over the diode could also be an issue. Diode test on your DMM should show ~0.25 on that. I know you can measure that in circuit on a Nanjg 105c, not sure about the BLF17DD.
I just woke up so my math is broken, but I’m almost 100% positive that the ATTiny’s VREF tolerance (+/-10%) cannot account for this problem.
To build the 20mm ‘Zener Mod’ Linear LED Driver as a regular single cell 7135 based driver, all I need to do is jumper R3 and leave D1 unpopulated… right?
Think so wight, but you’ll probably want better confirmation than mine before you proceed.
Are you planning on using a regular nanjg protection diode on this? If not then yes just jumper R3 but you could use a regular diode over R3 for polarity protection if you wanted.
Oh yeah, thanks Cereal_killer. I forgot about reverse polarity protection.
Is it okay to run them without the protection diode in a regular 4.2v single cell setup if we dont mind not having polarity protection?
I got the Diodes (BLF17DD part D1) from DigiKey, as in the shipping cart list. I don't see any white or line mark on these at all. The Nanjg ones are labeled S4 with the white mark on the 'S' side, and the DigiKey ones are labeled 41. Any idea how to place these?
Tom the correct values for the voltage ladder are R1-19100 ohm and R2-4700 ohm. The other values are for the gate on the FET and only the 130 is usually needed.
You might have I check the data sheet from the part documentation. It should orient the diode according to the printing somehow.
Ok - I'm asking about the Diode? The 10V 0.57A Diode? The ones I got from DigiKey are unmarked - cant' tell which end is the cathode. I'll try swapping it around I guess. Looks like I'm getting no power thru it to the MCU. Voltage read near nothing.
I don’t see why not. 4.2-4.35v is perfectly safe for the ATtiny13A, so you don’t need the 0.25v voltage drop from the diode. It seems that the only thing it’s protecting is the MCU. If you have physical reverse voltage protection then you don’t even have to think about it.
Check them with the diode test (beep) mode on your DMM. They only work one way, so it’s easy to figure out by comparing the two diodes. I’d also assume that the the text is rightside up on both diodes when they are facing the same direction, but I could be wrong about that! As I said, easy to find out using the DMM.
Edited, figured out how to do it without piggy backing, this is the bottom of a BLF15DD V3 I’ve modded to work in a piston drive Nitecore D10, the ground ring has the traces to it cut so it can be the contact for the piston, a wire runs threw the drill hole from that ring to MCU pin 3, the top ground ring is still ground as is the 3 sections with via’s on the bottom.
Ohh, missed the datasheet link on DigiKey. Been looking around at generic sources. No idea how to do a "diode test" on a DMM. Looks like my best guess on the cathode following the lettering was wrong - I have to flip it around. This is my last effort to get this board working - resistors I measured on the board were dead on - the diode was the only thing left I could try.
Anode left and cathode right of the lettering. I had to look it up myself just yesterday. But my memory, you know…the 1 went towards the ground ring, the 4 towards the battery positive. That’s what I remember. Anode, cathode, geode, whatever.
Cathode is the “line side” so print right side up, cathode(line) is on the right. The only + trace for the tiny 10 goes from the through via to D1 to Vcc. The via is a direct path from B+ To led+.