I meant the OTHER blinking! :zipper_mouth_face: But I donāt even like PWM, unless the light source can do the āpersistenceā part. (Yes, Iām still hooked on the hot wireā¦)
But Iām weird that way.
I work on machinery & tools that move dangerously. Take your PWM light & watch a running car engine at nightā¦ Scares the daylights out of me, no pun intended!! Itās SUPPOSED to look like itās moving in a dangerous manner, the better to remind you āDONāT PUT YOUR HANDS IN THERE!!āā¦
(Ironically, the other blinking actually is useful around automobiles, but in a whole different regime!)
Well, of course itās going to leak. Thereās that big, fat FET sitting right there between Out and GNDā¦
But I was thinking the MCU would drive relays (transistors or big, flappy brass reeds ā but youāre not building a sailboat motor controller, are you?) which would power 7135s off as a switch wouldā¦ Maybe I missed that part. Youād drive VDD directly from your ~25mA output pin? Now I wonder about batchesā¦ In parallel, would you be able to turn them all on (the 200uA would be easy, but what about that ~2.7v min. VDD?)? In series, I would LOVE to see the propagation delay scoped out!!! If you (say) doubled your pulse width due to the time it takes all the 7135s to āseeā the current, what would that do to your OTF? (See, itās not the PWM I dislike, but the way the LED presents itā¦) Youāre flipping the (x-number) of 7135s on/off with each pin, right? So the āblipā of current would have to propagate through the batch each cycle? What if you could use that to control the LED?
Just spitballing here, but I was thinking you would need another layer, which would allow you to fully power-off the 7135s and their LED ( s ) ā¦ (Yes, as you can see, I see the 7135 as a magic Ilim resistor( s ) dedicated to an LEDā¦ But seeing the package like that seems to work for me.) Anyway, if you cut power to the whole 7135, where would your quiescent current go? I think the answer is āawayā, but Iām still playing catch-up hereā¦
Because i want to make a driver with a soft-button, so this parasitic current will drain the battery even while
the flashlight is āoffā.
See for example the zebralights:
They also have this drain, but they managed to keep it so small that it doesnāt matter. This is exactly what i need, too.
This looks very promising, thanks for the measurement! At 164ĀµA an 18650 will still last over a year, so this is probably good enough. Also the NANJGs use an ATTiny13A, which according to the data sheet, draws 24ĀµA at 1.8V and 1MHz (idle mode). One chip that i might use, the PIC12F675, has a standby current of 1nA at 2V, and can even operate at 8.5ĀµA at 32kHz. What those datasheet values mean for a led driver we will see, but using a PIC might lower the parasitic drain a bit further.
Iāll measure that configuration, too, but iām starting to think that maybe you had a faulty 7135 in your batch? Did you perform the measurement only on one batch of 7135ās or different ones?
EDIT: found out by accident that āatā signs change the font instead of showing up as themselves
Thatās an interesting thought, the PWM making you not see the movement. But this would only be a problem at very low settings, and in an area where stuff moves dangerously, i would never go for moonlight mode
As soon as i give more than (average) 350mA to the LED, it will always be on, and just vary in brightness.
It might leak more than an open relay, but anything less than a few microamps i can happily ignore
Lets see if i understand you correctly: you are discussing whether i put the 7135ās in parallel or in series?
Series does not make any sense for a constant current chip. Youād get a constant current of 350mA like with a single chip, and also the excess voltage is probably burnt off to heat in a single one, while the others put their FETs in full-on mode. Also, then youād have to have higher voltages to supply those that do not sit at GND.
The chips will be connected in parallel. Then i do not need higher voltages for their supply. 2.7V min is no problem, as the cutoff voltage for a li-ion should be at 2.8, and as far as i know, the digital output can swing rail to rail.
Regarding the blip of current: That might be a problem at GHz frequencies, not at a few MHz. Also it is not important when a 7135 switches on or off, it is only important for how long it stays on, and that does not vary. So even if the ālastā 7135 got the on-pulse very late, the brightness you see would be exactly the same.
If i cut power to the chip, there can be no quiescent current. Current can only flow when there is a voltage driving it.
I can post schematics when i get around to drawing them, maybe those will clear things up a little further.
Replace āiā with āMCU by way of the Output Pinsā and youāll have it all in one sentence!
I was actually thinking of caps (or something) between the 7135s to extend that propagation delayā¦ but I canāt remember now why that was so interestingā¦
I apologize for the dalliance re: driving them, as I confess when I went to the Datasheet for the smallest PIC I could find, the DC Characteristics table listed the voltage on the Output pins minimum Vdd of 0.7 seemed low enough to be a problem, for batches of 7135s. Their minimum is 2.7v each, but only require 200uA. I just went back & found the PICās Maximum is not even listed, and the notes mention an IOH of 3ma, Vdd=4.5, which would drive enough 7135s to make us both silly, so Iāll just go back to paying attention now, and try to stop wandering into RF territory (good catch) anymoreā¦
Dim
(PS: if you replace āLEDā with āIndustrial DC Motorā you may find another field of opportunity to plowā¦) edit due to total brain f#rt in the one sentence that mattered
Another thought about efficiency:
I am going to use this with Nichia-219 LEDs, which have a higher Vf. That means the LEDs are less efficient than XM-Ls, but i donāt
have to worry about efficiency issues with a linear driver (vs. buck). Most of the inefficiency is bundled inside the led, and thereās not much more voltage to lose in the 7135
