LED Driver Schematic

Nothing in particular but it would be nice to understand the whole circuit. :beer:

You know that all of the output pins(left hand pin) of the 7135’s are connected by a trace that runs underneath them and that they are turned on/off by the IC using the Vdd trace that is connected to all of the right hand pins. When turned on, current flows through the 7135’s from the output pins to the ground tabs(large outer tab, also connected to center pin) and back to B-. The only other parts on the boards usually consist of a reverse polarity diode, a capacitor that I think is for mode memory, and 2 resistors that I’m guessing determine low voltage point.

The duck nailed it. Very simple schematic. If I get a chance I’ll draw one and post it.

That would be nice Relic.
Thanks Rufus for the info.

Here is a schematic for the NANJG 105C. Let me know of any errors or omissions and I’ll update the pic or add corrections to this comment.

Notes:

  • When looking at the battery side of the driver, the stars are number from right to left.
  • +Vin is the spring in the middle, -Vin is the ground ring on the edge of the driver.
  • R1 and R2 form a divider for battery level measurement and power cut detection.
  • D1 provides reverse batrery protection for the MCU, reduces the incoming voltage (driver rated to 6V in, MCU is 5V max), and prevents the capacitor C1 from being discharged by anything other than the MCU.
  • The 7135 chips are controlled my MCU PB1 via their Vdd (Pin3).

I just noticed I didn’t label the MCU; it is the square 8-pin block in the middle, Atmel ATTiny13A.
EDIT: Updated image to correct issues mentioned below by sixty545, Thanks! Original imaged deleted.
Edit: Added rev protection note, thanks texaspyro!

I was going to say “maybe they took it down to correct it”, but just realized you may be saying that’s your image…

No offense intended, but did you notice the labels are wrong? E.g. “Input pad” is actually “LED (+)” and “Output pad” is actually “LED (-)”…

Just sayin’…
(If it’s yours, you could edit that…)

Other than that little niggle, thank you for an awesome effort! That’s what makes BLF so much better than any other possibility of a place.

Dim

I found two errors in the battery voltage detector section. R1 should be connected to MCU pin 8, VCC and R2 should be 4K7. The detection level in the MCU is 1.1 V

Good catch, my first draft had it this way, then my clean(er) copy has the error. I misread the value of R2 as well.

Thanks! I will update.

appears to be a linear current sink - there is no duty cycle term in the power dissipation equation.
http://www.micro-bridge.com/data/add/amc7135.pdf

Your absolutely right and it makes way more sense anyway.
Conventions have changed a bit since I labeled that image. At that time led- was often called the output pad and since led+ feeds the IC and is directly connected to B+ on the other side I labeled it input +.

Even if y’all can’t agree what’s right! :slight_smile:

So when people stack the 7135 chips for more power, they’re basically changing the chip to a higher level of output as though a different chip were used? How is it that the chips can be added seemingly without discretion, in whatever number is wanted to step up output?

Wouldn’t it be nice if there were a plug in module for the blinkies labeled “pull” so they could easily be done away with without affecting the other performance of the board?

This really helps me understand the throughput, and why it’s better to have a driver than use direct drive. Thanks again.

[quote=Dimbo The Blinky]

Sorry to hijack this thread, but does C1 control mode memory on this driver? [/QUOTE]
No, It doesn’t.

[quote=Dimbo The Blinky]

IOW, can I short C1 (or replace it with some R) to eliminate mode memory on a NANJG 105C?[/QUOTE]
Nope, that won’t do it.

[quote=Dimbo The Blinky]

(Conversely and PERversely, increasing C1 to create “next-mode memory”…?)[/QUOTE]
Also, no.

PPtk

By soldering the correct star to the ground ring, you can pick your mide group. One group is 3 mode hi mid low. :wink:

How do you know which star is which group? Trial and error?

Argh! What I get for daring to dream. Thanks for waking me! Hijack deleted.

Dim.

The most important function of D1 is to provide reverse polarity protection for the processor chip…

This page shows what the stars do:

http://intl-outdoor.com/amc71353-5mode-circuit-board-nanjg-ak47c20-p-596.html

Woody

You are paralleling current sinks so each chip will adjust its internal resistance so that it sinks its setpoint current - with these chips you can get integer multiples of 0.35A. For in between values you can shunt this parallel network of ICs with a resistor.

There is another issue and that is the ‘compliance’ of the current source.

What he said. Where ever you buy the driver should have info on star connection/mode selection. If they dont, buy elsewhere. The last thing you want to do is swap a driver and STILL be stuck with blinky modes unless you have to be.

Thanks pyro for the rev protection note, forgot that little tidbit :wink:
As for the mode selection, if you buy the two group version, the stars have no effect on functionality. Only the four group version uses the stars.