Oshpark Projects

Everything from a 105C, except the 7135s of course, is the same as on the BLF-15/17/20DDs. The 17 & 20 use a big TO-252 (also called 'DPAK') FET, the 15DD uses a tiny little SOT-23 FET. These were all designed to use the same components as the 105C in the same circuit design, on purpose. Same resistors for the voltage divider (4.7K & 19.1K), same capacitor (10uF/16v), same polarity protection diode, same MCU.

To fix the voltage spike thing you'll need a second 10uF capacitor, but it's the same part with the same specs as the main capacitor used on the 105C.

To add the off-time function, you'll need to flash the off-time firmware and a different capacitor, a 1uF/16v, placed between MCU pin #2 and ground (here, cheaper than retail even with price breaks, worldwide shipping): http://www.ebay.com/itm/181283883536

There are plenty of threads already showing the traces underneath a 105C to figure out what connects where. The circuit is the same on the BLF drivers, the components are just in different locations. But the same parts connect to the same places.

See post #1045 for current status - new version that no longer requires an additional capacitor, but instead just relocates the single original cap

Updated shared-cart links for BLF drivers:

BLF-15DD: http://www.digikey.com/short/dcdj7

BLF 17DD & 20DD: http://www.digikey.com/short/dcndn

BLF-SRK-DD: http://www.digikey.com/short/dcdtq (last two items, the inductor & big schottky diode are optional - but if you want to use the inductor, you must also use the diode - either both parts together, or neither) (*note: this 5A/40V diode is a different part than used in earlier lists but is interchangeable, the old one is currently out of stock)

Those are parts lists for ONE driver. Adjust quantities to suit.

Please hold off on ordering these boards from Oshpark, they all need a new revision to add a dedicated spot for the second capacitor and to eliminate the gate & pulldown resistors. The parts lists will not change from what's shown here though. If you already have older revisions they can be used safely, just put the second capacitor where the diode goes, piggyback the diode onto the side of the capacitor, and replace the gate resistor with a jumper wire and skip the pulldown resistor.

I have not built or even looked closely at any of the recent updated Oshpark boards (like, the dedicated zener/resistor versions) so parts lists for those other boards will have to come from whoever has actually built (or designed) them.

edit: This is the capacitor for off-time memory builds, if you'd prefer to make a single order instead of some from here and some from over there, etc.: http://www.digikey.com/product-detail/en/C0805C105J4RACTU/399-8001-1-ND/3471724

See post #1045 for current status - new version that no longer requires an additional capacitor, but instead just relocates the single original cap

Thanks comfy, that is is the kind of 'my level information' that I need to hear every now and then :-)

It will make a lot more sense after you've built a few. :p

So if you are using the current versions of the boards the new carts are correct but if you use this new method to stabilize the modes you would add an extra cap to the old cart and use a jumper instead for the gate resistor?

The drivers are pretty darn simple, what’s confusing is keeping the different versions straight with up to date carts.

On every one of the modified nanjg boards(both 7135 and FET versions) there are just a few areas of them with easily understood functions. Once you understand those few functions the layout and parts become almost obvious.

B+ power comes into the boards and splits, one part feeding directly to led+ and the other going through the reverse polarity diode to power the mcu and to the voltage divider.

The voltage divider is 2 resistors connected in series going from the reverse polarity diode to ground. Pin 7 of the mcu connects to the junction between these 2 allowing the mcu to monitor the battery voltage as it drops. These 2 resistors drop the entire battery voltage between them passing only a very small amount of current. Most of the drop occurs in the first 19.1k ohm resistor leaving less than 1V left for the 4.7k ohm resistor to dissipate. Pin 7 monitors this smaller voltage and when it drops to ~.5V the mcu changes the pwm signal causing the led to blink and power down.

Pin 6 on the mcu is the pwm pin and sends pulses varying from very short(see ComfyChairs pics above) to constant on and controls the amount of time (duty cycle) that either the FET or the 7135’s are on and conducting current.

When they are on current flows through the board, the led, back to the board, and passes through either the FET or the 7135’s to the ground ring and back to the battery. The convention is actually that electrons flow the other way from negative to positive which is why the ground pin of the FET is called the source and led- is called the drain.

I believe C1 is just a filter on the input power of the mcu to protect it from voltage spikes caused by pwm but it may also have to do with the memory function. I haven’t had to learn about that one so I haven’t. :stuck_out_tongue:

Does the BLF15DD suffer from the spike as well?

The new shared carts have two 10uF capacitors, one of everything else. Parts required are the same if using either the current, older, or yet-to-come revisions. The new revisions will just add a dedicated spot for the new capacitor, in parallel with the polarity protection diode. Older revisions can use the same 'fix', like so:

Put the cap on the D1 pads, and put the diode alongside the capacitor.

If it's a driver that doesn't change modes correctly without a gate resistor, it's because of the voltage spike issue shutting down the MCU. The 15DDs I built didn't act right without a resistor, so I'd say that's one that needs the extra capacitor. I'm pretty sure Rufus also didn't have any luck running the little IRLM2502 without a resistor.

Apparently Dale was able to use the smaller FET on a modded Tiny10 without the resistor but I wouldn’t count on it.

Well I have pics in the 'scope thread that show the voltage spike even on drivers that change modes reliably, it just happens to not quite reach the point that the MCU shuts down. It's an easy fix and as far as I can tell has fewer drawbacks than using the gate resistors to hide the effects of the voltage spike. Much better to address the spike itself. The waveform on drivers using the gate resistor are just incredibly ugly, like I pretty much always suspected they would be.

comfy, if you have a look on the scope of the waveform of an ordinary 105C, would that also have the spike?

Yes it does. Battery voltage while running measured 3.78v. Those peaks are easily above 5 volts.

That's completely stock 105C hardware, 8x7135s, flashed with the same STAR clicky FW as in the other scope pics of the BLF drivers.

The size of the spike depends on the load being driven by the PWM pin. 7135s are a very different load than the FETs. If the spike doesn't hit the MCU's overvoltage limit, it runs reliably.

I have seen some BLF-DD drivers that are only just a little bit flaky, right on the margin of working right when testing out in the open on the bench, but do OK once inside a light. So these waveforms are likely exaggerated somewhat due to the test setup - battery box, clicky switch, longish wires from the box to the driver, and so on. But what you can know for sure, is that if it works reliably in this bench setup (and the scope shows the spike issue is down to acceptable levels) it will be solid when installed in a light.

There is no over-voltage limit circuitry built into the MCUs (there is an under-voltage brown-out detector that can be enabled). Over-volt them and they can die. That voltage spike does not appear to be enough to harm the chip, but it may be causing it to reset itself.

On the ones with issues, one thing they do pretty often, other than just shut off completely after a mode change, is they blink and end up 2 modes lower instead of one. It does act the same as if you tap the reset pin to ground.

This is a different driver, no gate resistor, and the original D1/C1 setup, without the extra cap in parallel w/the diode. CH1 (flat blue line, at 6.000V) is after the diode, CH2 (yellow) is B+ before the diode. These voltages are correct, I moved the probes to the contacts in the battery holder and verified with a separate DVOM. Battery no-load voltage was 4.08 - I'm really not cheating here and feeding the driver 6 volts! It's making that extra 2V all on its own.

The spike is most likely coming from the inductive kickback voltage from the emitter wires. When the FET switches the magnetic field in the wires collapses and generates a voltage spike. A cap across the protection diode is not a good way to stop it. Try a diode across the emitter wires at the driver (bar side to LED+, triangle side to LED-). The diode should have a decent current rating.

Comfy has a dedicated thread over here where I was just suggesting the same thing.

1A schottky diode (IN5817) between LED+ and LED- had no effect at all. On a driver with the gate resistor replaced with a jumper, the scope shows no change and the driver doesn't change modes reliably.

I just built a few 17mmblf drivers with rmm kit, does this voltage spike have an effect on those? I haven’t used them in any lights yet.

If it's one of the versions using the gate resistor and it changes modes correctly you can use them as-is.

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17DD with the extra cap & resistors eliminated:

Oh, and the AOD510 that didn't work before works properly now in the extra cap/no resistor setup. That's why I added it to the Digikey shared carts.