Oshpark Projects

I don't think they are needed. I believe the attiny has an internal pulldown on the output pins, and if they aren't working right with the wrong diodes that's no reason to add other stuff. With the right diode, the existing boards work fine.

Hey guess what

If you do that, it will then not only change modes reliably but will also work with fast-PWM firmwares. The one into the gate might not be needed, I tried it first by itself and it wasn't right (tried 10 ohm first, no change at all, then 100 ohm and it was better, but still not right), I didn't try yet with only the 10k pulldown.

Still though, why does it need these resistors, when the same circuit with the same components doesn't need them when on the 105C board?

So what have you got there? When I normally use FETs I place a 100ohm resistor between the MCU and the gate of the FET, and a 100k resistor from the gate to ground.

100 ohm inline with the gate, 10k to ground.

It works with nlite, and the other fast-PWM build I had done based on nlite with some minor changes. Moonlight isn't as low as it was with 7135s, but I don't have source code for either one to make any changes to that. luxdrv still makes the switch whine, but modes change like they should now.

I don't know for sure what the default PWM speeds are in the STAR versions, and I don't know them well enough yet to go changing stuff. For instance, in v1.1 Momentary, at the top it sez

#define F_CPU 4800000UL

but then farther down,

    // Set timer to do PWM for correct output pin and set prescaler timing
    TCCR0A = 0x23; // phase corrected PWM is 0x21 for PB1, fast-PWM is 0x23
    TCCR0B = 0x01; // pre-scaler for timer (1 => 1, 2 => 8, 3 => 64...)

I thought fast PWM had to have the CPU at 9600000? Makes my head hurt, I dunno. Anyway, whatever that one is, it works like that on the 46mm FET driver, using the same parts and no gate or pulldown resistors... :tired:

Oh, Matt, if you're going to go back and do some revisions, I have a suggestion for the SRK driver. The selector pads for the switch input are a royal pain, what do you think about something like this instead?

If you are building these with parts that you bought and were not stripped off a Nanjg, you could use the 19.1K or 4.7K values used in the battery voltage divider… no need to buy another value of resistor. The pulldown value is not critical. It just needs to keep the FET off during the time the processor is initializing the CPU. I’d probably go with the lower value resistor.

The series resistor is probably not needed. If used, I might go with something like 22 ohms, particularly if you are running faster PWM rates. Higher values will slow the switching times of the FET.

I soldered a wire across the gate resistor with the 10k pulldown still in place, and it went back to not working again. The last thing I can think of to try is to go back to a 10 or 22 ohm instead of the 100. I didn't try a low value there after I added the 10k one.

The only negative side effect so far is that a PWM value of '1' no longer turns the FET on, has to be a '2' or above for the lowest mode. That's with the noisy phase correct FWs, I haven't tried with the fast PWM yet.

You guys are amazing! I don’t understand enough to really understand what you guys are actually saying but I see progress and great minds working together and I love it. Thanks for all the frustrations and trials you guys are taking on.

Also, how the hell are you all soldering those tiny resistors in place? Please tell me you are using one of those little butane torches or hot air gun with a little nozzle.

It is easy either with a hot air gun or even with a soldering iron with solder paste, you can use the paste to hold the part in place then just touch it with your iron. The part will generally self center, and these boards actually aren't too bad because the parts are fairly spread apart.

I tried gate resistors of 10, 22, 47, 75, all those had major or minor glitches still present. I think I'll go with 130 ohm/10k ohm, I don't get any weirdness at all even running fast PWM nlite. Dunno why the gate resistor has to be so high, the other drivers I've seen worked with 10 & 10k...

There is hope for me yet. I know this probably belongs in your sales thread, but when do you expect your solder paste to come in?

Putting stuff together with just an iron is easy, just solder one pin or leg or whatever at a time, no big deal. It's when you have to remove a thing where you can't heat all the solder points at the same time that you'll wish you'd bought the hot air gun. And then once you have the hot air gun, you might as well use it instead of the iron whenever it makes things easier.

My first attempt on the 1st board design, failure. If I keep the connection the emitter will softly glow and smoke starts to rise off the board. I have yet to determine exactly where the smoke is coming from.

Well, I took pictures and was going to show you but Flickr stuck their heads up their butts and I can no longer use it. :frowning: So much for my Flickr Pro account, wonder if I can get my money back?

I used a solder paste mask for the MCU/FET side, free handed the back.

And yes, I see now that this diode is wrong. It’s the one that was listed when all this started…I jumped in and ordered everything that was listed exactly as was listed, even created an account with Digi-Key in able to do so…

So, I need to change that Diode and add a 200 Ohm resistor to the PWM leg of the FET between it and the MCU, do I also need to add a resistor between the PWM pad and ground?

I, uh, well…seem to have my ATiny upside down.

Oops!

That's a steady learning curve you are having, Dale ;-) , and I appreciate it that we all get to follow it (board without minus-ring and ATiny upside down in one picture )

Heh. :O

I bet the MCU still works after you turn it around. And if you got smoke, then the diode is at least able to pass electricity, see how it does before giving up on it. If it works the same it really doesn't matter, as long as it fits. If it's hard to get lined up on the existing tiny little pads, you can scrape off some of the mask over the trace to extend it out a bit.

I've been hacking away at them for the past two days, I think 3 boards are now totally destroyed (the components are still OK though, just too much soldering and scraping and soldering again and again...). Good thing they are cheap. And also that they are the alpha versions before the tweaks and updates.

Yes, neither resistor alone will make it work right - at least not with the fast PWM firmwares, which has been the main drawback to these things from the start. The resistors fix that.

The BLF comedy hour is proud to present, Dale the advanced learning curve electrician/comedian! Woohoo!

Ok, hi everybody. I’m Dale and I’m a flashaholic. A stupid one. :slight_smile: But hey, I’m also a SUCCESSFUL one! :slight_smile: I pulled the ATiny from the new BLF FET 17mm DD board and reversed it. Worked out pretty well. I pulled a 200 Ohm resistor from my Zener kit and stood it up, held it in place with tweezers and soldered it under the previously prepared PWM leg of the FET. Simple enough, the Hakko work station makes all this pretty simple, even for a rank amateur like myself.

Now for the fun and games! I soldered the power leads to the test emitter and, with my DMM between, applied power. Smoke! Aiiiiieeee! (Hooked the incoming power leads to the emitter, outgoing to the cell) Oops!

Ok, situation corrected. wired up properly now it’s gonna work right? Uh, well, seems like the little hemostats are clamped on the positive pad and negative ring at the same time. Little sparks dance around the outer thin ground ring towards the positive pad and smoke curls up! Aaaaaiiiieeeee!

Ok, now, everythings clear, we’re good to go (man I’m glad I’m using a 18500 lap pull here and not a Sony C5)

4 levels from .05 to 4.40A with nice even positive switching. Whew! Finally!

Ok, yes, I’m embarassed. But hey, it could happen to anybody! And probably will happen to a few of YOU! So I wrote this to make sure y’all are dotting your i’s crossing your t’s and minding your p’s and q’s. :stuck_out_tongue:

(And I just found out that minding your p’s and q’s is in reference to tending your own Pint or Quart of Ale, so cheers!)

See, I told you those little things are practically unkillable.

I think the only form of torture you left out is connecting it to household 115VAC! lol :D