Oshpark Projects

[Mattaus]

That is pretty cool. They must hate all our round PCBs. So much wasted board space.

[Werner]

I like the horse…

[DB_Custom (Dale)]

Impressive! Thanks for sharing that. I’d never have guessed…

OH SNAP! Our local college is purple and gold in their colors, the Crusaders… Their logo would look freaking awesome done on these boards! Keychains! :bigsmile: I might have to get someone to design that layout for me…

[texaspyro]

Where’s Waldo?

[Rufusbduck]

Added some stuff by CK and HQ to the op. CK, if you could start a thread for your projects I can add links. You don’t have to finalize them, that will happen as the projects get used and questions come up. Otherwise specific project questions get buried in this thread where they can be difficult to find.

[wight]

RBD, here is yet another new DD driver to add: 17mm single-sided DD/FET driver release: A17DD-SO8

I went with a different prefix so as to reduce confusion. We’ve currently got DD drivers which were created or modified by at least 3 different people using overlapping version numbering schemes and they all bear the BLFxxDD names.

[Rufusbduck]

Ok, I’ll post it the way you’ve written it. To anyone else: if there is a particular wording or description you want used please type it out so I can copy/paste it to the op. Thx.

[Mike_C]

@Rufusbduck

Wight and I were knocking our heads together over this. On a standard 105C board the reverse polarity diode is in the circuit with the voltage divider so some voltage is dropped across D1, then more across R1 and the remainder across R2. The mcu compares the voltage drop across R2 with an internal reference voltage and does what it’s programmed to do. The ratio of R1 and R2 determine the battery voltage at which the mcu is triggered. With one cell, 19.1k ohms and 4.7k ohms provide the correct trigger voltage. With two cells I came up with ~48k for R1 if I leave R2 at 4.7K. For three cells R1 will be an even larger value.

Sorry for bumping an old discussion…

I know I can connect the voltage divider before the reverse polarity diode, but to me a much cleaner design would be to connect the divider after it. I plan on using this diode as reverse polarity protection: ZLLS410TA Diodes Incorporated | Discrete Semiconductor Products | DigiKey (DigiKey part number ZLLS410TR-ND)
The specs say Vf is 0.38V. Can I count on that being accurate? Has anyone measured Vf on this particular diode? I plan on using it for a board with ATtiny13a in a 2S cell configuration (with zener diode on board).

Edit: Edited link and added DigiKey part number

[wight]

@Mike C

Sorry for bumping an old discussion…

I know I can connect the voltage divider before the reverse polarity diode, but to me a much cleaner design would be to connect the divider after it. I plan on using this diode as reverse polarity protection: Electronic Components and Parts Search | DigiKey Electronics
The specs say Vf is 0.38V. Can I count on that being accurate? Has anyone measured Vf on this particular diode? I plan on using it for a board with ATtiny13a in a 2S cell configuration (with zener diode on board).

Your link does not work for me. Post Digi-Key Part Number or use the “Short URL” button (chain links) in the upper right.

I think my position on this is well known, but here we go:

• No, you cannot depend on that number. The Vf depends on the load, they may publish something in the datasheet to help you nail it down, but you still can’t depend on it IMO. Temperature will likely also cause changes [EDIT: I assume…].
• 0.38v sounds high to me. I was already unhappy with 0.3v from the protection diodes we’ve been using!
• I don’t see why it’s cleaner. Do you mean visually cleaner or conceptually? Because the concept is definitely messier to me when you add the diode in.
• A standard Zener build does not have a protection diode. I assume you’ve already accounted for this in some way?

[Mike_C]

@wight

I think my position on this is well known, but here we go:

• No, you cannot depend on that number. The Vf depends on the load, they may publish something in the datasheet to help you nail it down, but you still can’t depend on it IMO. Temperature will likely also cause changes [EDIT: I assume…].
• 0.38v sounds high to me. I was already unhappy with 0.3v from the protection diodes we’ve been using!
• I don’t see why it’s cleaner. Do you mean visually cleaner or conceptually? Because the concept is definitely messier to me when you add the diode in.
• A standard Zener build does not have a protection diode. I assume you’ve already accounted for this in some way?

Sorry about the link, edited it: ZLLS410TA Diodes Incorporated | Discrete Semiconductor Products | DigiKey (DigiKey part number ZLLS410TR-ND)

With cleaner I mean that if the cells where inserted incorrectly, absolutely no current would sip through. The reverse polarity diode would block everything… Or so I would think.

@wight

A standard Zener build does not have a protection diode. I assume you’ve already accounted for this in some way?

Shouldn’t I include a protection diode in my design? My understanding of the schematics is that the zener won’t help against incorrectly inserted cells.

Edit: But if Vf over the diode is load dependent, it kind of makes the design obsolete. Didn’t know it would be, the specs specified a precise value. Thanks for the info, I’ll connect the divider before the protection diode.

[wight]

@Mike C

@wight

A standard Zener build does not have a protection diode. I assume you’ve already accounted for this in some way?

Shouldn’t I include a protection diode in my design? My understanding of the schematics is that the zener won’t help against incorrectly inserted cells.

Take a step back and identify what component you are concerned about damaging. Probably the MCU, right? Look at your schematic and imagine attaching a power source backwards. Now follow the path through which electricity would flow. I imagine that you’ll find that the MCU remains within spec?

@Mike C

Edit: But if Vf over the diode is load dependent, it kind of makes the design obsolete. Didn’t know it would be, the specs specified a precise value. Thanks for the info, I’ll connect the divider before the protection diode.

There is a ‘Datasheets ZLLS410’ link on the Digikey page. Follow that and check first graph on page 4. As you can see, at least 0.1v change can occur with load. Temperature also throws a (small) monkey wrench into things, the same graph shows that. This is “good enough” in some situations, but I don’t like it and I think if you look at the datasheet you will not like it either. The datasheet will tell you what you need to know though, please do not just rely on my opinion.

[Mike_C]

@wight

please do not just rely on my opinion.

Not so easy, being a beginner at all this.

I did take a look at the charts but as I have no idea how much the load/current would change I don’t really know what to expect. Temperature is an obvious issue though, flashlights can get pretty hot. It does seem pointless to have LVP if it isn’t as accurate as it can be, especially since the readings in the MCU might be around 10% inaccurate (based only on what I’ve read in various threads here).

I’ll continue my designing with the divider connected before the protection diode.

[texaspyro]

Zener mod’d drivers do not need a protection diode. The zener will clamp the processor voltage to –0.6V if the battery is connected backwards which won’t hurt anything.

[Mike_C]

Makes sense, but I’ll leave it there so the board can be used in non zener projects.

[wight]

@Mike C

Makes sense, but I’ll leave it there so the board can be used in non zener projects.

In that case you don’t want/need both. The Zener is always used with a limiting resistor, if the board is built without a Zener then the protection diode will take the place of the limiting resistor.

[Mike_C]

Oh yeah, of coarse! Don’t need the limiter if the zener is absent, and the footprint on the board is basically the same size.

[Rufusbduck]

The main reason the diode was moved was to make it possible to have low voltage monitoring on a Zener modded board. The voltage divider has to see the battery voltage before it’s been clamped by the Zener.

[Fritz_t_Cat]

The links listed at the top of this thread for BLF 15dd_PIC V1.0 go to “Page not found.”

[wight]

@Fritz t. Cat

The links listed at the top of this thread for BLF 15dd_PIC V1.0 go to “Page not found.”

I guess it’s been superseded by this one:
BLF_15dd_PIC_v2.1
https://oshpark.com/shared_projects/duTu1uYO

[Sirius9]

Oh man, this thread exploded in relatively short time, can’t follow all projects, can someone point me to 17mm driver that can run MT-G from one 18650 cell J)