17mm & 20/26/27mm single-sided DD/FET driver release: A17DD-SO8 / A20DD-SO8 / etc

BTW, anyone know why it uses a 22k resistor instead of the 1912 we had been using before?

I’ve tried both, and I found that 1912 makes the OTC work quite a bit better. The 22k resistor puts the useful OTC values at the far edge of the attiny’s measurement range and makes the OTC timings particularly temperature-sensitive.

wight states in the OP: "My 22k R1 replaces the 19.1k R1 due to the change in how the divider hooks up to B+. 22k is not guaranteed to be perfect, but it’s close enough for me and for now".

It was supposed to compensate for the design change in order to keep the LVP values the same (130 and 120), but I usually use lower values anyway. wight's and C_K's board all had the design change - changed from the original Nanjg, and the original BLF DD driver (https://budgetlightforum.com/t/-/27210). On the Nanjg and original BLF DD, the Batt+ came after the diode, while on the new designs, it's direct from Batt+. The diode has a voltage drop across it, so maybe the theory was it would be more reliable without the diode? This goes back a while. I thought at the time, there was a good reason for the change.

No idea it effected OTC though -- if the 19.1K is better on this exact board design for OTC, I'm thinking it can be used, just that we would have to come up with different values to use for LVP, as long as it stays in range of course.

Ahhh - wight or C_K would know this stuff cold (both MIA), RMM would also probably know. There are a few others around knowledgeable on issues like this.

The only purpose for the 4.7K and 19.1/22K resistors is LVP, so these can be changed to anything as long as LVP can be made to work.

Sorry, made lots of edits on this post...

Thank you!

What firmware you guys prefer for this driver?

If you don't mind buying preflashed micros DrJones guppy2drv sold by RMM is a pretty good choice. Lot of options, and it uses the off time memory.

Thanks!

I need to get some 1912 resistors to swap out on my current drivers so I can test it, but from what I’ve seen so far the 22K resistor is a downgrade. Both allow LVP to fall into the useful measuring range, but 22K seems to mess up the OTC.

With a 1912 resistor, useful OTC values (0.5s and 1.5s, room temperature) are about 200 and 100, and after being left in a freezer the medium press takes 2s instead of 1s.

With a 22K resistor, useful OTC values (~0.75s and 1.5s, room temperature) are about 250 and 190, and after being left in a freezer the medium press takes 10s instead of 1s. In both cases, the value stays at 255 for a while before dropping at all, so shorter lengths of time cannot be measured.

I tried using the memory decay trick to measure shorter times, but it doesn’t work when the OTC is enabled. If the OTC has power, it will keep the attiny powered up enough to keep memory from decaying, so the shortest amount of time I could measure was like 4s with that approach.

interesting. I have been using 22k because that’s what wight recommended. R1 was the only thing changed between your tests?

Where do I need to look for problems with a couple of my drivers. They don’t have modes, just single mode.

I want flash them on my own.

STAR (or derivative) is what I’ve used

So the only way to get Guppydrv or Moppydrv is buying preflashed chips from RMM? There’s no way of flashing it yourself?

Thank you! I will give it a try. Does every Nanjq compatible firmware (for example NLITE) work with this driver?

Yes I think so. Because it isn’t open source.

No :slight_smile: I like to know if every firmware build for Nanjq Drivers (for example the 105c) also works for the A17DD-SO8

I only found the download links for nlite there :frowning:

I dont think there is a download for guppydrv at nerd camp. As far as I know the only open source codes DrJones has are the ones found in ToyKeepers repository.

The OTC shouldn’t power the MCU because it’s not on the VCC. As far as I know, the MCU cannot be powered by any other pin than the VCC. The input capacitor would keep the MCU alive, but I can’t see the OTC doing it. On the other hand I’ve had to deal with some OTC weirdness myself, so I wouldn’t bet my savings on it…

In any case, if you want to shorten the measurable time of an OTC, put a so called bleed resistor on top of it. I’ve used values of about 360K for mine. I’ve had to deal with bleed resistors enough to incorporate a dedicated resistor spot for them on my driver boards. You just put them in parallel to the OTC, which basically means on top of it if there isn’t a dedicated spot.

It shouldn’t power the MCU, but it appears to do so anyway. The mem decay time goes from ~0.5s to ~4.0s depending on whether the OTC was charged when the light shut off.

Weirdness… And even more weirdness as that I have a 13A based driver where the memory decay time is about 10 seconds, and it doesn’t even have an OTC on it. It’s all this weirdness that has me back on OTCs but with bleed resistors. I use the memory decay trick for storage between short clicks, but no longer base on/off time checks on it.

The reason he went to the 22K instead of the 19.1K was simply because if you were using an attiny that you had pulled off of a 105C, the LVP values were close enough without having to reprogram. Unfortunately, it does seem to affect the OTC timing in weird ways...an unintended side effect. You'll find that on the zener mod drivers the LVP resistors affect the OTC timing very little, but on the 1S drivers (the newer ones with the cap on the battery side of the diode) it does make a big difference.

In short: if you can program your own MCUs, or are buying pre-programmed, just use a 19.1K instead of the 22K. If you are using a pulled MCU from another 105C driver, then you aren't using off-time memory and the 22K doesn't mess up anything.

I bought a pack of resistors from fasttech that includes 18K, 20K, 22K, no 19.1k. Since 22k can mess up the OTC which is a good alternative, 18k or 20k?

just order a bunch of them they are cheap
http://www.aliexpress.com/item/Free-shipping-500pcs-RES-ORIGINAL-SMD-Resistor-1-0805-19-1k-19-1K-chip-resistor-1/32268559656.html

I’m not sure if RMM carries extra resistors, but if so I’d like to add some to my next order.