Oshpark Projects

[wight]

@MRsDNF

Thanks RMM. I asume they only have four legs? I have components on order to program the Attiny MCU’s hopefully with the help of a very patient member her, I hope. Lets hope its not to late to teach an old Moose new tricks.

Aha, I knew something must have changed while I was gone! New tricks!

To better illustrate, here’s a different illustration of RMM’s adapter:

I haven’t used the adapter of course, but I assume that for optimal use solder is lightly wiped across the adapter and allowed to cool. Then one simply presses the MCU against the PCB where it would normally be soldered on. Once you’ve got it in place and held down you can program it normally. Someone may correct me here though. (?)

@Pablo E.

If i understand well how zener mod is done (i am a bit confused with post of different dates, where capacitor is placed before or after diode) i don’t have to tweak anything, zener can be placed just over left side of D1 and C1. Just a stroke of luck, I designed the board this way, keeping in mind being able to place a C2 for 25/45/85 MCUs.

I am not sure that I understand everything you said. The Zener mod is very simple, but due to my time away I had to think about it / double check a bit. The Zener mod requires two additional components: a low-value resistor (such as 200 ohm) and an appropriate zener (such as MMSZ5229B for example). The resistor should be placed between MCU Vcc and Vbat. The Zener should also be attached to MCU Vcc - it will pull the voltage down to the appropriate level. Without the resistor in place the Zener will burn up. See comfychair’s post #9 here using the userscript I posted in my post #104 here for a semi-illustrated semi-guide to the Zener mod.

Unless I am mistaken, this means that for a Zener build a person would replace D1 with the 200 ohm resistor, then place a Zener between the lefthand pad of the resistor and the lefthand pad of C1. I think that this will be a pain as you have things setup now: trying to set a 0603 or 0805 component on those little diode pads will result in the component wanting to walk/spin… probably getting stuck to C1 sometimes. Stacking the Zener on top will probably also be a bit of a pain.

@RMM

Every one has their own design choices, but given the choice I also never like to have exposed pads directly against the ground ring because the solder always goes there, and often can pull the component in that direction as well.

When designing a circuit, it is always important not to think not only about the circuit functionality, but about ease of assembly and installation. Often, due to space constraints, we have to sacrifice a little bit to make things fit, but it is always important to keep the end goal in mind (actually building the driver and being able to use it in a flashlight).

Everything RMM brings up here is important and worthwhile to think about. I personally also try to keep my component pads out of my GND ring. As you can see by looking at my drivers, I frequently fail. (a) the components can be pulled toward the ground ring (b) the GND ring can get unwanted solder wicked onto it. Mostly (a) is the big problem IMO: sometimes clearances demand that components stay far away from the edge of the flashlight, not skew on their pads towards the outside. Surface tension with solder is surprisingly strong sometimes and will pull a component right off of it’s pads. 7135’s and FETs are notorious for this, which is why I was very careful to implement a small “dam” of resist on drivers like the A17PZL. Without this the 7135’s will pull all the way to the edge of the GND ring. 2-pad passives are not as bad, but it’s still an issue.