ATTiny13A based drivers w/ off-time memory issues (operating as NEXT MODE memory and activating mem when it should be off)

[comfychair]

I have a cheap import DVOM with a 'capacitor' function, it seems to give readings close enough when checking known-value parts.

[texaspyro]

@comfychair

I have a cheap import DVOM with a ‘capacitor’ function, it seems to give readings close enough when checking known-value parts.

A big problem is the capacitor value changes with the applied voltage. Who knows what voltage the tester is testing at?

[RMM]

Capacitor issues aside, we know what the variable is that changed here and it isn't the capacitor properties/type of capacitor/heat/etc.--it is the capacitor location. I don't think that capacitor damage or installation is the issue here.

Regarding reflow temperature...I always use at least 350 and air speed of 5. I also solder 7135 chips with my iron set at 720, but I like to work fast. Everyone has their preferences. Total heat absorbed/temperature of the work piece is what matters.

[wight]

@texaspyro

It could be the caps you are using. SMD caps are evil little creatures. And the smaller their physical size and the closer they are run to their working voltage spec, the more evil they become. For instance, a 10uf 6V cap might actually act like a 1 uF or smaller cap if run at 5V. What you think are 1uF caps may be acting like 0.1uF caps… I always use the biggest package/highest voltage rating caps that I can fit on the board.

Also, note that capacitor values can change over time. Some dielectric types are particularly bad… avoid the cheaper/more unstable dieelectrics if a stable capacitance value is important. For instance X7R caps can be spec’d at +80/-20% values as shipped from the factory… and can get worse from there…

In regards to your initial paragraph here… I don’t see how your “for instance” is actually supporting “the closer they are run to their working voltage spec, the more evil they become.” Can you elaborate? It sounds as if you may actually mean “the further away they are run from their voltage spec, the more evil they become,” but I just can’t tell. I’d like to hear more about this, but I also don’t see where it’s relevant to the problem at hand.

[Crux]

A quick search found this useful article:

http://www.maximintegrated.com/en/app-notes/index.mvp/id/5527

I try to use C0G, NP0, X7R or X5R dielectric (in that order). I generally avoid Y5V Z5U. And using the highest voltage rated part for a given case size and value will go a long way to minimizing capacitance loss with applied voltage.

[wight]

I went back and re-read the OP. Cereal_killer mentioned to me previously about his offtime issues w/ the 22mm driver but I forgot about it (sorry!), and when I read the OP originally I somehow glossed over the fact that it was with one of my drivers. Sorry for totally ignoring this Cereal_killer, it wasn’t on purpose.

I’ve got a 22mm driver built up with the offtime cap in place (post #38). Mine works just fine setup for offtime with memory. This indicates that at least in the case of the 22mm driver it is not a layout issue. Cereal_killer, I don’t know if you added it later but I see that your picture in post #35 is of a 22mm board with the offtime cap position not populated.

[zoom_zoom]

Resurrected,

anyone have any idea what the problem is/was? I'm having similar issues.

[wight]

@zoom zoom

Resurrected,

anyone have any idea what the problem is/was? I’m having similar issues.

Without re-reading the thread, I suspect that this may be related to the 22k resistor I was recommending. ToyKeeper did some tests which indicate that this resistor is a very bad idea, 19.1k is still the way to go.

Take a look at the posts I mention in my own post #642 here for more information. If this doesn’t seem like what you are experiencing, doesn’t apply, or I just need to re-read this thread let me know.