[onerng talk] LED flashing error code

[Paul Campbell]

On Tuesday, 5 September 2017 4:16:48 AM NZST Hans wrote:
> I also stumbled across this page http://holdenc.altervista.org/avalanche/ in
> which the author uses a similar noise source and seems to be getting higher
> noise voltages at what appears to be much lower currents through the
> avalanche junction (of a 3904). Your circuit is limited at around 4mA (20V
> and 4k7 ohm), his is around 100uA (13V and 150k ohm). But as I say, the
> whole thing seems very sensitive to the exact components and values so I'm
> impressed you've made it work well in production.

I must admit I used someone else's original design and haven't played with 
this part of the design, I should try tweaking the current on the noise 
generator (though lower current may make it less repeatable).

Mostly I've tweaked the bias on the output amplifier to set the gain to pass a 
simple manufacturing test (the ratio of raw 1s vs 0s must meet a particular 
threshold before it can be shipped) - the original manufacturing run had a 
very low fallout, the latest a higher one so I suspect I'm going to need to 
revisit this area

> In the meantime I've ordered some garden variety (i.e. ebay) SOT-23 3904's,
> which I should have around anyway. I've also ordered a replacement OneRNG,
> but I would like to fix this one.

if they don't work (ie aren't really good 3904s) let me know and I'll send you 
some more 3904s from the original reel

	Paul