The factory visit has been postponed to tomorrow, but Mr Tang has pretty much solved the hard part having to do with machine settings and materials. There's still a minor issue with pressure damaging the cable attachment but the inside part is working now (which is not surprising, it was already working after fiddling all day on our first visit, before their material expired). The attachment too is quite likely an easy fix because, well, it's been fixed twice already on the two factory visits.
What they don't understand is that they need to change only one parameter at a time! This is the scientific method... But they often change 2 or more parameters each trial hoping to get lucky. Oh let's change the temperature and the material and try again. NO. First you change the temperature and try again, then try the material! Collect data points calmly, then reflect, make a theory and test.
All day at the rubber factory amidst toxic and quite possibly carcinogenic vapors. Head and throat aren't happy. Writing from a bus heading back, but not quite to the right place because it's too late and the right bus has already left. This bus will stop half an hour away but there's a connecting bus or a subway or something. Shouldn't be a problem. Just glad to breathe some fresh air. Compared to the burned rubber, the odor of mold in this old bus is a heavenly scent. There was one thing though which smelled worse than the rubber at the factory and that was Mr Tang's breath. That didn't help with communication as the safe distance was about 2-3 feet. Sonia was there to translate from broken mandarin to Hunan dialect. The lights today were pretty much off for some reason - perhaps the rain caused a black out and they were on a generator. Quite gloomy in there with some neon tubes hanging from the ceiling and bright clouds of burned rubber coming out of the machines.
What's up with the surprise? - ask all of those who have already prepared with beer bottles, popcorn and TV dinners and are eagerly awaiting in front of the screen for the awaited DreamLover 2000 last-before-launch super feature. Some of you may even have summoned friends and relatives and you may all be sitting on the sofa with the projector hooked up and the children put to bed.
Sorry folks. Not today, quite possibly tomorrow. Here's the full report. ...
We're pleased to inform you that the overmolding attempt was successful - the custom cable's exterior merges with the molded part. The factory trip for tomorrow is confirmed.
We'll finalize this part and try to make it look as good as possible.
The "surprise" grand announcement may get posted in as little as 24 hours.
Don't worry - we're not back to the drawing board. This receiver prototype was created as a sample; the PCB assembly house will use this to avoid screwing up!
We were able to get professional no-clean flux from the PCB factory and using this we resolved all problems related to hand assembly of boards. Chiefly, the problem had been erratic current consumption. This was tracked down to the flux we were using which contained conductive material. Using this flux yielded a 100% reliable and functional board.
The consumption in standby mode is 0.1mA. This includes the TVS diodes, two strategically placed components that prevent electrostatic electricity from damaging the circuit, but which also have some quiescent current.
The peak shown in the graph below (smoothed out by a capacitor) is the activation of the RF circuitry which periodically wakes to listen to incoming packets (about once every half second). After awakening it takes almost 3ms for all the relevant circuitry to become operational including the crystal oscillator used for RF communication, the oscillator and so forth. This is evident from the waveform (the little bump on the left is the "wake up" period). The real receiving time is 6ms, enough for packets to be received when the remote control is transmitting. For the savvy ones out there, current was measured through a 10ohm resistor so the reading must be interpreted as milliamperes and divided by 10.
