Stumbled on this interesting part from TI recently
TPL5111 solves a typical problem in low power wireless systems- things need to be off most of the time, and wake up periodically to transmit. The usual solution is to pick a microcontroller that can stay asleep in low power mode at a few uA, then wake up on RTC timer. That works most of the time, but sometimes even that is too much standby power. Imagine a system for example that has to work from a small coin cell for 5-10 years. Each uA of sleep current is an 8mAh a year. So in 10 years, 80mAh is wasted. (A typical CR2032 battery for example starts with only 220mAh)
TI’s solution is a timer that can stay on while drawing 35nA. Once set with a single resistor for a particular time interval, between 100ms and 2 hours, it turns power on to the system, waits to hear back from the micro via “done” pin and then turns things back off. TI even provides a handy table of resistor values vs timer settings. Not bad for $0.45@1k, plus there are many other scenarios such an almost zero power scheduler may be handy.
Apologies for site being down. Some pesky malware managed to find its way in and overwrite a bunch of system files. Things should be back to normal, but if anything is misbehaving, leave me a comment
And here is the second part of the $1 multimeter deal from the last Hamfest. Together with Micronta 22-201U analog meter reviewed here I picked up this 3.5 digit digital one of a similar age. The poor thing looks like it had a rather difficult life!
This one has been sitting since the summer- it took a while to get all the rain to evaporate from the inside! When I grabbed the pour fella, it had water up to the mirror.
$1 takes it!
Today we have a somewhat vintage teardown. Even though you can still buy this Watchdog BWD-HWA Water Alarm in home stores and online, the design itself probably goes quite a few decades back as we’ll see below. We’ll also learn a few things about low power design. Rumor has it these last forever on a nine volt battery!
I’ve been lucky enough recently to score a Keithley 2304 power supply off ebay for a measly $75. For those unfamiliar, these are high speed battery simulator units capable of measuring very low currents and also behaving like a battery and sinking current.
Original ebay picture
By popular demand, the breakout/passthrough combination boards family now includes a 1mm pitch variant:
This version handles up to 30 signals which seems to be a practical limit of most 1mm FPC connectors. Each signal is numbered and brought to a 0.1 in spacing header for easy connection to your favorite logger/analyzer/scope. Continue reading
It’s been a while since we’ve fixed anything. But no worries- something always breaks around here! Lately, our fancy electrical dryer decided to call it quits. Continue reading
Our rooftop solar system has been operating for a full year now- time to look at the results. Other than snow covering panels, it’s been pretty maintenance free and generated many referrals for the installers from various people asking questions and wanting to learn more about it.
Here is a product whose origin lies in the pain and suffering of an actual development project. Imagine you have a shiny new display made somewhere out there in a world that comes with a demo board and some datasheets. So you take a display, hook it up to your favorite development board and try to follow the documentation. Except nothing works. And yet a a demo next to you works well, but is very tiny, has no test points and not documented. So you poke at the fine pitch flex connector with a scope for a bit, and realize you need a better way to capture what’s going on. Off you go to the lab and cobble together what is essentially a pass-through: two FPC breakout boards back to back, with a 0.1″ header in between.
Now you can hook up your trusty Saleae Logic analyzer and look at what the demo board is actually sending down as opposed to what the datasheet says it should. This board is exactly that, but made into one neat package. It can handle standard 0.5mm pitch FPC connectors up to 40 pins wide.