Here's a possible solution. It's ethernet-connected and will switch a 10A output. It's made for UK use but would probably be fine if you have a 220V supply. It doesn't say whether it tracks NTP, but looking at the specs i'd suggest it's linux inside and can do that.
http://www.audon.co.uk/webcontrol/EZ-21g.html On Mon, May 2, 2016 at 7:21 PM, Adrian Godwin <artgod...@gmail.com> wrote: > They're a LED and some current limiting. Some are specced as low as 3V and > 10mA but they're optimised for 12-24. I'd definitely use a transistor and > at least 5V, especially from something like a Pi or Teensy, which have 3v3 > logic levels. > > My reading is that Bill doesn't want to mess around with micros and > electronics, though. He wants an off-the-shelf timeswitch that - for > perfectly understandable reasons of engineering pedantry - is always > correct. > > On Mon, May 2, 2016 at 5:56 PM, jimlux <jim...@earthlink.net> wrote: > >> On 5/2/16 8:24 AM, Nick Sayer via time-nuts wrote: >> >>> To flesh this out a bit more, on a Raspberry Pi, it would be easy to >>> make a cron job that would pulse a GPIO pin high. They really *want* you to >>> use Python (thus the name), but this is easy to do in just a shell script. >>> First, do this to set things up: >>> >>> #! /bin/sh >>> >>> GPIO_PIN=9 # pick whatever one you like >>> >>> echo $GPIO_PIN > /sys/class/gpio/export >>> echo out > /sys/class/gpio/gpio${GPIO_PIN}/direction >>> echo 0 > /sys/class/gpio/gpio${GPIO_PIN}/value >>> >>> Next, run this script out of cron: >>> >>> #! /bin/sh >>> >>> GPIO_PIN=9 >>> echo 1 > /sys/class/gpio/gpio${GPIO_PIN}/value >>> sleep 1 >>> echo 0 > /sys/class/gpio/gpio${GPIO_PIN}/value >>> >>> That will make a positive going pulse with the leading edge synchronized >>> to cron (for sufficiently vague definitions of “synchronized”). >>> >>> As for the hardware side, take the GPIO pin and connect a 10k resistor >>> between it and the base of a 2N4401 transistor. Connect the emitter to >>> ground and the collector is a classic “open collector” switching output. >>> Think of it like a switch connection to ground. When it’s on, there is a >>> low impedance path to ground. When it’s off, it’s high impedance. You can >>> use it to work a relay (be sure to add a flyback diode across the relay >>> coil) or directly to switch any load that doesn’t exceed the abilities of >>> the transistor. >>> >>> If you want to be a little safer, you can use an opto-isolator instead. >>> Connect the GPIO pin to a 150 Ω resistor and then to the anode of the LED >>> in an optoisolator. Connect the cathode to ground. The optoisolator itself >>> can be either a phototransistor type or a driver triac type (the latter >>> would be used to drive a power triac to switch AC loads on and off). >>> >>> >>> >> >> SSR data sheet at mouser (they are <$20) >> http://www.mouser.com/ds/2/307/g3na_ds_e_11_1_csm165-892371.pdf >> >> myriad varieties of inputs and outputs, whether it has an indicator (nice >> for testing), whether it's a zero voltage switch. >> >> BUT.. it kind of looks like it wants to see 4V to turn on for sure. Maybe >> your 5V USB powered widget puts out that on a GPIO pin, maybe it doesn't. >> I've had very mixed luck with driving SSRs directly from logic (because the >> real threshold voltage and the real logic output voltage vary with >> temperature, for instance). >> >> I'd use the extra transistor as an open collector and a 12V wall wart or >> similar to provide the current for the SSR input. >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.