Electronics > Projects, Designs, and Technical Stuff

Adresable relays

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JDubU:
Take a look at this:
https://www.tinyosshop.com/index.php?route=product/product&path=141_142&product_id=363

It has an on-board arduino that is pre-programmed to take single character ascii commands on its serial port to control the relays.  It also has an FTDI USB to serial chip as well as connectors for WiFi and Bluetooth to serial modules.  You can also reprogram the arduino to control the relays with a different command protocol.

There are a bunch of variations of this type of board from various sources.
For example:
https://www.tinyosshop.com/index.php?route=product/category&path=141
https://www.banggood.com/Wholesale-Relay-Module-c-8133.html

qwertis:
That is a lot food for thought! Thanks guys! :)

ajb:
You say "the delay has to be minimal" but in electronic terms incandescent bulbs take ages to turn on and off, so there's a definite upper limit to how fast an interface is really useful.  Consider that the luminous output of the bulb appears continuous despite the fact that on AC they bulb is actually turning off and on 100-120 times a second.  This is why DMX, which was developed in the 80s, boasts a typical refresh rate of only ~40Hz, because faster isn't useful with incandescent sources.  LEDs would be a different story, and in fact LED fixtures tend to use internal timing to provide for strobe effects instead of relying on direct DMX control for timing.

Anyway, your effective maximum useful update rate for the whole array of bulbs is only going to be on the order of 40Hz, and with only on-off control that's a data rate of 1200bos.  Assuming the bulbs are spread evenly, there's only a 1m from one unit to the next, so using anything RS485 based is probably unnecessary.  You can run the whole thing like a set of cascaded 1-bit shift registers, so you just need 5 wires (Gnd, +5v, Clock, Data, Latch), and just use direct 5v logic signalling.  Preferably you'd buffer the signals at each unit, and use a schmitt trigger at least for the clock and latch lines.  You could do this with discrete ICs, but you could also just use an MCU, at the data rates in question it would be perfectly easy to bitbang.  Or, if you wanted slightly higher data rates for whatever reason, you could use hardware SPI, with MOSI on one unit connected to MISO on the next, and send an 8-bit command to each node.  Either way, the whole thing is still a shift register, so you can implicitly address each node according to its position within the chain by setting the right bit(s) in the shifted-out data.

Side note, for switching the bulbs on and off, a zero-crossing SSR would be preferable to a mechanical relay to avoid the transients that would occur if your relay happens to switch on or off at the top of the half-wave.

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