The last few articles that I’ve posted have been all about reworking the AI-Thinker T5 board to get it functioning with the on-board ESP-13 module. You may also have noted that I chose to remove the relay and screw-down terminal, as I didn’t want anyone connecting AC mains voltage to something which obviously wasn’t designed for it, despite the promotional images showing a light-bulb. Well, here’s another product out of the Middle Kingdom which is not only cheaper than the T5, but apparently a good deal more functional (not too difficult, I know) and safer, too.
Itead Studio is probably a familiar name to most of us, having made a name for themselves producing hobby boards and modules and providing a low-cost PCB service to boot.
They have a new pair of products, going by the not-very-snappy names of Sonoff and Slampher. They are of interest to us because both contain an ESP8266 chip and provide WiFi control of mains powered devices. I don’t have either of these units myself (yet), but from all that has appeared so far, they do seem to be quite special. Sonoff is an in-line, relay based switch for small to medium sized appliances with a 10A rating.
Slampher is a screw-in base connector for light bulbs (it screws into the original socket and then the bulb screws into it) with an SSR which is rated at a more modest 2A.
They are cheap! Basically a single unit is being sold for around $5 at the moment. What’s more, they seem to be of quite decent quality, especially considering the price. From the tear-downs and information I’ve seen elsewhere so far, there’s a switching power supply built in to provide the low voltage DC supply to the logic, there are routed cut-outs on the PCB (on the Sonoff, anyway) to provide physical isolation between the AC mains side and the low-voltage DC side and the single user-input button has a long plastic stem to provide further insulation between the user and the PCB. The one area where the Sonoff may run afoul of regulatory requirements are the screw-down terminals for input and output connections, but otherwise both units look to be in a completely different league to most other offerings out there in the $10 range.
The units are basically switches, but in addition to the ESP8266 for WiFi, they also have a built in 433Mhz receiver and come with a tiny, key-fob sized 433Mhz remote control. So you have that long-stemmed switch on each unit which can be used to manually toggle the (mains) device under control on and off, or to configure individual Sonoffs or Slamphers to respond to one (of the four) channels on the remote control (so one remote can control four S&S switches). In addition to the manual and remote-control modes, the ESP8266 provides connectivity to enable remote switching from your network and Itead provide a free app and “cloud” service, so that your device could be switched on and off from a smart-phone anywhere in the world (no word on security yet, so it’s probably not a good idea to hook up anyone’s life-support system to one of these). Importantly though, the app does provide feedback for the current state of the switched device (even if it has been manually toggled using the switch on the Sonoff or Slampher), so you can always see if someone else has turned your office coffee-maker on at 03:00 (if you happen to be awake and watching the status on you smart phone at that time of the morning).
Pete Scargill has already been at work with a screwdriver and a USB adapter and apparently has reflashed one of the units he has to use MQTT (which opens the door to local monitoring and control of devices, without the need to utilize Itead’s cloud system).
Peter Oakes has produced a couple of nice videos, the first showing the operation of both units and how to set up the cloud interface and the second is a teardown of both units.
Now the strange thing is, these units first came to my attention because of an on-going fund-raiser on Indiegogo. I liked what I saw (and the price) enough to subscribe for a couple of units (my first crowdfunding effort), but after signing up I discovered that similar units are already on sale in the Itead on-line shop. Strange! Why would Itead run a campaign for units which are already in production? Well, it turns out that one reason is that the units available in their shop are earlier versions, which don’t have the 433Mhz remote control capability, so maybe they’re using Indiegogo not just to fund the production run of the newer models, but also to provide a little bit of extra “visibility” to their sales campaign? I don’t really know the answer, but I still like the products and the price enough that I’m in for a couple of Sonoffs and am seriously considering whether to buy in for a couple of the Slamphers (despite the awful name), too. As of the the time this article was penned, we both have twelve days left to decide.
Update – Not about the crowdfunding, but about the devices themselves …I’ve been trawling through the available documentation and it looks as though these devices “do the right thing” when it comes to power and insulation/isolation. The schematic shows that the Sonoff uses an iWatt iW1700 switcher chip to provide the low voltage supply to the ESP8266. This is a really nice little chip which, according to the datasheet, changes modes between PWM (pulse-width-modulation)
and PFM (pulse-frequency-modulation) depending upon the load requirements. It also has an exceptionally low stand-by current draw. Regulation is based on current sensing through the drive transistor and voltage sensing through the auxiliary primary winding of the isolating transformer, so there are no opto-isolators required between the secondary and the chip. At any rate, the supply and design provide “galvanic isolation” between the mains supply and the low-voltage electronics. Definitely a good thing.
Update – Well, the campaign kinda’ fizzled, which is what I hope the products themselves won’t do, either figuratively or literally. However, because I was so impressed with the iW1700 and because it matches the requirements of the ESP8266 so well (ultra-low power when the ESP is in sleep mode), I decided to order a bunch of the stand-alone AC supplies (which are available for just $2.50 each directly from ITEAD) as well as a single Sonoff (the version without the 433MHz remote control) just to play around with. ITEAD obviously ships more promptly than some Middle Kingdom suppliers and everything arrived on my doorstep just six days after ordering. I still haven’t had time to actually play with anything, but some photos and descriptions are in a newer post.