Link to other posts
Forget Me Not : eLDERmon Intro
Forget Me Not :  eLDERmon  Electrical
Forget Me Not :  eLDERmon  Outlets
Forget Me Not : eLDERmon Planning
Forget Me Not : eLDERmon Parts 1
Forget Me Not :  eLDERmon  Sponsor Parts
Forget Me Not : eLDERmon Hardware Hacking
Forget Me Not : eLDERmon GNUplot
Forget Me Not: eLDERmon Protocol
Forget Me Not : eLDERmon Hardware Hacking #2
Forget Me Not : eLDERmon Hardware Hacking #3
Forget Me Not : eLDERmon OpenHAB


While this is a repeat of my last blog, its important enough that it should be repeated.

The Forget Me Not challenge throws up opportunities for interfacing with electrical devices.

There are many ways this can be accomplished, but sadly I do see some dangerous practices, that are posted by the ignorant.


Electrical safety isn't something to be dismissed, since it can kill.
Generally the victim isn't someone working with the Mains voltage, but an unintentional contact (ie by accident)

The essential bit of safety around mains is ensuring there is two layers of insulation.

RF Controlled Outlets

I have used these RF controlled outlets before.


photo source (showing the later version)

They feature a programmable code, come in a variety of styles to suit different countries .... and they have very good instructions.

When I first ran across them, I thought I was going to have to hack the remote (the magazine publisher commented ...'finally some real hacking' ... or words to that effect), but a little digging and I found these guys already had the code sorted, and produced a library to use with Arduino and now Raspberry Pi.

So while I've seen various methods of controlling the mains voltage, in my opinion many are NOT safe, have not been tested and are often more expensive than some commercial units.

As I showed in my last blog, its often the unintended contact that causes problems.


One of the other things to consider is Insurance.

If for some reason the device that you built was to catch fire (possibly due to electrical spike, rather than poor construction) would your insurance cover you.?

In New Zealand with the Insurance companies getting a hiding over the Christchurch Earthquakes, many are finding ANY reason to invalidate claims.


While the RCswitch software could be set to send the code 1 to X times to ensure it got through, there is no feedback if the socket was turned on manually.

For this challenge knowing that the socket is ON is part of the automation, and short of always sending the OFF command (or an ALL OFF) it would be useful to know.

So I spent some time checking the internals.

This is the inside of the simple version.


This shows that pesky IC with no markings.

So not really a lot of room to add extra hardware.

By chance I also had another version by a different manufacturer.


The antenna seems to dominate the upper area, but much more space.


The underside shows a few more parts, but of more importance is the cut in the board to ensure the mains voltage can't track across the surface to the low voltage side.

The device is double insulated so no-one can come in contact with anything, but its nice to see they have gone the extra mile with safety.

I couldn't get this one to work with the RCswitch code ... however the nice Tektronix Oscilloscope coming will probably help resolve that.

Last time I looked, it wasn't available in NZ but the large Australian hardware Chain selling them is represented here ...

I'm now stuck with what do I do.

Do I design a new board that will receive codes and switch a relay, along with report the state back, or do I add a micro and transmitter just for feedback.?

I do have a lead (no pun intended) on another that might be better suited for modification.

I'm also thinking of other options that ideally would include current checking or measuring and provide feedback.

RF Transceivers

Thanks to EricTsai   electronichamsters

( Inexpensive & Flexible Home Automation / Wireless Sensors

I ordered a few (well 18 actually) RFM69xx modules, in varying frequencies.

As you can see by the picture below they are very small.

RFM69xx next to a AA battery.

Shortly my Rural delivery driver is going to get sick of coming up the drive for a signature, but unlike Xmas I can order what I want.

I have added some ATtiny85 in both DIP and SMD to my element14 basket, but I need a few more bits before I commit it.

So in the meantime I brought a couple and a programmer from my local supplier Hadley and they will be here tomorrow.

In the last challenge I had some issues with programming them, and while I want to sort it out, I have a few other tasks that deserve my attention.

So I guess I know what I'll be doing over the weekend.

I'm also hoping to do a comparison for the range, but I really need a fine day ... ie one where you want to go outside.


Frederick and Christopher you'll note that I did learn and did this early ...

edit 030914
Attachment is the codes the Watts Clever use.