X10 - AM486 - disable current sensing

At the time of the top usage of X10 there was lot of technical info on the net, today ... not so easy to find them.

I have to modify an old AM486 disabling the current sensing and I didn't find much around, so digging on my old notes here and some searches, I did come up with some info that I hope can be useful to others.

AM486

The AM486 is a X10 "Appliance module", produced by many companies, like X10, RCA, etc.
It is basically a mechanical relays for resistive loads, up to 15A.
Usually used to control incandescent lamps up to 500W.

It is important to point about the "resistive load" since the module is designed to mainly support that.

Among other characteristics in fact it has a function called "current sensing".

Current Sensing

What is the current sensing ?

Let see with an example.
Lets connect the AM486 to a floor lamp. The floor lamp already has its own on/off manual switch.
So normally that switch is left on the ON position and the only switch that control the lamp is the X10 one.

Nice. But it would be nice to be able to turn it off and on still manually.
So here the current sensing.  The circuit can detect small currents when the X10 unit is OFF, and if detect small currents it can automatically turn ON without the need to have an X10 command sent, i.e. has the capability to turn on a load locally.

Let see a table with various states :

Local switch    X10 Switch    Status load

OFF                OFF                OFF
OFF                ON                  OFF
ON                  OFF                ON
ON                  ON                  ON

Of course you can not achieve a real full local control but in some cases it can be acceptable.

Why disable the current sensing ?

Well, the first reason is that ANY type of load not resistive will trigger the circuit.
For example fluorescent lamps or small transformers.
This type of load always will allow a small current to leak and the circuit will detect it, forcing the load always ON.

i.e. will be impossible to turn off the load.

Disabling the current sensing

Disabling the current sensing is quite easy and fast .. if you know what to do :)

First of all, it is an hardware modification, so it involve modifying the circuit.
As usual all the warnings are active, you are dealing with a circuit connected to the grid !

If you don't know what you are doing, DON'T DO IT.
I'm NOT assuming responsibility in case of damages or injuries

To complicate things there are different version of AM486 on the market, so the modification depends about WHAT type of AM486 you have.

On "older" versions is enough to cut off a diode.

On "newer" ones there is a jumper to cut.

Older AM486

Older model doesn't have any jumper to disable the current sensing.
Look close to the big blue capacitor (in the picture is on the lower right corner)

Picture from the old Ido Bartana website
(https://web.archive.org/web/20080922131038/http://www.idobartana.com/hakb/)

If you don't see any jumper close by then is the old model.
The modification to do is just cutting out the 1n4004 diode located on the top left corner (in the picture above).

Picture from the old Ido Bartana website
(https://web.archive.org/web/20080922131038/http://www.idobartana.com/hakb/)

Picture from the old Ido Bartana website
(https://web.archive.org/web/20080922131038/http://www.idobartana.com/hakb/)

Newer AM486

Newer model does have a jumper to disable the current sensing.
Look close to the big blue capacitor (in the first picture above is on the lower right corner)

Picture from the old Ido Bartana website
(https://web.archive.org/web/20080922131038/http://www.idobartana.com/hakb/)

Reassemble the unit after the modification and voila'.

No more current sensing in the AM486 module.

Just for fun, I did find this old picture in a forum, is the schematic of the NEWER version of the AM486.
Repeat ... NEWER !

Resources

• Tony Laureanno X10 AM486 modifications
• Old Ido Bartana AM486 modifications