X-10 General Modification Principles


These instructions are based on Hans Attersjö's Home page; altered and corrected based on my and the experience of readers of this site.  I have attempted some, but not all of them and accept no responsibility for the effects of anyone making these modifications.   You follow these instructions at your own risk.


Most modules have a big, usually blue, capacitor in the order of 0.22uF 250V to 0.68uF 250V to drop the incoming power which is then rectified and stabilised to usually -12 or -15V. X10 was invented in England and at that time a positive logical ground was the standard but that is not the case now.  In the case of MEGA32 there are two capacitors in parallel. Change it to half of the original value (MEGA32 both of them) and 400 or 600V.  Note that these are DC working voltages.  If you try to be over-conservative with the capacitors you use, you will find that they are too large to fit physically into the housings.

Most modules uses a 10-22 Ohm 0.5W resistor in series with this capacitor in order to reduce the current when turning on power to the module. Change this one to twice the value and twice the power. In most cases it will work fine without this modification but with a  reduced Mean Time Between Failure (MTBF).

Specific X-10 Modules

Some modules like the WS467 have a voltage divider consisting of two capacitors. The value of the second smaller one, going to logical ground, should not be changed. You should instead replace it with the same value but with a 400-600V type. In the case of WS467, this is the 0.1uF. The first and bigger capacitor should be changed to half of the value but 400- 600V. This capacitor is also usually blue.

Almost all modules uses a serial capacitor to insulate the receive/ transmit circuit from the main supply and to adapt the impedance to the electrical power network. It is very difficult to tell what is the actual impedance of your electrical network (your antenna!) at 120 kHz . It will change with whatever you turn on or plug in and even your cable types might affect it. However, statistically and from a practical point of view, consider it to be twice as high on 230V as on 115V if you have the same power (kW) consumption. Therefore, change this receive/ transmit capacitor to 400-600V and just to be able to physically fit it at the same place, half of the value. As I said, we can consider the impedance of the electrical network to be twice as high on a 230V supply than on 115V supply so we have not really introduced any losses. Even this one is usually also blue.

If you would need to tune/test X10 receivers or transmitters without connecting them to the mains supply, you could use a resistor of 10-15 Ohm (4.7-6.8 Ohm on 115V) to simulate an average "antenna" impedance.

Most modules use a 330k resistor coming from the incoming supply to two diodes to generate the zero crossing pulse. This value is not very critical. However due to the voltage across this resistor I recommend a physically bigger resistor like a 330k-560k 0.5W.


If the module has a triac with a voltage rating of less than 400V change it to 400V or better 600V. If it has a 400V triac, use a MOV to protect the triac. Even on modules with 600V triacs I recommend a MOV. Note that this triac, in most cases, must have an insulated tab. See the modification of the WS467 for some sample triac data.

Appliance Modules

Appliance modules uses a "stepping relay" with a cam and a 115V coil. One should normally rewind this coil to 240V. Perhaps some trick with resistors or capacitors might work if there is physical space. I have not tried it. In fact I have not modified any appliance modules because they had plenty of 230V versions in stock here. I believe that the so called universal module also uses this principle

If you have 240V supply voltage, you have to drop away 130V to get 110V over the coil in the appliance module. If you would use a 100 Ohm resistor you would have, 130 squared, divided by 100 (16900/100)/2 = 84.5 Watts over the resistor! Divided by two, because halfwave is used. However, normally a short pulse is applied to the coil so this is not continuous power.

Leonard Simms in New Zealand (lgs@midland.co.nz) reported that he has successfully modified appliance modules by using a 100 Ohm/1Watt resistor in series with the coil. My first thought was to use a 5-10W resistor instead but after thinking a little bit, I believe he is right! Perhaps a 2W resistor would be a good compromise.

If you get and electronic failure like a blown thyristor or triac, you would have continuous power, instead of a pulse through both the coil and the resistor. A 1-2W resistor would probably just explode if this happens and probably do less damage than a 10W resistor which would heat up a lot more before it burns out.

Be careful, this could cause a fire risk. Also the optimum value or the resistor could be different between different type of modules. Some experimenting is needed. If you have a lot of patience, rewind the coil instead.

USA Heavy Duty Modules

BTW, even in the States, you can buy 220V (heavy duty) appliance modules. They apparently use them for 220V water heaters and such but they do have American plugs and outlets. Also those 220V outlets are not normal US standard so standard adapters can not be used. :-(

US Standard plug  Grounded plug  

      |   |          |   |         

                       O  Ground

15A/220V plug  20A/220V plug

 --   --       |   --   

    O            O    Ground

It is however very easy to change at least the output on such a module to accept a US standard plug. The contacts inside the are universal to accept both 15A and 20A and will work quite OK also with US standard plug. However, the plastic in the cover plate is covering some areas of the contact. Just open the module and examine the cover plate. You will find they have used a universal mould for this part and only removed some areas where they wanted to add plastic. There are clear marks how to cut the cover plate for all three types of plugs. I don't recommend cutting away the plastic without opening the module. It is too easy to get some plastic pieces in some unwanted areas. It will be a little bit hard to push in the connector but it works quite good.

MOVs and VDRs

If a module has a MOV, change the voltage. If it does not, add one. See the chapter about choosing components.

Auto-transformer solution

Another possibility is to use a 230V-110V step down transformer and add a capacitor of around 0.1uF/600V across input output so the 120 kHz can be transferred. Capacitor should be polyester, MKT or similar and although a 400V unit would work, a 600V capacitor would offer a better safety margins. This a solution you could use on something like a CP290 or TW523 Mini-Controllers and other units that don't drive a load. If you used this on an lamp or appliance module, you would obviously need 110V lamps or appliances! Well, you could also put a second transformer at the output to step up the 110V to 220V but some lamp modules will not like the inductive load of the transformer.

Something like this:

In 240V   --------o-------,|||
                   |       )|||
             0.47uF |       )|||
             600V ---      )|||
                  ---      )|||
                   |       )|||
                   |       )|||
Out 115V  --------o-------)|||  Transformer
Common 0V ----------------'|||

I have used this approach for the X-10 colour cameras and it works well.  You need to use this approach where the X-10 units do not use a capacitor power supply.

Voltages and Frequencies

Throughout this section you can read 115 volts as being 110 to 120 volts.  230 volts can be read as meaning 220 to 250 volts.  400 volt capacitors are often quoted; if possible you should use higher voltage capacitors if you can get them to fit; 400 volts is the absolute minimum.

The change from 60Hz to 50Hz is generally immaterial though transformers may get a little warmer.

Remember, get your parts from SmartHome who also have a superb downloadable catalogue.  Also watch the clearance and special offers which tend to go very quickly.

If you attempt these modifications, please let me know your results, and read the warning on the X-10 240 volt modifications  page.

Get free Dreamweaver templates and extensions at JustDreamweaver.com