True X10 Compatible Toggle Switch (Modification)
I have attached two PDF files (pages 1-4 and pages 5-7) with low-resolution photos, because of the 128kB limit. You'll need both documents.
Well, I finally got fed up with the non-toggle switch X10 solutions. I’m tired of push button switches, soft-start, finding a reduced dim setting for some reason when I did not intend one. I just want to enter a room, swipe my hand across an old-fashioned toggle switch as I have done for years - up for ON, down for OFF. I decided to see if I could modify a KR19A Keychain Remote and interface it to a standard toggle switch. Yes, I know of the ToggleLincs, but they are center-off and still don’t act/feel like every other toggle switch I have, and they are prohibitively expensive for me.
Disclaimer: This is being presented along the lines of “hey, look what I did”, and should not be taken as “hey, you should do this”. This is presented for academic purposes only. Anyone who wishes to try this does so at your own risk. The modifications enclosed herein require the knowledge of electronic engineering concepts and house wiring. There is no guarantee of success in any other application other than my own. Ok, now the lawyers are satisfied.
Let’s look as some of the X10 offerings. WS12A - push-push square button. I never liked those. Can’t just “swipe the wall” and flick the toggle. However, they do work without a neutral. The Decora incandescent and relay controllers - again, push-push (but not push upper end for ON and push lower end for OFF), and doesn’t fit in with existing non-Decora switches. Also, they will not work without a neutral at the switch box. SS13A “Stick-a-Switch” - nice, I use them in places. Unwieldy to replace at an existing wall box location, especially a multiple gang switchbox. I have to aim to hit the small buttons, and I find left-ON, right-OFF to be backwards, and three switches are overkill if I just want to control one thing. Then there’s the XPT module and associated faceplates. These work similarity to my mod as they do NOT control AC at the switchbox, they only send AC commands via existing wiring (and demands a neutral) and also require a controlled device elsewhere. They do offer a nice variety of switch combinations via changeable switchplates, but again, none are a true toggle. And the INSTEON offerings - very nice and VERY expensive. The ToggleLinc comes close, but the center OFF still bugs me.
I just want to flick a toggle switch like the old days! So I decided to build my own.
Initial Concept
I noticed the KR19A Keychain Remote was a small device with ON and OFF buttons. This could be glued or double-stick taped to the back of a standard AC switch, and was narrow enough to fit within a standard wall switchbox, or within a single width of a multiple gang box. The problem was how to interface the constant-connection standard AC switch to the push-ON / push-OFF operation of the KR19A.
Switch Interface
A standard single pole AC toggle switch was not a candidate because there are only two contacts, either connected or disconnected. A standard 3-way AC toggle switch is a double-pole double-throw switch. A common terminal is switched to either of two switch poles. This was close to the one-button for ON and one-button for OFF of the KR19A, but the AC off was not a center-off style (like the ToggleLinc). The standard 3-way AC toggle switch is in one position or the other, and remains in that position until changed. The challenge was to turn this constant connection into a push-button equivalent.
KR19A Modification
I snapped apart a KR19A and found the typical conductive ink / conductive button approach. The operation of the 1-ON and 1-OFF buttons utilized IC pins 1, 14, and 6. I needed to interface my AC switch these points. I figured I could use the characteristic of a capacitor to emulate the push-release function of the KR19A keypad. When a capacitor is switched into a circuit it acts initially as a short circuit. After a period of time, the capacitor builds up a charge and acts as an open circuit. By adjusting the resistor values shown in the schematic, I arrived at the R/C time constants that would result in the KR19A “thinking” a key was pressed for about one second. The resistor in parallel would discharge the other, non-connected capacitor, so it would be ready for the AC toggle switch to be changed to its position. So, basically, when I switch the AC switch ON, a capacitor “pushes” the ON button then stops one second later. The other OFF capacitor is also discharged. When I switch the AC switch OFF, a capacitor “pushes” the OFF button then stops one second later. The other ON capacitor is also discharged. This effectively interfaces the always-connected characteristic of the AC toggle switch to the push-release characteristic of the KR19A.
Construction
The standard operation of the KR19A had to be retained, that is, all keys (except dim) had to still function so as to program the House-Code and Unit-Code. I believe my circuit keeps a very slight load on the battery, and the battery will need to be replaced at some time. I would remove the toggle-switch- KR19A assembly from the wall box, pop the cover off, change the battery, reprogram the HC/UC and then reassemble.
This meant my modification could NOT interfere with the rubber keypad and the standard key press operation. I used small magnet wire attached to the appropriate IC pins and routed them immediately away from the IC and around to the PCB topside.
NOTE: I did find that I had to temporarily disconnect the wire from the common switch screw terminal - to remove the AC switch input from the KR19A - in order to use the KR19A buttons. There was no problem to disconnect the wire, reprogram the HC/UC, and reconnect the wire.
I epoxied the wires at two tack-down points as they went past the battery as to not interfere with battery removal and replacement. In the corner shown, I soldered the resistors and capacitors, using VERY SMALL surface-mount components, soldered larger 22awg wires to connect to the AC switch, and then encapsulated the wiring and components under epoxy. The corner of the KR19A plastic case was cut out to allow the wires an exit point. This construction allowed the KR19A housing to be easily separated, and the battery changed with no problem. Once snapped back together, the key buttons are very accessible for reprogramming. The modified KR19A was attached to the AC toggle switch using double-stick foam tape.
I had a thought about programming codes. Normally, one has to skip codes when using a KR19A, as it takes two sequential unit codes. So, if your House Code is ‘A’, and your desired device is Unit Code ‘1”, the second set of KR19A buttons take Unit Code ‘2’, like it or not. This initially alarmed me, as my ceiling lights are on L1, L2, L3, and I already have controls and macros that use these assignments. I did not want to change to L1, L3, L5. No worry, however. True, the KR19A controller for L1 will initiate L2 on button set 2 - but only if button set 2 were ever pressed, and they won’t be because the KR19A is inside the switchbox. So, KR19A #1 controls L1 (and never used L2), and KR19A #2 controls L2 (and never used L3), and KR19A #3 controls L3 (and never used L4). No problem assigning sequential unit codes!
Application
Since this toggle-switch-KR19A assembly replaces the local wall switch, I had to get another switching device. I had several locations where I wanted to use this toggle-switch-KR19A assembly. I was still annoyed with the soft-start modules, so they were out. In two locations, since I had no neutral wire present, I was forced to use a WS12A. With this modified assembly, I was open to ANY X10 powering module. I chose the XPFM Single Pole Fixture Module for CFL compatibility, full 15A capability, and no soft-start. Since this module is installed AT THE FIXTURE BOX, I knew a neutral would be present. I hoped the relay CLICK would not be too annoying.
Installation
I already had replaced my old metallic switch boxes with the blue CARLON Nonmetallic Old-Work Electrical Boxes, so I had no concerns about RF and metal enclosures. I also have a very sensitive WGL & Associates V572 RF Transceiver.
AFTER TURNING OFF ALL POWER, I accessed the switch fixture box. I removed the existing WS12A switch; it could just as well have been a standard non-X10 switch. I took the wires that are normally attached to the switch (hot in and switched out) and connected them with a wire nut. I understood that the toggle-switch-KR19A assembly would switch NO AC at the wall location. The wall location now simply served as a switch point for RF transmissions.
Since I connected the previously switched hot leads to the light fixture, I knew this fixture would now be 100% energized at all times. Leaving power OFF, I installed the XPFM Single Pole Fixture Module to regain control over the application of AC power.
SIDE NOTE: I had a horrible time installing the XPFM into the ceiling can - who ever said these fit a standard can has not tried it. However, that is an issue of the XPFM and not my toggle-switch-KR19A modification.
Operation
I reassembled the ceiling lamp fixture and restored AC power. I tested my circuit and toggle-switch-KR19A assembly. Flick UP and the light turns ON; Flick DOWN and the light turns OFF. Wonderful! The relay click, being up in the ceiling was not objectionable, and for me, was quite an acceptable tradeoff for eliminating the soft-start, or being able to control CFLs. The wall switch controls the light - just like a normal toggle switch - as well as any other X10 controller. Sure, there is the X10 command lag of 1-2 seconds from the time I flick the switch until the XPFM responds, since I am not instantly controlling a local switch, but rather I am evoking the RF-to-AC Line Command function. However, that is a characteristic of controlling an X10 device via the AC line from a non-local source. Still an acceptable tradeoff in regaining standard toggle switch functionality.
Just like a standard 3-way switch, the switch position does not necessary mean the controlled device is ON or OFF. If the switch is in the up-ON position, and another X10 device has turned the light OFF, I would need to flick the switch to the down-OFF position (issuing a meaningless OFF command), and then flick the switch to the up-ON position to turn the light back ON. It is true that the UP position always sends an ON command, and the DOWN position always sends an OFF command, unlike standard 3-way switch, where the position of the switch relative to ON/OFF depends on the position of other switches, and it is possible to have an circuit OFF with both switches in the UP position.
True, there are additional tradeoffs associated with this toggle-switch-KR19A modification. Below I list the pros and cons. I’m sure there are others I have not thought of.
Toggle-Switch-KR19A Assembly Pros
True flick-up-ON, flick-down-OFF toggle switch control.
True standard AC toggle look and feel, no center-OFF.
Works in a box with NO neutral (works in a box with NO AC whatsoever).
Can control any (or a number simultaneously) of X10 control modules.
Can initiate an X10 macro.
Eliminates soft start if a relay module is used.
Works with CFLs if a relay module is used.
Low cost.
Toggle-Switch-KR19A Assembly Cons
Requires modification of an X10 device.
Requires an additional control module wired at the point of control.
1-2 second delay for device to respond (normal X10 command delay).
No local dimming control.
User may have to flick-off; flick-on if initial “ON” did not work.
Eventually needs battery replacement and reprogramming.
Final Thoughts
All and all this was a simple modification for me, and I had more trouble installing the XPFM module than creating the modified toggle switch. But I love having my toggle switches back AND having X10 control as well. (For instance, my outdoor PR511 Motion Sensor Floodlights also turn on the nearest inside ceiling light as well when triggered.)
Since this Toggle-Switch-KR19A Assembly requires no AC wiring locally, I could move a toggle switch location or add additional toggle switch to an existing circuit once I had wired in the local controlled device. Yes, the SS13A “Stick-a-Switch” provides a convenient way to “stick” a switchplate to any wall location and instantly make a new switch without cutting a hole and mounting a switchbox. However, since I am a fanatic about true toggle switch operation, cutting a hole and mounting a switchbox - especially WITHOUT snaking any AC wiring - is a true solution for me.
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