Let's take a look at one of the many touch switch controllers on eBay and to be honest, I don't really recommend buying it from eBay because it, well, there are no standards on eBay You get random stuff, but the idea is with this controller, you've got four wires. You've got the brown Live Wire you've got the blue neutral wire which is common with the lights and you've got the red switched wire that goes out to the lights and you've got this black wire that comes out. The colors may be different. This is one of these things that I you know I've told you the colors on this one, but don't uh, just assume they're going to be the same with other controllers. Who knows the color codes in some of them? But this one with the ring crimp in it is the touch sensor and it's labeled on the back just as shown connected to a ring crimp. There's actually, if not marked, live, neutral or anything in this. However, I've rigged this up to show you a tolerating to some Christmas lights tungsten Christmas lights because they just seem an appropriate load and this is better for Tungsten loads. It is usable with LED lights, but uh, it is really just probably better suited with Facebook dimming, which it does to tungsten, noting that there's no interference suppression. So here's a little ring crimp and I've just touched the wire and it triggered it. So when you touch it, it comes on the low setting. Touch it again. medium Sen touch it. Oh that's wrong. Uh, low, medium high off low medium high I'm not sure that is full brightness, but that is probably part of that's configurable in the circuitry so to speak. This is hackable in a way and you can make it safer by putting a big resistor. Oh look, it even responds to just touching that that's very sensitive into just touching the insulation. but you could put a resistor in line with this if you wanted extra safety. This requires the use of a either a metal touch pad or a metal case light fitting that isn't grounded. It can't be grounded, it needs to use it as the antenna to pick the signal up. So looking inside this little box Baja it is clipped together by two clips on the other side, one of which I've already broken off because the first thing I did when I got this was I looked at it to see does it have any proper electrical separation? The unit is unplugged I feel they need to point that out so I can show you this is good surface mount in the back. it's got some physical components in the front. one moment please. I'm just going to get the uh this photographed and then we can continue. The reverse engineering is complete. Let's Zoom down a little bit in this and take a look at the circuitry. So this is the through-hole side of the circuit board. I've flipped the image so it correlates to what's down below. So this resistor here is part of the power supply blue, gray, orange, 683, six to eight thousand ohms that goes to a diode for half wave rectification and then to this smoothing capacitor, which is about 47 microfarad at 16 volt. and there's also a Zener or Zener diode on the other side the circuit board that caps the voltage to around about 6.8 volts. There is a track here, and a space for a bigger track, noting that this circuit provides quite low gate current just to keep the circuitry simple in the purse Supply symbol And it's only in pulses, so you'd have to use a very sensitive Triad but there is the option there to upgrade it if desired. This capacitor here is part of a filter circuit for the touch input, and this capacitor here is between you and domains. It's supposed to be two capacitors, but it has one and it is a 3kv Um 470 picofarad capacitor. So let you take a picture of that if you want to play along here and then I shall show you the other side of the circuit board. Things are worth mentioning in the earlier part of the video I Said it has to be used under sort of ungrounded metal frame, but light. Don't remove the ground if there's one on it. if that's the case. Uh, it's kind of designed for double insulated lights with a metal housing. If that's not the case, then you can theoretically put a rubber grommet and had a little touch pad onto the front of it using this circuit, even if the case is grounded and just touch that pad instead. On the other side of the circuit board, we have the rest of the power supply circuitry. So here's the Hat resistor on the other side, through the diode to the smoothing capacitor. Um, and there's this Zinner or Zener diode across that and that provides power to the chip. It's very low current. It's interesting to note that that case is labeled 110 to 240 volt. They've gone for a universal approach here, and they've compromised with some component values to try and fit that in. This resistor is possibly disputing a little bit more power, but having said that, it's a one watt resistable look of it and it's only dissipating about 0.4 Watts Um, Things worthy of Newton here. Um, the filter circuit is based around these capacitors. I'll show you that in the schematic, there's the triac drive circuitry which is a very interest because as a capacitor in Sears with the gate. Um, yes, this resistor to set the clock frequency. That's something you could play with if you wanted. It will vary the sort of ratio of brightness in the multiple settings, and this resistor isn't really worth changing. This is the one that's used to get the reference so it knows where the start of the sine wave is. Let me bring in the schematic. Here is the schematic: I shall Zoom down just a tiny bit more just to make that nice and big. So here's a power supply. Note that Live is labeled zero volts here. That's because all the circuitry is reference saliva. That's for two reasons. It is uh, switching the light to live via the triac, but also because it's relying on when you touch the pad. it's looking for leakage from the main side which the circuit is referenced to to ground via the capacitor and you touching it which provides the link and it needs to have its zero volt reference to Live. Uh, if you have one of these and it's not working very well, check the polarity of your wiring is correct and that uh, the Live is definitely live because otherwise it may not work. So the power supply is that resistor that diode charging that capacitor with the Zener Diode or Zener diode across it. If you prefer to shunt the voltage level to about 6.8 volts. I Measured 7 volts. the touch input has the pad. It's got the 470 picofard. The data sheet shows to a 1000 picofard or one nanofarad capacitors in series at rated one kilovolts each. They've used a the equivalent capacitance value, but with a single three kilovolt capacitor. I Just prefer. You know, in situations like this, you're better using multiple components for extra separation. they've also got a 3K resistor. The data sheet shows a 1K there and also a diode to the positive and negative reels, possibly to allow for the touching of that with a static discharge and the diodes would help divert it. While that limited the current, in the case of the chip itself, it may have the diodes inside and maybe that's why they used a higher value there. Um, the triac is driven via this 47 nanofarad capacitor. a 470 Ohm resistor is that 471? Let me just grab that. Yes, it is. I've double checked 471, 470 4710 and the triac, which is a Mac 9786 has a 10K resistor pulling it to the zero volt rail live to keep it turned off. and when this circuit sends a positive going pulse to that track, this capacitor limits how much current can flow. Switch: Just a single pulse is used to trigger that track. It doesn't need a continuous drive, all it needs is a pulse to turn it on and it will latch on. I'll show you the sine wave data afterwards so the chip knows where to get its timing from. in the sine wave, it has a resistor. a high value: 1.5 Meg ohm. Two resistors would have been nicer and serious as to the voltage rating, but it's connected to neutral, so it can tell when the sine wave has gone past the zero. Crossing Point That's when it changes priority and is effectively at the start of each half. There's a resistor here, which is not the value shown on the data sheet. it's much higher. This controls the oscillator speed inside for the timing. from the pointer to text the zero crossing point to the point it triggers the triac and the sine wave that could be experimented with. You could use our base value of resistor and a potential from that tweaker and that will vary the intensities associated with each sort of level. Um, as it is the circuitry it I Don't think it has a I Don't think it covers the Fool's sine wave. It's the lamp is never really going to reach full intensity. I Don't think? Not sure about that. Um. Or they might have just scaled up into the sine wave to make it so that it doesn't go too dim. That's possible as well. Uh, but that's good if it doesn't trigger too early in the sine wave, because, uh, that results in, uh, longer lamp life. This little pair of components here is our capacitor and a discharge resistor across it presumably that looks as though it's associated with the touch input. and it may be to add a slight time delay so that it's less prone to glitches and spikes that could false trigger it. and it requires a decisive touch. Hotels? Oh, there is no suppression circuitry. There's no inductor. The radio hams are not going to be too pleased about that because this means that this thing will cause electrical noise on the EM audio Spectrum radio spectrum. Anything else here? That is it. You could play around with these values. You could play around with that value. Um, that's more or less it. They're the two main things. You could experiment with. this capacitor value here in this uh, and it's associated with resistor and this one for the timing, which will change the sort of intensities. the waveform. The zero crossing point of a sine wave is when it goes from one priority to the other and it passes the zero volt line. Two things happen there: If the track was on. It will turn off because there's no current flowing through and it's a latching device, so it turns off at that point, ready for triggering the next half. It also starts a timer that is based on the value of that resistor and the number of times you touched it. To say, say, for instance, half intensity. It will time it until it's roughly halfway along the same wave. It will fire the track. The track will latch on, and the lamp will light for that half of the sine wave. Then when it crosses over, it starts the timer again, but it then fires and the other half of the sine wave for much lower intensity. It might actually be a much longer time delay and uh, fire at the end of the sine wave and the same again for the other half. For full intensity, will basically fire early on. So I wonder if that resistor will really affect the the full intensity then, because I'd expect for almost as soon as it detected the zero Crossing Point A very short delay afterwards, but still probably worth experimenting with, but that is more or less it. There's another possibility here. Did you see how it triggered when I touched the wire? You could theoretically put a metal pad in the back of a plastic housing and then touch the front of it. It may actually detect the capacitance through the plastic onto your fingers, but it's interesting. The data. Oh, that's wrong. The data sheet for the Tt6061a is available online. You can find that in Google It's an interesting circuit, but as I say, use with caution of buying from from eBay That's one where that thing I suggested they're putting a bit of foil behind the plastic case and detecting capacity through. That would actually be maybe a safer option. It's probably worth experimenting with. That and another thing you could do: the black lead that goes out. for the touch sensor. You could put a resistor, another resistor, or another capacitor in series of that just to act as extra insulation between you and that, but that is it. It's an interesting little circuit, and it does seem to work, so there's not much else to say about it. There are other versions. You may be able to find a version that when you touch it it either turns straight on, straight off or as you press the pad it will gradually increase intensity to fix level or when you touch it I Get take your finger off and touch and hold it again. It reduces intensity which is kind of more versatile. but this one low medium high is very simple. It's very straightforward, but that is it. A very simple circuit thanks to this chip and well it works.