1 00:00:00,200 --> 00:00:01,854 This is my stovetop. 2 00:00:01,854 --> 00:00:06,040 It’s a glass-top radiant electric stove and if you’ve ever used one of these, 3 00:00:06,040 --> 00:00:09,234 you might have noticed something interesting about its behavior. 4 00:00:09,234 --> 00:00:16,496 The heating elements quickly begin to glow once switched on  and you can feel the intense heat coming from them right away. 5 00:00:16,496 --> 00:00:21,281 but when you turn the control knob down to, say, medium power - 6 00:00:21,281 --> 00:00:23,883 the element simply goes out. 7 00:00:23,883 --> 00:00:27,671 It’s not still running but at half-power, it’s just off. 8 00:00:27,671 --> 00:00:31,068 But then, before too long, it comes back on… 9 00:00:31,068 --> 00:00:33,647 then switches back off. 10 00:00:33,647 --> 00:00:36,663 This pulsing behavior endlessly repeats. 11 00:00:36,663 --> 00:00:38,650 What’s causing that? 12 00:00:38,650 --> 00:00:42,417 The answer is this funky component called an infinite switch, 13 00:00:42,417 --> 00:00:46,515 also known by the much, MUCH better name Simmerstat. 14 00:00:46,515 --> 00:00:51,827 It may not look like  much, but each heating element in the cooktop is wired to one of these things, 15 00:00:51,827 --> 00:00:54,974 and the simmerstats are responsible for that pulsing. 16 00:00:54,974 --> 00:00:56,645 Let me show you - 17 00:00:56,645 --> 00:01:00,324 through the magic of buying two of them, and some other stuff, 18 00:01:00,324 --> 00:01:04,892 I’ve built this little box so I can control anything with a simmerstat. 19 00:01:04,892 --> 00:01:11,076 I’ll plug in a lamp to make what it’s doing obvious in addition to a mystery load on the other outlet 20 00:01:11,076 --> 00:01:13,136 which isn’t important right now. 21 00:01:13,136 --> 00:01:15,142 Let me just stick on a control knob. 22 00:01:15,142 --> 00:01:16,496 That’s better. 23 00:01:16,496 --> 00:01:21,999 Set to high, the simmerstat doesn’t interrupt power flowing through it at all, 24 00:01:21,999 --> 00:01:29,103 but when you move it off of the highest power setting, eventually power cuts out. 25 00:01:29,103 --> 00:01:31,906 However, the interruption is pretty brief. 26 00:01:31,906 --> 00:01:34,435 Eventually, power returns. 27 00:01:34,435 --> 00:01:41,186 These periodic interruptions will repeat indefinitely, but as you turn the control knob further clockwise, 28 00:01:41,186 --> 00:01:43,965 each interruption increases in length. 29 00:01:43,965 --> 00:01:51,650 Once you reach the medium setting, it will eventually settle into a point where it spends roughly equal time on and off. 30 00:01:51,650 --> 00:01:59,462 And then the trend will continue - if you go further, it only operates in brief pulses and those pulses get farther and farther apart. 31 00:01:59,560 --> 00:02:03,323 The reason the simmerstat behaves like this is because… 32 00:02:03,323 --> 00:02:06,121 This is kind of the only option. 33 00:02:06,121 --> 00:02:11,129 Electrically, the heating elements in a conventional electric stove are merely resistors, 34 00:02:11,129 --> 00:02:12,888 a very simple component. 35 00:02:12,888 --> 00:02:16,003 But those resistors are huge! 36 00:02:16,003 --> 00:02:23,329 Each one in this stovetop is capable of outputting at least 1,200 watts and the larger ones pump out three kilowatts. 37 00:02:23,329 --> 00:02:31,483 That’s great for boiling water, but way too much power for more gentile cooking tasks like, oh, what’s a good example, 38 00:02:31,483 --> 00:02:33,076 Oh! A simmer. 39 00:02:33,076 --> 00:02:37,744 To allow for that, we have to tame them and reduce their power output. 40 00:02:37,744 --> 00:02:39,708 But how would you do that? 41 00:02:39,708 --> 00:02:46,050 You might think of adding a second resistor in series with the cooktop element, maybe even a variable resistor. 42 00:02:46,050 --> 00:02:50,933 but at these power levels, that theoretical resistor would have to be gigantic 43 00:02:50,933 --> 00:03:00,151 and as it restricted current flow it would generate quite a lot of heat of its own which is both wasteful energy-wise and would require cooling. 44 00:03:00,151 --> 00:03:07,091 So instead you might want to use a variable transformer such as a variac to produce a range of voltages to choose from - 45 00:03:07,091 --> 00:03:11,671 lower the voltage and you lower the power consumed by those heating elements. 46 00:03:11,671 --> 00:03:13,720 But there we have a similar problem: 47 00:03:13,720 --> 00:03:20,430 to handle this much power, that variable transformer would have to  be quite large and thus quite expensive, 48 00:03:20,430 --> 00:03:23,135 and remember you’ll need four. 49 00:03:23,135 --> 00:03:30,257 So, to allow for fine control over the power output of the heating elements with minimal energy losses and component costs, 50 00:03:30,520 --> 00:03:32,406 the simmerstat was born. 51 00:03:32,406 --> 00:03:40,016 This device produces any arbitrary power level by repeatedly switching its load on and off for varying periods of time, 52 00:03:40,016 --> 00:03:43,198 a method known as duty-cycle control. 53 00:03:43,198 --> 00:03:50,598 Before I explain what’s going on inside here, though, I want to point out that these things aren’t by any means a recent development. 54 00:03:50,598 --> 00:03:53,417 In fact, the tech is quite old. 55 00:03:53,417 --> 00:04:00,028 Coil-top stoves going back to the 1940’s use these same exact controls to modulate their power output. 56 00:04:00,028 --> 00:04:03,713 As a matter of fact, the tech just had its 100th birthday. 57 00:04:03,713 --> 00:04:12,435 The first place I found it described is in this 1924 patent for Chester I Hall’s invention assigned to General Electric. 58 00:04:12,435 --> 00:04:17,001 Coil-style heating elements like this are also just giant resistors, 59 00:04:17,001 --> 00:04:25,089 so just as with the glass-top stoves which came later, the  simmerstat was the most cost-effective way to regulate their output. 60 00:04:25,089 --> 00:04:29,868 That means coil-top stoves are exhibiting this pulsing behavior, too. 61 00:04:29,868 --> 00:04:36,560 However you generally aren’t aware of this happening with a coil-top stove because you can’t see it. 62 00:04:36,560 --> 00:04:45,405 The heat produced by these coils is generated by a thin wire element embedded in the center of the hollow metal tube which actually forms the coil. 63 00:04:45,405 --> 00:04:52,308 But the gap between the wire that produce heat and the walls of the tube is filled with a sand-like material. 64 00:04:52,308 --> 00:04:58,275 The sand fills the tube so it can be bent into different shapes with the wire inside staying centered, 65 00:04:58,275 --> 00:05:00,180 which keeps you from getting electric shocks. 66 00:05:00,180 --> 00:05:01,513 Which is pretty nice. 67 00:05:01,513 --> 00:05:06,894 But to get the heat produced by the wire element out of the tube and into cookware, 68 00:05:06,894 --> 00:05:14,910 it must make its way to the outer surface,  meaning it also has to warm up all the sand in the way which is a lot of thermal mass. 69 00:05:14,910 --> 00:05:20,571 The upshot is that it takes a long time for these elements to get hot enough to visibly glow, 70 00:05:20,571 --> 00:05:25,068 so the pulsing behavior of the simmerstat is visibly obscured. 71 00:05:25,068 --> 00:05:30,134 The elements below a glass-top stove are very, very different though. 72 00:05:30,941 --> 00:05:33,538 If I explained them would that be a tangent? 73 00:05:34,594 --> 00:05:38,017 Well it’s not directly related to simmerstats so I suppose it would be, 74 00:05:38,017 --> 00:05:41,124 but too bad - I bought this so we gotta discuss it 75 00:05:41,124 --> 00:05:42,703 (I expensed it). 76 00:05:42,703 --> 00:05:48,959 This heating element assembly is what’s actually under the glass of many glass-top radiant electric stoves. 77 00:05:48,959 --> 00:05:58,025 It’s incredibly simple, just a flat disc of heat-resistant support material  hosting a very long zig-zaggy piece of nichrome wire. 78 00:05:58,025 --> 00:06:03,679 Actually, two - this is a selectable size burner just like this one on my stove at home, 79 00:06:03,679 --> 00:06:10,920 composed of a six-inch inner-section and an outer ring to fill it out to the whole 9 inch diameter for larger cookware. 80 00:06:10,920 --> 00:06:16,181 They’re not all made exactly like this, sometimes the heating elements are structured a little differently, 81 00:06:16,181 --> 00:06:20,952 but they all work the same way: when voltage is applied across the nichrome wires, 82 00:06:20,952 --> 00:06:26,084 they get very hot very quickly to the point of glowing brightly. 83 00:06:26,084 --> 00:06:33,404 That speed is the main functional advantage of a glass-top stove: near instant heat output from cold. 84 00:06:33,404 --> 00:06:40,354 But you’ll notice that in open-air this looks very bright and orangey like the heating elements of a toaster. 85 00:06:40,354 --> 00:06:44,512 That’s because, well, that’s pretty much what these are! 86 00:06:44,512 --> 00:06:50,073 But, you say, under the glass of a stove these appear a deep cherry red when operating. 87 00:06:50,073 --> 00:06:51,490 Why is that? 88 00:06:51,490 --> 00:06:58,406 Well, this glass is in fact a special ceramic material  with some very peculiar characteristics. 89 00:06:58,406 --> 00:07:03,104 It’s deliberately very bad at conducting heat energy through itself 90 00:07:03,104 --> 00:07:10,700 which keeps other areas of the stovetop cool to the touch even when parts right next to it are hot enough to melt lead. 91 00:07:10,700 --> 00:07:17,144 But the glass lets infrared radiation pass right through it almost completely unimpeded. 92 00:07:17,144 --> 00:07:22,983 That’s what allows the radiant heat produced by the heating elements under the glass to make it into your cookware, 93 00:07:22,983 --> 00:07:28,769 and why you can feel intense heat coming from them right away once they're switched on. 94 00:07:28,769 --> 00:07:33,255 The deep red color seen through the glass is the result of filtering: 95 00:07:33,255 --> 00:07:39,413 the glass is opaque to almost all wavelengths of visible light, making it appear black to our eyes. 96 00:07:39,413 --> 00:07:42,788 But since it passes infrared light just fine, 97 00:07:42,788 --> 00:07:50,035 the near-infrared frequencies at the very edge of the visible spectrum will escape that filtering and you can see them. 98 00:07:50,035 --> 00:07:51,908 Pretty wild, right? 99 00:07:52,000 --> 00:07:57,820 And if you’ve ever noticed the probe thing going across the center of one of these burners and wondered what it’s for, 100 00:07:57,820 --> 00:07:59,537 well two things, actually: 101 00:07:59,537 --> 00:08:05,584 this is a sensing probe for two thermostatic switches in this little remote enclosure. 102 00:08:05,584 --> 00:08:11,311 The first of those switches is very sensitive and closes its contacts in the presence of minimal heat 103 00:08:11,311 --> 00:08:17,371 to illuminate the hot surface indicator (or indicators) to warn you that the cooktop is still hot. 104 00:08:17,371 --> 00:08:20,599 Count your blessings if you get a separate light for each burner, 105 00:08:20,599 --> 00:08:26,098 more often than not they’re all wired in parallel so any one of them can light up just a single warning light. 106 00:08:26,098 --> 00:08:28,613 Those cost-cutting cost-cutters. 107 00:08:28,613 --> 00:08:33,353 But the other switch in here is wired in series with the heating element itself. 108 00:08:33,353 --> 00:08:37,932 Remember that this flat disc of searing heat is trapped below glass, 109 00:08:37,932 --> 00:08:46,635 and while that glass is transparent to infrared,  it’s not perfectly transparent so it will absorb some heat energy and get quite hot. 110 00:08:46,635 --> 00:08:50,462 Plus, even if it were perfectly transparent to infrared, 111 00:08:50,462 --> 00:08:57,575 there’s gonna be a piece of cookware on top of the glass which reflects some of the heat energy right back down and into the element. 112 00:08:57,575 --> 00:09:06,974 Therefore, tremendous heat builds up in the tiny little  sliver of air space between the glass and the bottom of this infernal frisbee. 113 00:09:06,974 --> 00:09:09,532 To protect the glass from getting too hot, 114 00:09:09,532 --> 00:09:16,992 the temperature probe will open a safety switch to remove power from the heating element and keep things from getting all melty. 115 00:09:16,992 --> 00:09:19,629 It usually resets in a matter of a few seconds, 116 00:09:19,629 --> 00:09:25,305 but will kill power again if it needs to in order to enforce a high temperature safety limit. 117 00:09:25,305 --> 00:09:30,924 This usually only occurs if the burner has been in continuous use at full power for several minutes, 118 00:09:30,924 --> 00:09:33,455 such as when bringing water to a boil. 119 00:09:33,455 --> 00:09:36,950 Anyway, this video is supposed to be about the simmerstat. 120 00:09:36,950 --> 00:09:39,923 But, before we talk ab - no I’m kidding. 121 00:09:39,923 --> 00:09:46,255 Earlier I said that these modulate the power output of the cooktop burners using duty cycle control. 122 00:09:46,255 --> 00:09:53,950 If that doesn’t mean anything to you,  that’s just a way to say “the percentage of time spent powered over an average.” 123 00:09:53,950 --> 00:10:02,940 Imagine you have a 1,200 watt burner unit but you only need 600 watts of output for whatever particular cooking task you’re doing. 124 00:10:02,940 --> 00:10:06,737 Well, If you run that burner with a 50% duty cycle, 125 00:10:06,737 --> 00:10:11,001 perhaps by running it for 5 seconds of every 10 second period, 126 00:10:11,001 --> 00:10:16,751 then although the actual heat output will be alternating between zero and 1,200W, 127 00:10:16,751 --> 00:10:22,391 over time the effective heat output is the full power multiplied by the duty cycle - 128 00:10:22,391 --> 00:10:27,589 in this case, 1,200 X .5, or 600 watts. 129 00:10:27,589 --> 00:10:33,550 Those of you who are more digitally minded might be thinking about pulse-width modulation just now. 130 00:10:33,550 --> 00:10:43,369 Duty cycle control and PWM are quite similar when it comes to their net effect of producing a lower average power output by cycling a… 131 00:10:43,369 --> 00:10:45,840 whatever on and off repeatedly, 132 00:10:45,840 --> 00:10:49,577 but the two terms technically describe different things. 133 00:10:49,577 --> 00:10:56,905 Some might choose to argue with me on that, but PWM isn’t necessarily trying to modulate the power output of anything. 134 00:10:56,905 --> 00:11:01,565 In fact it can be used as a signaling protocol for fairly complex tasks. 135 00:11:01,565 --> 00:11:06,419 Servo motors, for instance, are sometimes controlled through PWM signaling. 136 00:11:06,419 --> 00:11:11,151 The length of the pulses they receive encodes a position for it to assume. 137 00:11:11,151 --> 00:11:15,097 When you are using PWM simply to modulate power output, 138 00:11:15,097 --> 00:11:20,957 say when you use a PWM dimmer to reduce the intensity of DC-powered LEDs, 139 00:11:20,957 --> 00:11:24,890 strictly speaking that is still duty cycle control: 140 00:11:24,890 --> 00:11:31,157 the apparent brightness of the LEDs is determined by what percentage of time they spend on vs. off, 141 00:11:31,157 --> 00:11:35,058 which is literally just another way to say their duty cycle. 142 00:11:35,058 --> 00:11:42,143 Pulse width modulation in that context is simply a modern means to the end of attaining duty cycle control, 143 00:11:42,143 --> 00:11:47,540 with the added benefit of high switching frequencies  providing it with some functional advantages. 144 00:11:47,540 --> 00:11:51,580 But since the simmerstat is literally 100-year-old tech, 145 00:11:51,580 --> 00:11:54,009 well there ain’t anything modern in here. 146 00:11:54,009 --> 00:11:59,240 Yet it absolutely is a fully-functional,  fully-capable duty-cycle controller. 147 00:12:00,160 --> 00:12:02,061 How on Earth could that be? 148 00:12:02,061 --> 00:12:05,754 Well, let’s look inside the simmerstat to see what’s going on. 149 00:12:05,754 --> 00:12:10,456 That, uh... that is less clear than you’d think. 150 00:12:10,456 --> 00:12:13,581 So first, because we’re- I'm gonna turn this off now. 151 00:12:13,581 --> 00:12:17,324 Because we're dealing with the US split-phase electrical system here, 152 00:12:17,324 --> 00:12:23,655 in the 240V circuit this is used to control there are two hot wires and no neutral. 153 00:12:23,655 --> 00:12:30,781 The heating elements of a cooktop are wired across line one and line two just like any other 240V device. 154 00:12:30,781 --> 00:12:34,026 You can learn more about that in this video if you'd like. 155 00:12:34,026 --> 00:12:37,612 Because of this fact, this device has two switch contacts in it, 156 00:12:37,612 --> 00:12:39,302 here and here, 157 00:12:39,302 --> 00:12:46,020 so that it can open both sides of the circuit when  switched off and completely isolate the heating element from voltage. 158 00:12:46,020 --> 00:12:51,162 That makes the simmerstat at its core a double-pole single-throw switch. 159 00:12:51,162 --> 00:12:57,325 Now the left side of the simmerstat doesn’t actually matter at all for its power modulation purpose. 160 00:12:57,325 --> 00:13:00,724 That’s really just an extra isolation point breaking line 1, 161 00:13:00,724 --> 00:13:05,152 and it’s only ever open when the control knob is in the off position. 162 00:13:05,152 --> 00:13:07,800 In all other positions it’s closed. 163 00:13:07,800 --> 00:13:16,233 Oh, and this extra copper piece here is used to send power out to a pilot light to indicate that a cooktop burner is switched on. 164 00:13:16,233 --> 00:13:22,407 That’s why the terminal on the back is labeled P and why  they didn’t bother giving it a proper contact surface - 165 00:13:22,407 --> 00:13:27,644 it’s just sending a tiny little amount of current to a neon indicator like this one. 166 00:13:27,644 --> 00:13:34,255 You’ll notice, though, that the right side of  the simmerstat features a much more robust pair of switch contacts, 167 00:13:34,255 --> 00:13:37,804 one of which is attached to a wide copper bar. 168 00:13:37,804 --> 00:13:43,897 This is the contact that regularly opens and closes to modulate power output. 169 00:13:43,897 --> 00:13:46,078 Uh, to hopefully avoid confusion, 170 00:13:46,078 --> 00:13:51,020 remember that you only have to break one side of a circuit to kill current flow. 171 00:13:51,020 --> 00:13:58,998 When the other switch is closed but this one is  open the heating element will still have 120V potential on it from line 1 172 00:13:58,998 --> 00:14:05,145 but there isn't a complete circuit to line 2 for any power to actually flow through it. 173 00:14:05,145 --> 00:14:11,807 Except the pilot light - well the pilot light is only operating at 120V and the other side of it is connected to neutral 174 00:14:11,807 --> 00:14:15,167 so that stays on no matter what cooktop burner is doing. 175 00:14:15,478 --> 00:14:17,799 I’m very sorry our power system is weird. 176 00:14:17,799 --> 00:14:21,108 Just… ignore everything on the left. It doesn’t matter. 177 00:14:21,108 --> 00:14:21,957 Moving on, 178 00:14:21,957 --> 00:14:26,349 if we look at the backside of the copper bar hosting our main switch contact 179 00:14:26,349 --> 00:14:31,170 we’ll see something that looks an awful lot like a bimetallic strip. 180 00:14:31,170 --> 00:14:32,913 Because it is. 181 00:14:32,913 --> 00:14:35,860 These little heroes show up in the darndest places. 182 00:14:35,860 --> 00:14:37,651 Why’s it in here? 183 00:14:37,651 --> 00:14:45,914 Well, this copper bar carries the current flowing through to the cooktop heating element when the switch contact is closed and power is flowing. 184 00:14:45,914 --> 00:14:49,803 And there’s a small amount of electrical  resistance across the copper bar - 185 00:14:49,803 --> 00:14:51,927 it’s too small to measure with a multimeter 186 00:14:51,927 --> 00:14:58,564 but it’s enough to produce a bit of heat when the 10 or 11 amps drawn by the cooktop burner flows through it. 187 00:14:58,564 --> 00:15:02,396 Bimetallic strips deform when they change in temperature, 188 00:15:02,396 --> 00:15:08,509 and since there's one attached to this copper bar which we’ve just established gets warm when current flows through it, 189 00:15:08,509 --> 00:15:12,096 the bimetallic strip will start to bend as that happens. 190 00:15:12,096 --> 00:15:16,183 Now, unfortunately I can’t really demonstrate this well in-circuit. 191 00:15:16,183 --> 00:15:18,193 You’ll see why in just a moment. 192 00:15:18,193 --> 00:15:24,579 What I can do, though, is use this little heat gun and show you what happens when the support bar warms up. 193 00:15:24,579 --> 00:15:27,410 It’s pretty subtle, so watch closely. 194 00:15:27,410 --> 00:15:34,341 When hot, the copper bar bends such that the bottom switch  contact moves deeper into the simmerstat body 195 00:15:34,440 --> 00:15:37,240 and farther away from its partner above. 196 00:15:37,240 --> 00:15:40,092 Now, think about what that means. 197 00:15:40,092 --> 00:15:44,794 If the copper bar warms up whenever the switch is  closed and power is flowing, 198 00:15:44,794 --> 00:15:50,252 and that warmth causes the bar to bend such that the switch will open, 199 00:15:50,252 --> 00:15:54,134 then the switch does not want to stay closed. 200 00:15:54,134 --> 00:15:58,920 Any time it is closed, it heats up and the bimetallic strip then tries to open it. 201 00:15:59,720 --> 00:16:02,089 In practice, it looks like this. 202 00:16:02,089 --> 00:16:09,345 From below we can’t see the switch contacts but we can see the copper bar moving back and forth ever so slightly. 203 00:16:09,345 --> 00:16:16,516 Every time the switch is closed and power flows to the load, the copper bar begins to warm up because of internal resistance. 204 00:16:16,516 --> 00:16:19,732 We can see this quite clearly with the thermal camera. 205 00:16:19,732 --> 00:16:28,302 As that happens, the bimetallic strip bends the bar such that  the lower contact begins moving closer to the camera and away from its partner. 206 00:16:28,302 --> 00:16:33,876 Eventually the strip bends far enough to break the circuit, so current stops flowing. 207 00:16:33,876 --> 00:16:37,744 Once it does, though, the bar rapidly begins to cool down. 208 00:16:37,744 --> 00:16:42,244 That causes it to reverse course and start  moving closer to the other switch contact, 209 00:16:42,244 --> 00:16:45,089 then they actually touch, current can flow again, 210 00:16:45,089 --> 00:16:48,401 the bar warms up, and the cycle repeats. 211 00:16:48,401 --> 00:16:52,622 And now, let’s see if you make a Technology Connection. 212 00:16:52,622 --> 00:16:55,877 I'm using a lamp right now plugged into the simmerstat. 213 00:16:55,877 --> 00:17:00,663 And that lamp, because of the simmerstat, is flashing. 214 00:17:00,663 --> 00:17:06,131 I’ve covered a certain other piece of tech which we use to make lamps flash in the past. 215 00:17:06,131 --> 00:17:10,548 That piece of tech is put in-series with the lamps it’s meant to flash. 216 00:17:10,548 --> 00:17:16,061 Current flowing through it would cause a switch inside to briefly open then shut repeatedly. 217 00:17:16,061 --> 00:17:19,870 I’m speaking, of course, about the turn signal flasher. 218 00:17:19,870 --> 00:17:24,574 These old-school thermal flashers also work thanks to a bimetallic strip. 219 00:17:24,574 --> 00:17:30,097 That strip will deform when heated and open or close a switch (depending on the design particulars) 220 00:17:30,097 --> 00:17:38,347 which repeatedly applies and removes power to the incandescent lamps which form the turn signals to make them flash and thus more noticeable. 221 00:17:38,347 --> 00:17:44,704 Now that behavior is certainly a great deal faster than the pulsing the simmerstat is doing right now 222 00:17:44,704 --> 00:17:48,018 but it’s not really any different, is it? 223 00:17:48,018 --> 00:17:51,032 It’s the same thing, just sped up. 224 00:17:51,032 --> 00:18:03,726 And at its core, this simmerstat really is just an overgrown turn signal flasher capable of handling up to 11 amps of current at 240V, or 2600W. 225 00:18:03,726 --> 00:18:07,036 But the simmerstat is a flasher with a twist - 226 00:18:07,036 --> 00:18:09,759 uh, literally. 227 00:18:09,759 --> 00:18:16,929 The turn signal flasher has a fixed duty cycle and behavior, at least when controlling the same load at the same voltage. 228 00:18:16,929 --> 00:18:22,084 But the simmerstat can adjust its duty cycle based on the position of the control knob. 229 00:18:22,084 --> 00:18:24,629 Why? And how? 230 00:18:24,629 --> 00:18:27,950 Y'know, in Britain they call cooktop burners hobs. 231 00:18:27,950 --> 00:18:30,398 Does that mean that this is a hob knob? 232 00:18:30,398 --> 00:18:33,123 Anyway, when we were looking at this from above, 233 00:18:33,123 --> 00:18:37,403 you might have noticed that the switch contacts were nowhere near each other. 234 00:18:37,403 --> 00:18:41,276 They’re clearly sprung such that  they default to the open position, 235 00:18:41,276 --> 00:18:44,977 so what closes those switches in the first place? 236 00:18:44,977 --> 00:18:47,983 To find out, let’s switch to the Cam Cam. ♫ Offenbach plays out of nowhere ♫ 237 00:18:47,983 --> 00:18:50,000 It’s this cam! 238 00:18:50,601 --> 00:18:52,844 I don’t know how I live with me either. 239 00:18:52,844 --> 00:19:00,606 The control knob of the simmerstat is attached via a shaft to this plastic cam covered in a copious amount of grease. 240 00:19:00,606 --> 00:19:09,292 When assembled, the cam presses down on these protrusions once  rotated out of the off position, and that is what closes the switch contacts. 241 00:19:09,292 --> 00:19:12,904 You’ll notice the cam has two sections with different profiles - 242 00:19:12,904 --> 00:19:18,684 the inner section presses on and closes the switch  on the left of the simmerstat which remember, doesn't matter. 243 00:19:18,684 --> 00:19:20,421 It’s just a safety switch. 244 00:19:20,421 --> 00:19:27,014 But the outer section, which engages with bimetallic switch, has a very subtle ramp built into it. 245 00:19:27,014 --> 00:19:28,392 Can you see that? 246 00:19:28,392 --> 00:19:31,894 This is the off position which doesn’t press on the switch at all. 247 00:19:31,894 --> 00:19:37,221 But just to the left of that position, the cam profile gets very tall. 248 00:19:37,221 --> 00:19:40,926 That means it presses the switch down quite far. 249 00:19:40,926 --> 00:19:49,701 But then there’s a fairly steep dropoff before the cam very subtly gets thinner and thinner all the way back to the off position. 250 00:19:49,701 --> 00:19:51,800 Can you figure out why that might be? 251 00:19:51,800 --> 00:19:53,737 Vote now on your phones. 252 00:19:53,737 --> 00:20:04,049 What that varying cam profile actually does as you turn the knob is change the resting position of the two switch contacts in the bimetallic switch. 253 00:20:04,049 --> 00:20:11,298 You can see from below that as I turn it, the copper bar and bimetallic strip are moving up and down very slightly. 254 00:20:11,298 --> 00:20:13,681 This might seem pretty inconsequential, 255 00:20:13,681 --> 00:20:18,518 but that right there is actually the key to this whole device. 256 00:20:18,518 --> 00:20:22,485 But explaining why... is complicated. 257 00:20:22,485 --> 00:20:28,707 I’ve been stuck on this script for a while because  although this component is incredibly simple, 258 00:20:28,800 --> 00:20:34,440 there are three connected concepts all  working together here to make this what it is,   259 00:20:34,440 --> 00:20:38,441 and that makes it hard to explain without getting stuck in a loop. 260 00:20:38,441 --> 00:20:39,916 But I’ll try. 261 00:20:39,916 --> 00:20:42,159 Let’s revisit that footage from earlier. 262 00:20:42,159 --> 00:20:46,312 Here, the simmerstat was set to medium and I let it stabilize. 263 00:20:46,312 --> 00:20:50,975 In this condition, the switch is closed for about 5 seconds before it opens, 264 00:20:50,975 --> 00:20:54,757 and then it stays open for about 5 seconds, and this repeats. 265 00:20:54,757 --> 00:20:58,241 That’s how we get a 50% duty cycle. 266 00:20:58,241 --> 00:21:03,961 But why precisely is the switch opening and closing with such predictability? 267 00:21:03,961 --> 00:21:06,956 To find out, let’s look at the thermal camera again. 268 00:21:06,956 --> 00:21:13,789 You’ll notice that at this setting, the contact’s support bar seems to peak right near 100 degrees Celsius, 269 00:21:13,789 --> 00:21:16,166 then the temperature begins to fall. 270 00:21:16,166 --> 00:21:23,306 We then see that it consistently bottoms out right near 78 degrees Celsius and it begins to rise again. 271 00:21:23,306 --> 00:21:32,133 This tells us that the switch is actually opening and closing based upon the temperature of the support bar and its bimetallic strip. 272 00:21:32,133 --> 00:21:35,193 Simple enough, but why, though? 273 00:21:35,193 --> 00:21:40,452 Why is the circuit opening and closing at those specific temperatures? 274 00:21:40,452 --> 00:21:47,039 Well, that’s because of this cam and how far it’s pushing down on the top switch contact. 275 00:21:47,039 --> 00:21:53,048 Remember that the bottom switch contact  retreats into the body of the simmerstat as it warms up. 276 00:21:53,048 --> 00:22:00,600 How far that contact actually moves is a function of the temperature of the bimetallic strip in the support bar. 277 00:22:00,600 --> 00:22:03,922 And through the position of the cam and its profile, 278 00:22:03,922 --> 00:22:11,255 we have chosen to place the top switch contact at some specific point along that deflection path. 279 00:22:11,255 --> 00:22:19,303 In this position, the contacts are forced to stay together until the copper bar has reached 100 degrees Celsius. 280 00:22:19,303 --> 00:22:25,416 At that precise temperature, the deflection of the  bar is sufficient to open the switch. 281 00:22:25,416 --> 00:22:30,713 So really, the core function of this device... is a thermostat. 282 00:22:30,713 --> 00:22:32,105 Through turning the knob, 283 00:22:32,105 --> 00:22:39,059 we’re deciding how hot we want to allow that copper bar to get before it switches off the cooktop burner. 284 00:22:39,059 --> 00:22:45,364 So, the last piece of the puzzle is how that choice becomes a consistent duty cycle. 285 00:22:45,364 --> 00:22:52,361 Because remember, the goal of this device is not to maintain a specific temperature like the thermostat in an oven, 286 00:22:52,361 --> 00:22:58,114 but to maintain a specific duty cycle and thus power output for the cooktop burners. 287 00:22:58,114 --> 00:23:02,966 Yet somehow we’re doing that with what ostensibly is a thermostat. 288 00:23:02,966 --> 00:23:05,709 Well, here’s where I hope it all comes together. 289 00:23:05,709 --> 00:23:12,639 Remember that the copper bar inside here is both a thermostatic switch AND a heater. 290 00:23:12,639 --> 00:23:20,826 Whenever the switch is closed, it dissipates a consistent amount of power and that generates a consistent amount of heat within the bar. 291 00:23:20,826 --> 00:23:26,082 And like all heat-producing things, with a consistent power output 292 00:23:26,082 --> 00:23:36,321 how hot it actually gets and thus how far the bar will deflect is a function of how long that heater runs in a given period. 293 00:23:36,321 --> 00:23:39,046 And now physics becomes our friend. 294 00:23:39,046 --> 00:23:43,456 Let’s say I change the knob’s position to that of medium-high. 295 00:23:43,456 --> 00:23:48,222 What that will actually do is press down farther on the top switch contact 296 00:23:48,222 --> 00:23:55,265 to force the two contacts to remain together until the lower support bar has reached 130 degrees. 297 00:23:55,265 --> 00:23:57,936 So, let’s do that. 298 00:23:57,936 --> 00:24:03,077 The temperature of the bar, since power is now flowing through it, is climbing. 299 00:24:03,077 --> 00:24:09,826 But you’ll notice that the rate of change in temperature is slowing down as it continues to increase. 300 00:24:09,826 --> 00:24:17,511 What’s happening here is the result of the fact that the bar is approaching the limit to how hot it can possibly become 301 00:24:17,511 --> 00:24:25,132 before the heat it gains through its internal resistance  matches the heat that leaves through radiation to the air surrounding it. 302 00:24:25,132 --> 00:24:30,620 And as we approach that limit, heat gain slows significantly. 303 00:24:30,620 --> 00:24:36,243 This means that it will take longer to reach the new target temperature of 130 degrees, 304 00:24:36,243 --> 00:24:43,842 which in turn means that the switch contacts will stay  closed for a longer period of time before they open again. 305 00:24:43,842 --> 00:24:50,843 And adding to that, the temperature differential between the bar and the air around it is greater when it’s hotter 306 00:24:50,843 --> 00:24:57,402 which means that once it stops being heated, it’s going to lose heat energy faster than it did before. 307 00:24:57,402 --> 00:25:02,590 That shortens the time the switch spends open before it closes again, 308 00:25:02,590 --> 00:25:07,660 though that effect is minor compared to the stretching of the on-time. 309 00:25:07,660 --> 00:25:09,885 But what about going in the other direction? 310 00:25:09,885 --> 00:25:13,849 What happens when you turn the knob to, say, medium-low? 311 00:25:13,849 --> 00:25:21,152 Well, with the knob at the nine o’clock position, the cam is only very slightly pushing on the switch. 312 00:25:21,152 --> 00:25:28,793 It’s pushing so gently that the bar only needs to hit about 60 degrees Celsius before it bends enough to open the switch. 313 00:25:28,793 --> 00:25:34,260 Since that’s much closer to ambient temperature than 130 or even just 100 degrees, 314 00:25:34,260 --> 00:25:41,124 it takes a very short time for it to reach that temperature when being heated by the current passing through. 315 00:25:41,124 --> 00:25:47,544 And you’ll notice that the switch only closes again when the bar drops to about 40 degrees Celsius - 316 00:25:47,544 --> 00:25:51,653 but it takes quite a while for the bar to cool to that temperature, 317 00:25:51,653 --> 00:25:56,154 so the pulses it sends out are both short and infrequent. 318 00:25:56,154 --> 00:25:58,649 Do you see how this all fits together? 319 00:25:58,649 --> 00:26:04,875 We are really controlling this circuit based on the temperature of the heater inside of it. 320 00:26:04,875 --> 00:26:10,131 When calibrated correctly, that can be used as a duty cycle controller. 321 00:26:10,131 --> 00:26:16,626 Because to get that heater hotter, the heater itself must run with a longer duty cycle, 322 00:26:16,626 --> 00:26:25,310 so its average temperature becomes an effective proxy for the duty cycle necessary to attain that temperature. 323 00:26:25,310 --> 00:26:27,882 And that’s incredibly fortuitous. 324 00:26:27,882 --> 00:26:33,312 Just calibrate the bimetallic bar to dissipate the right amount of heat when the circuit is passing current, 325 00:26:33,312 --> 00:26:41,124 give the cam pressing on the switch a nice subtle ramp to allow you to break the circuit at a specific temperature of that bar, 326 00:26:41,124 --> 00:26:47,640 and you can produce any duty cycle  you need with incredibly crude technology. 327 00:26:47,640 --> 00:26:49,578 But it gets even better! 328 00:26:49,578 --> 00:26:54,566 Because the switching action occurs based on the temperature of the bimetallic strip, 329 00:26:54,566 --> 00:26:58,205 there’s a really helpful memory effect happening here. 330 00:26:58,205 --> 00:27:03,438 The main annoyance of using a conventional electric stove is the reaction time. 331 00:27:03,438 --> 00:27:07,020 The thermal mass of the materials involved retain heat for a while, 332 00:27:07,020 --> 00:27:11,678 either the coil of a coil-top stove or the glass of a glass-top. 333 00:27:11,678 --> 00:27:16,164 That’s useful because it helps smooth out the effect of the pulsing behavior 334 00:27:16,164 --> 00:27:22,238 but it also means it takes a good while for the cooktop to  react to a change in power level. 335 00:27:22,549 --> 00:27:28,471 The simmerstat can’t solve that problem, but consider what happens when you change the power level: 336 00:27:29,080 --> 00:27:34,640 If, say, you were on a medium-low heat  but needed to move to a medium-high heat,   337 00:27:34,640 --> 00:27:42,166 then your turning of the knob is simply changing how hot the internal heater needs to get before it cuts power. 338 00:27:42,166 --> 00:27:47,782 And if at the medium-low setting the heater was maintaining, let’s say, 80 degrees on average, 339 00:27:47,782 --> 00:27:54,762 then when you change the setting it’s gotta get all the way up to 130 degrees before it switches the element off. 340 00:27:54,762 --> 00:28:01,762 That means it’s going to produce a very long pulse of output and help the burner get to your new target as quickly as possible. 341 00:28:01,762 --> 00:28:06,964 The same goes when you lower the output - if it’s already quite hot, 342 00:28:06,964 --> 00:28:13,400 then turning the knob will open the switch and it won’t close again until the heater has fallen down to the new target,   343 00:28:13,400 --> 00:28:15,700 which is going to take a while. 344 00:28:15,700 --> 00:28:23,623 I first noticed this behavior of my glass-top stove and assumed that this was being accomplished with logic but nope! 345 00:28:23,623 --> 00:28:25,554 That’s just how this works! 346 00:28:25,554 --> 00:28:28,001 Now I’ve left something important out. 347 00:28:28,001 --> 00:28:34,361 You might wonder how the simmerstat can keep the element on at full-power when it's set to high. 348 00:28:34,361 --> 00:28:39,214 Well, that’s what that really high point on the cam profile was for. 349 00:28:39,214 --> 00:28:46,075 That just really jams that switch down so  it’ll never open no matter how hot the bar inside is getting. 350 00:28:46,075 --> 00:28:47,771 Pretty crude, huh? 351 00:28:47,771 --> 00:28:50,918 Except… the crudeness doesn’t stop there. 352 00:28:50,918 --> 00:28:59,510 This particular simmerstat only works correctly with fairly large heating elements that draw the 8.9 to 11 amps it’s rated for. 353 00:28:59,510 --> 00:29:05,548 That’s because how quickly the copper bar heats up  depends on how much current passes through it. 354 00:29:05,548 --> 00:29:11,544 If you try and control a load outside of that range,  things get out of whack. 355 00:29:11,544 --> 00:29:18,856 Through sheer dumb luck, this 1,100 watt hot plate draws about 9 amps at 120V, 356 00:29:18,856 --> 00:29:22,139 so this simmerstat works correctly with it. 357 00:29:22,139 --> 00:29:25,428 The hotplate has been my mystery load throughout the video. 358 00:29:25,428 --> 00:29:30,215 But if I plug in this smaller hotplate which only draws 900 watts, 359 00:29:30,215 --> 00:29:33,925 the duty cycles this is meant to produce get all out of whack. 360 00:29:33,925 --> 00:29:38,424 And with a load much smaller than that, it never interrupts power. 361 00:29:38,424 --> 00:29:44,176 You also might have noticed that the way this switches the load is terrible! 362 00:29:44,176 --> 00:29:50,411 Switches ideally should have a snap-action to reduce arcing when they break electrical loads. 363 00:29:50,411 --> 00:29:52,674 This fella just doesn’t. 364 00:29:52,674 --> 00:29:57,064 The contacts barely move despite switching 10 amps, 365 00:29:57,064 --> 00:30:00,685 and so some fairly nasty arcing occasionally happens. 366 00:30:00,685 --> 00:30:05,613 It’s not too too bad because these are just used to switch resistive loads, 367 00:30:05,613 --> 00:30:14,360 and the overextension of the switch as the cam presses down produces a wiping effect that helps to clean the contacts of carbon buildup and debris. 368 00:30:14,360 --> 00:30:18,820 Incidentally, that also happens inside the switches of  an electromechanical pinball machine 369 00:30:18,820 --> 00:30:22,156 and yes part three is coming I haven’t forgotten about it hold your horses! 370 00:30:22,156 --> 00:30:24,942 I just thought a script like this one would be faster. 371 00:30:24,942 --> 00:30:26,165 Why did I think that? 372 00:30:26,165 --> 00:30:28,695 I don’t know. It never works! 373 00:30:28,695 --> 00:30:37,969 Anyway, before I end this video I want to make sure I say that not all simmerstats are going to function exactly like these ones do. 374 00:30:37,969 --> 00:30:41,230 For instance, the simmerstats on my stove at home? 375 00:30:41,230 --> 00:30:50,386 Three of the four can’t possibly use the current flowing through  them to heat the bimetallic strip inside because they have selectable size elements. 376 00:30:50,386 --> 00:30:52,879 One even has three sizes. 377 00:30:52,879 --> 00:30:57,876 I suspect the core functionality of these simmerstats is exactly the same as this simple one, 378 00:30:57,876 --> 00:31:04,529 but there’s probably a dedicated resistor with its own path back to neutral producing the heat for the bimetallic strip, 379 00:31:04,529 --> 00:31:10,053 that way the duty cycles are consistent regardless of the load they're controlling at any particular time. 380 00:31:10,053 --> 00:31:14,118 I also think it might be controlling a relay or, another possibility, 381 00:31:14,118 --> 00:31:21,019 the knob could actually be controlling a variable resistor producing differing amounts of heat to open a limit switch. 382 00:31:21,019 --> 00:31:27,818 I kinda think that might be the case because these have a definite click as they cycle on and off which this basic model doesn’t. 383 00:31:27,818 --> 00:31:30,418 That’s just a guess, though - I’m not tearing this apart. 384 00:31:30,418 --> 00:31:31,479 I need it. 385 00:31:31,479 --> 00:31:37,529 And by the way, I built this box for this video  but I’ve been wanting to build something like it for quite a while 386 00:31:37,529 --> 00:31:41,264 specifically because of these cheap hotplates. 387 00:31:41,264 --> 00:31:46,710 If you’ve ever used one, you might have noticed that they are impossible to control! 388 00:31:46,710 --> 00:31:52,902 That’s because this knob is not controlling a simmerstat - it’s just a plain ol’ thermostat. 389 00:31:52,902 --> 00:31:57,816 Notice it only clicks on when you’re well away from the off position. 390 00:31:58,779 --> 00:32:01,697 You can kind make this work for what you need, 391 00:32:01,697 --> 00:32:09,443 but it’s incredibly hard because you don’t even know where it’s measuring the temperature and it’s going to change based on whatever cookware you're using 392 00:32:09,443 --> 00:32:12,420 It’s a bit easier to control this style of hotplate 393 00:32:12,420 --> 00:32:17,645 where the heating element is embedded in a metal disc and its average temperature kind of means something, 394 00:32:17,645 --> 00:32:23,142 but this coil style is flat-out impossible to control with a thermostat. 395 00:32:23,142 --> 00:32:28,955 I’m sure it’s just a lot cheaper than a proper simmerstat - I mean, these things are like $15. 396 00:32:28,955 --> 00:32:34,527 But it’s incredibly annoying and makes these pretty much only useful for boiling water. 397 00:32:34,527 --> 00:32:39,275 I thought I was going to end up building, like, an Arduino-based controller or something 398 00:32:39,275 --> 00:32:43,776 but it turns out you can just stick a simmerstat in a handy box and be done! 399 00:32:43,776 --> 00:32:46,005 I added the lights because it pleases me. 400 00:32:46,005 --> 00:32:50,242 The red one is the pilot light and the yellow one indicates power is flowing. 401 00:32:50,242 --> 00:32:53,182 Uh… I will not show you how I made that work. 402 00:32:53,182 --> 00:32:58,550 And a final point: it could be argued that we really shouldn’t be using these anymore. 403 00:32:58,550 --> 00:33:06,360 I mean, if you get an induction stove it’s not going to have them, but don’t get me started on the touch controls those often have - 404 00:33:06,360 --> 00:33:10,861 hey, note to appliance designers, nobody wants that! 405 00:33:10,861 --> 00:33:12,630 Just use knobs. 406 00:33:12,630 --> 00:33:22,035 Touch controls on a stove would be like taking away a car’s turn signal stalks and forcing people to adapt to weird buttons for no good reason at all. 407 00:33:22,035 --> 00:33:31,078 Anyway, what I mean by that is the simmerstat works great with coil-top stoves since these heating elements retain so much heat, 408 00:33:31,078 --> 00:33:40,340 but with glass-tops, where radiant heat is transmitted  right through immediately, the switching frequency is arguably too slow. 409 00:33:40,340 --> 00:33:45,371 I don’t often notice this,  and to be honest I’m not sure it actually matters, 410 00:33:45,440 --> 00:33:49,316 but when I’m frying up some veggies in a thinner piece of cookware, 411 00:33:49,316 --> 00:33:52,702 I can tell when the element is running and when it’s not. 412 00:33:52,702 --> 00:33:59,947 The sizzling gets a little louder whenever it’s on and if there’s any water in the bottom of the pan, it bubbles more vigorously. 413 00:33:59,947 --> 00:34:03,166 Again, I’m honestly unsure of how much that actually matters, 414 00:34:03,166 --> 00:34:07,947 but I’m not a good enough cook to pretend my opinion is any good. 415 00:34:07,947 --> 00:34:11,985 Anyway, with modern high-power solid-state switching components, 416 00:34:11,985 --> 00:34:17,086 cooktop burners could in theory be controlled with as much finesse as a dimmer switch provides. 417 00:34:17,086 --> 00:34:22,554 That would cost more, of course, but at this point I’m not sure how much it would. 418 00:34:22,554 --> 00:34:29,345 I mean, induction stoves have some wild power-switching circuitry in them and they’re not very expensive anymore. 419 00:34:29,345 --> 00:34:34,286 Now, the main thing I’d be worried about in this hypothetical is actually noise. 420 00:34:34,286 --> 00:34:38,282 These fellas make a fairly noticeably humming when they’re switched on, 421 00:34:38,282 --> 00:34:44,865 and adding some high-frequency switching to that mix could turn that hum into a weird ring. 422 00:34:44,865 --> 00:34:53,152 But hey, even just, like, a 1 Hz switching frequency would be a huge improvement over the simmerstats in my stove at home. 423 00:34:53,152 --> 00:34:54,823 Something to think about. 424 00:34:54,823 --> 00:34:57,119 OK. Well, that’s it! 425 00:34:57,119 --> 00:34:58,399 I think. 426 00:34:58,399 --> 00:35:01,342 Didn’t imagine this script would get so out of hand. 427 00:35:01,342 --> 00:35:04,906 I mean it’s literally just a bimetallic strip in a box with a knob. 428 00:35:04,906 --> 00:35:08,965 But at this point, I don’t know why I’m surprised. 429 00:35:08,965 --> 00:35:12,591 Here - how ‘bout we gey a taste of November in April? 430 00:35:12,591 --> 00:35:16,690 I think I’m gonna make something actually simple before the month is out. 431 00:35:16,690 --> 00:35:18,417 Can I rise to the challenge? 432 00:35:18,417 --> 00:35:21,448 Find out on the next… whatever. 433 00:35:21,448 --> 00:35:22,667 Whenever it happens. 434 00:35:23,972 --> 00:35:24,787 Bye. 435 00:35:25,530 --> 00:35:28,081 ♫ dutifully smooth jazz ♫ 436 00:35:29,434 --> 00:35:33,028 I’ll plug in a lamp to make what it’s doing obvious in addition to the 437 00:35:33,028 --> 00:35:34,900 eahhhh 438 00:35:34,900 --> 00:35:36,376 The ans- [strange noises] 439 00:35:36,376 --> 00:35:39,249 However, the interruption is pretty brief. 440 00:35:39,249 --> 00:35:42,255 Eventually, power returns. 441 00:35:43,404 --> 00:35:44,745 [eventually stretches on] 442 00:35:45,056 --> 00:35:46,114 [laughs] 443 00:35:46,114 --> 00:35:49,489 This is gonna be harder to time than I thought it was going to be 444 00:35:49,489 --> 00:35:52,448 Once you reach the medium setting, now - 445 00:35:52,448 --> 00:35:55,223 oh right, that’s what’s supposed to happen 446 00:35:55,223 --> 00:35:58,699 These periodic interruptions will repeat indefinitely, 447 00:35:58,699 --> 00:36:03,331 but as you continue to control the turn knob further clockwise [breaks into laughter] 448 00:36:03,331 --> 00:36:08,395 Earlier I said these modulate the power output of the cooktop burners (loud thud) 449 00:36:08,395 --> 00:36:10,489 that was loud! 450 00:36:10,489 --> 00:36:13,826 But to maintain a specissssffsfsfsfssfs 451 00:36:15,035 --> 00:36:17,528 You've heard of a flash in the pan, 452 00:36:17,528 --> 00:36:20,276 what about a flash below the pan? 453 00:36:20,276 --> 00:36:23,884 I think that joke needs a little more time in the oven, don't you? 454 00:36:23,884 --> 00:36:26,052 Half-baked at best. 455 00:36:26,052 --> 00:36:28,878 But hey, at least I made a meal out of it. 456 00:36:28,878 --> 00:36:30,521 Soup's on!