Resistance of incandescent light bulbs - Page 1
Forum section: electronics / projects

author: RoGeorge
author_rank: Super Contributor
timestamp: September 30, 2021, 04:35:15 pm
content: Some Python script to control a Rigol DP832 power source, and the measured data points (mA for the given V) from two different models of miniature light bulbs, like the ones used to stabilize the amplitude in a Wien bridge oscillator:Code:import ividp832a = ivi.rigol.rigolDP832A("TCPIP0::192.168.1.4::INSTR")dp832a.outputs.enabled = Trueimport numpy as npimport timev = i = r = []# test voltage: first = 0.5V# last = 3.5V# step = 0.1V## wait to settle after each voltage step = 5s#for v_test in np.arange(0.5, 3.5, 0.01):# print(i)dp832a.outputs.voltage_level = v_testtime.sleep(5) # wait x seconds for the lightbulb to light upp3 = dp832a._ask(":MEAS:ALL? CH3").split(",")# print (p3)r3 = float(p3)/float(p3)v.append(float(p3))r.append(r3)i.append(float(p3))# print ("%.3f" % r3, "ohms at", "%.3f" % float(p3), "volts")print ("%.3f" % r3, "%.3f" % float(p3))dp832a.outputs.voltage_level = 0Measured data from miniature light bulb model 1:Code:7.846 0.0105.583 0.0205.172 0.0305.089 0.0405.122 0.0505.137 0.0605.185 0.0705.353 0.0805.500 0.0905.667 0.1005.825 0.1106.066 0.1206.269 0.1306.495 0.1406.740 0.1506.965 0.1607.181 0.1707.442 0.1807.717 0.1917.964 0.2018.234 0.2118.456 0.2218.735 0.2318.981 0.2419.247 0.2519.480 0.2619.734 0.2719.986 0.28110.193 0.29010.434 0.30010.670 0.31010.901 0.32111.128 0.33111.343 0.34011.561 0.35011.733 0.36011.900 0.37012.105 0.38012.303 0.39012.497 0.40012.703 0.41012.893 0.42013.079 0.43013.259 0.44013.402 0.45013.575 0.46013.746 0.47013.916 0.48014.083 0.49014.251 0.50014.407 0.51014.563 0.52014.681 0.53014.832 0.54014.986 0.55015.135 0.56015.282 0.57015.423 0.58015.573 0.59015.709 0.60015.891 0.61015.992 0.62116.123 0.63016.251 0.64016.383 0.65016.510 0.66016.633 0.67016.800 0.68016.922 0.69017.002 0.70117.118 0.71017.237 0.72117.390 0.73017.506 0.74117.617 0.75017.769 0.76017.875 0.77017.979 0.78018.126 0.79018.186 0.80018.291 0.81018.390 0.82018.536 0.83018.636 0.84118.736 0.85118.868 0.86018.967 0.87119.102 0.88119.155 0.89119.246 0.90119.372 0.91019.465 0.92119.596 0.93119.684 0.94119.808 0.95119.894 0.96120.019 0.97120.100 0.98120.181 0.99120.265 1.00120.381 1.01120.459 1.02120.579 1.03120.657 1.04120.775 1.05120.847 1.06120.963 1.07121.070 1.08121.099 1.09121.210 1.10121.278 1.11121.389 1.12121.492 1.13121.556 1.14021.665 1.15021.765 1.16021.828 1.17021.933 1.18021.994 1.19022.055 1.20022.152 1.21022.252 1.21922.349 1.22922.409 1.23922.505 1.24922.609 1.25922.664 1.26922.763 1.27922.860 1.28922.877 1.29922.972 1.30923.065 1.31923.159 1.32923.255 1.33923.307 1.34923.399 1.35923.494 1.37023.585 1.38023.636 1.39023.725 1.40023.774 1.41023.862 1.42023.951 1.43023.998 1.44024.088 1.45024.169 1.46024.256 1.47024.347 1.48024.431 1.49024.476 1.50024.559 1.51024.600 1.52024.682 1.53024.765 1.54024.846 1.55024.928 1.56024.965 1.57025.044 1.58025.125 1.59025.203 1.60025.283 1.61125.360 1.62125.437 1.63125.474 1.64125.545 1.65025.622 1.66025.695 1.67025.771 1.68025.847 1.69025.924 1.70125.992 1.71026.065 1.72026.137 1.73026.208 1.74026.281 1.75026.347 1.76026.379 1.77026.449 1.78026.520 1.79026.589 1.80026.658 1.81026.725 1.82026.792 1.83026.860 1.84026.929 1.85026.994 1.86027.061 1.87027.127 1.88027.152 1.89027.222 1.90027.287 1.91027.355 1.92027.419 1.93027.482 1.94027.545 1.95027.610 1.96027.673 1.97027.737 1.98027.838 1.99027.901 2.00127.960 2.01027.983 2.02028.046 2.03028.105 2.04028.166 2.05028.226 2.06128.286 2.07128.381 2.08028.439 2.09028.498 2.10028.556 2.11028.617 2.12028.674 2.13128.732 2.14028.750 2.15128.846 2.16128.901 2.17128.955 2.18029.011 2.19029.065 2.20029.158 2.21029.214 2.22029.269 2.23029.325 2.24029.375 2.25029.430 2.26029.521 2.27029.576 2.28029.590 2.29029.642 2.30029.734 2.31029.783 2.32029.837 2.33029.889 2.34029.941 2.35029.991 2.36030.080 2.37030.132 2.38030.179 2.39030.230 2.40030.318 2.41030.369 2.42030.379 2.43030.430 2.44130.517 2.45030.564 2.46030.613 2.47030.660 2.48030.743 2.49030.791 2.50030.837 2.51030.884 2.52030.968 2.53031.016 2.54031.063 2.55031.148 2.56031.155 2.57031.202 2.58031.246 2.59031.329 2.60031.374 2.61031.418 2.62031.501 2.63031.545 2.64031.590 2.65031.669 2.66031.713 2.67031.756 2.68031.838 2.69031.881 2.70031.886 2.71031.966 2.72032.008 2.73032.050 2.74032.130 2.75032.174 2.76032.216 2.77132.256 2.78032.336 2.79132.376 2.80032.418 2.81132.495 2.82132.537 2.83132.613 2.84132.653 2.85132.656 2.86132.732 2.87132.772 2.88132.812 2.89132.888 2.90132.925 2.91132.964 2.92133.039 2.93133.076 2.94133.152 2.95033.186 2.96033.262 2.97033.301 2.98033.338 2.99033.412 3.00033.448 3.01033.486 3.02033.521 3.03033.557 3.04033.631 3.05033.667 3.06033.738 3.07033.774 3.08033.843 3.09033.880 3.10033.914 3.11033.984 3.12034.020 3.13034.091 3.14034.124 3.15034.195 3.16034.190 3.16934.224 3.17934.296 3.18934.332 3.20034.402 3.21034.435 3.22034.470 3.23034.539 3.24034.573 3.25034.645 3.26034.676 3.27034.746 3.28034.780 3.29034.811 3.30034.882 3.31034.912 3.32034.945 3.33034.975 3.34035.045 3.35035.076 3.36035.144 3.37035.175 3.38035.242 3.39035.275 3.40135.341 3.41035.372 3.42135.435 3.43035.464 3.44035.530 3.45035.559 3.46035.624 3.47035.653 3.48035.719 3.49035.708 3.49935.774 3.50935.802 3.51935.867 3.52935.894 3.539Measured data from miniature light bulb model 2:Code:22.326 0.50022.364 0.51022.600 0.52022.742 0.53022.970 0.54023.301 0.55023.525 0.56023.746 0.57024.062 0.58024.284 0.59024.490 0.60024.801 0.61025.016 0.62025.313 0.63025.510 0.64025.802 0.65025.996 0.66026.286 0.67026.574 0.68026.653 0.69026.938 0.70027.111 0.71027.392 0.72027.663 0.73027.835 0.74028.105 0.75028.264 0.76028.530 0.77028.793 0.78028.949 0.79029.204 0.80029.462 0.81029.606 0.82029.867 0.83030.118 0.84030.267 0.85130.507 0.86030.540 0.87030.787 0.88031.028 0.89031.163 0.90131.393 0.91031.636 0.92131.765 0.93132.000 0.94132.227 0.95132.350 0.96132.577 0.97132.803 0.98132.920 0.99133.146 1.00133.360 1.01133.579 1.02133.693 1.03133.909 1.04134.019 1.05134.119 1.06134.330 1.07134.530 1.08134.625 1.09134.832 1.10135.038 1.11135.242 1.12135.325 1.13035.523 1.14035.724 1.15035.913 1.16035.997 1.17036.196 1.18036.385 1.19036.573 1.20036.760 1.20936.837 1.21937.024 1.22937.210 1.23937.173 1.24937.368 1.25937.547 1.26937.735 1.27937.806 1.28937.994 1.29938.175 1.30938.349 1.31938.416 1.32938.599 1.33938.776 1.34938.951 1.35939.131 1.37039.193 1.38039.368 1.39039.540 1.40039.598 1.41039.768 1.42039.936 1.43040.109 1.44040.163 1.45040.215 1.46040.382 1.47040.553 1.48040.716 1.49040.880 1.50040.930 1.51041.086 1.52041.245 1.53041.406 1.54041.563 1.55041.608 1.56041.761 1.57041.915 1.58042.074 1.59042.227 1.60042.379 1.61042.419 1.62042.567 1.63042.719 1.64042.860 1.65042.899 1.66043.046 1.67043.085 1.68043.233 1.69043.380 1.70043.517 1.71043.660 1.72043.803 1.73043.944 1.74043.975 1.75044.110 1.76044.248 1.77044.389 1.78044.527 1.79044.665 1.80044.802 1.81044.825 1.82044.958 1.83045.093 1.84045.230 1.85045.361 1.86045.386 1.87045.516 1.88045.647 1.89045.673 1.90045.806 1.91045.938 1.92046.067 1.93046.193 1.94046.321 1.95046.450 1.96046.469 1.97046.595 1.98046.721 1.99046.845 2.00046.970 2.01047.093 2.02047.219 2.03047.341 2.04047.463 2.05047.584 2.06047.707 2.07147.821 2.08047.721 2.09047.841 2.10047.959 2.11048.082 2.12048.199 2.13048.318 2.14048.435 2.15148.548 2.16048.666 2.17148.774 2.18048.888 2.19049.002 2.20049.007 2.21049.231 2.22049.234 2.23049.348 2.24049.453 2.25049.566 2.26049.676 2.27049.784 2.28049.895 2.29050.004 2.30050.113 2.31050.216 2.32050.220 2.33050.329 2.34050.436 2.35050.542 2.36050.647 2.37050.755 2.38050.855 2.39050.962 2.40051.066 2.41051.169 2.42051.272 2.43051.375 2.44051.479 2.45051.581 2.46051.682 2.47051.781 2.48051.875 2.49051.977 2.50052.075 2.51052.176 2.52052.273 2.53052.373 2.54052.473 2.55052.573 2.56052.668 2.57052.657 2.58052.754 2.59052.850 2.60052.945 2.61053.040 2.62053.135 2.63053.232 2.64053.435 2.65053.523 2.66053.616 2.67053.709 2.68053.804 2.69053.896 2.70053.988 2.71054.078 2.72054.171 2.73054.261 2.74054.354 2.75054.446 2.76054.537 2.77154.627 2.78054.716 2.79154.804 2.80054.895 2.81154.981 2.82154.961 2.83055.050 2.84155.135 2.85055.224 2.86155.310 2.87155.396 2.88155.482 2.89155.565 2.90155.650 2.91055.735 2.92155.926 2.93056.008 2.94056.091 2.95056.169 2.96056.254 2.97056.338 2.98056.421 2.99056.503 3.00056.585 3.01056.664 3.02056.747 3.03056.826 3.04056.907 3.05056.987 3.06057.063 3.07057.145 3.08057.115 3.09057.299 3.10057.378 3.11057.453 3.12057.531 3.13057.609 3.14057.685 3.15057.761 3.15957.834 3.16957.913 3.17957.989 3.18958.069 3.20058.147 3.21058.221 3.22058.298 3.23058.371 3.24058.450 3.25058.633 3.26058.704 3.27058.781 3.28058.857 3.29058.929 3.30059.005 3.31059.077 3.32059.151 3.33059.220 3.34059.294 3.35059.263 3.36059.336 3.37059.406 3.38059.477 3.39059.552 3.40059.622 3.41059.693 3.42059.758 3.43059.826 3.44059.894 3.45059.962 3.46060.133 3.47060.202 3.48060.269 3.490Inrush current for some other 3 more types of slightly bigger incandescent light bulbs:

author: bob91343
author_rank: Super Contributor
timestamp: September 30, 2021, 06:22:34 pm
content: I was taught that the cold resistance of a typical incandescent lamp is about one-tenth of its hot resistance.

author: Alti
author_rank: Frequent Contributor
timestamp: September 30, 2021, 06:55:38 pm
content: Also worth noting that with R at 25oC it means the peak current reaches sqrt2*Urms/R only when the turn on happens to be at exactly 90 degrees phase angle (at peak voltage). At all other turn-on times, with such tremendous powers pushed into light filament (adiabatic heating), it is already going to be preheated near peak voltage.Halogens have super high R_hot/R_cold, some around 16-17. But when you measure inrush when powering at voltage zero crossing, you realize Irms_cold/Irms_hot rarely reaches 13 in practical circuit.

author: aiq25
author_rank: Regular Contributor
timestamp: September 30, 2021, 06:56:44 pm
content: I had to do that while working on a DC to AC (12V to 110AC) inverter because it was the best load to try in terms of inrush current.

author: Benta
author_rank: Super Contributor
timestamp: September 30, 2021, 08:40:26 pm
content: So what's the question?

author: RoGeorge
author_rank: Super Contributor
timestamp: September 30, 2021, 08:58:33 pm
content: No question, just some measurements.Good for example to make a light bulb simulation model, or to make a rough approximation of the expected current when the voltage is lower than nominal, things like this. I measured mine to find the expected resistance of the light-bulb when used as an amplitude stabilizer in a Wien bridge generator like this one:https://en.wikipedia.org/wiki/Wien_bridge_oscillator

author: mawyatt
author_rank: Super Contributor
timestamp: October 03, 2021, 01:57:34 pm
content: Interesting measurements, wonder if someone has used a PTC Fuse in place of the bulb for the WB Oscillator?Best,

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 03, 2021, 03:36:13 pm
content: Quote from: aiq25 on September 30, 2021, 06:56:44 pmI always thought that motors tend to be the most difficult sort of load to deal with, although that is solved to some extent with V/Hz ramp up.Quote from: mawyatt on October 03, 2021, 01:57:34 pmThose are extremely nonlinear with respect to resistance over temperature. It would be difficult to get it to stabilize.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 03, 2021, 04:28:33 pm
content: Quote from: mawyatt on October 03, 2021, 01:57:34 pmThanksthose are measurements from a couple of years ago, posted now because somebody was asking in another topic about the SPICE model of light bulb, to simulate a WB oscillator, so I thought those two measured charts would help making a rough approximation of what to expect from a miniature incandescent filament (light bulb of about 5mm/0.2inch diameter and 3.5V nominal or so).I would be curious, too, to see the comparison in terms of a Wien Bridge distortions when the amplitude of the oscillator is stabilized using a light bulb vs a PTC Fuse.As a wild guess, I would expect to see better result with the light bulb, simply because most of the WB schematics I've seen use either a light bulb, a FET, or the more elaborated servo method of Jim Williams described in the"Max Wien, Mr. Hewlett, and a Rainy Sunday Afternoon".The advantage of the light bulb is that it has a big thermal inertia, while I was measuring I noticed that the filament needs 3-5 seconds to reach its final light intensity. I would expect a fuse to be optimized for fast time response, therefore low thermal inertia.Another concern would be the I-V curve, where the light bulb is very close to a pure resistor (the filament resistance is in fact a temperature controlled resistor, and the temperature of the filament is constant for fast voltage variations) therefore a linear element (an LTI system can not change a spectrum, so no distortions added). I suspect that, temperature aside, a complex material like the one used in making a PTC fuse might have a V-I curve with more non linearities than the filament, a metal alloy, might have.Again, no idea if the above guesses will hold when tested in practice.