{"id":30239,"date":"2023-10-17T13:59:24","date_gmt":"2023-10-17T20:59:24","guid":{"rendered":"https:\/\/digilent.com\/blog\/?p=30239"},"modified":"2023-10-18T09:00:28","modified_gmt":"2023-10-18T16:00:28","slug":"ignite-a-neon-lamp-using-the-analog-discovery-3","status":"publish","type":"post","link":"https:\/\/digilent.com\/blog\/ignite-a-neon-lamp-using-the-analog-discovery-3\/","title":{"rendered":"Ignite a Neon Lamp Using the Analog Discovery 3"},"content":{"rendered":"<p>Hi there Digilent Blog readers! I\u2019m Dr. Brian Faulkner, professor of Electrical Engineering at Milwaukee School of Engineering in Milwaukee, Wisconsin, USA, where I teach introductory circuit theory and power systems engineering. <a href=\"https:\/\/digilent.com\/shop\/analog-discovery-3\/\">The Analog Discovery 3<\/a> is a wallet-sized powerhouse and I\u2019m a huge fanboy. We will use the 5 volt peak waveform generator to light a 90 volt neon glow lamp, all without danger of electrocution!<\/p>\n<hr \/>\n<h2>Equipment:<\/h2>\n<p>&nbsp;<\/p>\n<h4>A Neon Lamp<\/h4>\n<p>In the awesome rock band that is analog electronics, transducers and actuators are the lead vocals. They\u2019re the components that DO something. They accomplish what the system is built to, either to learn about the physical world or to act in the physical world.<\/p>\n<ul>\n<li>Neon bulbs require about 90 volts to \u201cignite\u201d the gas in the tube and glow.<\/li>\n<li>After lighting, they maintain a near-constant voltage of about 60 V if the current is at least a few microamps, and when the current drops too low they go dark again.<\/li>\n<li>I find that neon lamps that require 120 V to ignite just barely don\u2019t work, get a 90V lamp like the NE-2 1A1.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig_1a_Neon_Bulb1-150x150.jpg\" alt=\"\" width=\"206\" height=\"206\" class=\"alignnone wp-image-30184 \" \/> <img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-1b-Neon_schematic_symbol-600x438.png\" alt=\"\" width=\"285\" height=\"208\" class=\"alignnone wp-image-30185 \" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-1b-Neon_schematic_symbol-600x438.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-1b-Neon_schematic_symbol-1024x748.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-1b-Neon_schematic_symbol.png 1244w\" sizes=\"auto, (max-width: 285px) 100vw, 285px\" \/><\/p>\n<p><em>Figure 1a and 1b: Neon lamp photograph and schematic.<\/em><\/p>\n<p><em>\u00a0<\/em><\/p>\n<h4>A Transformer<\/h4>\n<p>In the awesome rock band of analog electronics, we have exciting components like amplifiers, timers, and transformers on guitar. And this experiment has some pretty good solo parts for the transformer.<\/p>\n<ul>\n<li>I\u2019m using a TRA1370 that I found lying round in the parts room that was donated to the school a few years back. I\u2019m using the center tap to get the step-up ratio I want.<\/li>\n<\/ul>\n<p style=\"padding-left: 120px;\">-You need a turns ratio of about 10:1.<\/p>\n<p style=\"padding-left: 120px;\">-You need a core at least the size of a golf ball. Small audio transformers won\u2019t work, their magnetizing reactance and saturation flux are too small. Every transformer I\u2019ve ripped out of an old power supply has worked.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2a-transformer_pinout-600x320.png\" alt=\"\" width=\"369\" height=\"197\" class=\" wp-image-30189\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2a-transformer_pinout-600x320.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2a-transformer_pinout.png 732w\" sizes=\"auto, (max-width: 369px) 100vw, 369px\" \/><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2b-Transformer_schematic_symbol-600x433.png\" alt=\"\" width=\"254\" height=\"183\" class=\"alignnone wp-image-30190\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2b-Transformer_schematic_symbol-600x433.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2b-Transformer_schematic_symbol-1024x738.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2b-Transformer_schematic_symbol-1536x1107.png 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-2b-Transformer_schematic_symbol.png 1562w\" sizes=\"auto, (max-width: 254px) 100vw, 254px\" \/><\/p>\n<p><em>Figure 2a and 2b: Transformer and schematic. This transformer is center tap, I just ignore wire 3.<\/em><\/p>\n<p>&nbsp;<\/p>\n<h4>An Analog Discovery 2 or Analog Discovery 3<\/h4>\n<p>In the awesome rock band of analog electronics, we\u2019ve got measurement instrumentation and power supply on drums and bass, backing up the rest of the crew and keeping time.<\/p>\n<ol>\n<li>Have the Waveforms software installed, plus a breadboard and jumper wires.<\/li>\n<li>The output voltage of the waveform generator is limited to 5 V peak since they run on USB. We will use a transformer to increase this maximum, as well as use two waveform generators together for an extra doubling of voltage.<\/li>\n<li>The measurement voltage range on the scope is. We will build an attenuator to measure high voltage anyway.<\/li>\n<li>The output current is limited to about 40mA. We exploit this limitation as a backup safety feature.<\/li>\n<li>None of the improved specs of the Analog Discovery 3 over the Analog Discovery 2 matter in this experiment. I will be showing the 3 in the photos of my breadboard setup.<\/li>\n<\/ol>\n<figure id=\"attachment_30194\" aria-describedby=\"caption-attachment-30194\" style=\"width: 600px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-3-AD2-and-AD3-600x409.jpg\" alt=\"\" width=\"600\" height=\"409\" class=\"wp-image-30194 size-medium\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-3-AD2-and-AD3-600x409.jpg 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-3-AD2-and-AD3-1024x698.jpg 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-3-AD2-and-AD3-1536x1047.jpg 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-3-AD2-and-AD3-2048x1396.jpg 2048w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-3-AD2-and-AD3-135x93.jpg 135w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><figcaption id=\"caption-attachment-30194\" class=\"wp-caption-text\"><em>Figure 3: The back-jeans-pocket sized powerhouse!<\/em><\/figcaption><\/figure>\n<h4><\/h4>\n<h4>Resistors<\/h4>\n<p>Ah resistors. Necessary, but boring support components. The roadies in the rock band of electronics. This experiment uses high voltage, but very low currents so \u00bc watt resistors are adequate.<\/p>\n<p>2x 100k\u03a9 , 1x 10k\u03a9 resistor, 1x 1M\u03a9 resistor (I use 1 Meg resistors far more often than my undergraduate instructors led me to believe I would.)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-4-Resistors-1-600x592.jpg\" alt=\"\" width=\"315\" height=\"311\" class=\"alignnone wp-image-30243 \" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-4-Resistors-1-600x592.jpg 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-4-Resistors-1-1024x1010.jpg 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-4-Resistors-1-1536x1515.jpg 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-4-Resistors-1-2048x2020.jpg 2048w\" sizes=\"auto, (max-width: 315px) 100vw, 315px\" \/><\/p>\n<p><em>Figure 4: Resistors. They are not fun but they\u2019re important.<\/em><\/p>\n<hr \/>\n<h2><\/h2>\n<h2>Guide:<\/h2>\n<h4><\/h4>\n<h4>Drive the Step-up Transformer<\/h4>\n<p>The Analog Discovery 3 has a maximum AC output voltage of 5 Vpk, and a maximum measurement range of 25 V on the scope channels.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-5-Transformer_test_AD3-1-600x262.png\" alt=\"\" width=\"600\" height=\"262\" class=\"alignnone size-medium wp-image-30244\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-5-Transformer_test_AD3-1-600x262.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-5-Transformer_test_AD3-1-1024x447.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-5-Transformer_test_AD3-1.png 1140w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p><em>Figure 5: Transformer measurement circuit diagram.<\/em><\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-6-Scorch_marks_transformer-1-600x314.png\" alt=\"\" width=\"600\" height=\"314\" class=\"alignnone size-medium wp-image-30245\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-6-Scorch_marks_transformer-1-600x314.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-6-Scorch_marks_transformer-1-1024x536.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-6-Scorch_marks_transformer-1-1536x804.png 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-6-Scorch_marks_transformer-1-2048x1072.png 2048w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p><em>Figure 6: Transformer test on the breadboard.<\/em><\/p>\n<p>&nbsp;<\/p>\n<ol>\n<li>Build the transformer measurement circuit shown in Figure 5. One lead on both the primary and secondary is connected to ground.<\/li>\n<li>Set the waveform generator to 2 Vpk and 1 kHz.<\/li>\n<li>You should see a 2 V sine wave on channel 1 and a much larger sine wave on channel 2 as in Figure 7. If you use the same pins I did on the transformer, the voltage is also inverted. Neon bulbs do not care about polarity so this is fine.<\/li>\n<li>Scale the V\/div on channel 2 and channel 1 large enough so that the voltage step-up effect is clearly visible. I\u2019ve got both channels of 5 V\/div.<\/li>\n<li>Change the amplitude of the waveform generator so that the output is greater than 20 Vpk but less than 25 Vpk.<\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-7-Transformer_test_waveforms_amplification-1-600x463.png\" alt=\"\" width=\"437\" height=\"337\" class=\"alignnone wp-image-30246\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-7-Transformer_test_waveforms_amplification-1-600x463.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-7-Transformer_test_waveforms_amplification-1-1024x790.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-7-Transformer_test_waveforms_amplification-1.png 1059w\" sizes=\"auto, (max-width: 437px) 100vw, 437px\" \/><\/p>\n<p><em>Figure 7: Woah nelly that\u2019s a lot of extra volts! Step up transformers are just so much cooler than step down.<\/em><\/p>\n<p>&nbsp;<\/p>\n<h4>Drive Two Waveform Generators Back-to-Back<\/h4>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-8-back_to_back_AD3-1-600x398.png\" alt=\"\" width=\"502\" height=\"333\" class=\"alignnone wp-image-30247\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-8-back_to_back_AD3-1-600x398.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-8-back_to_back_AD3-1-1024x679.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-8-back_to_back_AD3-1.png 1258w\" sizes=\"auto, (max-width: 502px) 100vw, 502px\" \/><\/p>\n<p><em>Figure 8: Bipolar AC drive circuit.<\/em><\/p>\n<p>&nbsp;<\/p>\n<ol>\n<li>Enable the second waveform generator channel and synchronize them as shown in Figure 9<\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-9-synchronize_channels-600x171.png\" alt=\"\" width=\"502\" height=\"143\" class=\"alignnone wp-image-30248\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-9-synchronize_channels-600x171.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-9-synchronize_channels-1024x292.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-9-synchronize_channels.png 1475w\" sizes=\"auto, (max-width: 502px) 100vw, 502px\" \/><\/p>\n<p><em>Figure 9: Enabling second waveform generator channel.<\/em><\/p>\n<p style=\"padding-left: 40px;\">2. Build the circuit shown in Figure 8. Pin 2 of the transformer is now driven by the second waveform generator channel and is NOT connected to ground.<\/p>\n<p style=\"padding-left: 40px;\">3. Use the 1+ and 1- pins (differential scope) for channel 1: it measures between the two wavegen outputs. Unlike most scopes I\u2019ve used, using the differential measurement is not a huge pain that requires checking out extra parts, it just goes and I never worry about it.<\/p>\n<p style=\"padding-left: 40px;\">4. Set the second wavegen channel to the 1Vpk and 180 degrees out of phase. The two channels together have a maximum output of 10 Vpk working together.<\/p>\n<p style=\"padding-left: 40px;\">5. Verify that the input voltage on channel 1 is the sum of the two waveform generator channel voltages: 2 V peak when each channel is at 1 Vpk.<\/p>\n<p style=\"padding-left: 40px;\">6. Crank up the voltage until the output exceeds the 25V maximum measurement capability of the AD2 as shown in Figure 10.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-10-back_to_back_waveforms-463x600.png\" alt=\"\" width=\"363\" height=\"470\" class=\"alignnone wp-image-30249\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-10-back_to_back_waveforms-463x600.png 463w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-10-back_to_back_waveforms-790x1024.png 790w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-10-back_to_back_waveforms.png 1045w\" sizes=\"auto, (max-width: 363px) 100vw, 363px\" \/><\/p>\n<p><em>Figure 10: 2 volts in, 25 volts out. Nearly the same waveform as before, but our maximum is now doubled.<\/em><\/p>\n<h4><\/h4>\n<h4>Build an Attenuator to Measure High Voltages<\/h4>\n<p>The AD2 is incapable of measuring more than 25 V natively. To measure higher voltages when driving the transformer harder, we will use a resistive divider. The divider resistance (1.1M\u03a9 ) is much higher than the internal resistance of the transformer (\u22486k\u03a9 ) to avoid loading down the transformer output.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-11-attenuator_AD3_schematic-600x297.png\" alt=\"\" width=\"600\" height=\"297\" class=\"alignnone size-medium wp-image-30250\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-11-attenuator_AD3_schematic-600x297.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-11-attenuator_AD3_schematic-1024x507.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-11-attenuator_AD3_schematic-1536x761.png 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-11-attenuator_AD3_schematic.png 1641w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p><em>Figure 11: Transformer circuit with attenuator to measure high voltages.<\/em><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-12-Attenuator-600x330.jpg\" alt=\"\" width=\"600\" height=\"330\" class=\"alignnone size-medium wp-image-30251\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-12-Attenuator-600x330.jpg 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-12-Attenuator-1024x563.jpg 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-12-Attenuator-1536x844.jpg 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-12-Attenuator-2048x1125.jpg 2048w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p><em>Figure 12: Who knew all those voltage divider calculations we did in circuits class were good for something?<\/em><\/p>\n<p>&nbsp;<\/p>\n<ol>\n<li>Add the attenuator resistors R1 and R2 as shown in Figure 11.<\/li>\n<li>Connect channel 2 to measure the voltage across R2, rather than directly measuring the very large transformer output voltage. R2\u2019s voltage is 1\/11<sup>th<\/sup> the transformer voltage.<\/li>\n<li>Click Add Channel -&gt; Custom<\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-13-add_channel-600x528.png\" alt=\"\" width=\"314\" height=\"276\" class=\"alignnone wp-image-30252\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-13-add_channel-600x528.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-13-add_channel.png 857w\" sizes=\"auto, (max-width: 314px) 100vw, 314px\" \/><\/p>\n<p><em>Figure 13: Adding a math channel does not require digging around in 15 menus to find<\/em><\/p>\n<p style=\"padding-left: 40px;\">4. Program the math channel to multiply channel 2 by 11, so the display reads the actual transformer voltage as shown. The Waveforms interface is easy to use. It\u2019s just very easy.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-14-programming_math_channel-519x600.png\" alt=\"\" width=\"305\" height=\"353\" class=\"alignnone wp-image-30253\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-14-programming_math_channel-519x600.png 519w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-14-programming_math_channel-885x1024.png 885w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-14-programming_math_channel.png 927w\" sizes=\"auto, (max-width: 305px) 100vw, 305px\" \/><\/p>\n<p><em>Figure 14: Programming a math channel is very easy.<\/em><\/p>\n<p>&nbsp;<\/p>\n<p style=\"padding-left: 40px;\">5. Raise both waveform generator channels to 5 V peak to achieve maximum output voltage. The input voltage is now 10 V peak from the sum of the two waveform generators. You should have an output voltage from the transformer of about 100 V peak as shown in Figure 15. Don\u2019t worry about polarity.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-15-math_channel_waveforms_attenuator-491x600.png\" alt=\"\" width=\"426\" height=\"521\" class=\"alignnone wp-image-30254\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-15-math_channel_waveforms_attenuator-491x600.png 491w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-15-math_channel_waveforms_attenuator-838x1024.png 838w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-15-math_channel_waveforms_attenuator.png 1071w\" sizes=\"auto, (max-width: 426px) 100vw, 426px\" \/><\/p>\n<p><em>Figure 15: Input and output waveforms of dual drive, measured with attenuator.<\/em><\/p>\n<p>&nbsp;<\/p>\n<h4>Ignite the Neon<\/h4>\n<p>Neon will not turn on for less than 90 V. If it glows, that means there is real high voltage present! Misuse of the math channel or instruments cannot make neon glow.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-16-Ignite_neon_schematic-600x297.png\" alt=\"\" width=\"600\" height=\"297\" class=\"alignnone size-medium wp-image-30256\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-16-Ignite_neon_schematic-600x297.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-16-Ignite_neon_schematic-1024x507.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-16-Ignite_neon_schematic-1536x761.png 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/Fig-16-Ignite_neon_schematic.png 1549w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p><em>Figure 16: Neon glow bulb circuit.<\/em><\/p>\n<ol>\n<li>Turn off the waveform generator before making modifications.\n<ul>\n<li>If you touch the high voltage output, it tingles and surprises you but the maximum output current is too low to be harmful.<\/li>\n<\/ul>\n<\/li>\n<li>Add a neon bulb and resistor to the circuit as shown in Figure 16. The resistor protects the neon from carrying excessive current.<\/li>\n<li>The neon should begin to glow. Neon lamps are non-linear devices, so they distort sinusoidal waveforms as shown in Figure 17.<\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17b-Glowing-Neon-600x598.jpg\" alt=\"\" width=\"339\" height=\"338\" class=\"alignnone wp-image-30259\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17b-Glowing-Neon-600x598.jpg 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17b-Glowing-Neon-1024x1020.jpg 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17b-Glowing-Neon-150x150.jpg 150w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17b-Glowing-Neon-1536x1530.jpg 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17b-Glowing-Neon-2048x2040.jpg 2048w\" sizes=\"auto, (max-width: 339px) 100vw, 339px\" \/>\u00a0 \u00a0<img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17a-neon-glow-waveforms-368x600.png\" alt=\"\" width=\"326\" height=\"532\" class=\"alignnone wp-image-30258\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17a-neon-glow-waveforms-368x600.png 368w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17a-neon-glow-waveforms-627x1024.png 627w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-17a-neon-glow-waveforms.png 710w\" sizes=\"auto, (max-width: 326px) 100vw, 326px\" \/><\/p>\n<p><em>Figure 17a and 17b: Neon bulb glowing and waveform distortion.<\/em><\/p>\n<p>If you see the lamp start glowing before you plug in the second leg as shown in Figure 18, you are completing the circuit through capacitive coupling. Your body is a conductor separated by the insulating air from the blue ground rail conductor. <em>You<\/em> are a capacitor. These currents are so small that they are harmless, just a few microamps. The brightness of a neon lamp is proportional to the current, as shown in the figure 18 the lamp is just barely lit. These currents are below my threshold of perception, I am unable to feel anything, but they\u2019re there because the neon is glowing.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-18-Capacitive_Coupling-600x523.jpg\" alt=\"\" width=\"529\" height=\"461\" class=\"alignnone wp-image-30261\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-18-Capacitive_Coupling-600x523.jpg 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-18-Capacitive_Coupling-1024x892.jpg 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-18-Capacitive_Coupling-1536x1339.jpg 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-18-Capacitive_Coupling-2048x1785.jpg 2048w\" sizes=\"auto, (max-width: 529px) 100vw, 529px\" \/><\/p>\n<p><em>Figure 18: Capacitive coupling is spooky.<\/em><\/p>\n<h4><\/h4>\n<h4>Measure the Neon Current<\/h4>\n<p>You want to know what the current is? Just add one more resistor. This is where I\u2019d like to have an <a href=\"https:\/\/digilent.com\/shop\/analog-discovery-pro-3000-series-portable-high-resolution-mixed-signal-oscilloscopes\/\">Analog Discovery Pro<\/a> with the four voltage channels. We must give up being able to measure the input voltage to see the output current and output voltage together, but we know we have high voltage so that\u2019s fine.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-19-Neon_current_schematic-600x297.png\" alt=\"\" width=\"600\" height=\"297\" class=\"alignnone size-medium wp-image-30262\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-19-Neon_current_schematic-600x297.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-19-Neon_current_schematic-1024x507.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-19-Neon_current_schematic.png 1451w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p><em>Figure 19: Measuring current. I like to use the \u201cjump\u201d notation for wires that cross but do not connect just to be extra clear, in addition to using a different color.<\/em><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-20-Current-Measurement-600x311.jpg\" alt=\"\" width=\"600\" height=\"311\" class=\"alignnone size-medium wp-image-30263\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-20-Current-Measurement-600x311.jpg 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-20-Current-Measurement-1024x531.jpg 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-20-Current-Measurement-1536x797.jpg 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-20-Current-Measurement-2048x1062.jpg 2048w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/p>\n<p><em>Figure 20: Measuring the neon current waveform.<\/em><\/p>\n<ol>\n<li>Add a 10k resistor in series with the neon to use as a current sense resistor with one end to ground, and use Channel 1 of the scope to measure its voltage as shown in Figure 19.<\/li>\n<li>Add another math channel, this time setting the mode to current. We have a 10 resistor, so divide the value by 10 thousand.<\/li>\n<\/ol>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-21-current_channel-518x600.png\" alt=\"\" width=\"296\" height=\"343\" class=\"alignnone wp-image-30264\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-21-current_channel-518x600.png 518w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-21-current_channel-884x1024.png 884w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-21-current_channel.png 938w\" sizes=\"auto, (max-width: 296px) 100vw, 296px\" \/><\/p>\n<p><em>Figure 21: Making a current channel is also easy, just click the units option.<\/em><\/p>\n<ul><\/ul>\n<p style=\"padding-left: 40px;\">3. The little \u201cnotch\u201d taken out of the voltage waveform occurs just as the neon begins to conduct, at around 90 V just like it should be. It continues to conduct until almost the next zero crossing.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-22-Neon_current_1kHz_waveforms-600x354.png\" alt=\"\" width=\"386\" height=\"228\" class=\"alignnone wp-image-30265\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-22-Neon_current_1kHz_waveforms-600x354.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-22-Neon_current_1kHz_waveforms-1024x604.png 1024w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-22-Neon_current_1kHz_waveforms-1536x907.png 1536w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-22-Neon_current_1kHz_waveforms.png 1679w\" sizes=\"auto, (max-width: 386px) 100vw, 386px\" \/><\/p>\n<p><em>Figure 22: Current and voltage waveforms from the math channels. Peak currents are just under a half a milliamp.<\/em><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-23-Neon_current_50Hz_waveforms-597x600.png\" alt=\"\" width=\"389\" height=\"391\" class=\"alignnone wp-image-30266\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-23-Neon_current_50Hz_waveforms-597x600.png 597w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-23-Neon_current_50Hz_waveforms-1019x1024.png 1019w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-23-Neon_current_50Hz_waveforms-150x150.png 150w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-23-Neon_current_50Hz_waveforms-1528x1536.png 1528w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-23-Neon_current_50Hz_waveforms.png 1705w\" sizes=\"auto, (max-width: 389px) 100vw, 389px\" \/><\/p>\n<p><em>Figure 23: Waveforms at 50 Hz show the glow start and stop much more clearly.<\/em><\/p>\n<p>At lower frequencies (50 Hz), the extinction of the glow at a voltage near 60 V is much more obvious, since the transient behavior of the glow and the capacitance of the neon bulb itself are less pronounced, so the waveform is much cleaner. As seen in Figure 23, the current starts very abruptly when the ignition voltage is reached, and the current stops when the glow extinguishes when the voltage falls below the minimum glow voltage.<\/p>\n<p>&nbsp;<\/p>\n<h4>It\u2019s the Current (Density Through the Heart) That Kills You, Not the (No Load) Voltage<\/h4>\n<p>Wait one second, is it safe to ask undergraduates to use a 120 V output?<\/p>\n<ul>\n<li>The Analog Discovery 2\u2019s maximum output current capability is about 40 mA. Dividing that by the turns ratio of about 1:10, the output current on the secondary could be, at most, 4 mA. This limit applies before and above any imperfections of the transformer. Touching the transformer output causes a weird, unpleasant tingling sensation, but it is not painful due to the small maximum current. See Figure 24.<\/li>\n<li>The primary low voltage winding of this transformer has resistance of about 50 ohms, and the secondary high voltage winding about 1200\u03a9. The total cantilever impedance reflected to the secondary side is (50\u03a9)10^2 + 1200\u03a9 = 62000\u03a9 . A human body represents a load of about 1000\u03a9, so the human body is exposed to a voltage of about 1\/7 the terminal open-circuit voltage if touching the H winding, about 14 Vac, a nonlethal voltage commonly output by benchtop waveform generators.<\/li>\n<li>The leakage reactance of the transformer further limits current to the load of a human body.<\/li>\n<li>I did once do this experiment with a push-pull AB current amplifier on the waveform generator, giving the full 800 mA capacity of the DC supplies as AC. That one bit me painfully when I touched the secondary of the transformer. Don\u2019t do that.<\/li>\n<li>A student with an implanted medical device vulnerable to electrical disruption (such as a pacemaker), should notify their instructor before attempting this experiment.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-24-output_limit-600x562.png\" alt=\"\" width=\"277\" height=\"259\" class=\"alignnone wp-image-30267\" srcset=\"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-24-output_limit-600x562.png 600w, https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-24-output_limit.png 970w\" sizes=\"auto, (max-width: 277px) 100vw, 277px\" \/><\/p>\n<p><em>Figure 24: Output voltage waveform when loaded with a 1k resistor, similar in value to a human body\u2019s internal tissues when the skin has broken down.<\/em><\/p>\n<p>&nbsp;<\/p>\n<p>Note the AD2 overcurrent protection kicking in when the output current gets too high in Figure 24. Even without the overcurrent protection, the peak would be only about 10-15 V if you follow the trajectory of the sine wave that has been decapitated by the overcurrent protection, because the internal resistance of this transformer is rather high.<\/p>\n<p>&nbsp;<\/p>\n<h4>Wrap Up<\/h4>\n<p>Neon glowed with high voltage. We didn\u2019t electrocute ourselves with high voltage. We didn\u2019t destroy our measurement instruments with high voltage. Analog electronics is cool! There are so many interesting experiments that you can do. Parts are cheaper than ever, and the instrumentation is more accessible than ever too.<\/p>\n<p>To the professors in the audience: I\u2019ve rewritten all my circuit labs here at MSOE all around the Analog Discovery 2. All 30ish of them are compatible with the new <a href=\"https:\/\/digilent.com\/shop\/analog-discovery-3\/\">Analog Discovery 3<\/a> and feature at least one sensor or transducer. If you are looking for circuits lab experiments that don\u2019t put your students to sleep, drop me an email (faulkner@msoe.edu). Taking circuit theory isn\u2019t the price of admission to interesting subjects like controls and instrumentation, it can be fun on its own, and it <em>should<\/em> be fun.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<div class='watch-action'><div class='watch-position align-left'><div class='action-like'><a class='lbg-style6 like-30239 jlk' data-task='like' data-post_id='30239' data-nonce='87acbb1af5' rel='nofollow'><img src='https:\/\/digilent.com\/blog\/wp-content\/plugins\/wti-like-post-pro\/images\/pixel.gif' title='Like' \/><span class='lc-30239 lc'>+3<\/span><\/a><\/div><div class='action-unlike'><a class='unlbg-style6 unlike-30239 jlk' data-task='unlike' data-post_id='30239' data-nonce='87acbb1af5' rel='nofollow'><img src='https:\/\/digilent.com\/blog\/wp-content\/plugins\/wti-like-post-pro\/images\/pixel.gif' title='Unlike' \/><span class='unlc-30239 unlc'>0<\/span><\/a><\/div><\/div> <div class='status-30239 status align-left'><\/div><\/div><div class='wti-clear'><\/div>","protected":false},"excerpt":{"rendered":"<p>Hi there Digilent Blog readers! I\u2019m Dr. Brian Faulkner, professor of Electrical Engineering at Milwaukee School of Engineering in Milwaukee, Wisconsin, USA, where I teach introductory circuit theory and power &hellip; <\/p>\n","protected":false},"author":47,"featured_media":30261,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[20,4327,1563],"tags":[4342,4432,4566,4564,4565,452,4447],"ppma_author":[4569],"class_list":["post-30239","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-products","category-projects","category-guide","tag-ad2","tag-ad3","tag-neon","tag-neon-lamp","tag-resistors","tag-waveforms","tag-wavegen"],"jetpack_featured_media_url":"https:\/\/digilent.com\/blog\/wp-content\/uploads\/2023\/10\/fig-18-Capacitive_Coupling-scaled.jpg","authors":[{"term_id":4569,"user_id":0,"is_guest":1,"slug":"dr-brian-faulkner","display_name":"Brian Faulkner","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&r=g","1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":"","9":"","10":""}],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/posts\/30239","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/users\/47"}],"replies":[{"embeddable":true,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/comments?post=30239"}],"version-history":[{"count":15,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/posts\/30239\/revisions"}],"predecessor-version":[{"id":30277,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/posts\/30239\/revisions\/30277"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/media\/30261"}],"wp:attachment":[{"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/media?parent=30239"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/categories?post=30239"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/tags?post=30239"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/digilent.com\/blog\/wp-json\/wp\/v2\/ppma_author?post=30239"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}