United States Patent 9,784,449
Flame Sensing System
Issued 10/10/2017 to Margolin
Application Number 14,316,489
Filed 6/26/2014
Jed Margolin
ABSTRACT OF THE DISCLOSURE
This invention relates to the field of sensing flames in equipment such as gas furnaces by using the electrical properties of flames. In a first group of embodiments flame rectification is used to cause distortion of a signal having a selected waveform. A harmonic of the distorted waveform is detected thereby providing flame proof. In a second group of embodiments flame rectification is used as a mixer to cause two signals having selected waveforms to produce sum and difference signals. The sum and/or difference signals are detected thereby providing flame proof.
References
The listed links are the original links. In some cases they may be broken.
The PDF version was made from the original link.
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IDS 1: U.S. Patent 1,688,126 Method of and Apparatus for Control of Liquid Fuel Burners issued Oct 16, 1928 to R.F. Metcalfe, assigned to Socony Burner Corporation (Metcalfe Figure 1 Contacts 7 and 8; Page 3, right column, lines 70 – 79) |
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IDS 2: U.S. Patent 2,112,736 Flame Detector issued March 29, 1938 to William D. Cockrell, assigned to General Electric (Page 1, left column, line 41 – Page 2, right column, line 15) |
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IDS 3: U.S. Patent 2,136,256 Furnace Control System issued Nov 8, 1938 to A.L Sweet, assigned to General Electric Company (age 1, left column, line 4 – Page 2, left column line 2) |
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IDS 4: U.S. Patent 3,301,307 Device for detecting the configuration of a burning flame issued Jan 31, 1967 to Kazuo Kobayashi, et al, assigned to Ngk Insulators Ltd (Column 2, lines 3 -15) |
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IDS 5: U.S. Patent 4,082,493 Gas Burner Control System issued April 4, 1978 to Dahlgren, assigned to Cam-Stat, Incorporated (Dahlgren Figure 2 and Column 3, lines 32 – 42; Table at Column 3, lines 20-30) |
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IDS 6: U.S. Patent 8,310,801 Flame sensing voltage dependent on application issued November 13, 2012 to McDonald, et al., assigned to Honeywell (Column 2, lines 10 – 44) |
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IDS 7: U.S. Patent 6,404,342 Flame detector using filtering of ultraviolet radiation flicker issued June 11, 2002 to Planer, et al. and assigned to Honeywell (Column 1, lines 21 – 32) |
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IDS 8: Prediction and Measurement of Electron Density and Collision Frequency in a Weakly Ionised Pine Fire by Mphale, Mohan, and Heron; Int J Infrared Milli Waves (2007) 28:251–262; DOI 10.1007/s10762-007-9199-7; http://eprints.jcu.edu.au/2655/1/17300_Mphale_et_al_2007.pdf |
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IDS 9: Conduction of Electricity Through Gases by J. J. Thomson; Cambridge University Press; 1903,1906; Chapter IX Ionization in Gases from Flames; page 228, PDF page 8; http://trove.nla.gov.au/goto?i=book&w=808233&d=http%3A%2F%2Fopenlibrary.org%2Fbooks%2FOL7102511M |
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IDS 10: About Plasmas from the Coalition For Plasma Science; Plasma and Flames – The Burning Question; http://www.plasmacoalition.org/plasma_writeups/flame.pdf |
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IDS 11: Plasma Fundamentals and Applications; by Dr. I.J. Van der Walt, Senior Scientist, Necsa contains a chart (PDF page 8) |
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IDS 12: Introduction to Combustion; by Stephen R. Turns, McGraw Hill Education (India); Page 108, PDF page 3; page 159, bottom of PDF page 5. |
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IDS 13: Burning Sulfur Compounds; Banks Engineering – Tulsa; http://www.banksengineering.com/Burning%20Sulfur%20Compounds.pdf |
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IDS 14: Alkali metal halide, Wikipedia January 19, 2014; http://en.wikipedia.org/wiki/Alkali_metal_halide |
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IDS 15: Alkali Metal, Wikipedia January 19, 2014; http://en.wikipedia.org/wiki/Alkali_metal |
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IDS 16: U.S. Patent 4,317,487 Method of recovering oil and other hydrocarbon values from subterranean formations issued March 2, 1982 to Merkl, and assigned to Molecular Energy Research Company, Inc. |
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IDS 17: Grades of Propane - Gas Purity and Quality |
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IDS 18: The Truth About Propane |
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IDS 19: U.S. Patent 307,031 Electrical indicator issued October 21, 1884 to T. A. Edison. |
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IDS 20: U.S. Patent 803,684 Instrument for converting alternating electric currents into continuous current issued November 7, 1905 to J.A. Fleming, assigned to Marconi Wireless Telegraph Company Of America. |
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IDS 21: Definition of “Electrolyte” retrieved from Wikipedia 1/31/2014; |
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IDS 22: Dissertation Counter Electromotive Force in the Aluminum Rectifier; Albert Lewis Fitch, Press of the New Era Printing Co.; Lancaster, Pa; 1917; Pages 15-17). |
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IDS 23: U.S. Patent 1,077,628 Electrolytic condenser issued November 4, 1913 to Mershon {Ref. 27} Page 1, lines 40-50 |
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IDS 24: General Descriptions of Aluminum Electrolytic Capacitors, 1-1 Principles of Aluminum Electrolytic Capacitors’ Nichicon; Page 1. http://www.nichicon.co.jp/english/products/pdf/aluminum.pdf |
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IDS 25: Batteries and electrochemical capacitors; Héctor D. Abruña, Yasukuki Kiya, and Jay C. Henderson; Physics Today December 2008, page 43-47 https://ecee.colorado.edu/~ecen4555/SourceMaterial/ElectricalEnerStor1208.pdf . |
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IDS 26: Electroplating; from Wikipedia, retrieved 2/1/2014. http://en.wikipedia.org/wiki/Electroplating |
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IDS 27: U.S. Patent 3,956,080 Coated valve metal article formed by spark anodizing issued May 11, 1976 to Hradcovsky, et al.; Column 2 lines 10 – 48. |
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IDS 28: The front pages of the datasheets for the 5U4GB, 5Y3GT, and 6X4/12X4 vacuum tube rectifiers |
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IDS 29: Visual Analyzer 2011 XE Beta 0.3.2 - Visual Analyzer is a real time software program that contains a comprehensive set of measurement instruments, including an FFT Analyzer. It runs on a PC running Windows and can use existing internal sound hardware or can use external hardware. http://www.sillanumsoft.org/ |
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IDS 30: The Art of Electronics, Paul Horowitz and Winfield Hill, Cambridge University Press, 1991, pages 885-886. |
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IDS 31: Sine-Wave Oscillator, Ron Mancini and Richard Palmer , Texas Instruments, Application Note SLOA060 - March 2001; http://www.ti.com/litv/pdf/sloa060 |
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IDS 32: Datasheet for LM13700, Texas Instruments, Figure 37 Sinusoidal VCO. |
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IDS 33: U.S. Patent 2,709,799 Flame Detector System issued May 31, 1955 to M. H. Norton, assigned to Petcar Research. |
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IDS 34: U.S. Patent 2,804,608 Flame Detector System issued August 27, 1957 to Carbauh, assigned to Petcar Research Corp. |
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Examiner’s References:
U.S. Patent 6,501,383 Method and device for monitoring a flame issued December 31, 2002 to Haupenthal
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U.S. Patent 6,486,486 Flame monitoring system issued November 26, 2002 to Haupenthal
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Publication 2008/0266000 Digital Frequency Multiplier published October 30, 2008; Ngo et al.
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Examiner’s References
Publication 2014/0085503 Mobile Communication Apparatus and Flashlight Controlling Method Wen-Yueh Su; et al. published March 27, 2014.
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US Patent 5,547,369 Camera, spectrum analysis system, and combustion evaluation apparatus employing them issued August 20, 1996 to Sohma, et al.
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Examiner’s References
US Patent 5,051,590 Fiber optic flame detection and temperature measurement system having one or more in-line temperature dependent optical filters issued September 24, 1991 to Kern.
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US Patent 5,300,836 Flame rod structure, and a compensating circuit and control method thereof issued April 5, 1994 to Cha.
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Publication 2012/0280134 Monitoring of the presence of two flames in a fuel combustion device published November 8, 2012; Diebold.
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Publication 2014/0162197 Multijet Burner with charge interaction published June 12, 2014; Krichtafovitch.
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Publication 2015/0362177 Flame position control electrodes published 12-2015; Krichtafovitch.
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Issued October 10, 2017
A. July 2024 - When I did the R&D for this patent I did it all with MSI. I didn’t know if it could be done in the microcontroller family I was using (the Texas Instruments MSG430G2xxx family) and I didn’t want to spend the time to find out. I also didn’t want people to think this was a software patent. Because it was MSI I wire-wrapped the several boards it took to do it. But as a result I could look at every signal in the process in real time.
It wasn’t until my patent application was allowed that I decided to see if I could do it with the MSP430G2xxx. In the first version I used it only to produce the four signals I needed (874 Hz, 1262 Hz, 388 Hz, and 388 Hz in quadrature.). I continued to do the quadrature detection in hardware. Then I did the version where I used the MSP430G2xxx ADC and did the quadrature detection in software. It totally worked.
Since then I have done a version using the Raspberry Pi Pico. If you want to see the original write-up for the MSP430G2xxx version Click Here.
The Raspberry Pi Pico module is amazing. It is much faster than the MSP430G2xxx, has much more memory, has two cores, a 12-bit ADC, and is available with onboard WiFi and Bluetooth. The module comes in a 40-pin wide-DIP. As I write this in July 2024 the Raspberry Pi Pico module costs $4.00. The Raspberry Pi Pico W (the one with WiFi and Bluetooth) costs $6.00 . You can get the RPI Pico from Digikey as well as from places such as https://www.pishop.us/. This is more specifically what the Pico has:
RP2040 microcontroller chip designed by Raspberry Pi in the United Kingdom
Dual-core Arm Cortex M0+ processor, flexible clock running up to 133 MHz
264kB of SRAM, and 2MB of on-board flash memory
USB 1.1 with device and host support
26 × multi-function GPIO pins
2 × SPI, 2 × I2C, 2 × UART, 3 × 12-bit ADC, 16 × controllable PWM channels
Accelerated floating-point libraries on-chip
8 × Programmable I/O (PIO) state machines for custom peripheral support
Note that the Pico has two cores. I am only using one of them. The other one could be used as the furnace controller running its own code. That means the flame sensing system is practically free.
I have done two versions.
Version 1: The Pico produces the four signals (874 Hz, 1262 Hz, 388 Hz, and 388 Hz in quadrature), uses the Pico ADC to read the result of flame rectification, does the quadrature detection in software, and sends the results out in real time through the uart.
Version 2: The Pico produces the four signals (874 Hz, 1262 Hz, 388 Hz, and 388 Hz in quadrature) and does the quadrature detection in hardware so you can verify that it does what the patent teaches. The Pico also uses the ADC to read the outputs and send them out in real time through the uart.
B. I was offering to sell non-exclusive licenses. That offer ended 11/6/2024.
These are the two boards I made with the Raspberry Pi Pico.
Flame Sense 1: The Pico produces the four signals (874 Hz, 1262 Hz, 388 Hz, and 388 Hz in quadrature), uses the Pico ADC to read the result of flame rectification, does the quadrature detection in software, and sends the results out in real time through the uart.
Schematic (PDF): Click Here
This is the typical output using the Flame Simulator board showing the difference between Flame and No Flame:
Cos (abs) Sine (abs) Cos (abs) Sine (abs) Cos (abs,scaled) Sine (abs,scaled)
0005AC5F 00002678 00,371,807. 00,009,848. 00,005,809. 00,000,153.
Scaled Magnitude = 00,000,730. Flame Good
Threshold Pot = 353
Cos (abs) Sine (abs) Cos (abs) Sine (abs) Cos (abs,scaled) Sine (abs,scaled)
00005485 000019E6 00,021,637. 00,006,630. 00,000,338. 00,000,103.
Scaled Magnitude = 00,000,045. No Flame
Threshold Pot = 353
The ratio of On to Off is 730/45 = 16.2
This is the typical output using the Meker Burner showing the difference between Flame and No Flame:
Cos (abs) Sine (abs) Cos (abs) Sine (abs) Cos (abs,scaled) Sine (abs,scaled)
0006616E 0000606F 00,418,158. 00,024,687. 00,006,533. 00,000,385.
Scaled Magnitude = 00,000,828. Flame Good
Threshold Pot = 353
Cos (abs) Sine (abs) Cos (abs) Sine (abs) Cos (abs,scaled) Sine (abs,scaled)
00006724 000017D6 00,026,404. 00,006,102. 00,000,412. 00,000,095.
Scaled Magnitude = 00,000,054. No Flame
Threshold Pot = 353
The ratio of On to Off is 828/54 = 15.3
Flame Sense 2: The Pico produces the four signals (874 Hz, 1262 Hz, 388 Hz, and 388 Hz in quadrature) and does the quadrature detection in hardware so you can verify that it does what the patent teaches. The Pico also uses the ADC to read the outputs and send them out in real time through the uart.
Schematic (PDF): Click Here
This is the typical output using the Flame Simulator board showing the difference between Flame and No Flame:
Sine Cosine Magnitude Threshold Flame
-0308 -1121 1198 0521 Flame On
Sine Cosine Magnitude Threshold Flame
-0103 -0098 0127 0521 Flame Off
The ratio of On to Off is 1198/127 = 9.4
This is the typical output using the Meker Burner showing the difference between Flame and No Flame:
Sine Cosine Magnitude Threshold Flame
0454 1217 1330 0522 Flame On
Sine Cosine Magnitude Threshold Flame
0080 -0109 0129 0520 Flame Off
The ratio of On to Off is 1330/129 = 10.3
The setup for the Flame 1 board with the Meker Burner:
This board produces a simulated flame signal used for testing.
Schematic (PDF): Click Here
I have found an interesting patent. U.S. Patent 10,732,147 In situ fuel-to-air ratio (FAR) sensor for combustion using a fourier based flame ionization probe issued August 4, 2020 to Deivasigamani, et al. The patent is assigned to Intellihot, Inc. (https://www.intellihot.com/) They make on-demand water heaters. On-demand water heaters are also called tankless water heaters. They heat the water fast enough that it doesn’t have to be heated and stored first. Hence no tank. A whole house on-demand water heater requires a large amount of energy to heat water fast enough so it doesn’t have to be heated and stored first so they have to use gas, either natural gas or propane. Houses don’t have enough service to do it with electricity. As with all gas appliances proof of flame is essential for safety.
There are electrically powered on-demand water heaters but they are useful only for spot use such as for a single sink or shower. See https://www.thisoldhouse.com/plumbing/21019184/read-this-before-you-buy-a-tankless-water-heater
And BTW, modern hot water heater tanks are so well insulated that there is very little heat loss. My hot water heater is electric and the outside of the tank is always stone cold.
For the PDF of the Intellihot patent (includes drawings) Click Here.
For the html of the patent (no drawings) Click Here.
What makes this patent interesting is:
1. This patent is basically for the same thing as mine except they use an FFT. Since you already know exactly what frequency (or frequencies) you are looking for I think an FFT is overkill. I use quadrature synchronous detection of the exact frequency that I am looking for. Indeed, an FFT is quadrature detection (the sine and cosine outputs) only it does it for a number of frequencies with a filter for each bin. If you want narrowband detection it does it for a large number of frequencies. And it requires a data buffer in order to do the butterfly. The FFT is a faster way for doing the DFT (Discrete Fourier Transform). If you have a fast enough processor (with a fast enough MAC or multiple MACs) you wouldn’t even need a buffer to do a DFT. You can consider my system a DFT with just one bin. No data buffers are needed.
2. The Intellihot patent application was filed February 4, 2018. It does not claim priority from anything before that.
a. My patent application claims priority from my U.S. Provisional Application No. 62/005,199 filed on May 30, 2014.
b. My patent application was filed June 26, 2014.
c. My patent application was published by the USPTO December 3, 2015.
d. My patent was issued October 10, 2017.
My Patent was issued before Intellihot even filed their application.
Their Patent application does not list my Patent as a reference even though their patent application reads directly on it.
We had a saying at Atari when things like this happened with our games, “It’s just like ours but with the serial numbers filed off.”
Jed Margolin
Virginia City Highlands
Nevada
7/14/2024, 11/6/2024