Science time (III) Giving second life for an ancient Gas Chromatograph

A project log for Retro-futuristic automobile control panel

Conversion of dashboard from an old, Communist clone of the French Renault 12 (Dacia 1310)

[skaarj][skaarj] 06/09/2016 at 11:572 Comments

Greetings, fellow hackers.

Now I (really?) understand the philosophy of the jury. Push everyone to hack more. If you have success with your project, push for more and rise up. If you fail, push for more and rise up. Never give up. Never let yourself go down. This is the true hacking philosophy: if you fail, or you are pushed away to give up, nobody cares. There will be other people ready to take your place and push further for nothing.

Instead of receiving some bucks in order to get access to latest tech, now I must hack my way to the 3rd round prize by resurrecting some ancient tech dinosaur in order to get things done.

So from this moment I am no longer questioning the second round results.

Allright, Science time.

I need to "smell" the exhaust gases from the engine in normal working conditions and in the presence of hydrogen-oxygen mixture injected through the air intake manifold.

And for that I need a Chromatograph, so let's see what this device does and how it works.

This is a block schematic of a generic Chromatograph:

A light gas is used as a sample carrier - usually Hydrogen (flamable!) or Helium (preferred). The sample is injected before the column (some long metalic hose) which is supposed to be heated. Heat can also be applied to a second column (not shown in the figure). The column hose is extremely thin - with microns in diameter. Lighter gases come out first, heavier gases come out later. There is also some theory about gases being attracted or repelled by the column internal coating, which also influences how fast they are separated and how fast they travel through the column. The sampling time lasts for minutes, then the TCD (thermal conductivity detector) or FID (flame ionization detector) outputs some analog signal at a corresponding time, which is the percentage of compound (separated) gas coming out. The higher the spike recorded on the graph, the higher the concentration of that separate compound is. The later it is recorded, the heavier the gas is.

The most common sensors (detectors) are as following:

TCD - thermal conductivity detector. If some gas passes around a electrically heated tungsten filament, its temperature modifies (usualy increases) and its electrical resistance also increases. The carrier gas alone (helium) has high thermal conductivity and keeps the filament cool, maintaining an uniform electrical resistivity. When the carrier gas brings a foreign gas, resulting gas mixture thermal conductivity decreases so it does not allow all the heat to dissipate (as before) and forces the filament to get hotter. Its electrical resistivity increases and the corresponding current variation is recorded as a response.

FID - flame ionization detector - it has two electrodes placed close to a flame fueled by carrier gas + air (in this case - hydrogen). This detector is used to identify the presence of hydrocarbons, so these are pyrolized by the flame. The hydrocarbons will split into ions (at cathode) and electrons (at anode) which generates a current between the elctrodes. It does not work with other gases (non-hydrocarbons) as these are unable to pyrolize.

Both sensor responses are recorded as spikes on a graphing device, which form a Chromatogram of the sample gases analyzed.

There are also catalytic sensors, infrared sensors, mass spectroscopy detectors and a lot more. All detect gases in their way but the output is recorded as spikes.

That's it. Simple in theory, headache to build - or to pay for an expansive one.

As I announced yesterday on #Hacker Channel, I found a 40-years old Chromatograph Station inside an abandoned warehouse at my work place. It's a true monster. They told me it worked with vacuum tubes and it's entirely trashed. During immemorial times, many generation of rats made it their home....

I'm happy the camera cannot record the horrible smell.

From top to bottom:

- Hole Depth display;

- Mud Temperature in, Mud Density in, Mud Temperature out, Mud Density out (there's a special prepared mud circulating through the drilling hole);

- Paper recorder 1 for Chroma 1;

- Chromatograph 1 (gas in - quantity of gases present on mud before it enters the drilling hole);

- Chromatograph 2 (gas out - quantity of gases the mud brings from the bottom of the hole);

- Mud Pressure Display Unit;

- Some unit full of rat poo;

- Chromatograph 3 (spare/backup);

- Calculation Unit containing two mathematics calculators and an alarm buzzer;

- Paper recorder 2 for Chroma 2. FULL OF RATS. Everything is trashed inside, nothing can be recovered. Not even the rats, they became aggressive when I invaded their home. There's a horrible smell I do not wish to describe. Public toilets smell nice comparing to that.

I brought in my office the three Chromas, a paper recorder and two mud weight (density) - mud in and mud out. The smell is unbelievable. Colleagues ran away and told the boss I turned the office into a piggery, again. Nobody allowed me to bring the rest of the system inside.

Chroma 1, Chroma 2, Paper recorder which was supposed to log someH2S variations.

Mud Weight units + spare chroma

Spare Chroma is trashed by the rats. They ate most of the hoses and left a lot of garbage and droppings. Maybe I can scrap some components. I'm happy there are no vacuum tubes in the whole system. It's less dangerous when I will try to power it on.

The column is that spiral metallic hose.

Gas Column is missing in Chroma 2. Recovered from Spare Chroma.

Chroma 1 and Chroma 2, before surgery.

Trashed paper recorder. Also needs surgery.

Hydrogen Sulfide (H2S) sensor. I removed it from the circuit. Need information from both Chromas to go through its electric connections.

Trashed power supply was removed from Chroma 1 and Chroma 2.

They were destroyed by rats. I don't want people to feel sick so no pictures of them. Only by special request.

Rebuilt two PSUs on some cheap Chinese experimental PCBs. Input 220VAC, output +/-15V (small box) to power a signal amplifier instrumentation barrier (big white box in the right side). Spare parts taken from the supplies at work. I reused the original socket.

The other one inserted inside Chroma 2 - that white box mounted in the middle unit.

This is the original 24V stabilizer. Art work.

Power distribution Unit which supplies 24V for pump, gas heater, DAC/ADC/instrumentation preamplifier and TCD sensor.

And the PCB back side...

I replaced the FID sensors (flame ionization) with TCD (thermal conductivity detectors) - spares from the newer chromatographs I have at work place, so a new instrumentation preamplifier+DAC/ADC is needed. After consulting the service schematics, I came out with this beauty on a Chinese experimental PCB.

I am unable to paste those service manual pages, as I will break my confidentiality contract with the Company and boss will throw me out without any comments.

Rebuilt an analog-to-digital/digital-to-analog converter. I will later want to log everything on some normal computing unit.

Board also contains three op-amp, an ADC, some open collector ICs, reed relays and of course the power stabilizer.

I also built a digital output bus for parallel port.

Notice the old-school analog to digital converter (resistors + capacitors) near the data bus on the left side.

Old school wiring insanity. Welcome back to the Madhouse. Again.

Original socket reused. The original board is oxidized, filled with rats poo and it's not fit for the new sensors. Colleagues ran away - again - when I started to touch that pooed thing in order to throw it out.

Hacking inside rat poo is pure insanity. Instead, this instrumentation preamplifier DAC/ADC board should perform wonderful. Boss will also cancel my contract if any magic smoke is released, he likes what I do but he's angry I did not inform him earlier about my intentions. I need to be extremely careful.

Relay 1 (bottom) activates the pump. Relay 2 activates the heater. Black relay switches on the board. Reed Relays (4 pieces) set 4 different temperatures to the heater. Multi-turn pots adjust the sensor signal levels.

I need Helium as a carrier gas, connecting the pipe line....

Everything wired up and ready to go.

Electronic recorder repaired. Ground is common, so I need two signal lines - from Chroma 1 and Chroma 2.

110 Volts is for pussies.

In EU we have 220 Volts because blowing things gets funnier.

Carrier line connected. There are two pipes with free ends: transparent one is the sample gas for Chroma 2, the small pipe at the left corner is sample gas for Chroma 1. Both Chromas are connected to the two input lines of paper recorder.

No magic smoke so far.

I turned the warehouse upside down until I found some spare recorder papers. Rats did not get them. This is good.

Made in Germany. Quality guaranteed.

Powering up again.

Still no magic smoke from the boards. Instead it comes out from the heater and from the red temperature sensor labeled "MC".

No lights are present on the panels and the silence is very suspect.

Initially these Chromas were designed to use Hydrogen as a carrier gas due to the specifics of the FID sensors. We're closer to the 21st century due to the new TCD sensors and now I have Helium, which is a stable gas and it's not starting fires. And it gives people funny voices when inhaled. Air and Carrier Gas (helium) flows adjusted for both Chromas. Flame generator removed. I don't want to risk burning things. Air flow also closed. There's no need for air. Nothing burns, so no air.

Helium is injected through a 7 micron hole in the mixture chamber, which is heated and receives the sample gas from the column.

After one minute, pumps started to work with big noise. Again, all the colleagues jumped from their chairs and ran out scared. Someone wants to call the emergency number and ask for the nearby asylum. [skaarj] is suspiciously calm, he built strange devices all day long, no smoke came out so far and apparently he really enjoys messing up with stinking rats shit&piss.

One more minute, the system starts huffing and puffing, electronic recorder starts to spin slowly and.....


We've got our carrier gas recorded!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Need to refill the pencil, someone brought me some ink from a printer refill kit.

Now, need some sample gas. Nobody is willing to fart in the hoses, so I need some magic approach....

Pumps suck in some magic smoke from a highly toxic source.

And we have some reading. Need to grease all the mechanics inside the recorder.

Sample gas input, one more time...

One more minute, huffing, puffing...

And we've got ourselves a spike!

Red label says something in German - "clean with alcohol only".

Allright, explaining one more time how this works...

H2 input - carrier gas input, I used Helium;

Data line - I want to log everything to some PC using parallel port as an input;

- Sample gas goes through both CG and Sample hose connectors;

- OUT hose connector releases the gases after they pass through the Chroma;

- Recorder DIN5 connector - output analog data, it passes the electric analog signal to the recorder;

- MAINS: 220V input without any magic smoke;

- FID sensors are replaced with TCD so no need to burn any hydrogen;

- power supplies and ADC/DAC converter rebuilt.

Allright, so we've got a working 40-years old, rat-pooed chromatograph which would make all Hackaday staff, editors and jury scratch their heads. We've got some readings from a highly toxic magic smoke source.

The next step is to record all the spikes coming out from these calibration sample gases:

H2S, Carbon Monoxide, Carbon Dioxide, Methane, low-end (2%) hydrocarbons...

And some nitrogen compound I am unable to identify properly .

I need to record each of them and see at what time the corresponding spike is recorded. Then I need to record all of them mixed and the Chromas should output the spikes in some order, depending on how heavy the compounds are.

Lighter gases should come out earlier and heavier gases should come out later.

At this time the stage is prepared for recording the exhaust gases (chroma out) and input mixture gases (gasoline, air, later added hydrogen-oxygen mixture) and compare the resulting charts - for these two cases:

1. The automobile engine runs normally on gasoline;

2. Engine runs with injected hydrogen-oxygen mixture (releases from electrolysis) through the air intake manifold.

The output charts results are compared with the calibration gases charts and see what kind of gases are recorded - where (meaning "at what time") the resulting spikes are placed comparing to the reference (calibration gases) spikes.

Still no magic smoke so far....



kernel panic: improbability coefficient below zero


johnowhitaker wrote 06/09/2016 at 18:07 point

Great! I am very impressed - well done for getting that beast up and running so fast.

  Are you sure? yes | no

[skaarj] wrote 06/09/2016 at 19:17 point

Thank you.  

Does a 14 hours interval of working time really means "so fast"?

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